0,0 → 1,998 |
/* An expandable hash tables datatype. |
Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2009, 2010 |
Free Software Foundation, Inc. |
Contributed by Vladimir Makarov (vmakarov@cygnus.com). |
|
This file is part of the libiberty library. |
Libiberty is free software; you can redistribute it and/or |
modify it under the terms of the GNU Library General Public |
License as published by the Free Software Foundation; either |
version 2 of the License, or (at your option) any later version. |
|
Libiberty 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 |
Library General Public License for more details. |
|
You should have received a copy of the GNU Library General Public |
License along with libiberty; see the file COPYING.LIB. If |
not, write to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor, |
Boston, MA 02110-1301, USA. */ |
|
/* This package implements basic hash table functionality. It is possible |
to search for an entry, create an entry and destroy an entry. |
|
Elements in the table are generic pointers. |
|
The size of the table is not fixed; if the occupancy of the table |
grows too high the hash table will be expanded. |
|
The abstract data implementation is based on generalized Algorithm D |
from Knuth's book "The art of computer programming". Hash table is |
expanded by creation of new hash table and transferring elements from |
the old table to the new table. */ |
|
#ifdef HAVE_CONFIG_H |
#include "config.h" |
#endif |
|
#include <sys/types.h> |
|
#ifdef HAVE_STDLIB_H |
#include <stdlib.h> |
#endif |
#ifdef HAVE_STRING_H |
#include <string.h> |
#endif |
#ifdef HAVE_MALLOC_H |
#include <malloc.h> |
#endif |
#ifdef HAVE_LIMITS_H |
#include <limits.h> |
#endif |
#ifdef HAVE_INTTYPES_H |
#include <inttypes.h> |
#endif |
#ifdef HAVE_STDINT_H |
#include <stdint.h> |
#endif |
|
#include <stdio.h> |
|
#include "libiberty.h" |
#include "ansidecl.h" |
#include "hashtab.h" |
|
#ifndef CHAR_BIT |
#define CHAR_BIT 8 |
#endif |
|
static unsigned int higher_prime_index (unsigned long); |
static hashval_t htab_mod_1 (hashval_t, hashval_t, hashval_t, int); |
static hashval_t htab_mod (hashval_t, htab_t); |
static hashval_t htab_mod_m2 (hashval_t, htab_t); |
static hashval_t hash_pointer (const void *); |
static int eq_pointer (const void *, const void *); |
static int htab_expand (htab_t); |
static PTR *find_empty_slot_for_expand (htab_t, hashval_t); |
|
/* At some point, we could make these be NULL, and modify the |
hash-table routines to handle NULL specially; that would avoid |
function-call overhead for the common case of hashing pointers. */ |
htab_hash htab_hash_pointer = hash_pointer; |
htab_eq htab_eq_pointer = eq_pointer; |
|
/* Table of primes and multiplicative inverses. |
|
Note that these are not minimally reduced inverses. Unlike when generating |
code to divide by a constant, we want to be able to use the same algorithm |
all the time. All of these inverses (are implied to) have bit 32 set. |
|
For the record, here's the function that computed the table; it's a |
vastly simplified version of the function of the same name from gcc. */ |
|
#if 0 |
unsigned int |
ceil_log2 (unsigned int x) |
{ |
int i; |
for (i = 31; i >= 0 ; --i) |
if (x > (1u << i)) |
return i+1; |
abort (); |
} |
|
unsigned int |
choose_multiplier (unsigned int d, unsigned int *mlp, unsigned char *shiftp) |
{ |
unsigned long long mhigh; |
double nx; |
int lgup, post_shift; |
int pow, pow2; |
int n = 32, precision = 32; |
|
lgup = ceil_log2 (d); |
pow = n + lgup; |
pow2 = n + lgup - precision; |
|
nx = ldexp (1.0, pow) + ldexp (1.0, pow2); |
mhigh = nx / d; |
|
*shiftp = lgup - 1; |
*mlp = mhigh; |
return mhigh >> 32; |
} |
#endif |
|
struct prime_ent |
{ |
hashval_t prime; |
hashval_t inv; |
hashval_t inv_m2; /* inverse of prime-2 */ |
hashval_t shift; |
