Perl executable. It is far from complete and probably contains many errors.
Please refer any questions or comments to the author below.
+=head1 Variables
+
=head2 Datatypes
Perl has three typedefs that handle Perl's three main data types:
Perl also uses two special typedefs, I32 and I16, which will always be at
least 32-bits and 16-bits long, respectively.
-=head2 Working with SV's
+=head2 Working with SVs
An SV can be created and loaded with one command. There are four types of
values that can be loaded: an integer value (IV), a double (NV), a string,
string's length by using C<strlen>, which depends on the string terminating
with a NUL character.
-All SV's that will contain strings should, but need not, be terminated
+All SVs that will contain strings should, but need not, be terminated
with a NUL character. If it is not NUL-terminated there is a risk of
core dumps and corruptions from code which passes the string to C
functions or system calls which expect a NUL-terminated string.
variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do not
care what the length of the data is, use the global variable C<na>. Remember,
however, that Perl allows arbitrary strings of data that may both contain
-NUL's and might not be terminated by a NUL.
+NULs and might not be terminated by a NUL.
If you want to know if the scalar value is TRUE, you can use:
line and all will be well.
To free an SV that you've created, call C<SvREFCNT_dec(SV*)>. Normally this
-call is not necessary (see the section on L<Mortality>).
+call is not necessary (see L<Reference Counts and Mortality>).
=head2 What's Really Stored in an SV?
In general, though, it's best to use the C<Sv*V> macros.
-=head2 Working with AV's
+=head2 Working with AVs
There are two ways to create and load an AV. The first method creates an
empty AV:
AV* newAV();
-The second method both creates the AV and initially populates it with SV's:
+The second method both creates the AV and initially populates it with SVs:
AV* av_make(I32 num, SV **ptr);
The second argument points to an array containing C<num> C<SV*>'s. Once the
-AV has been created, the SV's can be destroyed, if so desired.
+AV has been created, the SVs can be destroyed, if so desired.
-Once the AV has been created, the following operations are possible on AV's:
+Once the AV has been created, the following operations are possible on AVs:
void av_push(AV*, SV*);
SV* av_pop(AV*);
This returns NULL if the variable does not exist.
-=head2 Working with HV's
+=head2 Working with HVs
To create an HV, you use the following routine:
HV* newHV();
-Once the HV has been created, the following operations are possible on HV's:
+Once the HV has been created, the following operations are possible on HVs:
SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);
The C<klen> parameter is the length of the key being passed in (Note that
you cannot pass 0 in as a value of C<klen> to tell Perl to measure the
length of the key). The C<val> argument contains the SV pointer to the
-scalar being stored, and C<hash> is the pre-computed hash value (zero if
+scalar being stored, and C<hash> is the precomputed hash value (zero if
you want C<hv_store> to calculate it for you). The C<lval> parameter
indicates whether this fetch is actually a part of a store operation, in
which case a new undefined value will be added to the HV with the supplied
while (i--)
hash = hash * 33 + *s++;
+=head2 Hash API Extensions
+
+Beginning with version 5.004, the following functions are also supported:
+
+ HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash);
+ HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash);
+
+ bool hv_exists_ent (HV* tb, SV* key, U32 hash);
+ SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash);
+
+ SV* hv_iterkeysv (HE* entry);
+
+Note that these functions take C<SV*> keys, which simplifies writing
+of extension code that deals with hash structures. These functions
+also allow passing of C<SV*> keys to C<tie> functions without forcing
+you to stringify the keys (unlike the previous set of functions).
+
+They also return and accept whole hash entries (C<HE*>), making their
+use more efficient (since the hash number for a particular string
+doesn't have to be recomputed every time). See L<API LISTING> later in
+this document for detailed descriptions.
+
+The following macros must always be used to access the contents of hash
+entries. Note that the arguments to these macros must be simple
+variables, since they may get evaluated more than once. See
+L<API LISTING> later in this document for detailed descriptions of these
+macros.
