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NAME
    perlapi - autogenerated documentation for the perl public API

DESCRIPTION
    This file contains the documentation of the perl public API generated
    by embed.pl, specifically a listing of functions, macros, flags, and
    variables that may be used by extension writers.  The interfaces of any
    functions that are not listed here are subject to change without
    notice. For this reason, blindly using functions listed in proto.h is
    to be avoided when writing extensions.

    Note that all Perl API global variables must be referenced with the
    "PL_" prefix. Some macros are provided for compatibility with the
    older, unadorned names, but this support may be disabled in a future
    release.

    The listing is alphabetical, case insensitive.

"Gimme" Values
    GIMME  A backward-compatible version of "GIMME_V" which can only
     return "G_SCALAR" or "G_ARRAY"; in a void context, it returns
     "G_SCALAR". Deprecated.  Use "GIMME_V" instead.

      U32   GIMME

    GIMME_V The XSUB-writer's equivalent to Perl's "wantarray". Returns
     "G_VOID", "G_SCALAR" or "G_ARRAY" for void, scalar or list con-
     text, respectively.

      U32   GIMME_V

    G_ARRAY Used to indicate list context. See "GIMME_V", "GIMME" and
     perlcall.

    G_DISCARD
     Indicates that arguments returned from a callback should be
     discarded. See perlcall.

    G_EVAL Used to force a Perl "eval" wrapper around a callback. See
     perlcall.

    G_NOARGS
     Indicates that no arguments are being sent to a callback. See
     perlcall.

    G_SCALAR
     Used to indicate scalar context.  See "GIMME_V", "GIMME", and
     perlcall.

    G_VOID Used to indicate void context. See "GIMME_V" and perlcall.

Array Manipulation Functions
    AvFILL Same as "av_len()". Deprecated, use "av_len()" instead.

      int   AvFILL(AV* av)

    av_clear
     Clears an array, making it empty. Does not free the memory
     used by the array itself.

      void  av_clear(AV* ar)

    av_delete
     Deletes the element indexed by "key" from the array. Returns
     the deleted element. "flags" is currently ignored.

      SV*   av_delete(AV* ar, I32 key, I32 flags)

    av_exists
     Returns true if the element indexed by "key" has been initial-
     ized.

     This relies on the fact that uninitialized array elements are
     set to &PL_sv_undef.

      bool  av_exists(AV* ar, I32 key)

    av_extend
     Pre-extend an array. The "key" is the index to which the array
     should be extended.

      void  av_extend(AV* ar, I32 key)

    av_fetch
     Returns the SV at the specified index in the array. The "key"
     is the index. If "lval" is set then the fetch will be part of
     a store.  Check that the return value is non-null before deref-
     erencing it to a "SV*".

     See "Understanding the Magic of Tied Hashes and Arrays" in
     perlguts for more information on how to use this function on
     tied arrays.

      SV**  av_fetch(AV* ar, I32 key, I32 lval)

    av_fill Ensure than an array has a given number of elements, equivalent
     to Perl's "$#array = $fill;".

      void  av_fill(AV* ar, I32 fill)

    av_len Returns the highest index in the array. Returns -1 if the
     array is empty.

      I32   av_len(AV* ar)

    av_make Creates a new AV and populates it with a list of SVs. The SVs
     are copied into the array, so they may be freed after the call
     to av_make. The new AV will have a reference count of 1.

      AV*   av_make(I32 size, SV** svp)

    av_pop Pops an SV off the end of the array. Returns &PL_sv_undef if
     the array is empty.

      SV*   av_pop(AV* ar)

    av_push Pushes an SV onto the end of the array. The array will grow
     automatically to accommodate the addition.

      void  av_push(AV* ar, SV* val)

    av_shift
     Shifts an SV off the beginning of the array.

      SV*   av_shift(AV* ar)

    av_store
     Stores an SV in an array. The array index is specified as
     "key". The return value will be NULL if the operation failed
     or if the value did not need to be actually stored within the
     array (as in the case of tied arrays). Otherwise it can be
     dereferenced to get the original "SV*". Note that the caller
     is responsible for suitably incrementing the reference count of
     "val" before the call, and decrementing it if the function
     returned NULL.

     See "Understanding the Magic of Tied Hashes and Arrays" in
     perlguts for more information on how to use this function on
     tied arrays.

      SV**  av_store(AV* ar, I32 key, SV* val)

    av_undef
     Undefines the array. Frees the memory used by the array
     itself.

      void  av_undef(AV* ar)

    av_unshift
     Unshift the given number of "undef" values onto the beginning
     of the array. The array will grow automatically to accommodate
     the addition. You must then use "av_store" to assign values to
     these new elements.

      void  av_unshift(AV* ar, I32 num)

    get_av Returns the AV of the specified Perl array. If "create" is set
     and the Perl variable does not exist then it will be created.
     If "create" is not set and the variable does not exist then
     NULL is returned.

     NOTE: the perl_ form of this function is deprecated.

      AV*   get_av(const char* name, I32 create)

    newAV  Creates a new AV. The reference count is set to 1.

      AV*   newAV()

    Nullav Null AV pointer.

    sortsv Sort an array. Here is an example:

    sortsv(AvARRAY(av), av_len(av)+1, Perl_sv_cmp_locale);

     See lib/sort.pm for details about controlling the sorting algo-
     rithm.

      void  sortsv(SV ** array, size_t num_elts, SVCOMPARE_t cmp)

Callback Functions
    call_argv
     Performs a callback to the specified Perl sub. See perlcall.

     NOTE: the perl_ form of this function is deprecated.

      I32   call_argv(const char* sub_name, I32 flags, char** argv)

    call_method
     Performs a callback to the specified Perl method. The blessed
     object must be on the stack. See perlcall.

     NOTE: the perl_ form of this function is deprecated.

      I32   call_method(const char* methname, I32 flags)

    call_pv Performs a callback to the specified Perl sub. See perlcall.

     NOTE: the perl_ form of this function is deprecated.

      I32   call_pv(const char* sub_name, I32 flags)

    call_sv Performs a callback to the Perl sub whose name is in the SV.
     See perlcall.

     NOTE: the perl_ form of this function is deprecated.

      I32   call_sv(SV* sv, I32 flags)

    ENTER  Opening bracket on a callback. See "LEAVE" and perlcall.

       ENTER;

    eval_pv Tells Perl to "eval" the given string and return an SV* result.

     NOTE: the perl_ form of this function is deprecated.

      SV*   eval_pv(const char* p, I32 croak_on_error)

    eval_sv Tells Perl to "eval" the string in the SV.

     NOTE: the perl_ form of this function is deprecated.

      I32   eval_sv(SV* sv, I32 flags)

    FREETMPS
     Closing bracket for temporaries on a callback. See "SAVETMPS"
     and perlcall.

       FREETMPS;

    LEAVE  Closing bracket on a callback. See "ENTER" and perlcall.

       LEAVE;

    SAVETMPS
     Opening bracket for temporaries on a callback. See "FREETMPS"
     and perlcall.

       SAVETMPS;

Character classes
    isALNUM Returns a boolean indicating whether the C "char" is an ASCII
     alphanumeric character (including underscore) or digit.

      bool  isALNUM(char ch)

    isALPHA Returns a boolean indicating whether the C "char" is an ASCII
     alphabetic character.

      bool  isALPHA(char ch)

    isDIGIT Returns a boolean indicating whether the C "char" is an ASCII
     digit.

      bool  isDIGIT(char ch)

    isLOWER Returns a boolean indicating whether the C "char" is a lower-
     case character.

      bool  isLOWER(char ch)

    isSPACE Returns a boolean indicating whether the C "char" is whites-
     pace.

      bool  isSPACE(char ch)

    isUPPER Returns a boolean indicating whether the C "char" is an upper-
     case character.

      bool  isUPPER(char ch)

    toLOWER Converts the specified character to lowercase.

      char  toLOWER(char ch)

    toUPPER Converts the specified character to uppercase.

      char  toUPPER(char ch)

Cloning an interpreter
    perl_clone
     Create and return a new interpreter by cloning the current one.

     perl_clone takes these flags as paramters:

     CLONEf_COPY_STACKS - is used to, well, copy the stacks also,
     without it we only clone the data and zero the stacks, with it
     we copy the stacks and the new perl interpreter is ready to run
     at the exact same point as the previous one. The pseudo-fork
     code uses COPY_STACKS while the threads->new doesn't.

     CLONEf_KEEP_PTR_TABLE perl_clone keeps a ptr_table with the
     pointer of the old variable as a key and the new variable as a
     value, this allows it to check if something has been cloned and
     not clone it again but rather just use the value and increase
     the refcount. If KEEP_PTR_TABLE is not set then perl_clone will
     kill the ptr_table using the function "ptr_ta-
     ble_free(PL_ptr_table); PL_ptr_table = NULL;", reason to keep
     it around is if you want to dup some of your own variable who
     are outside the graph perl scans, example of this code is in
     threads.xs create

     CLONEf_CLONE_HOST This is a win32 thing, it is ignored on unix,
     it tells perls win32host code (which is c++) to clone itself,
     this is needed on win32 if you want to run two threads at the
     same time, if you just want to do some stuff in a separate perl
     interpreter and then throw it away and return to the original
     one, you don't need to do anything.

      PerlInterpreter*     perl_clone(PerlInterpreter* interp, UV flags)

CV Manipulation Functions
    CvSTASH Returns the stash of the CV.

      HV*   CvSTASH(CV* cv)

    get_cv Returns the CV of the specified Perl subroutine.  If "create"
     is set and the Perl subroutine does not exist then it will be
     declared (which has the same effect as saying "sub name;"). If
     "create" is not set and the subroutine does not exist then NULL
     is returned.

     NOTE: the perl_ form of this function is deprecated.

      CV*   get_cv(const char* name, I32 create)

    Nullcv Null CV pointer.

Embedding Functions
    load_module
     Loads the module whose name is pointed to by the string part of
     name. Note that the actual module name, not its filename,
     should be given.  Eg, "Foo::Bar" instead of "Foo/Bar.pm".
     flags can be any of PERL_LOADMOD_DENY, PERL_LOADMOD_NOIMPORT,
     or PERL_LOADMOD_IMPORT_OPS (or 0 for no flags). ver, if speci-
     fied, provides version semantics similar to "use Foo::Bar VER-
     SION". The optional trailing SV* arguments can be used to
     specify arguments to the module's import() method, similar to
     "use Foo::Bar VERSION LIST".

      void  load_module(U32 flags, SV* name, SV* ver, ...)

    nothreadhook
     Stub that provides thread hook for perl_destruct when there are
     no threads.

      int   nothreadhook()

    perl_alloc
     Allocates a new Perl interpreter. See perlembed.

      PerlInterpreter*     perl_alloc()

    perl_construct
     Initializes a new Perl interpreter. See perlembed.

      void  perl_construct(PerlInterpreter* interp)

    perl_destruct
     Shuts down a Perl interpreter. See perlembed.

      int   perl_destruct(PerlInterpreter* interp)

    perl_free
     Releases a Perl interpreter. See perlembed.

      void  perl_free(PerlInterpreter* interp)

    perl_parse
     Tells a Perl interpreter to parse a Perl script.  See perlem-
     bed.

      int   perl_parse(PerlInterpreter* interp, XSINIT_t xsinit, int argc, char** argv, char** env)

    perl_run
     Tells a Perl interpreter to run.  See perlembed.

      int   perl_run(PerlInterpreter* interp)

    require_pv
     Tells Perl to "require" the file named by the string argument.
     It is analogous to the Perl code "eval "require '$file'"".
     It's even implemented that way; consider using Perl_load_module
     instead.

     NOTE: the perl_ form of this function is deprecated.

      void  require_pv(const char* pv)

Functions in file pp_pack.c
    pack_cat
     The engine implementing pack() Perl function.

      void  pack_cat(SV *cat, char *pat, char *patend, SV **beglist, SV **endlist, SV ***next_in_list, U32 flags)

    unpack_str
     The engine implementing unpack() Perl function.

      I32   unpack_str(char *pat, char *patend, char *s, char *strbeg, char *strend, char **new_s, I32 ocnt, U32 flags)

Global Variables
    PL_modglobal
     "PL_modglobal" is a general purpose, interpreter global HV for
     use by extensions that need to keep information on a per-
     interpreter basis. In a pinch, it can also be used as a symbol
     table for extensions to share data among each other. It is a
     good idea to use keys prefixed by the package name of the
     extension that owns the data.

      HV*   PL_modglobal

    PL_na  A convenience variable which is typically used with "SvPV" when
     one doesn't care about the length of the string.  It is usually
     more efficient to either declare a local variable and use that
     instead or to use the "SvPV_nolen" macro.

      STRLEN PL_na

    PL_sv_no
     This is the "false" SV. See "PL_sv_yes". Always refer to this
     as &PL_sv_no.

      SV   PL_sv_no

    PL_sv_undef
     This is the "undef" SV. Always refer to this as &PL_sv_undef.

      SV   PL_sv_undef

    PL_sv_yes
     This is the "true" SV. See "PL_sv_no". Always refer to this
     as &PL_sv_yes.

      SV   PL_sv_yes

GV Functions
    GvSV  Return the SV from the GV.

      SV*   GvSV(GV* gv)

    gv_fetchmeth
     Returns the glob with the given "name" and a defined subroutine
     or "NULL". The glob lives in the given "stash", or in the
     stashes accessible via @ISA and UNIVERSAL::.

