Branch
Hash :
6ca831b0
Author :
Date :
2025-09-16T18:57:41
stringeq: prefer memeq to memcmp in other modules * lib/argmatch.c, lib/argmatch.h, lib/backupfile.c, lib/bcp47.c: * lib/boot-time.c, lib/csharpcomp.c, lib/csharpexec.c: * lib/file-has-acl.c, lib/gen-uni-tables.c, lib/get_ppid_of.c: * lib/get_progname_of.c, lib/getlogin_r.c, lib/getprogname.c: * lib/getumask.c, lib/isnan.c, lib/mbchar.h, lib/mem-hash-map.c: * lib/memcoll.c, lib/progname.c, lib/progreloc.c: * lib/pthread_sigmask.c, lib/quotearg.c, lib/readutmp.c: * lib/same.c, lib/signbitd.c, lib/signbitf.c, lib/signbitl.c: * lib/string-desc.c, lib/string.c, lib/string.in.h: * lib/unictype/3level.h, lib/unictype/3levelbit.h: * lib/uniname/uniname.c, lib/vc-mtime.c: Prefer memeq to memcmp when either will do. Do not make this change to files shared with glibc. Do not make the change to test files, at least not for now. * lib/gen-uni-tables.c (memeq): New static function, in same style. * modules/argmatch, modules/backupfile, modules/bcp47: * modules/boot-time, modules/csharpcomp, modules/csharpexec: * modules/file-has-acl: * modules/get_ppid_of, modules/get_progname_of: * modules/getlogin_r, modules/getprogname, modules/getumask: * modules/isnan, modules/mbchar, modules/mem-hash-map: * modules/memcoll, modules/progname, modules/pthread_sigmask: * modules/quotearg, modules/readutmp, modules/relocatable-prog: * modules/relocatable-prog-wrapper, modules/same, modules/signbit: * modules/string-desc, modules/stringeq, modules/uniname/uniname: * modules/vc-mtime: (Depends-on): Add stringeq.
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/* Simple hash table (no removals) where the keys are memory blocks.
Copyright (C) 1994-2025 Free Software Foundation, Inc.
Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, October 1994.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published
by the Free Software Foundation, either version 3 of the License,
or (at your option) any later version.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
/* Specification. */
#include "mem-hash-map.h"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <limits.h>
#include <sys/types.h>
#include "next-prime.h"
/* Since this simple implementation of hash tables allows only insertion, no
removal of entries, the right data structure for the memory holding all keys
is an obstack. */
#include "obstack.h"
/* Use checked memory allocation. */
#include "xalloc.h"
#define obstack_chunk_alloc xmalloc
#define obstack_chunk_free free
typedef struct hash_entry
{
size_t used; /* Hash code of the key, or 0 for an unused entry. */
const void *key; /* Key. */
size_t keylen;
void *data; /* Value. */
struct hash_entry *next;
}
hash_entry;
/* Initialize a hash table. INIT_SIZE > 1 is the initial number of available
entries.
Return 0 always. */
int
hash_init (hash_table *htab, size_t init_size)
{
/* We need the size to be a prime. */
init_size = next_prime (init_size);
/* Initialize the data structure. */
htab->size = init_size;
htab->filled = 0;
htab->first = NULL;
htab->table = XCALLOC (init_size + 1, hash_entry);
obstack_init (&htab->mem_pool);
return 0;
}
/* Delete a hash table's contents.
Return 0 always. */
int
hash_destroy (hash_table *htab)
{
free (htab->table);
obstack_free (&htab->mem_pool, NULL);
return 0;
}
/* Compute a hash code for a key consisting of KEYLEN bytes starting at KEY
in memory. */
static size_t
compute_hashval (const void *key, size_t keylen)
{
size_t cnt;
size_t hval;
/* Compute the hash value for the given string. The algorithm
is taken from [Aho,Sethi,Ullman], fixed according to
https://haible.de/bruno/hashfunc.html. */
cnt = 0;
hval = keylen;
while (cnt < keylen)
{
hval = (hval << 9) | (hval >> (sizeof (size_t) * CHAR_BIT - 9));
hval += (size_t) *(((const char *) key) + cnt++);
}
return hval != 0 ? hval : ~((size_t) 0);
}
/* References:
[Aho,Sethi,Ullman] Compilers: Principles, Techniques and Tools, 1986
[Knuth] The Art of Computer Programming, part3 (6.4) */
/* Look up a given key in the hash table.
Return the index of the entry, if present, or otherwise the index a free
entry where it could be inserted. */
static size_t
lookup (const hash_table *htab,
const void *key, size_t keylen,
size_t hval)
{
size_t hash;
size_t idx;
hash_entry *table = htab->table;
/* First hash function: simply take the modul but prevent zero. */
hash = 1 + hval % htab->size;
idx = hash;
if (table[idx].used)
{
if (table[idx].used == hval && table[idx].keylen == keylen
&& memeq (table[idx].key, key, keylen))
return idx;
/* Second hash function as suggested in [Knuth]. */
hash = 1 + hval % (htab->size - 2);
do
{
if (idx <= hash)
idx = htab->size + idx - hash;
else
idx -= hash;
/* If entry is found use it. */
if (table[idx].used == hval && table[idx].keylen == keylen
&& memeq (table[idx].key, key, keylen))
return idx;
}
while (table[idx].used);
}
return idx;
}
/* Look up the value of a key in the given table.