+
+ HePV(HE* he, STRLEN len)
+ HeVAL(HE* he)
+ HeHASH(HE* he)
+ HeSVKEY(HE* he)
+ HeSVKEY_force(HE* he)
+ HeSVKEY_set(HE* he, SV* sv)
+
+These two lower level macros are defined, but must only be used when
+dealing with keys that are not C<SV*>s:
+
+ HeKEY(HE* he)
+ HeKLEN(HE* he)
+
+
=head2 References
References are a special type of scalar that point to other data types
SV* sv_bless(SV* sv, HV* stash);
The C<sv> argument must be a reference. The C<stash> argument specifies
-which class the reference will belong to. See the section on L<Stashes>
-for information on converting class names into stashes.
+which class the reference will belong to. See
+L<Stashes and Globs> for information on converting class names into stashes.
/* Still under construction */
C<TRUE> argument to enable certain extra features. Those bits are:
GV_ADDMULTI Marks the variable as multiply defined, thus preventing the
- "Indentifier <varname> used only once: possible typo" warning.
+ "Name <varname> used only once: possible typo" warning.
GV_ADDWARN Issues the warning "Had to create <varname> unexpectedly" if
the variable did not exist before the function was called.
=head2 Reference Counts and Mortality
-Perl uses an reference count-driven garbage collection mechanism. SV's,
-AV's, or HV's (xV for short in the following) start their life with a
+Perl uses an reference count-driven garbage collection mechanism. SVs,
+AVs, or HVs (xV for short in the following) start their life with a
reference count of 1. If the reference count of an xV ever drops to 0,
then it will be destroyed and its memory made available for reuse.
stopping any memory leak.
There are some convenience functions available that can help with the
-destruction of xV's. These functions introduce the concept of "mortality".
+destruction of xVs. These functions introduce the concept of "mortality".
An xV that is mortal has had its reference count marked to be decremented,
but not actually decremented, until "a short time later". Generally the
term "short time later" means a single Perl statement, such as a call to
-an XSUB function. The actual determinant for when mortal xV's have their
+an XSUB function. The actual determinant for when mortal xVs have their
reference count decremented depends on two macros, SAVETMPS and FREETMPS.
See L<perlcall> and L<perlxs> for more details on these macros.
SV to a mortal SV (and thus defers a call to C<SvREFCNT_dec>), and the
third creates a mortal copy of an existing SV.
-The mortal routines are not just for SV's -- AV's and HV's can be
+The mortal routines are not just for SVs -- AVs and HVs can be
made mortal by passing their address (type-casted to C<SV*>) to the
C<sv_2mortal> or C<sv_mortalcopy> routines.
=head2 Stashes and Globs
-A stash is a hash table (associative array) that contains all of the
-different objects that are contained within a package. Each key of the
-stash is a symbol name (shared by all the different types of objects
-that have the same name), and each value in the hash table is called a
-GV (for Glob Value). This GV in turn contains references to the various
-objects of that name, including (but not limited to) the following:
+A "stash" is a hash that contains all of the different objects that
+are contained within a package. Each key of the stash is a symbol
+name (shared by all the different types of objects that have the same
+name), and each value in the hash table is a GV (Glob Value). This GV
+in turn contains references to the various objects of that name,
+including (but not limited to) the following:
Scalar Value
Array Value
For more information on references and blessings, consult L<perlref>.
-=head2 Magic
+=head2 Double-Typed SVs
+
+Scalar variables normally contain only one type of value, an integer,
+double, pointer, or reference. Perl will automatically convert the
+actual scalar data from the stored type into the requested type.
+
+Some scalar variables contain more than one type of scalar data. For
+example, the variable C<$!> contains either the numeric value of C<errno>
+or its string equivalent from either C<strerror> or C<sys_errlist[]>.
+
+To force multiple data values into an SV, you must do two things: use the
+C<sv_set*v> routines to add the additional scalar type, then set a flag
+so that Perl will believe it contains more than one type of data. The
+four macros to set the flags are:
+
+ SvIOK_on
+ SvNOK_on
+ SvPOK_on
+ SvROK_on
+
+The particular macro you must use depends on which C<sv_set*v> routine
+you called first. This is because every C<sv_set*v> routine turns on
+only the bit for the particular type of data being set, and turns off
+all the rest.