     The argument "level" should be either 0 or -1. If "level==0",
     as a side-effect creates a glob with the given "name" in the
     given "stash" which in the case of success contains an alias
     for the subroutine, and sets up caching info for this glob.
     Similarly for all the searched stashes.

     This function grants "SUPER" token as a postfix of the stash
     name. The GV returned from "gv_fetchmeth" may be a method cache
     entry, which is not visible to Perl code. So when calling
     "call_sv", you should not use the GV directly; instead, you
     should use the method's CV, which can be obtained from the GV
     with the "GvCV" macro.

      GV*   gv_fetchmeth(HV* stash, const char* name, STRLEN len, I32 level)

    gv_fetchmethod
     See gv_fetchmethod_autoload.

      GV*   gv_fetchmethod(HV* stash, const char* name)

    gv_fetchmethod_autoload
     Returns the glob which contains the subroutine to call to
     invoke the method on the "stash". In fact in the presence of
     autoloading this may be the glob for "AUTOLOAD".  In this case
     the corresponding variable $AUTOLOAD is already setup.

     The third parameter of "gv_fetchmethod_autoload" determines
     whether AUTOLOAD lookup is performed if the given method is not
     present: non-zero means yes, look for AUTOLOAD; zero means no,
     don't look for AUTOLOAD.  Calling "gv_fetchmethod" is equiva-
     lent to calling "gv_fetchmethod_autoload" with a non-zero
     "autoload" parameter.

     These functions grant "SUPER" token as a prefix of the method
     name. Note that if you want to keep the returned glob for a
     long time, you need to check for it being "AUTOLOAD", since at
     the later time the call may load a different subroutine due to
     $AUTOLOAD changing its value. Use the glob created via a side
     effect to do this.

     These functions have the same side-effects and as "gv_fetch-
     meth" with "level==0". "name" should be writable if contains
     ':' or "' ''". The warning against passing the GV returned by
     "gv_fetchmeth" to "call_sv" apply equally to these functions.

      GV*   gv_fetchmethod_autoload(HV* stash, const char* name, I32 autoload)

    gv_fetchmeth_autoload
     Same as gv_fetchmeth(), but looks for autoloaded subroutines
     too. Returns a glob for the subroutine.

     For an autoloaded subroutine without a GV, will create a GV
     even if "level < 0". For an autoloaded subroutine without a
     stub, GvCV() of the result may be zero.

      GV*   gv_fetchmeth_autoload(HV* stash, const char* name, STRLEN len, I32 level)

    gv_stashpv
     Returns a pointer to the stash for a specified package. "name"
     should be a valid UTF-8 string. If "create" is set then the
     package will be created if it does not already exist. If "cre-
     ate" is not set and the package does not exist then NULL is
     returned.

      HV*   gv_stashpv(const char* name, I32 create)

    gv_stashsv
     Returns a pointer to the stash for a specified package, which
     must be a valid UTF-8 string. See "gv_stashpv".

      HV*   gv_stashsv(SV* sv, I32 create)

Handy Values
    HEf_SVKEY
     This flag, used in the length slot of hash entries and magic
     structures, specifies the structure contains an "SV*" pointer
     where a "char*" pointer is to be expected. (For information
     only--not to be used).

    Nullch Null character pointer. =for hackers Found in file handy.h

    Nullsv Null SV pointer.

Hash Manipulation Functions
    get_hv Returns the HV of the specified Perl hash. If "create" is set
     and the Perl variable does not exist then it will be created.
     If "create" is not set and the variable does not exist then
     NULL is returned.

     NOTE: the perl_ form of this function is deprecated.

      HV*   get_hv(const char* name, I32 create)

    HeHASH Returns the computed hash stored in the hash entry.

      U32   HeHASH(HE* he)

    HeKEY  Returns the actual pointer stored in the key slot of the hash
     entry. The pointer may be either "char*" or "SV*", depending on
     the value of "HeKLEN()".  Can be assigned to. The "HePV()" or
     "HeSVKEY()" macros are usually preferable for finding the value
     of a key.

      void*  HeKEY(HE* he)

    HeKLEN If this is negative, and amounts to "HEf_SVKEY", it indicates
     the entry holds an "SV*" key. Otherwise, holds the actual
     length of the key. Can be assigned to. The "HePV()" macro is
     usually preferable for finding key lengths.

      STRLEN HeKLEN(HE* he)

    HePV  Returns the key slot of the hash entry as a "char*" value,
     doing any necessary dereferencing of possibly "SV*" keys. The
     length of the string is placed in "len" (this is a macro, so do
     not use &len). If you do not care about what the length of the
     key is, you may use the global variable "PL_na", though this is
     rather less efficient than using a local variable. Remember
     though, that hash keys in perl are free to contain embedded
     nulls, so using "strlen()" or similar is not a good way to find
     the length of hash keys. This is very similar to the "SvPV()"
     macro described elsewhere in this document.

      char*  HePV(HE* he, STRLEN len)

    HeSVKEY Returns the key as an "SV*", or "Nullsv" if the hash entry does
     not contain an "SV*" key.

      SV*   HeSVKEY(HE* he)

    HeSVKEY_force
     Returns the key as an "SV*". Will create and return a tempo-
     rary mortal "SV*" if the hash entry contains only a "char*"
     key.

      SV*   HeSVKEY_force(HE* he)

    HeSVKEY_set
     Sets the key to a given "SV*", taking care to set the appropri-
     ate flags to indicate the presence of an "SV*" key, and returns
     the same "SV*".

      SV*   HeSVKEY_set(HE* he, SV* sv)

    HeVAL  Returns the value slot (type "SV*") stored in the hash entry.

      SV*   HeVAL(HE* he)

    HvNAME Returns the package name of a stash. See "SvSTASH", "CvSTASH".

      char*  HvNAME(HV* stash)

    hv_clear
     Clears a hash, making it empty.

      void  hv_clear(HV* tb)

    hv_delete
     Deletes a key/value pair in the hash. The value SV is removed
     from the hash and returned to the caller. The "klen" is the
     length of the key. The "flags" value will normally be zero; if
     set to G_DISCARD then NULL will be returned.

      SV*   hv_delete(HV* tb, const char* key, I32 klen, I32 flags)

    hv_delete_ent
     Deletes a key/value pair in the hash. The value SV is removed
     from the hash and returned to the caller. The "flags" value
     will normally be zero; if set to G_DISCARD then NULL will be
     returned. "hash" can be a valid precomputed hash value, or 0
     to ask for it to be computed.

      SV*   hv_delete_ent(HV* tb, SV* key, I32 flags, U32 hash)

    hv_exists
     Returns a boolean indicating whether the specified hash key
     exists. The "klen" is the length of the key.

      bool  hv_exists(HV* tb, const char* key, I32 klen)

    hv_exists_ent
     Returns a boolean indicating whether the specified hash key
     exists. "hash" can be a valid precomputed hash value, or 0 to
     ask for it to be computed.

      bool  hv_exists_ent(HV* tb, SV* key, U32 hash)

    hv_fetch
     Returns the SV which corresponds to the specified key in the
     hash. The "klen" is the length of the key. If "lval" is set
     then the fetch will be part of a store. Check that the return
     value is non-null before dereferencing it to an "SV*".

     See "Understanding the Magic of Tied Hashes and Arrays" in
     perlguts for more information on how to use this function on
     tied hashes.

      SV**  hv_fetch(HV* tb, const char* key, I32 klen, I32 lval)

    hv_fetch_ent
     Returns the hash entry which corresponds to the specified key
     in the hash. "hash" must be a valid precomputed hash number
     for the given "key", or 0 if you want the function to compute
     it. IF "lval" is set then the fetch will be part of a store.
     Make sure the return value is non-null before accessing it.
     The return value when "tb" is a tied hash is a pointer to a
     static location, so be sure to make a copy of the structure if
     you need to store it somewhere.

     See "Understanding the Magic of Tied Hashes and Arrays" in
     perlguts for more information on how to use this function on
     tied hashes.

      HE*   hv_fetch_ent(HV* tb, SV* key, I32 lval, U32 hash)

    hv_iterinit
     Prepares a starting point to traverse a hash table. Returns
     the number of keys in the hash (i.e. the same as "HvKEYS(tb)").
     The return value is currently only meaningful for hashes with-
     out tie magic.

     NOTE: Before version 5.004_65, "hv_iterinit" used to return the
     number of hash buckets that happen to be in use.  If you still
     need that esoteric value, you can get it through the macro
     "HvFILL(tb)".

      I32   hv_iterinit(HV* tb)

    hv_iterkey
     Returns the key from the current position of the hash iterator.
     See "hv_iterinit".

      char*  hv_iterkey(HE* entry, I32* retlen)

    hv_iterkeysv
     Returns the key as an "SV*" from the current position of the
     hash iterator. The return value will always be a mortal copy
     of the key. Also see "hv_iterinit".

      SV*   hv_iterkeysv(HE* entry)

    hv_iternext
     Returns entries from a hash iterator. See "hv_iterinit".

     You may call "hv_delete" or "hv_delete_ent" on the hash entry
     that the iterator currently points to, without losing your
     place or invalidating your iterator. Note that in this case
     the current entry is deleted from the hash with your iterator
     holding the last reference to it. Your iterator is flagged to
     free the entry on the next call to "hv_iternext", so you must
     not discard your iterator immediately else the entry will leak
     - call "hv_iternext" to trigger the resource deallocation.

      HE*   hv_iternext(HV* tb)

    hv_iternextsv
     Performs an "hv_iternext", "hv_iterkey", and "hv_iterval" in
     one operation.

      SV*   hv_iternextsv(HV* hv, char** key, I32* retlen)

    hv_iternext_flags
     Returns entries from a hash iterator. See "hv_iterinit" and
     "hv_iternext". The "flags" value will normally be zero; if
     HV_ITERNEXT_WANTPLACEHOLDERS is set the placeholders keys (for
     restricted hashes) will be returned in addition to normal keys.
     By default placeholders are automatically skipped over. Cur-
     rently a placeholder is implemented with a value that is liter-
     ally <&Perl_sv_undef> (a regular "undef" value is a normal
     read-write SV for which "!SvOK" is false). Note that the imple-
     mentation of placeholders and restricted hashes may change, and
     the implementation currently is insufficiently abstracted for
     any change to be tidy.

     NOTE: this function is experimental and may change or be
     removed without notice.

      HE*   hv_iternext_flags(HV* tb, I32 flags)

    hv_iterval
     Returns the value from the current position of the hash itera-
     tor. See "hv_iterkey".

      SV*   hv_iterval(HV* tb, HE* entry)

    hv_magic
     Adds magic to a hash. See "sv_magic".

      void  hv_magic(HV* hv, GV* gv, int how)

    hv_store
     Stores an SV in a hash. The hash key is specified as "key" and
     "klen" is the length of the key.  The "hash" parameter is the
     precomputed hash value; if it is zero then Perl will compute
     it. The return value will be NULL if the operation failed or
     if the value did not need to be actually stored within the hash
     (as in the case of tied hashes).  Otherwise it can be derefer-
     enced to get the original "SV*".  Note that the caller is
     responsible for suitably incrementing the reference count of
     "val" before the call, and decrementing it if the function
     returned NULL.

     See "Understanding the Magic of Tied Hashes and Arrays" in
     perlguts for more information on how to use this function on
     tied hashes.

      SV**  hv_store(HV* tb, const char* key, I32 klen, SV* val, U32 hash)

    hv_store_ent
     Stores "val" in a hash. The hash key is specified as "key".
     The "hash" parameter is the precomputed hash value; if it is
     zero then Perl will compute it. The return value is the new
     hash entry so created. It will be NULL if the operation failed
     or if the value did not need to be actually stored within the
     hash (as in the case of tied hashes). Otherwise the contents
     of the return value can be accessed using the "He?" macros
     described here. Note that the caller is responsible for suit-
     ably incrementing the reference count of "val" before the call,
     and decrementing it if the function returned NULL.

     See "Understanding the Magic of Tied Hashes and Arrays" in
     perlguts for more information on how to use this function on
     tied hashes.

      HE*   hv_store_ent(HV* tb, SV* key, SV* val, U32 hash)

    hv_undef
     Undefines the hash.

      void  hv_undef(HV* tb)

    newHV  Creates a new HV. The reference count is set to 1.

      HV*   newHV()

    Nullhv Null HV pointer.

Magical Functions
    mg_clear
     Clear something magical that the SV represents. See
     "sv_magic".

      int   mg_clear(SV* sv)

    mg_copy Copies the magic from one SV to another.  See "sv_magic".

      int   mg_copy(SV* sv, SV* nsv, const char* key, I32 klen)

    mg_find Finds the magic pointer for type matching the SV. See
     "sv_magic".

      MAGIC* mg_find(SV* sv, int type)

    mg_free Free any magic storage used by the SV. See "sv_magic".

      int   mg_free(SV* sv)

    mg_get Do magic after a value is retrieved from the SV.  See
     "sv_magic".

      int   mg_get(SV* sv)

    mg_length
     Report on the SV's length. See "sv_magic".