}; |
|
static struct prime_ent const prime_tab[] = { |
{ 7, 0x24924925, 0x9999999b, 2 }, |
{ 13, 0x3b13b13c, 0x745d1747, 3 }, |
{ 31, 0x08421085, 0x1a7b9612, 4 }, |
{ 61, 0x0c9714fc, 0x15b1e5f8, 5 }, |
{ 127, 0x02040811, 0x0624dd30, 6 }, |
{ 251, 0x05197f7e, 0x073260a5, 7 }, |
{ 509, 0x01824366, 0x02864fc8, 8 }, |
{ 1021, 0x00c0906d, 0x014191f7, 9 }, |
{ 2039, 0x0121456f, 0x0161e69e, 10 }, |
{ 4093, 0x00300902, 0x00501908, 11 }, |
{ 8191, 0x00080041, 0x00180241, 12 }, |
{ 16381, 0x000c0091, 0x00140191, 13 }, |
{ 32749, 0x002605a5, 0x002a06e6, 14 }, |
{ 65521, 0x000f00e2, 0x00110122, 15 }, |
{ 131071, 0x00008001, 0x00018003, 16 }, |
{ 262139, 0x00014002, 0x0001c004, 17 }, |
{ 524287, 0x00002001, 0x00006001, 18 }, |
{ 1048573, 0x00003001, 0x00005001, 19 }, |
{ 2097143, 0x00004801, 0x00005801, 20 }, |
{ 4194301, 0x00000c01, 0x00001401, 21 }, |
{ 8388593, 0x00001e01, 0x00002201, 22 }, |
{ 16777213, 0x00000301, 0x00000501, 23 }, |
{ 33554393, 0x00001381, 0x00001481, 24 }, |
{ 67108859, 0x00000141, 0x000001c1, 25 }, |
{ 134217689, 0x000004e1, 0x00000521, 26 }, |
{ 268435399, 0x00000391, 0x000003b1, 27 }, |
{ 536870909, 0x00000019, 0x00000029, 28 }, |
{ 1073741789, 0x0000008d, 0x00000095, 29 }, |
{ 2147483647, 0x00000003, 0x00000007, 30 }, |
/* Avoid "decimal constant so large it is unsigned" for 4294967291. */ |
{ 0xfffffffb, 0x00000006, 0x00000008, 31 } |
}; |
|
/* The following function returns an index into the above table of the |
nearest prime number which is greater than N, and near a power of two. */ |
|
static unsigned int |
higher_prime_index (unsigned long n) |
{ |
unsigned int low = 0; |
unsigned int high = sizeof(prime_tab) / sizeof(prime_tab[0]); |
|
while (low != high) |
{ |
unsigned int mid = low + (high - low) / 2; |
if (n > prime_tab[mid].prime) |
low = mid + 1; |
else |
high = mid; |
} |
|
/* If we've run out of primes, abort. */ |
if (n > prime_tab[low].prime) |
{ |
fprintf (stderr, "Cannot find prime bigger than %lu\n", n); |
abort (); |
} |
|
return low; |
} |
|
/* Returns non-zero if P1 and P2 are equal. */ |
|
static int |
eq_pointer (const PTR p1, const PTR p2) |
{ |
return p1 == p2; |
} |
|
|
/* The parens around the function names in the next two definitions |
are essential in order to prevent macro expansions of the name. |
The bodies, however, are expanded as expected, so they are not |
recursive definitions. */ |
|
/* Return the current size of given hash table. */ |
|
#define htab_size(htab) ((htab)->size) |
|
size_t |
(htab_size) (htab_t htab) |
{ |
return htab_size (htab); |
} |
|
/* Return the current number of elements in given hash table. */ |
|
#define htab_elements(htab) ((htab)->n_elements - (htab)->n_deleted) |
|
size_t |
(htab_elements) (htab_t htab) |
{ |
return htab_elements (htab); |
} |
|
/* Return X % Y. */ |
|
static inline hashval_t |
htab_mod_1 (hashval_t x, hashval_t y, hashval_t inv, int shift) |
{ |
/* The multiplicative inverses computed above are for 32-bit types, and |
requires that we be able to compute a highpart multiply. */ |
#ifdef UNSIGNED_64BIT_TYPE |
__extension__ typedef UNSIGNED_64BIT_TYPE ull; |
if (sizeof (hashval_t) * CHAR_BIT <= 32) |
{ |
hashval_t t1, t2, t3, t4, q, r; |
|
t1 = ((ull)x * inv) >> 32; |
t2 = x - t1; |
t3 = t2 >> 1; |
t4 = t1 + t3; |
q = t4 >> shift; |
r = x - (q * y); |
|
return r; |
} |
#endif |
|
/* Otherwise just use the native division routines. */ |
return x % y; |
} |
|
/* Compute the primary hash for HASH given HTAB's current size. */ |
|
static inline hashval_t |
htab_mod (hashval_t hash, htab_t htab) |
{ |
const struct prime_ent *p = &prime_tab[htab->size_prime_index]; |
return htab_mod_1 (hash, p->prime, p->inv, p->shift); |
} |
|
/* Compute the secondary hash for HASH given HTAB's current size. */ |
|
static inline hashval_t |
htab_mod_m2 (hashval_t hash, htab_t htab) |
{ |