+
+For example, to create a new Perl variable called "dberror" that contains
+both the numeric and descriptive string error values, you could use the
+following code:
+
+ extern int dberror;
+ extern char *dberror_list;
+
+ SV* sv = perl_get_sv("dberror", TRUE);
+ sv_setiv(sv, (IV) dberror);
+ sv_setpv(sv, dberror_list[dberror]);
+ SvIOK_on(sv);
+
+If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
+macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
+
+=head2 Magic Variables
[This section still under construction. Ignore everything here. Post no
bills. Everything not permitted is forbidden.]
overridden, and multiple instances of the same type of magic can be
associated with an SV.
-The C<name> and C<namlem> arguments are used to associate a string with
-the magic, typically the name of a variable. C<namlem> is stored in the
-C<mg_len> field and if C<name> is non-null and C<namlem> >= 0 a malloc'd
+The C<name> and C<namlen> arguments are used to associate a string with
+the magic, typically the name of a variable. C<namlen> is stored in the
+C<mg_len> field and if C<name> is non-null and C<namlen> >= 0 a malloc'd
copy of the name is stored in C<mg_ptr> field.
The sv_magic function uses C<how> to determine which, if any, predefined
. vtbl_pos $. scalar variable
~ None Used by certain extensions
-When an upper-case and lower-case letter both exist in the table, then the
-upper-case letter is used to represent some kind of composite type (a list
-or a hash), and the lower-case letter is used to represent an element of
+When an uppercase and lowercase letter both exist in the table, then the
+uppercase letter is used to represent some kind of composite type (a list
+or a hash), and the lowercase letter is used to represent an element of
that composite type.
The '~' magic type is defined specifically for use by extensions and
This routine returns a pointer to the C<MAGIC> structure stored in the SV.
If the SV does not have that magical feature, C<NULL> is returned. Also,
-if the SV is not of type SVt_PVMG, Perl may core-dump.
+if the SV is not of type SVt_PVMG, Perl may core dump.
int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);
This routine checks to see what types of magic C<sv> has. If the mg_type
-field is an upper-case letter, then the mg_obj is copied to C<nsv>, but
-the mg_type field is changed to be the lower-case letter.
-
-=head2 Double-Typed SV's
-
-Scalar variables normally contain only one type of value, an integer,
-double, pointer, or reference. Perl will automatically convert the
-actual scalar data from the stored type into the requested type.
-
-Some scalar variables contain more than one type of scalar data. For
-example, the variable C<$!> contains either the numeric value of C<errno>
-or its string equivalent from either C<strerror> or C<sys_errlist[]>.
+field is an uppercase letter, then the mg_obj is copied to C<nsv>, but
+the mg_type field is changed to be the lowercase letter.
-To force multiple data values into an SV, you must do two things: use the
-C<sv_set*v> routines to add the additional scalar type, then set a flag
-so that Perl will believe it contains more than one type of data. The
-four macros to set the flags are:
+=head1 Subroutines
- SvIOK_on
- SvNOK_on
- SvPOK_on
- SvROK_on
-
-The particular macro you must use depends on which C<sv_set*v> routine
-you called first. This is because every C<sv_set*v> routine turns on
-only the bit for the particular type of data being set, and turns off
-all the rest.
-
-For example, to create a new Perl variable called "dberror" that contains
-both the numeric and descriptive string error values, you could use the
-following code:
-
- extern int dberror;
- extern char *dberror_list;
-
- SV* sv = perl_get_sv("dberror", TRUE);
- sv_setiv(sv, (IV) dberror);
- sv_setpv(sv, dberror_list[dberror]);
- SvIOK_on(sv);
-
-If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
-macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
-
-=head2 XSUB's and the Argument Stack
+=head2 XSUBs and the Argument Stack
The XSUB mechanism is a simple way for Perl programs to access C subroutines.
An XSUB routine will have a stack that contains the arguments from the Perl
stack should be extended by.
Now that there is room on the stack, values can be pushed on it using the
-macros to push IV's, doubles, strings, and SV pointers respectively:
+macros to push IVs, doubles, strings, and SV pointers respectively:
PUSHi(IV)
PUSHn(double)
removing Perl's dependency on the "normal" standard I/O suite and allowing
other stdio implementations to be used. This involves creating a new
abstraction layer that then calls whichever implementation of stdio Perl
-was compiled with. All XSUB's should now use the functions in the PerlIO
+was compiled with. All XSUBs should now use the functions in the PerlIO
abstraction layer and not make any assumptions about what kind of stdio
is being used.