      U32   mg_length(SV* sv)

    mg_magical
     Turns on the magical status of an SV. See "sv_magic".

      void  mg_magical(SV* sv)

    mg_set Do magic after a value is assigned to the SV. See "sv_magic".

      int   mg_set(SV* sv)

    SvGETMAGIC
     Invokes "mg_get" on an SV if it has 'get' magic.  This macro
     evaluates its argument more than once.

      void  SvGETMAGIC(SV* sv)

    SvLOCK Arranges for a mutual exclusion lock to be obtained on sv if a
     suitable module has been loaded.

      void  SvLOCK(SV* sv)

    SvSETMAGIC
     Invokes "mg_set" on an SV if it has 'set' magic.  This macro
     evaluates its argument more than once.

      void  SvSETMAGIC(SV* sv)

    SvSetMagicSV
     Like "SvSetSV", but does any set magic required afterwards.

      void  SvSetMagicSV(SV* dsb, SV* ssv)

    SvSetMagicSV_nosteal
     Like "SvSetMagicSV", but does any set magic required after-
     wards.

      void  SvSetMagicSV_nosteal(SV* dsv, SV* ssv)

    SvSetSV Calls "sv_setsv" if dsv is not the same as ssv. May evaluate
     arguments more than once.

      void  SvSetSV(SV* dsb, SV* ssv)

    SvSetSV_nosteal
     Calls a non-destructive version of "sv_setsv" if dsv is not the
     same as ssv. May evaluate arguments more than once.

      void  SvSetSV_nosteal(SV* dsv, SV* ssv)

    SvSHARE Arranges for sv to be shared between threads if a suitable mod-
     ule has been loaded.

      void  SvSHARE(SV* sv)

Memory Management
    Copy  The XSUB-writer's interface to the C "memcpy" function. The
     "src" is the source, "dest" is the destination, "nitems" is the
     number of items, and "type" is the type.  May fail on overlap-
     ping copies. See also "Move".

      void  Copy(void* src, void* dest, int nitems, type)

    Move  The XSUB-writer's interface to the C "memmove" function.  The
     "src" is the source, "dest" is the destination, "nitems" is the
     number of items, and "type" is the type.  Can do overlapping
     moves. See also "Copy".

      void  Move(void* src, void* dest, int nitems, type)

    New   The XSUB-writer's interface to the C "malloc" function.

      void  New(int id, void* ptr, int nitems, type)

    Newc  The XSUB-writer's interface to the C "malloc" function, with
     cast.

      void  Newc(int id, void* ptr, int nitems, type, cast)

    NEWSV  Creates a new SV. A non-zero "len" parameter indicates the
     number of bytes of preallocated string space the SV should
     have. An extra byte for a tailing NUL is also reserved.
     (SvPOK is not set for the SV even if string space is allo-
     cated.) The reference count for the new SV is set to 1.  "id"
     is an integer id between 0 and 1299 (used to identify leaks).

      SV*   NEWSV(int id, STRLEN len)

    Newz  The XSUB-writer's interface to the C "malloc" function. The
     allocated memory is zeroed with "memzero".

      void  Newz(int id, void* ptr, int nitems, type)

    Poison Fill up memory with a pattern (byte 0xAB over and over again)
     that hopefully catches attempts to access uninitialized memory.

      void  Poison(void* dest, int nitems, type)

    Renew  The XSUB-writer's interface to the C "realloc" function.

      void  Renew(void* ptr, int nitems, type)

    Renewc The XSUB-writer's interface to the C "realloc" function, with
     cast.

      void  Renewc(void* ptr, int nitems, type, cast)

    Safefree
     The XSUB-writer's interface to the C "free" function.

      void  Safefree(void* ptr)

    savepv Perl's version of "strdup()". Returns a pointer to a newly
     allocated string which is a duplicate of "pv". The size of the
     string is determined by "strlen()". The memory allocated for
     the new string can be freed with the "Safefree()" function.

      char*  savepv(const char* pv)

    savepvn Perl's version of what "strndup()" would be if it existed.
     Returns a pointer to a newly allocated string which is a dupli-
     cate of the first "len" bytes from "pv". The memory allocated
     for the new string can be freed with the "Safefree()" function.

      char*  savepvn(const char* pv, I32 len)

    savesharedpv
     A version of "savepv()" which allocates the duplicate string in
     memory which is shared between threads.

      char*  savesharedpv(const char* pv)

    StructCopy
     This is an architecture-independent macro to copy one structure
     to another.

      void  StructCopy(type src, type dest, type)

    Zero  The XSUB-writer's interface to the C "memzero" function.  The
     "dest" is the destination, "nitems" is the number of items, and
     "type" is the type.

      void  Zero(void* dest, int nitems, type)

Miscellaneous Functions
    fbm_compile
     Analyses the string in order to make fast searches on it using
     fbm_instr() -- the Boyer-Moore algorithm.

      void  fbm_compile(SV* sv, U32 flags)

    fbm_instr
     Returns the location of the SV in the string delimited by "str"
     and "strend". It returns "Nullch" if the string can't be
     found. The "sv" does not have to be fbm_compiled, but the
     search will not be as fast then.

      char*  fbm_instr(unsigned char* big, unsigned char* bigend, SV* littlesv, U32 flags)

    form  Takes a sprintf-style format pattern and conventional (non-SV)
     arguments and returns the formatted string.

    (char *) Perl_form(pTHX_ const char* pat, ...)

     can be used any place a string (char *) is required:

    char * s = Perl_form("%d.%d",major,minor);

     Uses a single private buffer so if you want to format several
     strings you must explicitly copy the earlier strings away (and
     free the copies when you are done).

      char*  form(const char* pat, ...)

    getcwd_sv
     Fill the sv with current working directory

      int   getcwd_sv(SV* sv)

    strEQ  Test two strings to see if they are equal. Returns true or
     false.

      bool  strEQ(char* s1, char* s2)

    strGE  Test two strings to see if the first, "s1", is greater than or
     equal to the second, "s2". Returns true or false.

      bool  strGE(char* s1, char* s2)

    strGT  Test two strings to see if the first, "s1", is greater than the
     second, "s2". Returns true or false.

      bool  strGT(char* s1, char* s2)

    strLE  Test two strings to see if the first, "s1", is less than or
     equal to the second, "s2". Returns true or false.

      bool  strLE(char* s1, char* s2)

    strLT  Test two strings to see if the first, "s1", is less than the
     second, "s2". Returns true or false.

      bool  strLT(char* s1, char* s2)

    strNE  Test two strings to see if they are different. Returns true or
     false.

      bool  strNE(char* s1, char* s2)

    strnEQ Test two strings to see if they are equal. The "len" parameter
     indicates the number of bytes to compare. Returns true or
     false. (A wrapper for "strncmp").

      bool  strnEQ(char* s1, char* s2, STRLEN len)

    strnNE Test two strings to see if they are different. The "len"
     parameter indicates the number of bytes to compare. Returns
     true or false. (A wrapper for "strncmp").

      bool  strnNE(char* s1, char* s2, STRLEN len)

Numeric functions
    grok_bin
     converts a string representing a binary number to numeric form.

     On entry start and *len give the string to scan, *flags gives
     conversion flags, and result should be NULL or a pointer to an
     NV. The scan stops at the end of the string, or the first
     invalid character. On return *len is set to the length scanned
     string, and *flags gives output flags.

     If the value is <= UV_MAX it is returned as a UV, the output
     flags are clear, and nothing is written to *result. If the
     value is > UV_MAX "grok_bin" returns UV_MAX, sets
     "PERL_SCAN_GREATER_THAN_UV_MAX" in the output flags, and writes
     the value to *result (or the value is discarded if result is
     NULL).

     The hex number may optionally be prefixed with "0b" or "b"
     unless "PERL_SCAN_DISALLOW_PREFIX" is set in *flags on entry.
     If "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then the
     binary number may use '_' characters to separate digits.

      UV   grok_bin(char* start, STRLEN* len, I32* flags, NV *result)

    grok_hex
     converts a string representing a hex number to numeric form.

     On entry start and *len give the string to scan, *flags gives
     conversion flags, and result should be NULL or a pointer to an
     NV. The scan stops at the end of the string, or the first non-
     hex-digit character. On return *len is set to the length
     scanned string, and *flags gives output flags.

     If the value is <= UV_MAX it is returned as a UV, the output
     flags are clear, and nothing is written to *result. If the
     value is > UV_MAX "grok_hex" returns UV_MAX, sets
     "PERL_SCAN_GREATER_THAN_UV_MAX" in the output flags, and writes
     the value to *result (or the value is discarded if result is
     NULL).

     The hex number may optionally be prefixed with "0x" or "x"
     unless "PERL_SCAN_DISALLOW_PREFIX" is set in *flags on entry.
     If "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then the hex
     number may use '_' characters to separate digits.

      UV   grok_hex(char* start, STRLEN* len, I32* flags, NV *result)

    grok_number
     Recognise (or not) a number. The type of the number is
     returned (0 if unrecognised), otherwise it is a bit-ORed combi-
     nation of IS_NUMBER_IN_UV, IS_NUMBER_GREATER_THAN_UV_MAX,
     IS_NUMBER_NOT_INT, IS_NUMBER_NEG, IS_NUMBER_INFINITY, IS_NUM-
     BER_NAN (defined in perl.h).

     If the value of the number can fit an in UV, it is returned in
     the *valuep IS_NUMBER_IN_UV will be set to indicate that *val-
     uep is valid, IS_NUMBER_IN_UV will never be set unless *valuep
     is valid, but *valuep may have been assigned to during process-
     ing even though IS_NUMBER_IN_UV is not set on return. If val-
     uep is NULL, IS_NUMBER_IN_UV will be set for the same cases as
     when valuep is non-NULL, but no actual assignment (or SEGV)
     will occur.

     IS_NUMBER_NOT_INT will be set with IS_NUMBER_IN_UV if trailing
     decimals were seen (in which case *valuep gives the true value
     truncated to an integer), and IS_NUMBER_NEG if the number is
     negative (in which case *valuep holds the absolute value).
     IS_NUMBER_IN_UV is not set if e notation was used or the number
     is larger than a UV.

      int   grok_number(const char *pv, STRLEN len, UV *valuep)

    grok_numeric_radix
     Scan and skip for a numeric decimal separator (radix).

      bool  grok_numeric_radix(const char **sp, const char *send)

    grok_oct
      UV   grok_oct(char* start, STRLEN* len, I32* flags, NV *result)

    scan_bin
     For backwards compatibility. Use "grok_bin" instead.

      NV   scan_bin(char* start, STRLEN len, STRLEN* retlen)

    scan_hex
     For backwards compatibility. Use "grok_hex" instead.

      NV   scan_hex(char* start, STRLEN len, STRLEN* retlen)

    scan_oct
     For backwards compatibility. Use "grok_oct" instead.

      NV   scan_oct(char* start, STRLEN len, STRLEN* retlen)

Optree Manipulation Functions
    cv_const_sv
     If "cv" is a constant sub eligible for inlining. returns the
     constant value returned by the sub. Otherwise, returns NULL.

     Constant subs can be created with "newCONSTSUB" or as described
     in "Constant Functions" in perlsub.

      SV*   cv_const_sv(CV* cv)

    newCONSTSUB
     Creates a constant sub equivalent to Perl "sub FOO () { 123 }"
     which is eligible for inlining at compile-time.

      CV*   newCONSTSUB(HV* stash, char* name, SV* sv)

    newXS  Used by "xsubpp" to hook up XSUBs as Perl subs.

Stack Manipulation Macros
    dMARK  Declare a stack marker variable, "mark", for the XSUB. See
     "MARK" and "dORIGMARK".

       dMARK;

    dORIGMARK
     Saves the original stack mark for the XSUB. See "ORIGMARK".

       dORIGMARK;

    dSP   Declares a local copy of perl's stack pointer for the XSUB,
     available via the "SP" macro. See "SP".

       dSP;

    EXTEND Used to extend the argument stack for an XSUB's return values.
     Once used, guarantees that there is room for at least "nitems"
     to be pushed onto the stack.

      void  EXTEND(SP, int nitems)

    MARK  Stack marker variable for the XSUB. See "dMARK".

    ORIGMARK
     The original stack mark for the XSUB. See "dORIGMARK".

    POPi  Pops an integer off the stack.

      IV   POPi

    POPl  Pops a long off the stack.

      long  POPl

    POPn  Pops a double off the stack.

      NV   POPn

    POPp  Pops a string off the stack. Deprecated. New code should pro-
     vide a STRLEN n_a and use POPpx.

      char*  POPp

    POPpbytex
     Pops a string off the stack which must consist of bytes i.e.
     characters < 256. Requires a variable STRLEN n_a in scope.

      char*  POPpbytex

    POPpx  Pops a string off the stack. Requires a variable STRLEN n_a in
     scope.

      char*  POPpx

    POPs  Pops an SV off the stack.

      SV*   POPs

    PUSHi  Push an integer onto the stack. The stack must have room for
     this element. Handles 'set' magic. See "XPUSHi".

      void  PUSHi(IV iv)

    PUSHMARK
     Opening bracket for arguments on a callback. See "PUTBACK" and
     perlcall.

       PUSHMARK;

    PUSHn  Push a double onto the stack. The stack must have room for
     this element. Handles 'set' magic. See "XPUSHn".

      void  PUSHn(NV nv)

    PUSHp  Push a string onto the stack. The stack must have room for
     this element. The "len" indicates the length of the string.
     Handles 'set' magic. See "XPUSHp".

      void  PUSHp(char* str, STRLEN len)

    PUSHs  Push an SV onto the stack. The stack must have room for this
     element.  Does not handle 'set' magic. See "XPUSHs".

      void  PUSHs(SV* sv)

    PUSHu  Push an unsigned integer onto the stack.  The stack must have
     room for this element. See "XPUSHu".

      void  PUSHu(UV uv)

    PUTBACK Closing bracket for XSUB arguments. This is usually handled by
     "xsubpp". See "PUSHMARK" and perlcall for other uses.