If found, return 0 and set *RESULT to it. Otherwise return -1. */
int
hash_find_entry (const hash_table *htab, const void *key, size_t keylen,
void **result)
{
hash_entry *table = htab->table;
size_t idx = lookup (htab, key, keylen, compute_hashval (key, keylen));
if (table[idx].used == 0)
return -1;
*result = table[idx].data;
return 0;
}
/* Insert the pair (KEY[0..KEYLEN-1], DATA) in the hash table at index IDX.
HVAL is the key's hash code. IDX depends on it. The table entry at index
IDX is known to be unused. */
static void
insert_entry_2 (hash_table *htab,
const void *key, size_t keylen,
size_t hval, size_t idx, void *data)
{
hash_entry *table = htab->table;
table[idx].used = hval;
table[idx].key = key;
table[idx].keylen = keylen;
table[idx].data = data;
/* List the new value in the list. */
if (htab->first == NULL)
{
table[idx].next = &table[idx];
htab->first = &table[idx];
}
else
{
table[idx].next = htab->first->next;
htab->first->next = &table[idx];
htab->first = &table[idx];
}
++htab->filled;
}
/* Grow the hash table. */
static void
resize (hash_table *htab)
{
size_t old_size = htab->size;
hash_entry *table = htab->table;
size_t idx;
htab->size = next_prime (htab->size * 2);
htab->filled = 0;
htab->first = NULL;
htab->table = XCALLOC (1 + htab->size, hash_entry);
for (idx = 1; idx <= old_size; ++idx)
if (table[idx].used)
insert_entry_2 (htab, table[idx].key, table[idx].keylen,
table[idx].used,
lookup (htab, table[idx].key, table[idx].keylen,
table[idx].used),
table[idx].data);
free (table);
}
/* Try to insert the pair (KEY[0..KEYLEN-1], DATA) in the hash table.
Return non-NULL (more precisely, the address of the KEY inside the table's
memory pool) if successful, or NULL if there is already an entry with the
given key. */
const void *
hash_insert_entry (hash_table *htab,
const void *key, size_t keylen,
void *data)
{
size_t hval = compute_hashval (key, keylen);
hash_entry *table = htab->table;
size_t idx = lookup (htab, key, keylen, hval);
if (table[idx].used)
/* We don't want to overwrite the old value. */
return NULL;
else
{
/* An empty bucket has been found. */
void *keycopy = obstack_copy (&htab->mem_pool, key, keylen);
insert_entry_2 (htab, keycopy, keylen, hval, idx, data);
if (100 * htab->filled > 75 * htab->size)
/* Table is filled more than 75%. Resize the table. */
resize (htab);
return keycopy;
}
}
/* Insert the pair (KEY[0..KEYLEN-1], DATA) in the hash table.
Return 0. */
int
hash_set_value (hash_table *htab,
const void *key, size_t keylen,
void *data)
{
size_t hval = compute_hashval (key, keylen);
hash_entry *table = htab->table;
size_t idx = lookup (htab, key, keylen, hval);
if (table[idx].used)
{
/* Overwrite the old value. */
table[idx].data = data;
return 0;
}
else
{
/* An empty bucket has been found. */
void *keycopy = obstack_copy (&htab->mem_pool, key, keylen);
insert_entry_2 (htab, keycopy, keylen, hval, idx, data);
if (100 * htab->filled > 75 * htab->size)
/* Table is filled more than 75%. Resize the table. */
resize (htab);
return 0;
}
}
/* Steps *PTR forward to the next used entry in the given hash table. *PTR
should be initially set to NULL. Store information about the next entry
in *KEY, *KEYLEN, *DATA.
Return 0 normally, -1 when the whole hash table has been traversed. */
int
hash_iterate (hash_table *htab, void **ptr, const void **key, size_t *keylen,
void **data)
{
hash_entry *curr;
if (*ptr == NULL)
{
if (htab->first == NULL)
return -1;
curr = htab->first;
}
else
{
if (*ptr == htab->first)
return -1;
curr = (hash_entry *) *ptr;
}
curr = curr->next;
*ptr = (void *) curr;
*key = curr->key;
*keylen = curr->keylen;
*data = curr->data;
return 0;
}
/* Steps *PTR forward to the next used entry in the given hash table. *PTR
should be initially set to NULL. Store information about the next entry
in *KEY, *KEYLEN, *DATAP. *DATAP is set to point to the storage of the
value; modifying **DATAP will modify the value of the entry.
Return 0 normally, -1 when the whole hash table has been traversed. */
int
hash_iterate_modify (hash_table *htab, void **ptr,
const void **key, size_t *keylen,
void ***datap)
{
hash_entry *curr;
if (*ptr == NULL)
{
if (htab->first == NULL)
return -1;
curr = htab->first;
}
else
{
if (*ptr == htab->first)
return -1;
curr = (hash_entry *) *ptr;
}
curr = curr->next;
*ptr = (void *) curr;
*key = curr->key;
*keylen = curr->keylen;
*datap = &curr->data;
return 0;
}