For a complete description of the PerlIO abstraction, consult L<perlapio>.
-=head2 Scratchpads
-
=head2 Putting a C value on Perl stack
A lot of opcodes (this is an elementary operation in the internal perl
reuse specially assigned SVs (I<target>s) which are (as a corollary)
not constantly freed/created.
-Each of the targets is created only once (but see
+Each of the targets is created only once (but see
L<Scratchpads and recursion> below), and when an opcode needs to put
an integer, a double, or a string on stack, it just sets the
corresponding parts of its I<target> and puts the I<target> on stack.
=head2 Scratchpads
-The question remains on when the SV's which are I<target>s for opcodes
+The question remains on when the SVs which are I<target>s for opcodes
are created. The answer is that they are created when the current unit --
a subroutine or a file (for opcodes for statements outside of
subroutines) -- is compiled. During this time a special anonymous Perl
array is created, which is called a scratchpad for the current
unit.
-A scratchpad keeps SV's which are lexicals for the current unit and are
+A scratchpad keeps SVs which are lexicals for the current unit and are
targets for opcodes. One can deduce that an SV lives on a scratchpad
by looking on its flags: lexicals have C<SVs_PADMY> set, and
I<target>s have C<SVs_PADTMP> set.
-The correspondence between OP's and I<target>s is not 1-to-1. Different
-OP's in the compile tree of the unit can use the same target, if this
+The correspondence between OPs and I<target>s is not 1-to-1. Different
+OPs in the compile tree of the unit can use the same target, if this
would not conflict with the expected life of the temporary.
-=head2 Scratchpads and recursions
+=head2 Scratchpads and recursion
In fact it is not 100% true that a compiled unit contains a pointer to
the scratchpad AV. In fact it contains a pointer to an AV of
The I<target>s on this scratchpad are C<undef>s, but they are already
marked with correct flags.
-=head2 API LISTING
+=head1 Compiled code
+
+=head2 Code tree
+
+Here we describe the internal form your code is converted to by
+Perl. Start with a simple example:
+
+ $a = $b + $c;
+
+This is converted to a tree similar to this one:
+
+ assign-to
+ / \
+ + $a
+ / \
+ $b $c
+
+(but slightly more complicated). This tree reflect the way Perl
+parsed your code, but has nothing to do with the execution order.
+There is an additional "thread" going through the nodes of the tree
+which shows the order of execution of the nodes. In our simplified
+example above it looks like:
+
+ $b ---> $c ---> + ---> $a ---> assign-to
+
+But with the actual compile tree for C<$a = $b + $c> it is different:
+some nodes I<optimized away>. As a corollary, though the actual tree
+contains more nodes than our simplified example, the execution order
+is the same as in our example.
+
+=head2 Examining the tree
+
+If you have your perl compiled for debugging (usually done with C<-D
+optimize=-g> on C<Configure> command line), you may examine the
+compiled tree by specifying C<-Dx> on the Perl command line. The
+output takes several lines per node, and for C<$b+$c> it looks like
+this:
+
+ 5 TYPE = add ===> 6
+ TARG = 1
+ FLAGS = (SCALAR,KIDS)
+ {
+ TYPE = null ===> (4)
+ (was rv2sv)
+ FLAGS = (SCALAR,KIDS)
+ {
+ 3 TYPE = gvsv ===> 4
+ FLAGS = (SCALAR)
+ GV = main::b
+ }
+ }
+ {
+ TYPE = null ===> (5)
+ (was rv2sv)
+ FLAGS = (SCALAR,KIDS)
+ {
+ 4 TYPE = gvsv ===> 5
+ FLAGS = (SCALAR)
+ GV = main::c
+ }
+ }
+
+This tree has 5 nodes (one per C<TYPE> specifier), only 3 of them are
+not optimized away (one per number in the left column). The immediate
+children of the given node correspond to C<{}> pairs on the same level
+of indentation, thus this listing corresponds to the tree:
+
+ add
+ / \
+ null null
+ | |
+ gvsv gvsv
+
+The execution order is indicated by C<===E<gt>> marks, thus it is C<3
+4 5 6> (node C<6> is not included into above listing), i.e.,
+C<gvsv gvsv add whatever>.