       PUTBACK;

    SP   Stack pointer. This is usually handled by "xsubpp". See "dSP"
     and "SPAGAIN".

    SPAGAIN Refetch the stack pointer. Used after a callback. See perl-
     call.

       SPAGAIN;

    XPUSHi Push an integer onto the stack, extending the stack if neces-
     sary. Handles 'set' magic. See "PUSHi".

      void  XPUSHi(IV iv)

    XPUSHn Push a double onto the stack, extending the stack if necessary.
     Handles 'set' magic. See "PUSHn".

      void  XPUSHn(NV nv)

    XPUSHp Push a string onto the stack, extending the stack if necessary.
     The "len" indicates the length of the string. Handles 'set'
     magic. See "PUSHp".

      void  XPUSHp(char* str, STRLEN len)

    XPUSHs Push an SV onto the stack, extending the stack if necessary.
     Does not handle 'set' magic. See "PUSHs".

      void  XPUSHs(SV* sv)

    XPUSHu Push an unsigned integer onto the stack, extending the stack if
     necessary. See "PUSHu".

      void  XPUSHu(UV uv)

    XSRETURN
     Return from XSUB, indicating number of items on the stack.
     This is usually handled by "xsubpp".

      void  XSRETURN(int nitems)

    XSRETURN_IV
     Return an integer from an XSUB immediately. Uses "XST_mIV".

      void  XSRETURN_IV(IV iv)

    XSRETURN_NO
     Return &PL_sv_no from an XSUB immediately. Uses "XST_mNO".

       XSRETURN_NO;

    XSRETURN_NV
     Return a double from an XSUB immediately. Uses "XST_mNV".

      void  XSRETURN_NV(NV nv)

    XSRETURN_PV
     Return a copy of a string from an XSUB immediately. Uses
     "XST_mPV".

      void  XSRETURN_PV(char* str)

    XSRETURN_UNDEF
     Return &PL_sv_undef from an XSUB immediately. Uses
     "XST_mUNDEF".

       XSRETURN_UNDEF;

    XSRETURN_YES
     Return &PL_sv_yes from an XSUB immediately. Uses "XST_mYES".

       XSRETURN_YES;

    XST_mIV Place an integer into the specified position "pos" on the
     stack. The value is stored in a new mortal SV.

      void  XST_mIV(int pos, IV iv)

    XST_mNO Place &PL_sv_no into the specified position "pos" on the stack.

      void  XST_mNO(int pos)

    XST_mNV Place a double into the specified position "pos" on the stack.
     The value is stored in a new mortal SV.

      void  XST_mNV(int pos, NV nv)

    XST_mPV Place a copy of a string into the specified position "pos" on
     the stack. The value is stored in a new mortal SV.

      void  XST_mPV(int pos, char* str)

    XST_mUNDEF
     Place &PL_sv_undef into the specified position "pos" on the
     stack.

      void  XST_mUNDEF(int pos)

    XST_mYES
     Place &PL_sv_yes into the specified position "pos" on the
     stack.

      void  XST_mYES(int pos)

SV Flags
    svtype An enum of flags for Perl types.  These are found in the file
     sv.h in the "svtype" enum. Test these flags with the "SvTYPE"
     macro.

    SVt_IV Integer type flag for scalars. See "svtype".

    SVt_NV Double type flag for scalars. See "svtype".

    SVt_PV Pointer type flag for scalars. See "svtype".

    SVt_PVAV
     Type flag for arrays. See "svtype".

    SVt_PVCV
     Type flag for code refs.  See "svtype".

    SVt_PVHV
     Type flag for hashes. See "svtype".

    SVt_PVMG
     Type flag for blessed scalars. See "svtype".

SV Manipulation Functions
    get_sv Returns the SV of the specified Perl scalar. If "create" is
     set and the Perl variable does not exist then it will be cre-
     ated. If "create" is not set and the variable does not exist
     then NULL is returned.

     NOTE: the perl_ form of this function is deprecated.

      SV*   get_sv(const char* name, I32 create)

    looks_like_number
     Test if the content of an SV looks like a number (or is a num-
     ber). "Inf" and "Infinity" are treated as numbers (so will not
     issue a non-numeric warning), even if your atof() doesn't grok
     them.

      I32   looks_like_number(SV* sv)

    newRV_inc
     Creates an RV wrapper for an SV.  The reference count for the
     original SV is incremented.

      SV*   newRV_inc(SV* sv)

    newRV_noinc
     Creates an RV wrapper for an SV.  The reference count for the
     original SV is not incremented.

      SV*   newRV_noinc(SV *sv)

    newSV  Create a new null SV, or if len > 0, create a new empty SVt_PV
     type SV with an initial PV allocation of len+1. Normally
     accessed via the "NEWSV" macro.

      SV*   newSV(STRLEN len)

    newSViv Creates a new SV and copies an integer into it. The reference
     count for the SV is set to 1.

      SV*   newSViv(IV i)

    newSVnv Creates a new SV and copies a floating point value into it.
     The reference count for the SV is set to 1.

      SV*   newSVnv(NV n)

    newSVpv Creates a new SV and copies a string into it. The reference
     count for the SV is set to 1. If "len" is zero, Perl will com-
     pute the length using strlen(). For efficiency, consider using
     "newSVpvn" instead.

      SV*   newSVpv(const char* s, STRLEN len)

    newSVpvf
     Creates a new SV and initializes it with the string formatted
     like "sprintf".

      SV*   newSVpvf(const char* pat, ...)

    newSVpvn
     Creates a new SV and copies a string into it. The reference
     count for the SV is set to 1. Note that if "len" is zero, Perl
     will create a zero length string. You are responsible for
     ensuring that the source string is at least "len" bytes long.

      SV*   newSVpvn(const char* s, STRLEN len)

    newSVpvn_share
     Creates a new SV with its SvPVX pointing to a shared string in
     the string table. If the string does not already exist in the
     table, it is created first. Turns on READONLY and FAKE.  The
     string's hash is stored in the UV slot of the SV; if the "hash"
     parameter is non-zero, that value is used; otherwise the hash
     is computed. The idea here is that as the string table is used
     for shared hash keys these strings will have SvPVX == HeKEY and
     hash lookup will avoid string compare.

      SV*   newSVpvn_share(const char* s, I32 len, U32 hash)

    newSVrv Creates a new SV for the RV, "rv", to point to. If "rv" is not
     an RV then it will be upgraded to one. If "classname" is non-
     null then the new SV will be blessed in the specified package.
     The new SV is returned and its reference count is 1.

      SV*   newSVrv(SV* rv, const char* classname)

    newSVsv Creates a new SV which is an exact duplicate of the original
     SV. (Uses "sv_setsv").

      SV*   newSVsv(SV* old)

    newSVuv Creates a new SV and copies an unsigned integer into it.  The
     reference count for the SV is set to 1.

      SV*   newSVuv(UV u)

    new_vstring
     Returns a pointer to the next character after the parsed
     vstring, as well as updating the passed in sv.

     Function must be called like

      sv = NEWSV(92,5);
      s = new_vstring(s,sv);

     The sv must already be large enough to store the vstring passed
     in.

      char*  new_vstring(char *vstr, SV *sv)

    SvCUR  Returns the length of the string which is in the SV. See
     "SvLEN".

      STRLEN SvCUR(SV* sv)

    SvCUR_set
     Set the length of the string which is in the SV.  See "SvCUR".

      void  SvCUR_set(SV* sv, STRLEN len)

    SvEND  Returns a pointer to the last character in the string which is
     in the SV. See "SvCUR".  Access the character as *(SvEND(sv)).

      char*  SvEND(SV* sv)

    SvGROW Expands the character buffer in the SV so that it has room for
     the indicated number of bytes (remember to reserve space for an
     extra trailing NUL character). Calls "sv_grow" to perform the
     expansion if necessary. Returns a pointer to the character
     buffer.

      char * SvGROW(SV* sv, STRLEN len)

    SvIOK  Returns a boolean indicating whether the SV contains an inte-
     ger.

      bool  SvIOK(SV* sv)

    SvIOKp Returns a boolean indicating whether the SV contains an inte-
     ger. Checks the private setting. Use "SvIOK".

      bool  SvIOKp(SV* sv)

    SvIOK_notUV
     Returns a boolean indicating whether the SV contains a signed
     integer.

      void  SvIOK_notUV(SV* sv)

    SvIOK_off
     Unsets the IV status of an SV.

      void  SvIOK_off(SV* sv)

    SvIOK_on
     Tells an SV that it is an integer.

      void  SvIOK_on(SV* sv)

    SvIOK_only
     Tells an SV that it is an integer and disables all other OK
     bits.

      void  SvIOK_only(SV* sv)

    SvIOK_only_UV
     Tells and SV that it is an unsigned integer and disables all
     other OK bits.

      void  SvIOK_only_UV(SV* sv)

    SvIOK_UV
     Returns a boolean indicating whether the SV contains an
     unsigned integer.

      void  SvIOK_UV(SV* sv)

    SvIV  Coerces the given SV to an integer and returns it. See "SvIVx"
     for a version which guarantees to evaluate sv only once.

      IV   SvIV(SV* sv)

    SvIVx  Coerces the given SV to an integer and returns it. Guarantees
     to evaluate sv only once. Use the more efficient "SvIV" other-
     wise.

      IV   SvIVx(SV* sv)

    SvIVX  Returns the raw value in the SV's IV slot, without checks or
     conversions. Only use when you are sure SvIOK is true. See
     also "SvIV()".

      IV   SvIVX(SV* sv)

    SvLEN  Returns the size of the string buffer in the SV, not including
     any part attributable to "SvOOK". See "SvCUR".

      STRLEN SvLEN(SV* sv)

    SvNIOK Returns a boolean indicating whether the SV contains a number,
     integer or double.

      bool  SvNIOK(SV* sv)

    SvNIOKp Returns a boolean indicating whether the SV contains a number,
     integer or double. Checks the private setting. Use "SvNIOK".

      bool  SvNIOKp(SV* sv)

    SvNIOK_off
     Unsets the NV/IV status of an SV.

      void  SvNIOK_off(SV* sv)

    SvNOK  Returns a boolean indicating whether the SV contains a double.

      bool  SvNOK(SV* sv)

    SvNOKp Returns a boolean indicating whether the SV contains a double.
     Checks the private setting. Use "SvNOK".

      bool  SvNOKp(SV* sv)

    SvNOK_off
     Unsets the NV status of an SV.

      void  SvNOK_off(SV* sv)

    SvNOK_on
     Tells an SV that it is a double.

      void  SvNOK_on(SV* sv)

    SvNOK_only
     Tells an SV that it is a double and disables all other OK bits.

      void  SvNOK_only(SV* sv)

    SvNV  Coerce the given SV to a double and return it. See "SvNVx" for
     a version which guarantees to evaluate sv only once.

      NV   SvNV(SV* sv)

    SvNVX  Returns the raw value in the SV's NV slot, without checks or
     conversions. Only use when you are sure SvNOK is true. See
     also "SvNV()".

      NV   SvNVX(SV* sv)

    SvNVx  Coerces the given SV to a double and returns it. Guarantees to
     evaluate sv only once. Use the more efficient "SvNV" otherwise.

