hv.h revision 7c478bd95313f5f23a4c958a745db2134aa03244
/* hv.h
*
* Copyright (C) 1991, 1992, 1993, 1996, 1997, 1998, 1999,
* 2000, 2001, 2002, by Larry Wall and others
*
* You may distribute under the terms of either the GNU General Public
* License or the Artistic License, as specified in the README file.
*
*/
/* typedefs to eliminate some typing */
/* entry in hash value chain */
struct he {
};
/* hash key -- defined separately for use as shared pointer */
struct hek {
/* the hash-key is \0-terminated */
/* after the \0 there is a byte for flags, such as whether the key
is UTF-8 */
};
/* hash structure: */
/* This structure must match the beginning of struct xpvmg in sv.h. */
struct xpvhv {
char * xhv_array; /* pointer to malloced string */
#define xhv_placeholders xnv_nv
char *xhv_name; /* name, if a symbol table */
};
/* hash a key */
/* FYI: This is the "One-at-a-Time" algorithm by Bob Jenkins
* from requirements by Colin Plumb.
/* The use of a temporary pointer and the casting games
* is needed to serve the dual purposes of
* (a) the hashed data being interpreted as "unsigned char" (new since 5.8,
* a "char" can be either signed or signed, depending on the compiler)
* (b) catering for old code that uses a "char"
*
* The "hash seed" feature was added in Perl 5.8.1 to perturb the results
* to avoid "algorithmic complexity attacks".
*
* If USE_HASH_SEED is defined, hash randomisation is done by default
* If USE_HASH_SEED_EXPLICIT is defined, hash randomisation is done
* only if the environment variable PERL_HASH_SEED is set.
* For maximal control, one can define PERL_HASH_SEED.
* (see also erl.c:perl_parse()).
*/
#ifndef PERL_HASH_SEED
# if defined(USE_HASH_SEED) || defined(USE_HASH_SEED_EXPLICIT)
# define PERL_HASH_SEED PL_hash_seed
# else
# define PERL_HASH_SEED 0
# endif
#endif
STMT_START { \
register const char *s_PeRlHaSh_tmp = str; \
register const unsigned char *s_PeRlHaSh = (const unsigned char *)s_PeRlHaSh_tmp; \
while (i_PeRlHaSh--) { \
hash_PeRlHaSh += *s_PeRlHaSh++; \
} \
} STMT_END
/* Only hv.c and mod_perl should be doing this. */
#ifdef PERL_HASH_INTERNAL_ACCESS
STMT_START { \
register const char *s_PeRlHaSh_tmp = str; \
register const unsigned char *s_PeRlHaSh = (const unsigned char *)s_PeRlHaSh_tmp; \
while (i_PeRlHaSh--) { \
hash_PeRlHaSh += *s_PeRlHaSh++; \
} \
} STMT_END
#endif
/*
=head1 Hash Manipulation Functions
=for apidoc AmU||HEf_SVKEY
This flag, used in the length slot of hash entries and magic structures,
specifies the structure contains an C<SV*> pointer where a C<char*> pointer
is to be expected. (For information only--not to be used).
=head1 Handy Values
=for apidoc AmU||Nullhv
Null HV pointer.
=head1 Hash Manipulation Functions
=for apidoc Am|char*|HvNAME|HV* stash
Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
=for apidoc Am|void*|HeKEY|HE* he
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.
=for apidoc Am|STRLEN|HeKLEN|HE* he
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.
=for apidoc Am|SV*|HeVAL|HE* he
Returns the value slot (type C<SV*>) stored in the hash entry.
=for apidoc Am|U32|HeHASH|HE* he
Returns the computed hash stored in the hash entry.
=for apidoc Am|char*|HePV|HE* he|STRLEN len
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<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 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.
=for apidoc Am|SV*|HeSVKEY|HE* he
Returns the key as an C<SV*>, or C<Nullsv> if the hash entry does not
contain an C<SV*> key.
=for apidoc Am|SV*|HeSVKEY_force|HE* he
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.
=for apidoc Am|SV*|HeSVKEY_set|HE* he|SV* sv
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*>.
=cut
*/
/* the number of keys (including any placeholers) */
/* The number of placeholders in the enumerated-keys hash */
/* the number of keys that exist() (i.e. excluding placeholders) */
/*
* HvKEYS gets the number of keys that actually exist(), and is provided
* for backwards compatibility with old XS code. The core uses HvUSEDKEYS
* (keys, excluding placeholdes) and HvTOTALKEYS (including placeholders)
*/
/* This is an optimisation flag. It won't be set if all hash keys have a 0
* flag. Currently the only flags relate to utf8.
* Hence it won't be set if all keys are 8 bit only. It will be set if any key
* is utf8 (including 8 bit keys that were entered as utf8, and need upgrading
* when retrieved during iteration. It may still be set when there are no longer
* any utf8 keys.
* See HVhek_ENABLEHVKFLAGS for the trigger.
*/
/* Maybe amagical: */
/* #define HV_AMAGICmb(hv) (SvFLAGS(hv) & (SVpgv_badAM | SVpgv_AM)) */
/*
#define HV_AMAGICbad(hv) (SvFLAGS(hv) & SVpgv_badAM)
#define HV_badAMAGIC_on(hv) (SvFLAGS(hv) |= SVpgv_badAM)
#define HV_badAMAGIC_off(hv) (SvFLAGS(hv) &= ~SVpgv_badAM)
*/
* (may change, but Storable is a core module) */
#define HVhek_MASK 0xFF
/* Which flags enable HvHASKFLAGS? Somewhat a hack on a hack, as
HVhek_REHASH is only needed because the rehash flag has to be duplicated
into all keys as hv_iternext has no access to the hash flags. At this
point Storable's tests get upset, because sometimes hashes are "keyed"
and sometimes not, depending on the order of data insertion, and whether
it triggered rehashing. So currently HVhek_REHAS is exempt.
*/
/* calculate HV array allocation */
#if defined(STRANGE_MALLOC) || defined(MYMALLOC)
#else
# define MALLOC_OVERHEAD 16
# define PERL_HV_ARRAY_ALLOC_BYTES(size) \
(((size) < 64) \
#endif
/* Flags for hv_iternext_flags. */
/* available as a function in hv.c */