+
+=head2 Compile pass 1: check routines
+
+The tree is created by the I<pseudo-compiler> while yacc code feeds it
+the constructions it recognizes. Since yacc works bottom-up, so does
+the first pass of perl compilation.
+
+What makes this pass interesting for perl developers is that some
+optimization may be performed on this pass. This is optimization by
+so-called I<check routines>. The correspondence between node names
+and corresponding check routines is described in F<opcode.pl> (do not
+forget to run C<make regen_headers> if you modify this file).
+
+A check routine is called when the node is fully constructed except
+for the execution-order thread. Since at this time there is no
+back-links to the currently constructed node, one can do most any
+operation to the top-level node, including freeing it and/or creating
+new nodes above/below it.
+
+The check routine returns the node which should be inserted into the
+tree (if the top-level node was not modified, check routine returns
+its argument).
+
+By convention, check routines have names C<ck_*>. They are usually
+called from C<new*OP> subroutines (or C<convert>) (which in turn are
+called from F<perly.y>).
+
+=head2 Compile pass 1a: constant folding
+
+Immediately after the check routine is called the returned node is
+checked for being compile-time executable. If it is (the value is
+judged to be constant) it is immediately executed, and a I<constant>
+node with the "return value" of the corresponding subtree is
+substituted instead. The subtree is deleted.
+
+If constant folding was not performed, the execution-order thread is
+created.
+
+=head2 Compile pass 2: context propagation
+
+When a context for a part of compile tree is known, it is propagated
+down through the tree. Aat this time the context can have 5 values
+(instead of 2 for runtime context): void, boolean, scalar, list, and
+lvalue. In contrast with the pass 1 this pass is processed from top
+to bottom: a node's context determines the context for its children.
+
+Additional context-dependent optimizations are performed at this time.
+Since at this moment the compile tree contains back-references (via
+"thread" pointers), nodes cannot be free()d now. To allow
+optimized-away nodes at this stage, such nodes are null()ified instead
+of free()ing (i.e. their type is changed to OP_NULL).
+
+=head2 Compile pass 3: peephole optimization
+
+After the compile tree for a subroutine (or for an C<eval> or a file)
+is created, an additional pass over the code is performed. This pass
+is neither top-down or bottom-up, but in the execution order (with
+additional compilications for conditionals). These optimizations are
+done in the subroutine peep(). Optimizations performed at this stage
+are subject to the same restrictions as in the pass 2.
+
+=head1 API LISTING
This is a listing of functions, macros, flags, and variables that may be
useful to extension writers or that may be found while reading other
=item G_ARRAY
-Used to indicate array context. See C<GIMME> and L<perlcall>.
+Used to indicate array context. See C<GIMME_V>, C<GIMME> and L<perlcall>.
=item G_DISCARD
=item GIMME
-The XSUB-writer's equivalent to Perl's C<wantarray>. Returns C<G_SCALAR> or
-C<G_ARRAY> for scalar or array context.
+A backward-compatible version of C<GIMME_V> which can only return
+C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
+
+=item GIMME_V
+
+The XSUB-writer's equivalent to Perl's C<wantarray>. Returns
+C<G_VOID>, C<G_SCALAR> or C<G_ARRAY> for void, scalar or array
+context, respectively.
=item G_NOARGS
=item G_SCALAR
-Used to indicate scalar context. See C<GIMME> and L<perlcall>.
+Used to indicate scalar context. See C<GIMME_V>, C<GIMME>, and L<perlcall>.
+
+=item G_VOID
+
+Used to indicate void context. See C<GIMME_V> and L<perlcall>.
=item gv_fetchmeth
Returns the glob with the given C<name> and a defined subroutine or
-C<NULL>. The glob lives in the given C<stash>, or in the stashes accessable
-via @ISA and @<UNIVERSAL>.
+C<NULL>. The glob lives in the given C<stash>, or in the stashes
+accessable via @ISA and @<UNIVERSAL>.
+
+The argument C<level> should be either 0 or -1. If C<level==0>, as a
+side-effect creates a glob with the given C<name> in the given
+C<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.