      NV   SvNVx(SV* sv)

    SvOK  Returns a boolean indicating whether the value is an SV.

      bool  SvOK(SV* sv)

    SvOOK  Returns a boolean indicating whether the SvIVX is a valid off-
     set value for the SvPVX.  This hack is used internally to speed
     up removal of characters from the beginning of a SvPV. When
     SvOOK is true, then the start of the allocated string buffer is
     really (SvPVX - SvIVX).

      bool  SvOOK(SV* sv)

    SvPOK  Returns a boolean indicating whether the SV contains a charac-
     ter string.

      bool  SvPOK(SV* sv)

    SvPOKp Returns a boolean indicating whether the SV contains a charac-
     ter string. Checks the private setting.  Use "SvPOK".

      bool  SvPOKp(SV* sv)

    SvPOK_off
     Unsets the PV status of an SV.

      void  SvPOK_off(SV* sv)

    SvPOK_on
     Tells an SV that it is a string.

      void  SvPOK_on(SV* sv)

    SvPOK_only
     Tells an SV that it is a string and disables all other OK bits.
     Will also turn off the UTF8 status.

      void  SvPOK_only(SV* sv)

    SvPOK_only_UTF8
     Tells an SV that it is a string and disables all other OK bits,
     and leaves the UTF8 status as it was.

      void  SvPOK_only_UTF8(SV* sv)

    SvPV  Returns a pointer to the string in the SV, or a stringified
     form of the SV if the SV does not contain a string. The SV may
     cache the stringified version becoming "SvPOK". Handles 'get'
     magic. See also "SvPVx" for a version which guarantees to eval-
     uate sv only once.

      char*  SvPV(SV* sv, STRLEN len)

    SvPVbyte
     Like "SvPV", but converts sv to byte representation first if
     necessary.

      char*  SvPVbyte(SV* sv, STRLEN len)

    SvPVbytex
     Like "SvPV", but converts sv to byte representation first if
     necessary. Guarantees to evaluate sv only once; use the more
     efficient "SvPVbyte" otherwise.

      char*  SvPVbytex(SV* sv, STRLEN len)

    SvPVbytex_force
     Like "SvPV_force", but converts sv to byte representation first
     if necessary. Guarantees to evaluate sv only once; use the
     more efficient "SvPVbyte_force" otherwise.

      char*  SvPVbytex_force(SV* sv, STRLEN len)

    SvPVbyte_force
     Like "SvPV_force", but converts sv to byte representation first
     if necessary.

      char*  SvPVbyte_force(SV* sv, STRLEN len)

    SvPVbyte_nolen
     Like "SvPV_nolen", but converts sv to byte representation first
     if necessary.

      char*  SvPVbyte_nolen(SV* sv)

    SvPVutf8
     Like "SvPV", but converts sv to utf8 first if necessary.

      char*  SvPVutf8(SV* sv, STRLEN len)

    SvPVutf8x
     Like "SvPV", but converts sv to utf8 first if necessary.  Guar-
     antees to evaluate sv only once; use the more efficient
     "SvPVutf8" otherwise.

      char*  SvPVutf8x(SV* sv, STRLEN len)

    SvPVutf8x_force
     Like "SvPV_force", but converts sv to utf8 first if necessary.
     Guarantees to evaluate sv only once; use the more efficient
     "SvPVutf8_force" otherwise.

      char*  SvPVutf8x_force(SV* sv, STRLEN len)

    SvPVutf8_force
     Like "SvPV_force", but converts sv to utf8 first if necessary.

      char*  SvPVutf8_force(SV* sv, STRLEN len)

    SvPVutf8_nolen
     Like "SvPV_nolen", but converts sv to utf8 first if necessary.

      char*  SvPVutf8_nolen(SV* sv)

    SvPVx  A version of "SvPV" which guarantees to evaluate sv only once.

      char*  SvPVx(SV* sv, STRLEN len)

    SvPVX  Returns a pointer to the physical string in the SV. The SV
     must contain a string.

      char*  SvPVX(SV* sv)

    SvPV_force
     Like "SvPV" but will force the SV into containing just a string
     ("SvPOK_only"). You want force if you are going to update the
     "SvPVX" directly.

      char*  SvPV_force(SV* sv, STRLEN len)

    SvPV_force_nomg
     Like "SvPV" but will force the SV into containing just a string
     ("SvPOK_only"). You want force if you are going to update the
     "SvPVX" directly. Doesn't process magic.

      char*  SvPV_force_nomg(SV* sv, STRLEN len)

    SvPV_nolen
     Returns a pointer to the string in the SV, or a stringified
     form of the SV if the SV does not contain a string. The SV may
     cache the stringified form becoming "SvPOK". Handles 'get'
     magic.

      char*  SvPV_nolen(SV* sv)

    SvREFCNT
     Returns the value of the object's reference count.

      U32   SvREFCNT(SV* sv)

    SvREFCNT_dec
     Decrements the reference count of the given SV.

      void  SvREFCNT_dec(SV* sv)

    SvREFCNT_inc
     Increments the reference count of the given SV.

      SV*   SvREFCNT_inc(SV* sv)

    SvROK  Tests if the SV is an RV.

      bool  SvROK(SV* sv)

    SvROK_off
     Unsets the RV status of an SV.

      void  SvROK_off(SV* sv)

    SvROK_on
     Tells an SV that it is an RV.

      void  SvROK_on(SV* sv)

    SvRV  Dereferences an RV to return the SV.

      SV*   SvRV(SV* sv)

    SvSTASH Returns the stash of the SV.

      HV*   SvSTASH(SV* sv)

    SvTAINT Taints an SV if tainting is enabled

      void  SvTAINT(SV* sv)

    SvTAINTED
     Checks to see if an SV is tainted. Returns TRUE if it is, FALSE
     if not.

      bool  SvTAINTED(SV* sv)

    SvTAINTED_off
     Untaints an SV. Be very careful with this routine, as it short-
     circuits some of Perl's fundamental security features. XS mod-
     ule authors should not use this function unless they fully
     understand all the implications of unconditionally untainting
     the value. Untainting should be done in the standard perl fash-
     ion, via a carefully crafted regexp, rather than directly
     untainting variables.

      void  SvTAINTED_off(SV* sv)

    SvTAINTED_on
     Marks an SV as tainted.

      void  SvTAINTED_on(SV* sv)

    SvTRUE Returns a boolean indicating whether Perl would evaluate the SV
     as true or false, defined or undefined. Does not handle 'get'
     magic.

      bool  SvTRUE(SV* sv)

    SvTYPE Returns the type of the SV. See "svtype".

      svtype SvTYPE(SV* sv)

    SvUNLOCK
     Releases a mutual exclusion lock on sv if a suitable module has
     been loaded.

      void  SvUNLOCK(SV* sv)

    SvUOK  Returns a boolean indicating whether the SV contains an
     unsigned integer.

      void  SvUOK(SV* sv)

    SvUPGRADE
     Used to upgrade an SV to a more complex form. Uses
     "sv_upgrade" to perform the upgrade if necessary. See
     "svtype".

      void  SvUPGRADE(SV* sv, svtype type)

    SvUTF8 Returns a boolean indicating whether the SV contains UTF-8
     encoded data.

      void  SvUTF8(SV* sv)

    SvUTF8_off
     Unsets the UTF8 status of an SV.

      void  SvUTF8_off(SV *sv)

    SvUTF8_on
     Turn on the UTF8 status of an SV (the data is not changed, just
     the flag). Do not use frivolously.

      void  SvUTF8_on(SV *sv)

    SvUV  Coerces the given SV to an unsigned integer and returns it.
     See "SvUVx" for a version which guarantees to evaluate sv only
     once.

      UV   SvUV(SV* sv)

    SvUVX  Returns the raw value in the SV's UV slot, without checks or
     conversions. Only use when you are sure SvIOK is true. See
     also "SvUV()".

      UV   SvUVX(SV* sv)

    SvUVx  Coerces the given SV to an unsigned integer and returns it.
     Guarantees to evaluate sv only once. Use the more efficient
     "SvUV" otherwise.

      UV   SvUVx(SV* sv)

    sv_2bool
     This function is only called on magical items, and is only used
     by sv_true() or its macro equivalent.

      bool  sv_2bool(SV* sv)

    sv_2cv Using various gambits, try to get a CV from an SV; in addition,
     try if possible to set *st and *gvp to the stash and GV associ-
     ated with it.

      CV*   sv_2cv(SV* sv, HV** st, GV** gvp, I32 lref)

    sv_2io Using various gambits, try to get an IO from an SV: the IO slot
     if its a GV; or the recursive result if we're an RV; or the IO
     slot of the symbol named after the PV if we're a string.

      IO*   sv_2io(SV* sv)

    sv_2iv Return the integer value of an SV, doing any necessary string
     conversion, magic etc. Normally used via the "SvIV(sv)" and
     "SvIVx(sv)" macros.

      IV   sv_2iv(SV* sv)

    sv_2mortal
     Marks an existing SV as mortal. The SV will be destroyed
     "soon", either by an explicit call to FREETMPS, or by an
     implicit call at places such as statement boundaries. See also
     "sv_newmortal" and "sv_mortalcopy".

      SV*   sv_2mortal(SV* sv)

    sv_2nv Return the num value of an SV, doing any necessary string or
     integer conversion, magic etc. Normally used via the "SvNV(sv)"
     and "SvNVx(sv)" macros.

      NV   sv_2nv(SV* sv)

    sv_2pvbyte
     Return a pointer to the byte-encoded representation of the SV,
     and set *lp to its length. May cause the SV to be downgraded
     from UTF8 as a side-effect.

     Usually accessed via the "SvPVbyte" macro.

      char*  sv_2pvbyte(SV* sv, STRLEN* lp)

    sv_2pvbyte_nolen
     Return a pointer to the byte-encoded representation of the SV.
     May cause the SV to be downgraded from UTF8 as a side-effect.

     Usually accessed via the "SvPVbyte_nolen" macro.

      char*  sv_2pvbyte_nolen(SV* sv)

    sv_2pvutf8
     Return a pointer to the UTF8-encoded representation of the SV,
     and set *lp to its length. May cause the SV to be upgraded to
     UTF8 as a side-effect.

     Usually accessed via the "SvPVutf8" macro.

      char*  sv_2pvutf8(SV* sv, STRLEN* lp)

    sv_2pvutf8_nolen
     Return a pointer to the UTF8-encoded representation of the SV.
     May cause the SV to be upgraded to UTF8 as a side-effect.

     Usually accessed via the "SvPVutf8_nolen" macro.

      char*  sv_2pvutf8_nolen(SV* sv)

    sv_2pv_flags
     Returns a pointer to the string value of an SV, and sets *lp to
     its length. If flags includes SV_GMAGIC, does an mg_get()
     first. Coerces sv to a string if necessary. Normally invoked
     via the "SvPV_flags" macro. "sv_2pv()" and "sv_2pv_nomg" usu-
     ally end up here too.

      char*  sv_2pv_flags(SV* sv, STRLEN* lp, I32 flags)

    sv_2pv_nolen
     Like "sv_2pv()", but doesn't return the length too. You should
     usually use the macro wrapper "SvPV_nolen(sv)" instead.
    char*   sv_2pv_nolen(SV* sv)

    sv_2uv Return the unsigned integer value of an SV, doing any necessary
     string conversion, magic etc. Normally used via the "SvUV(sv)"
     and "SvUVx(sv)" macros.

      UV   sv_2uv(SV* sv)

    sv_backoff
     Remove any string offset. You should normally use the
     "SvOOK_off" macro wrapper instead.

      int   sv_backoff(SV* sv)

    sv_bless
     Blesses an SV into a specified package. The SV must be an RV.
     The package must be designated by its stash (see
     "gv_stashpv()").  The reference count of the SV is unaffected.

      SV*   sv_bless(SV* sv, HV* stash)

    sv_catpv
     Concatenates the string onto the end of the string which is in
     the SV. If the SV has the UTF8 status set, then the bytes
     appended should be valid UTF8. Handles 'get' magic, but not
     'set' magic. See "sv_catpv_mg".

      void  sv_catpv(SV* sv, const char* ptr)

    sv_catpvf
     Processes its arguments like "sprintf" and appends the format-
     ted output to an SV. If the appended data contains "wide"
     characters (including, but not limited to, SVs with a UTF-8 PV
     formatted with %s, and characters >255 formatted with %c), the
     original SV might get upgraded to UTF-8.  Handles 'get' magic,
     but not 'set' magic. "SvSETMAGIC()" must typically be called
     after calling this function to handle 'set' magic.

      void  sv_catpvf(SV* sv, const char* pat, ...)

    sv_catpvf_mg
     Like "sv_catpvf", but also handles 'set' magic.

      void  sv_catpvf_mg(SV *sv, const char* pat, ...)

    sv_catpvn
     Concatenates the string onto the end of the string which is in
     the SV. The "len" indicates number of bytes to copy. If the
     SV has the UTF8 status set, then the bytes appended should be
     valid UTF8. Handles 'get' magic, but not 'set' magic. See
     "sv_catpvn_mg".

      void  sv_catpvn(SV* sv, const char* ptr, STRLEN len)

    sv_catpvn_flags
     Concatenates the string onto the end of the string which is in
     the SV. The "len" indicates number of bytes to copy. If the
     SV has the UTF8 status set, then the bytes appended should be
     valid UTF8. If "flags" has "SV_GMAGIC" bit set, will "mg_get"
     on "dsv" if appropriate, else not. "sv_catpvn" and "sv_cat-
     pvn_nomg" are implemented in terms of this function.

      void  sv_catpvn_flags(SV* sv, const char* ptr, STRLEN len, I32 flags)

    sv_catpvn_mg
     Like "sv_catpvn", but also handles 'set' magic.

      void  sv_catpvn_mg(SV *sv, const char *ptr, STRLEN len)

    sv_catpv_mg
     Like "sv_catpv", but also handles 'set' magic.

      void  sv_catpv_mg(SV *sv, const char *ptr)

    sv_catsv
     Concatenates the string from SV "ssv" onto the end of the
     string in SV "dsv". Modifies "dsv" but not "ssv". Handles
     'get' magic, but not 'set' magic. See "sv_catsv_mg".

      void  sv_catsv(SV* dsv, SV* ssv)

    sv_catsv_flags
     Concatenates the string from SV "ssv" onto the end of the
     string in SV "dsv". Modifies "dsv" but not "ssv". If "flags"
     has "SV_GMAGIC" bit set, will "mg_get" on the SVs if appropri-
     ate, else not. "sv_catsv" and "sv_catsv_nomg" are implemented
     in terms of this function.

      void  sv_catsv_flags(SV* dsv, SV* ssv, I32 flags)

    sv_catsv_mg
     Like "sv_catsv", but also handles 'set' magic.

      void  sv_catsv_mg(SV *dstr, SV *sstr)

    sv_chop Efficient removal of characters from the beginning of the
     string buffer. SvPOK(sv) must be true and the "ptr" must be a
     pointer to somewhere inside the string buffer. The "ptr"
     becomes the first character of the adjusted string. Uses the
     "OOK hack".

      void  sv_chop(SV* sv, char* ptr)

    sv_clear
     Clear an SV: call any destructors, free up any memory used by
     the body, and free the body itself. The SV's head is not freed,
     although its type is set to all 1's so that it won't inadver-
     tently be assumed to be live during global destruction etc.
     This function should only be called when REFCNT is zero. Most
     of the time you'll want to call "sv_free()" (or its macro wrap-
     per "SvREFCNT_dec") instead.

      void  sv_clear(SV* sv)

    sv_cmp Compares the strings in two SVs.  Returns -1, 0, or 1 indicat-
     ing whether the string in "sv1" is less than, equal to, or
     greater than the string in "sv2". Is UTF-8 and 'use bytes'
     aware, handles get magic, and will coerce its args to strings
     if necessary. See also "sv_cmp_locale".