const struct prime_ent *p = &prime_tab[htab->size_prime_index]; |
return 1 + htab_mod_1 (hash, p->prime - 2, p->inv_m2, p->shift); |
} |
|
/* This function creates table with length slightly longer than given |
source length. Created hash table is initiated as empty (all the |
hash table entries are HTAB_EMPTY_ENTRY). The function returns the |
created hash table, or NULL if memory allocation fails. */ |
|
htab_t |
htab_create_alloc (size_t size, htab_hash hash_f, htab_eq eq_f, |
htab_del del_f, htab_alloc alloc_f, htab_free free_f) |
{ |
return htab_create_typed_alloc (size, hash_f, eq_f, del_f, alloc_f, alloc_f, |
free_f); |
} |
|
/* As above, but uses the variants of ALLOC_F and FREE_F which accept |
an extra argument. */ |
|
htab_t |
htab_create_alloc_ex (size_t size, htab_hash hash_f, htab_eq eq_f, |
htab_del del_f, void *alloc_arg, |
htab_alloc_with_arg alloc_f, |
htab_free_with_arg free_f) |
{ |
htab_t result; |
unsigned int size_prime_index; |
|
size_prime_index = higher_prime_index (size); |
size = prime_tab[size_prime_index].prime; |
|
result = (htab_t) (*alloc_f) (alloc_arg, 1, sizeof (struct htab)); |
if (result == NULL) |
return NULL; |
result->entries = (PTR *) (*alloc_f) (alloc_arg, size, sizeof (PTR)); |
if (result->entries == NULL) |
{ |
if (free_f != NULL) |
(*free_f) (alloc_arg, result); |
return NULL; |
} |
result->size = size; |
result->size_prime_index = size_prime_index; |
result->hash_f = hash_f; |
result->eq_f = eq_f; |
result->del_f = del_f; |
result->alloc_arg = alloc_arg; |
result->alloc_with_arg_f = alloc_f; |
result->free_with_arg_f = free_f; |
return result; |
} |
|
/* |
|
@deftypefn Supplemental htab_t htab_create_typed_alloc (size_t @var{size}, @ |
htab_hash @var{hash_f}, htab_eq @var{eq_f}, htab_del @var{del_f}, @ |
htab_alloc @var{alloc_tab_f}, htab_alloc @var{alloc_f}, @ |
htab_free @var{free_f}) |
|
This function creates a hash table that uses two different allocators |
@var{alloc_tab_f} and @var{alloc_f} to use for allocating the table itself |
and its entries respectively. This is useful when variables of different |
types need to be allocated with different allocators. |
|
The created hash table is slightly larger than @var{size} and it is |
initially empty (all the hash table entries are @code{HTAB_EMPTY_ENTRY}). |
The function returns the created hash table, or @code{NULL} if memory |
allocation fails. |
|
@end deftypefn |
|
*/ |
|
htab_t |
htab_create_typed_alloc (size_t size, htab_hash hash_f, htab_eq eq_f, |
htab_del del_f, htab_alloc alloc_tab_f, |
htab_alloc alloc_f, htab_free free_f) |
{ |
htab_t result; |
unsigned int size_prime_index; |
|
size_prime_index = higher_prime_index (size); |
size = prime_tab[size_prime_index].prime; |
|
result = (htab_t) (*alloc_tab_f) (1, sizeof (struct htab)); |
if (result == NULL) |
return NULL; |
result->entries = (PTR *) (*alloc_f) (size, sizeof (PTR)); |
if (result->entries == NULL) |
{ |
if (free_f != NULL) |
(*free_f) (result); |
return NULL; |
} |
result->size = size; |
result->size_prime_index = size_prime_index; |
result->hash_f = hash_f; |
result->eq_f = eq_f; |
result->del_f = del_f; |
result->alloc_f = alloc_f; |
result->free_f = free_f; |
return result; |
} |
|
|
/* Update the function pointers and allocation parameter in the htab_t. */ |
|
void |
htab_set_functions_ex (htab_t htab, htab_hash hash_f, htab_eq eq_f, |
htab_del del_f, PTR alloc_arg, |
htab_alloc_with_arg alloc_f, htab_free_with_arg free_f) |
{ |
htab->hash_f = hash_f; |
htab->eq_f = eq_f; |
htab->del_f = del_f; |
htab->alloc_arg = alloc_arg; |
htab->alloc_with_arg_f = alloc_f; |
htab->free_with_arg_f = free_f; |
} |
|
/* These functions exist solely for backward compatibility. */ |
|
#undef htab_create |
htab_t |
htab_create (size_t size, htab_hash hash_f, htab_eq eq_f, htab_del del_f) |
{ |