-As a side-effect creates a glob with the given C<name> in the given C<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 C<"SUPER"> token as a postfix of the stash name.
+
+The GV returned from C<gv_fetchmeth> may be a method cache entry,
+which is not visible to Perl code. So when calling C<perl_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 C<GvCV> macro.
GV* gv_fetchmeth _((HV* stash, char* name, STRLEN len, I32 level));
=item gv_fetchmethod
+=item gv_fetchmethod_autoload
+
Returns the glob which contains the subroutine to call to invoke the
-method on the C<stash>. In fact in the presense of autoloading this may
-be the glob for "AUTOLOAD". In this case the corresponing variable
+method on the C<stash>. In fact in the presense of autoloading this may
+be the glob for "AUTOLOAD". In this case the corresponding variable
$AUTOLOAD is already setup.
-Note that if you want to keep this glob for a long time, you need to
-check for it being "AUTOLOAD", since at the later time the the call
+The third parameter of C<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
+C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload> with a
+non-zero C<autoload> parameter.
+
+These functions grant C<"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.
-This function grants C<"SUPER"> token as prefix of name or postfix of
-the stash name.
-
-Has the same side-effects and as C<gv_fetchmeth()>. C<name> should be
-writable if contains C<':'> or C<'\''>.
+These functions have the same side-effects and as C<gv_fetchmeth> with
+C<level==0>. C<name> should be writable if contains C<':'> or C<'\''>.
+The warning against passing the GV returned by C<gv_fetchmeth> to
+C<perl_call_sv> apply equally to these functions.
GV* gv_fetchmethod _((HV* stash, char* name));
+ GV* gv_fetchmethod_autoload _((HV* stash, char* name,
+ I32 autoload));
=item gv_stashpv
Return the SV from the GV.
-=item he_delayfree
+=item HEf_SVKEY
-Releases a hash entry, such as while iterating though the hash, but
-delays actual freeing of key and value until the end of the current
-statement (or thereabouts) with C<sv_2mortal>. See C<hv_iternext>.
+This flag, used in the length slot of hash entries and magic
+structures, specifies the structure contains a C<SV*> pointer where a
+C<char*> pointer is to be expected. (For information only--not to be used).
- void he_delayfree _((HV* hv, HE* hent));
+=item HeHASH
-=item he_free
+Returns the computed hash (type C<U32>) stored in the hash entry.
-Releases a hash entry, such as while iterating though the hash. See
-C<hv_iternext>.
+ HeHASH(HE* he)
+
+=item HeKEY
+
+Returns the actual pointer stored in the key slot of the hash entry.
+The pointer may be either C<char*> or C<SV*>, depending on the value of
+C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
+are usually preferable for finding the value of a key.
+
+ HeKEY(HE* he)
+
+=item HeKLEN
+
+If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
+holds an C<SV*> key. Otherwise, holds the actual length of the key.
+Can be assigned to. The C<HePV()> macro is usually preferable for finding
+key lengths.
+
+ HeKLEN(HE* he)
+
+=item HePV
+
+Returns the key slot of the hash entry as a C<char*> value, doing any
+necessary dereferencing of possibly C<SV*> keys. The length of
+the string is placed in C<len> (this is a macro, so do I<not> use
+C<&len>). If you do not care about what the length of the key is,
+you may use the global variable C<na>. Remember though, that hash
+keys in perl are free to contain embedded nulls, so using C<strlen()>
+or similar is not a good way to find the length of hash keys.
+This is very similar to the C<SvPV()> macro described elsewhere in
+this document.
+
+ HePV(HE* he, STRLEN len)
+
+=item HeSVKEY
+
+Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
+does not contain an C<SV*> key.
- void he_free _((HV* hv, HE* hent));
+ HeSVKEY(HE* he)
+
+=item HeSVKEY_force
+
+Returns the key as an C<SV*>. Will create and return a temporary
+mortal C<SV*> if the hash entry contains only a C<char*> key.
+
+ HeSVKEY_force(HE* he)
+
+=item HeSVKEY_set
+
+Sets the key to a given C<SV*>, taking care to set the appropriate flags
+to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
+
+ HeSVKEY_set(HE* he, SV* sv)
+
+=item HeVAL
+
+Returns the value slot (type C<SV*>) stored in the hash entry.