      I32   sv_cmp(SV* sv1, SV* sv2)

    sv_cmp_locale
     Compares the strings in two SVs in a locale-aware manner. Is
     UTF-8 and 'use bytes' aware, handles get magic, and will coerce
     its args to strings if necessary. See also "sv_cmp_locale".
     See also "sv_cmp".

      I32   sv_cmp_locale(SV* sv1, SV* sv2)

    sv_collxfrm
     Add Collate Transform magic to an SV if it doesn't already have
     it.

     Any scalar variable may carry PERL_MAGIC_collxfrm magic that
     contains the scalar data of the variable, but transformed to
     such a format that a normal memory comparison can be used to
     compare the data according to the locale settings.

      char*  sv_collxfrm(SV* sv, STRLEN* nxp)

    sv_copypv
     Copies a stringified representation of the source SV into the
     destination SV. Automatically performs any necessary mg_get
     and coercion of numeric values into strings. Guaranteed to
     preserve UTF-8 flag even from overloaded objects. Similar in
     nature to sv_2pv[_flags] but operates directly on an SV instead
     of just the string. Mostly uses sv_2pv_flags to do its work,
     except when that would lose the UTF-8'ness of the PV.

      void  sv_copypv(SV* dsv, SV* ssv)

    sv_dec Auto-decrement of the value in the SV, doing string to numeric
     conversion if necessary. Handles 'get' magic.

      void  sv_dec(SV* sv)

    sv_derived_from
     Returns a boolean indicating whether the SV is derived from the
     specified class.  This is the function that implements "UNIVER-
     SAL::isa". It works for class names as well as for objects.

      bool  sv_derived_from(SV* sv, const char* name)

    sv_eq  Returns a boolean indicating whether the strings in the two SVs
     are identical. Is UTF-8 and 'use bytes' aware, handles get
     magic, and will coerce its args to strings if necessary.

      I32   sv_eq(SV* sv1, SV* sv2)

    sv_force_normal
     Undo various types of fakery on an SV: if the PV is a shared
     string, make a private copy; if we're a ref, stop refing; if
     we're a glob, downgrade to an xpvmg. See also "sv_force_nor-
     mal_flags".

      void  sv_force_normal(SV *sv)

    sv_force_normal_flags
     Undo various types of fakery on an SV: if the PV is a shared
     string, make a private copy; if we're a ref, stop refing; if
     we're a glob, downgrade to an xpvmg. The "flags" parameter gets
     passed to "sv_unref_flags()" when unrefing. "sv_force_normal"
     calls this function with flags set to 0.

      void  sv_force_normal_flags(SV *sv, U32 flags)

    sv_free Decrement an SV's reference count, and if it drops to zero,
     call "sv_clear" to invoke destructors and free up any memory
     used by the body; finally, deallocate the SV's head itself.
     Normally called via a wrapper macro "SvREFCNT_dec".

      void  sv_free(SV* sv)

    sv_gets Get a line from the filehandle and store it into the SV,
     optionally appending to the currently-stored string.

      char*  sv_gets(SV* sv, PerlIO* fp, I32 append)

    sv_grow Expands the character buffer in the SV. If necessary, uses
     "sv_unref" and upgrades the SV to "SVt_PV". Returns a pointer
     to the character buffer.  Use the "SvGROW" wrapper instead.

      char*  sv_grow(SV* sv, STRLEN newlen)

    sv_inc Auto-increment of the value in the SV, doing string to numeric
     conversion if necessary. Handles 'get' magic.

      void  sv_inc(SV* sv)

    sv_insert
     Inserts a string at the specified offset/length within the SV.
     Similar to the Perl substr() function.

      void  sv_insert(SV* bigsv, STRLEN offset, STRLEN len, char* little, STRLEN littlelen)

    sv_isa Returns a boolean indicating whether the SV is blessed into the
     specified class.  This does not check for subtypes; use
     "sv_derived_from" to verify an inheritance relationship.

      int   sv_isa(SV* sv, const char* name)

    sv_isobject
     Returns a boolean indicating whether the SV is an RV pointing
     to a blessed object. If the SV is not an RV, or if the object
     is not blessed, then this will return false.

      int   sv_isobject(SV* sv)

    sv_iv  A private implementation of the "SvIVx" macro for compilers
     which can't cope with complex macro expressions. Always use the
     macro instead.

      IV   sv_iv(SV* sv)

    sv_len Returns the length of the string in the SV. Handles magic and
     type coercion. See also "SvCUR", which gives raw access to the
     xpv_cur slot.

      STRLEN sv_len(SV* sv)

    sv_len_utf8
     Returns the number of characters in the string in an SV, count-
     ing wide UTF8 bytes as a single character. Handles magic and
     type coercion.

      STRLEN sv_len_utf8(SV* sv)

    sv_magic
     Adds magic to an SV. First upgrades "sv" to type "SVt_PVMG" if
     necessary, then adds a new magic item of type "how" to the head
     of the magic list.

      void  sv_magic(SV* sv, SV* obj, int how, const char* name, I32 namlen)

    sv_magicext
     Adds magic to an SV, upgrading it if necessary. Applies the
     supplied vtable and returns pointer to the magic added.

     Note that sv_magicext will allow things that sv_magic will not.
     In particular you can add magic to SvREADONLY SVs and and more
     than one instance of the same 'how'

     I "namelen" is greater then zero then a savepvn() copy of
     "name" is stored, if "namelen" is zero then "name" is stored
     as-is and - as another special case - if "(name && namelen ==
     HEf_SVKEY)" then "name" is assumed to contain an "SV*" and has
     its REFCNT incremented

     (This is now used as a subroutine by sv_magic.)

      MAGIC * sv_magicext(SV* sv, SV* obj, int how, MGVTBL *vtbl, const char* name, I32 namlen     )

    sv_mortalcopy
     Creates a new SV which is a copy of the original SV (using
     "sv_setsv"). The new SV is marked as mortal. It will be
     destroyed "soon", either by an explicit call to FREETMPS, or by
     an implicit call at places such as statement boundaries.  See
     also "sv_newmortal" and "sv_2mortal".

      SV*   sv_mortalcopy(SV* oldsv)

    sv_newmortal
     Creates a new null SV which is mortal. The reference count of
     the SV is set to 1. It will be destroyed "soon", either by an
     explicit call to FREETMPS, or by an implicit call at places
     such as statement boundaries. See also "sv_mortalcopy" and
     "sv_2mortal".

      SV*   sv_newmortal()

    sv_newref
     Increment an SV's reference count. Use the "SvREFCNT_inc()"
     wrapper instead.

      SV*   sv_newref(SV* sv)

    sv_nolocking
     Dummy routine which "locks" an SV when there is no locking mod-
     ule present. Exists to avoid test for a NULL function pointer
     and because it could potentially warn under some level of
     strict-ness.

      void  sv_nolocking(SV *)

    sv_nosharing
     Dummy routine which "shares" an SV when there is no sharing
     module present. Exists to avoid test for a NULL function
     pointer and because it could potentially warn under some level
     of strict-ness.

      void  sv_nosharing(SV *)

    sv_nounlocking
     Dummy routine which "unlocks" an SV when there is no locking
     module present. Exists to avoid test for a NULL function
     pointer and because it could potentially warn under some level
     of strict-ness.

      void  sv_nounlocking(SV *)

    sv_nv  A private implementation of the "SvNVx" macro for compilers
     which can't cope with complex macro expressions. Always use the
     macro instead.

      NV   sv_nv(SV* sv)

    sv_pos_b2u
     Converts the value pointed to by offsetp from a count of bytes
     from the start of the string, to a count of the equivalent num-
     ber of UTF8 chars. Handles magic and type coercion.

      void  sv_pos_b2u(SV* sv, I32* offsetp)

    sv_pos_u2b
     Converts the value pointed to by offsetp from a count of UTF8
     chars from the start of the string, to a count of the equiva-
     lent number of bytes; if lenp is non-zero, it does the same to
     lenp, but this time starting from the offset, rather than from
     the start of the string. Handles magic and type coercion.

      void  sv_pos_u2b(SV* sv, I32* offsetp, I32* lenp)

    sv_pv  Use the "SvPV_nolen" macro instead

      char*  sv_pv(SV *sv)

    sv_pvbyte
     Use "SvPVbyte_nolen" instead.

      char*  sv_pvbyte(SV *sv)

    sv_pvbyten
     A private implementation of the "SvPVbyte" macro for compilers
     which can't cope with complex macro expressions. Always use the
     macro instead.

      char*  sv_pvbyten(SV *sv, STRLEN *len)

    sv_pvbyten_force
     A private implementation of the "SvPVbytex_force" macro for
     compilers which can't cope with complex macro expressions.
     Always use the macro instead.

      char*  sv_pvbyten_force(SV* sv, STRLEN* lp)

    sv_pvn A private implementation of the "SvPV" macro for compilers
     which can't cope with complex macro expressions. Always use the
     macro instead.

      char*  sv_pvn(SV *sv, STRLEN *len)

    sv_pvn_force
     Get a sensible string out of the SV somehow. A private imple-
     mentation of the "SvPV_force" macro for compilers which can't
     cope with complex macro expressions. Always use the macro
     instead.

      char*  sv_pvn_force(SV* sv, STRLEN* lp)

    sv_pvn_force_flags
     Get a sensible string out of the SV somehow. If "flags" has
     "SV_GMAGIC" bit set, will "mg_get" on "sv" if appropriate, else
     not. "sv_pvn_force" and "sv_pvn_force_nomg" are implemented in
     terms of this function. You normally want to use the various
     wrapper macros instead: see "SvPV_force" and "SvPV_force_nomg"

      char*  sv_pvn_force_flags(SV* sv, STRLEN* lp, I32 flags)

    sv_pvutf8
     Use the "SvPVutf8_nolen" macro instead

      char*  sv_pvutf8(SV *sv)

    sv_pvutf8n
     A private implementation of the "SvPVutf8" macro for compilers
     which can't cope with complex macro expressions. Always use the
     macro instead.

      char*  sv_pvutf8n(SV *sv, STRLEN *len)

    sv_pvutf8n_force
     A private implementation of the "SvPVutf8_force" macro for com-
     pilers which can't cope with complex macro expressions. Always
     use the macro instead.

      char*  sv_pvutf8n_force(SV* sv, STRLEN* lp)

    sv_reftype
     Returns a string describing what the SV is a reference to.

      char*  sv_reftype(SV* sv, int ob)

    sv_replace
     Make the first argument a copy of the second, then delete the
     original. The target SV physically takes over ownership of the
     body of the source SV and inherits its flags; however, the tar-
     get keeps any magic it owns, and any magic in the source is
     discarded. Note that this is a rather specialist SV copying
     operation; most of the time you'll want to use "sv_setsv" or
     one of its many macro front-ends.

      void  sv_replace(SV* sv, SV* nsv)

    sv_report_used
     Dump the contents of all SVs not yet freed. (Debugging aid).

      void  sv_report_used()

    sv_reset
     Underlying implementation for the "reset" Perl function.  Note
     that the perl-level function is vaguely deprecated.

      void  sv_reset(char* s, HV* stash)

    sv_rvweaken
     Weaken a reference: set the "SvWEAKREF" flag on this RV; give
     the referred-to SV "PERL_MAGIC_backref" magic if it hasn't
     already; and push a back-reference to this RV onto the array of
     backreferences associated with that magic.

      SV*   sv_rvweaken(SV *sv)

    sv_setiv
     Copies an integer into the given SV, upgrading first if neces-
     sary. Does not handle 'set' magic. See also "sv_setiv_mg".

      void  sv_setiv(SV* sv, IV num)

    sv_setiv_mg
     Like "sv_setiv", but also handles 'set' magic.

      void  sv_setiv_mg(SV *sv, IV i)

    sv_setnv
     Copies a double into the given SV, upgrading first if neces-
     sary. Does not handle 'set' magic. See also "sv_setnv_mg".

      void  sv_setnv(SV* sv, NV num)

    sv_setnv_mg
     Like "sv_setnv", but also handles 'set' magic.

      void  sv_setnv_mg(SV *sv, NV num)

    sv_setpv
     Copies a string into an SV. The string must be null-termi-
     nated. Does not handle 'set' magic. See "sv_setpv_mg".

      void  sv_setpv(SV* sv, const char* ptr)

    sv_setpvf
     Processes its arguments like "sprintf" and sets an SV to the
     formatted output. Does not handle 'set' magic. See "sv_set-
     pvf_mg".

      void  sv_setpvf(SV* sv, const char* pat, ...)

    sv_setpvf_mg
     Like "sv_setpvf", but also handles 'set' magic.

      void  sv_setpvf_mg(SV *sv, const char* pat, ...)

    sv_setpvn
     Copies a string into an SV. The "len" parameter indicates the
     number of bytes to be copied. Does not handle 'set' magic.
     See "sv_setpvn_mg".

      void  sv_setpvn(SV* sv, const char* ptr, STRLEN len)

    sv_setpvn_mg
     Like "sv_setpvn", but also handles 'set' magic.

      void  sv_setpvn_mg(SV *sv, const char *ptr, STRLEN len)

    sv_setpv_mg
     Like "sv_setpv", but also handles 'set' magic.

      void  sv_setpv_mg(SV *sv, const char *ptr)

    sv_setref_iv
     Copies an integer into a new SV, optionally blessing the SV.
     The "rv" argument will be upgraded to an RV. That RV will be
     modified to point to the new SV.  The "classname" argument
     indicates the package for the blessing. Set "classname" to
     "Nullch" to avoid the blessing. The new SV will be returned
     and will have a reference count of 1.