+
+ HeVAL(HE* he)
=item hv_clear
void hv_clear _((HV* tb));
+=item hv_delayfree_ent
+
+Releases a hash entry, such as while iterating though the hash, but
+delays actual freeing of key and value until the end of the current
+statement (or thereabouts) with C<sv_2mortal>. See C<hv_iternext>
+and C<hv_free_ent>.
+
+ void hv_delayfree_ent _((HV* hv, HE* entry));
+
=item hv_delete
Deletes a key/value pair in the hash. The value SV is removed from the hash
SV* hv_delete _((HV* tb, char* key, U32 klen, I32 flags));
+=item 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 C<flags> value will normally be zero; if set
+to G_DISCARD then null will be returned. C<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));
+
=item hv_exists
Returns a boolean indicating whether the specified hash key exists. The
bool hv_exists _((HV* tb, char* key, U32 klen));
+=item hv_exists_ent
+
+Returns a boolean indicating whether the specified hash key exists. C<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));
+
=item hv_fetch
Returns the SV which corresponds to the specified key in the hash. The
SV** hv_fetch _((HV* tb, char* key, U32 klen, I32 lval));
+=item hv_fetch_ent
+
+Returns the hash entry which corresponds to the specified key in the hash.
+C<hash> must be a valid precomputed hash number for the given C<key>, or
+0 if you want the function to compute it. IF C<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 C<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.
+
+ HE* hv_fetch_ent _((HV* tb, SV* key, I32 lval, U32 hash));
+
+=item hv_free_ent
+
+Releases a hash entry, such as while iterating though the hash. See
+C<hv_iternext> and C<hv_delayfree_ent>.
+
+ void hv_free_ent _((HV* hv, HE* entry));
+
=item hv_iterinit
Prepares a starting point to traverse a hash table.
char* hv_iterkey _((HE* entry, I32* retlen));
+=item hv_iterkeysv
+
+Returns the key as an C<SV*> from the current position of the hash
+iterator. The return value will always be a mortal copy of the
+key. Also see C<hv_iterinit>.
+
+ SV* hv_iterkeysv _((HE* entry));
+
=item hv_iternext
Returns entries from a hash iterator. See C<hv_iterinit>.
=item hv_store
Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
-the length of the key. The C<hash> parameter is the pre-computed hash
+the length of the key. The C<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, otherwise it can be dereferenced to get the
original C<SV*>.
SV** hv_store _((HV* tb, char* key, U32 klen, SV* val, U32 hash));
+=item hv_store_ent
+
+Stores C<val> in a hash. The hash key is specified as C<key>. The C<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 entry was stored in a tied hash.
+Otherwise the contents of the return value can be accessed using the
+C<He???> macros described here.
+
+ HE* hv_store_ent _((HV* tb, SV* key, SV* val, U32 hash));
+
=item hv_undef
Undefines the hash.
=item newSV
Creates a new SV. The C<len> parameter indicates the number of bytes of
-pre-allocated string space the SV should have. The reference count for the
+preallocated string space the SV should have. The reference count for the
new SV is set to 1.
SV* newSV _((STRLEN len));
I32 perl_eval_sv _((SV* sv, I32 flags));
+=item perl_eval_pv
+
+Tells Perl to C<eval> the given string and return an SV* result.
+
+ SV* perl_eval_pv _((char* p, I32 croak_on_error));
+
=item perl_free
Releases a Perl interpreter. See L<perlembed>.
=item SPAGAIN
-Re-fetch the stack pointer. Used after a callback. See L<perlcall>.
+Refetch the stack pointer. Used after a callback. See L<perlcall>.
SPAGAIN;
=head1 EDITOR
-Jeff Okamoto <okamoto@corp.hp.com>
+Jeff Okamoto <F<okamoto@corp.hp.com>>
With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
Bowers, Matthew Green, Tim Bunce, Spider Boardman, and Ulrich Pfeifer.
-API Listing by Dean Roehrich <roehrich@cray.com>.
+API Listing by Dean Roehrich <F<roehrich@cray.com>>.
=head1 DATE
-Version 30: 1997/1/17
+Version 31.6: 1997/4/14