      SV*   sv_setref_iv(SV* rv, const char* classname, IV iv)

    sv_setref_nv
     Copies a double into a new SV, optionally blessing the SV. The
     "rv" argument will be upgraded to an RV.  That RV will be modi-
     fied to point to the new SV. The "classname" argument indi-
     cates the package for the blessing. Set "classname" to
     "Nullch" to avoid the blessing. The new SV will be returned
     and will have a reference count of 1.

      SV*   sv_setref_nv(SV* rv, const char* classname, NV nv)

    sv_setref_pv
     Copies a pointer into a new SV, optionally blessing the SV.
     The "rv" argument will be upgraded to an RV. That RV will be
     modified to point to the new SV.  If the "pv" argument is NULL
     then "PL_sv_undef" will be placed into the SV. The "classname"
     argument indicates the package for the blessing.  Set "class-
     name" to "Nullch" to avoid the blessing.  The new SV will be
     returned and will have a reference count of 1.

     Do not use with other Perl types such as HV, AV, SV, CV,
     because those objects will become corrupted by the pointer copy
     process.

     Note that "sv_setref_pvn" copies the string while this copies
     the pointer.

      SV*   sv_setref_pv(SV* rv, const char* classname, void* pv)

    sv_setref_pvn
     Copies a string into a new SV, optionally blessing the SV. The
     length of the string must be specified with "n".  The "rv"
     argument will be upgraded to an RV. That RV will be modified
     to point to the new SV. The "classname" argument indicates the
     package for the blessing. Set "classname" to "Nullch" to avoid
     the blessing. The new SV will be returned and will have a ref-
     erence count of 1.

     Note that "sv_setref_pv" copies the pointer while this copies
     the string.

      SV*   sv_setref_pvn(SV* rv, const char* classname, char* pv, STRLEN n)

    sv_setref_uv
     Copies an unsigned integer into a new SV, optionally blessing
     the SV. The "rv" argument will be upgraded to an RV. That RV
     will be modified to point to the new SV.  The "classname" argu-
     ment indicates the package for the blessing. Set "classname"
     to "Nullch" to avoid the blessing. The new SV will be returned
     and will have a reference count of 1.

      SV*   sv_setref_uv(SV* rv, const char* classname, UV uv)

    sv_setsv
     Copies the contents of the source SV "ssv" into the destination
     SV "dsv". The source SV may be destroyed if it is mortal, so
     don't use this function if the source SV needs to be reused.
     Does not handle 'set' magic. Loosely speaking, it performs a
     copy-by-value, obliterating any previous content of the desti-
     nation.

     You probably want to use one of the assortment of wrappers,
     such as "SvSetSV", "SvSetSV_nosteal", "SvSetMagicSV" and
     "SvSetMagicSV_nosteal".

      void  sv_setsv(SV* dsv, SV* ssv)

    sv_setsv_flags
     Copies the contents of the source SV "ssv" into the destination
     SV "dsv". The source SV may be destroyed if it is mortal, so
     don't use this function if the source SV needs to be reused.
     Does not handle 'set' magic. Loosely speaking, it performs a
     copy-by-value, obliterating any previous content of the desti-
     nation. If the "flags" parameter has the "SV_GMAGIC" bit set,
     will "mg_get" on "ssv" if appropriate, else not. "sv_setsv" and
     "sv_setsv_nomg" are implemented in terms of this function.

     You probably want to use one of the assortment of wrappers,
     such as "SvSetSV", "SvSetSV_nosteal", "SvSetMagicSV" and
     "SvSetMagicSV_nosteal".

     This is the primary function for copying scalars, and most
     other copy-ish functions and macros use this underneath.

      void  sv_setsv_flags(SV* dsv, SV* ssv, I32 flags)

    sv_setsv_mg
     Like "sv_setsv", but also handles 'set' magic.

      void  sv_setsv_mg(SV *dstr, SV *sstr)

    sv_setuv
     Copies an unsigned integer into the given SV, upgrading first
     if necessary. Does not handle 'set' magic. See also
     "sv_setuv_mg".

      void  sv_setuv(SV* sv, UV num)

    sv_setuv_mg
     Like "sv_setuv", but also handles 'set' magic.

      void  sv_setuv_mg(SV *sv, UV u)

    sv_taint
     Taint an SV. Use "SvTAINTED_on" instead.
    void sv_taint(SV* sv)

    sv_tainted
     Test an SV for taintedness. Use "SvTAINTED" instead.
    bool sv_tainted(SV* sv)

    sv_true Returns true if the SV has a true value by Perl's rules.  Use
     the "SvTRUE" macro instead, which may call "sv_true()" or may
     instead use an in-line version.

      I32   sv_true(SV *sv)

    sv_unmagic
     Removes all magic of type "type" from an SV.

      int   sv_unmagic(SV* sv, int type)

    sv_unref
     Unsets the RV status of the SV, and decrements the reference
     count of whatever was being referenced by the RV. This can
     almost be thought of as a reversal of "newSVrv".  This is
     "sv_unref_flags" with the "flag" being zero. See "SvROK_off".

      void  sv_unref(SV* sv)

    sv_unref_flags
     Unsets the RV status of the SV, and decrements the reference
     count of whatever was being referenced by the RV. This can
     almost be thought of as a reversal of "newSVrv".  The "cflags"
     argument can contain "SV_IMMEDIATE_UNREF" to force the refer-
     ence count to be decremented (otherwise the decrementing is
     conditional on the reference count being different from one or
     the reference being a readonly SV). See "SvROK_off".

      void  sv_unref_flags(SV* sv, U32 flags)

    sv_untaint
     Untaint an SV. Use "SvTAINTED_off" instead.
    void sv_untaint(SV* sv)

    sv_upgrade
     Upgrade an SV to a more complex form. Generally adds a new
     body type to the SV, then copies across as much information as
     possible from the old body. You generally want to use the
     "SvUPGRADE" macro wrapper. See also "svtype".

      bool  sv_upgrade(SV* sv, U32 mt)

    sv_usepvn
     Tells an SV to use "ptr" to find its string value. Normally
     the string is stored inside the SV but sv_usepvn allows the SV
     to use an outside string. The "ptr" should point to memory
     that was allocated by "malloc". The string length, "len", must
     be supplied. This function will realloc the memory pointed to
     by "ptr", so that pointer should not be freed or used by the
     programmer after giving it to sv_usepvn.  Does not handle 'set'
     magic. See "sv_usepvn_mg".

      void  sv_usepvn(SV* sv, char* ptr, STRLEN len)

    sv_usepvn_mg
     Like "sv_usepvn", but also handles 'set' magic.

      void  sv_usepvn_mg(SV *sv, char *ptr, STRLEN len)

    sv_utf8_decode
     Convert the octets in the PV from UTF-8 to chars. Scan for
     validity and then turn off SvUTF8 if needed so that we see
     characters. Used as a building block for decode_utf8 in
     Encode.xs

     NOTE: this function is experimental and may change or be
     removed without notice.

      bool  sv_utf8_decode(SV *sv)

    sv_utf8_downgrade
     Attempt to convert the PV of an SV from UTF8-encoded to byte
     encoding. This may not be possible if the PV contains non-byte
     encoding characters; if this is the case, either returns false
     or, if "fail_ok" is not true, croaks.

     This is not as a general purpose Unicode to byte encoding
     interface: use the Encode extension for that.

     NOTE: this function is experimental and may change or be
     removed without notice.

      bool  sv_utf8_downgrade(SV *sv, bool fail_ok)

    sv_utf8_encode
     Convert the PV of an SV to UTF8-encoded, but then turn off the
     "SvUTF8" flag so that it looks like octets again. Used as a
     building block for encode_utf8 in Encode.xs

      void  sv_utf8_encode(SV *sv)

    sv_utf8_upgrade
     Convert the PV of an SV to its UTF8-encoded form. Forces the
     SV to string form if it is not already. Always sets the SvUTF8
     flag to avoid future validity checks even if all the bytes have
     hibit clear.

     This is not as a general purpose byte encoding to Unicode
     interface: use the Encode extension for that.

      STRLEN sv_utf8_upgrade(SV *sv)

    sv_utf8_upgrade_flags
     Convert the PV of an SV to its UTF8-encoded form. Forces the
     SV to string form if it is not already. Always sets the SvUTF8
     flag to avoid future validity checks even if all the bytes have
     hibit clear. If "flags" has "SV_GMAGIC" bit set, will "mg_get"
     on "sv" if appropriate, else not. "sv_utf8_upgrade" and
     "sv_utf8_upgrade_nomg" are implemented in terms of this func-
     tion.

     This is not as a general purpose byte encoding to Unicode
     interface: use the Encode extension for that.

      STRLEN sv_utf8_upgrade_flags(SV *sv, I32 flags)

    sv_uv  A private implementation of the "SvUVx" macro for compilers
     which can't cope with complex macro expressions. Always use the
     macro instead.

      UV   sv_uv(SV* sv)

    sv_vcatpvfn
     Processes its arguments like "vsprintf" and appends the format-
     ted output to an SV. Uses an array of SVs if the C style vari-
     able argument list is missing (NULL). When running with taint
     checks enabled, indicates via "maybe_tainted" if results are
     untrustworthy (often due to the use of locales).

     Usually used via one of its frontends "sv_catpvf" and "sv_cat-
     pvf_mg".

      void  sv_vcatpvfn(SV* sv, const char* pat, STRLEN patlen, va_list* args, SV** svargs, I32 svmax, bool *maybe_tainted)

    sv_vsetpvfn
     Works like "vcatpvfn" but copies the text into the SV instead
     of appending it.

     Usually used via one of its frontends "sv_setpvf" and "sv_set-
     pvf_mg".

      void  sv_vsetpvfn(SV* sv, const char* pat, STRLEN patlen, va_list* args, SV** svargs, I32 svmax, bool *maybe_tainted)

Unicode Support
    bytes_from_utf8
     Converts a string "s" of length "len" from UTF8 into byte
     encoding. Unlike <utf8_to_bytes> but like "bytes_to_utf8",
     returns a pointer to the newly-created string, and updates
     "len" to contain the new length.  Returns the original string
     if no conversion occurs, "len" is unchanged. Do nothing if
     "is_utf8" points to 0. Sets "is_utf8" to 0 if "s" is converted
     or contains all 7bit characters.

     NOTE: this function is experimental and may change or be
     removed without notice.

      U8*   bytes_from_utf8(U8 *s, STRLEN *len, bool *is_utf8)

    bytes_to_utf8
     Converts a string "s" of length "len" from ASCII into UTF8
     encoding. Returns a pointer to the newly-created string, and
     sets "len" to reflect the new length.

     NOTE: this function is experimental and may change or be
     removed without notice.

      U8*   bytes_to_utf8(U8 *s, STRLEN *len)

    ibcmp_utf8
     Return true if the strings s1 and s2 differ case-insensitively,
     false if not (if they are equal case-insensitively). If u1 is
     true, the string s1 is assumed to be in UTF-8-encoded Unicode.
     If u2 is true, the string s2 is assumed to be in UTF-8-encoded
     Unicode.  If u1 or u2 are false, the respective string is
     assumed to be in native 8-bit encoding.

     If the pe1 and pe2 are non-NULL, the scanning pointers will be
     copied in there (they will point at the beginning of the next
     character). If the pointers behind pe1 or pe2 are non-NULL,
     they are the end pointers beyond which scanning will not con-
     tinue under any circustances. If the byte lengths l1 and l2
     are non-zero, s1+l1 and s2+l2 will be used as goal end pointers
     that will also stop the scan, and which qualify towards defin-
     ing a successful match: all the scans that define an explicit
     length must reach their goal pointers for a match to succeed).

     For case-insensitiveness, the "casefolding" of Unicode is used
     instead of upper/lowercasing both the characters, see
     http://www.unicode.org/unicode/reports/tr21/ (Case Mappings).

      I32   ibcmp_utf8(const char* a, char **pe1, UV l1, bool u1, const char* b, char **pe2, UV l2, bool u2)

    is_utf8_char
     Tests if some arbitrary number of bytes begins in a valid UTF-8
     character. Note that an INVARIANT (i.e. ASCII) character is a
     valid UTF-8 character. The actual number of bytes in the UTF-8
     character will be returned if it is valid, otherwise 0.

      STRLEN is_utf8_char(U8 *p)

    is_utf8_string
     Returns true if first "len" bytes of the given string form a
     valid UTF8 string, false otherwise. Note that 'a valid UTF8
     string' does not mean 'a string that contains UTF8' because a
     valid ASCII string is a valid UTF8 string.

      bool  is_utf8_string(U8 *s, STRLEN len)

    pv_uni_display
     Build to the scalar dsv a displayable version of the string
     spv, length len, the displayable version being at most pvlim
     bytes long (if longer, the rest is truncated and "..." will be
     appended).

     The flags argument can have UNI_DISPLAY_ISPRINT set to display
     isPRINT()able characters as themselves, UNI_DISPLAY_BACKSLASH
     to display the \\[nrfta\\] as the backslashed versions (like
     '\n') (UNI_DISPLAY_BACKSLASH is preferred over UNI_DIS-
     PLAY_ISPRINT for \\). UNI_DISPLAY_QQ (and its alias UNI_DIS-
     PLAY_REGEX) have both UNI_DISPLAY_BACKSLASH and UNI_DIS-
     PLAY_ISPRINT turned on.

     The pointer to the PV of the dsv is returned.

      char*  pv_uni_display(SV *dsv, U8 *spv, STRLEN len, STRLEN pvlim, UV flags)

    sv_recode_to_utf8
     The encoding is assumed to be an Encode object, on entry the PV
     of the sv is assumed to be octets in that encoding, and the sv
     will be converted into Unicode (and UTF-8).

     If the sv already is UTF-8 (or if it is not POK), or if the
     encoding is not a reference, nothing is done to the sv. If the
     encoding is not an "Encode::XS" Encoding object, bad things
     will happen. (See lib/encoding.pm and Encode).

     The PV of the sv is returned.

      char*  sv_recode_to_utf8(SV* sv, SV *encoding)

    sv_uni_display
     Build to the scalar dsv a displayable version of the scalar sv,
     the displayable version being at most pvlim bytes long (if
     longer, the rest is truncated and "..." will be appended).

     The flags argument is as in pv_uni_display().

     The pointer to the PV of the dsv is returned.

      char*  sv_uni_display(SV *dsv, SV *ssv, STRLEN pvlim, UV flags)

    to_utf8_case
     The "p" contains the pointer to the UTF-8 string encoding the
     character that is being converted.

     The "ustrp" is a pointer to the character buffer to put the
     conversion result to. The "lenp" is a pointer to the length of
     the result.

     The "swashp" is a pointer to the swash to use.

     Both the special and normal mappings are stored lib/uni-
     core/To/Foo.pl, and loaded by SWASHGET, using
     lib/utf8_heavy.pl. The special (usually, but not always, a
     multicharacter mapping), is tried first.

     The "special" is a string like "utf8::ToSpecLower", which means
     the hash %utf8::ToSpecLower. The access to the hash is through
     Perl_to_utf8_case().

     The "normal" is a string like "ToLower" which means the swash
     %utf8::ToLower.

      UV   to_utf8_case(U8 *p, U8* ustrp, STRLEN *lenp, SV **swash, char *normal, char *special)

    to_utf8_fold
     Convert the UTF-8 encoded character at p to its foldcase ver-
     sion and store that in UTF-8 in ustrp and its length in bytes
     in lenp.  Note that the ustrp needs to be at least
     UTF8_MAXLEN_FOLD+1 bytes since the foldcase version may be
     longer than the original character (up to three characters).

     The first character of the foldcased version is returned (but
     note, as explained above, that there may be more.)

      UV   to_utf8_fold(U8 *p, U8* ustrp, STRLEN *lenp)

    to_utf8_lower
     Convert the UTF-8 encoded character at p to its lowercase ver-
     sion and store that in UTF-8 in ustrp and its length in bytes
     in lenp.  Note that the ustrp needs to be at least
     UTF8_MAXLEN_UCLC+1 bytes since the lowercase version may be
     longer than the original character (up to two characters).

     The first character of the lowercased version is returned (but
     note, as explained above, that there may be more.)

      UV   to_utf8_lower(U8 *p, U8* ustrp, STRLEN *lenp)

    to_utf8_title
     Convert the UTF-8 encoded character at p to its titlecase ver-
     sion and store that in UTF-8 in ustrp and its length in bytes
     in lenp.  Note that the ustrp needs to be at least
     UTF8_MAXLEN_UCLC+1 bytes since the titlecase version may be
     longer than the original character (up to two characters).

     The first character of the titlecased version is returned (but
     note, as explained above, that there may be more.)

      UV   to_utf8_title(U8 *p, U8* ustrp, STRLEN *lenp)

    to_utf8_upper
     Convert the UTF-8 encoded character at p to its uppercase ver-
     sion and store that in UTF-8 in ustrp and its length in bytes
     in lenp.  Note that the ustrp needs to be at least
     UTF8_MAXLEN_UCLC+1 bytes since the uppercase version may be
     longer than the original character (up to two characters).

     The first character of the uppercased version is returned (but
     note, as explained above, that there may be more.)

      UV   to_utf8_upper(U8 *p, U8* ustrp, STRLEN *lenp)

    utf8n_to_uvchr
     Returns the native character value of the first character in
     the string "s" which is assumed to be in UTF8 encoding;
     "retlen" will be set to the length, in bytes, of that charac-
     ter.

     Allows length and flags to be passed to low level routine.

      UV   utf8n_to_uvchr(U8 *s, STRLEN curlen, STRLEN* retlen, U32 flags)

    utf8n_to_uvuni
     Bottom level UTF-8 decode routine. Returns the unicode code
     point value of the first character in the string "s" which is
     assumed to be in UTF8 encoding and no longer than "curlen";
     "retlen" will be set to the length, in bytes, of that charac-
     ter.

     If "s" does not point to a well-formed UTF8 character, the
     behaviour is dependent on the value of "flags": if it contains
     UTF8_CHECK_ONLY, it is assumed that the caller will raise a
     warning, and this function will silently just set "retlen" to
     "-1" and return zero. If the "flags" does not contain
     UTF8_CHECK_ONLY, warnings about malformations will be given,
     "retlen" will be set to the expected length of the UTF-8 char-
     acter in bytes, and zero will be returned.

     The "flags" can also contain various flags to allow deviations
     from the strict UTF-8 encoding (see utf8.h).

     Most code should use utf8_to_uvchr() rather than call this
     directly.

      UV   utf8n_to_uvuni(U8 *s, STRLEN curlen, STRLEN* retlen, U32 flags)

    utf8_distance
     Returns the number of UTF8 characters between the UTF-8 point-
     ers "a" and "b".

     WARNING: use only if you *know* that the pointers point inside
     the same UTF-8 buffer.

      IV   utf8_distance(U8 *a, U8 *b)

    utf8_hop
     Return the UTF-8 pointer "s" displaced by "off" characters,
     either forward or backward.

     WARNING: do not use the following unless you *know* "off" is
     within the UTF-8 data pointed to by "s" *and* that on entry "s"
     is aligned on the first byte of character or just after the
     last byte of a character.

      U8*   utf8_hop(U8 *s, I32 off)

    utf8_length
     Return the length of the UTF-8 char encoded string "s" in char-
     acters. Stops at "e" (inclusive). If "e < s" or if the scan
     would end up past "e", croaks.

      STRLEN utf8_length(U8* s, U8 *e)

    utf8_to_bytes
     Converts a string "s" of length "len" from UTF8 into byte
     encoding. Unlike "bytes_to_utf8", this over-writes the origi-
     nal string, and updates len to contain the new length. Returns
     zero on failure, setting "len" to -1.

     NOTE: this function is experimental and may change or be
     removed without notice.

      U8*   utf8_to_bytes(U8 *s, STRLEN *len)

    utf8_to_uvchr
     Returns the native character value of the first character in
     the string "s" which is assumed to be in UTF8 encoding;
     "retlen" will be set to the length, in bytes, of that charac-
     ter.

     If "s" does not point to a well-formed UTF8 character, zero is
     returned and retlen is set, if possible, to -1.

      UV   utf8_to_uvchr(U8 *s, STRLEN* retlen)

    utf8_to_uvuni
     Returns the Unicode code point of the first character in the
     string "s" which is assumed to be in UTF8 encoding; "retlen"
     will be set to the length, in bytes, of that character.

     This function should only be used when returned UV is consid-
     ered an index into the Unicode semantic tables (e.g. swashes).

     If "s" does not point to a well-formed UTF8 character, zero is
     returned and retlen is set, if possible, to -1.

      UV   utf8_to_uvuni(U8 *s, STRLEN* retlen)

    uvchr_to_utf8
     Adds the UTF8 representation of the Native codepoint "uv" to
     the end of the string "d"; "d" should be have at least
     "UTF8_MAXLEN+1" free bytes available. The return value is the
     pointer to the byte after the end of the new character. In
     other words,

    d = uvchr_to_utf8(d, uv);

     is the recommended wide native character-aware way of saying

    *(d++) = uv;

      U8*   uvchr_to_utf8(U8 *d, UV uv)

    uvuni_to_utf8_flags
     Adds the UTF8 representation of the Unicode codepoint "uv" to
     the end of the string "d"; "d" should be have at least
     "UTF8_MAXLEN+1" free bytes available. The return value is the
     pointer to the byte after the end of the new character. In
     other words,

    d = uvuni_to_utf8_flags(d, uv, flags);

     or, in most cases,

    d = uvuni_to_utf8(d, uv);

     (which is equivalent to)

    d = uvuni_to_utf8_flags(d, uv, 0);

     is the recommended Unicode-aware way of saying

    *(d++) = uv;

      U8*   uvuni_to_utf8_flags(U8 *d, UV uv, UV flags)

Variables created by "xsubpp" and "xsubpp" internal functions
    ax   Variable which is setup by "xsubpp" to indicate the stack base
     offset, used by the "ST", "XSprePUSH" and "XSRETURN" macros.
     The "dMARK" macro must be called prior to setup the "MARK"
     variable.

      I32   ax

    CLASS  Variable which is setup by "xsubpp" to indicate the class name
     for a C++ XS constructor. This is always a "char*". See
     "THIS".

      char*  CLASS

    dAX   Sets up the "ax" variable. This is usually handled automati-
     cally by "xsubpp" by calling "dXSARGS".

       dAX;

    dITEMS Sets up the "items" variable. This is usually handled automat-
     ically by "xsubpp" by calling "dXSARGS".

       dITEMS;

    dXSARGS Sets up stack and mark pointers for an XSUB, calling dSP and
     dMARK. Sets up the "ax" and "items" variables by calling "dAX"
     and "dITEMS". This is usually handled automatically by
     "xsubpp".

       dXSARGS;

    dXSI32 Sets up the "ix" variable for an XSUB which has aliases.  This
     is usually handled automatically by "xsubpp".

       dXSI32;

    items  Variable which is setup by "xsubpp" to indicate the number of
     items on the stack. See "Variable-length Parameter Lists" in
     perlxs.

      I32   items

    ix   Variable which is setup by "xsubpp" to indicate which of an
     XSUB's aliases was used to invoke it. See "The ALIAS: Keyword"
     in perlxs.

      I32   ix

    newXSproto
     Used by "xsubpp" to hook up XSUBs as Perl subs. Adds Perl pro-
     totypes to the subs.

    RETVAL Variable which is setup by "xsubpp" to hold the return value
     for an XSUB. This is always the proper type for the XSUB. See
     "The RETVAL Variable" in perlxs.

      (whatever)   RETVAL

    ST   Used to access elements on the XSUB's stack.

      SV*   ST(int ix)

    THIS  Variable which is setup by "xsubpp" to designate the object in
     a C++ XSUB. This is always the proper type for the C++ object.
     See "CLASS" and "Using XS With C++" in perlxs.

      (whatever)   THIS

    XS   Macro to declare an XSUB and its C parameter list. This is
     handled by "xsubpp".

    XSRETURN_EMPTY
     Return an empty list from an XSUB immediately.

       XSRETURN_EMPTY;

    XS_VERSION
     The version identifier for an XS module.  This is usually han-
     dled automatically by "ExtUtils::MakeMaker". See "XS_VER-
     SION_BOOTCHECK".

    XS_VERSION_BOOTCHECK
     Macro to verify that a PM module's $VERSION variable matches
     the XS module's "XS_VERSION" variable. This is usually handled
     automatically by "xsubpp". See "The VERSIONCHECK: Keyword" in
     perlxs.

       XS_VERSION_BOOTCHECK;

Warning and Dieing
    croak  This is the XSUB-writer's interface to Perl's "die" function.
     Normally use this function the same way you use the C "printf"
     function. See "warn".

     If you want to throw an exception object, assign the object to
     $@ and then pass "Nullch" to croak():

   errsv = get_sv("@", TRUE);
   sv_setsv(errsv, exception_object);
   croak(Nullch);

      void  croak(const char* pat, ...)

    warn  This is the XSUB-writer's interface to Perl's "warn" function.
     Use this function the same way you use the C "printf" function.
     See "croak".

      void  warn(const char* pat, ...)

AUTHORS
    Until May 1997, this document was maintained by Jeff Okamoto
    <okamoto@corp.hp.com>. It is now maintained as part of Perl itself.

    With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
    Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil Bow-
    ers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer, Stephen
    McCamant, and Gurusamy Sarathy.

    API Listing originally by Dean Roehrich <roehrich@cray.com>.

    Updated to be autogenerated from comments in the source by Benjamin
    Stuhl.

SEE ALSO
   perlguts(1),perlxs(1),perlxstut(1),perlintern(1)