return htab_create_alloc (size, hash_f, eq_f, del_f, xcalloc, free); |
} |
|
htab_t |
htab_try_create (size_t size, htab_hash hash_f, htab_eq eq_f, htab_del del_f) |
{ |
return htab_create_alloc (size, hash_f, eq_f, del_f, calloc, free); |
} |
|
/* This function frees all memory allocated for given hash table. |
Naturally the hash table must already exist. */ |
|
void |
htab_delete (htab_t htab) |
{ |
size_t size = htab_size (htab); |
PTR *entries = htab->entries; |
int i; |
|
if (htab->del_f) |
for (i = size - 1; i >= 0; i--) |
if (entries[i] != HTAB_EMPTY_ENTRY && entries[i] != HTAB_DELETED_ENTRY) |
(*htab->del_f) (entries[i]); |
|
if (htab->free_f != NULL) |
{ |
(*htab->free_f) (entries); |
(*htab->free_f) (htab); |
} |
else if (htab->free_with_arg_f != NULL) |
{ |
(*htab->free_with_arg_f) (htab->alloc_arg, entries); |
(*htab->free_with_arg_f) (htab->alloc_arg, htab); |
} |
} |
|
/* This function clears all entries in the given hash table. */ |
|
void |
htab_empty (htab_t htab) |
{ |
size_t size = htab_size (htab); |
PTR *entries = htab->entries; |
int i; |
|
if (htab->del_f) |
for (i = size - 1; i >= 0; i--) |
if (entries[i] != HTAB_EMPTY_ENTRY && entries[i] != HTAB_DELETED_ENTRY) |
(*htab->del_f) (entries[i]); |
|
/* Instead of clearing megabyte, downsize the table. */ |
if (size > 1024*1024 / sizeof (PTR)) |
{ |
int nindex = higher_prime_index (1024 / sizeof (PTR)); |
int nsize = prime_tab[nindex].prime; |
|
if (htab->free_f != NULL) |
(*htab->free_f) (htab->entries); |
else if (htab->free_with_arg_f != NULL) |
(*htab->free_with_arg_f) (htab->alloc_arg, htab->entries); |
if (htab->alloc_with_arg_f != NULL) |
htab->entries = (PTR *) (*htab->alloc_with_arg_f) (htab->alloc_arg, nsize, |
sizeof (PTR *)); |
else |
htab->entries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR *)); |
htab->size = nsize; |
htab->size_prime_index = nindex; |
} |
else |
memset (entries, 0, size * sizeof (PTR)); |
htab->n_deleted = 0; |
htab->n_elements = 0; |
} |
|
/* Similar to htab_find_slot, but without several unwanted side effects: |
- Does not call htab->eq_f when it finds an existing entry. |
- Does not change the count of elements/searches/collisions in the |
hash table. |
This function also assumes there are no deleted entries in the table. |
HASH is the hash value for the element to be inserted. */ |
|
static PTR * |
find_empty_slot_for_expand (htab_t htab, hashval_t hash) |
{ |
hashval_t index = htab_mod (hash, htab); |
size_t size = htab_size (htab); |
PTR *slot = htab->entries + index; |
hashval_t hash2; |
|
if (*slot == HTAB_EMPTY_ENTRY) |
return slot; |
else if (*slot == HTAB_DELETED_ENTRY) |
abort (); |
|
hash2 = htab_mod_m2 (hash, htab); |
for (;;) |
{ |
index += hash2; |
if (index >= size) |
index -= size; |
|
slot = htab->entries + index; |
if (*slot == HTAB_EMPTY_ENTRY) |
return slot; |
else if (*slot == HTAB_DELETED_ENTRY) |
abort (); |
} |
} |
|
/* The following function changes size of memory allocated for the |
entries and repeatedly inserts the table elements. The occupancy |
of the table after the call will be about 50%. Naturally the hash |
table must already exist. Remember also that the place of the |
table entries is changed. If memory allocation failures are allowed, |
this function will return zero, indicating that the table could not be |
expanded. If all goes well, it will return a non-zero value. */ |
|
static int |
htab_expand (htab_t htab) |
{ |
PTR *oentries; |
PTR *olimit; |
PTR *p; |
PTR *nentries; |
size_t nsize, osize, elts; |
unsigned int oindex, nindex; |
|
oentries = htab->entries; |
oindex = htab->size_prime_index; |
osize = htab->size; |
olimit = oentries + osize; |
elts = htab_elements (htab); |
|
/* Resize only when table after removal of unused elements is either |
too full or too empty. */ |
if (elts * 2 > osize || (elts * 8 < osize && osize > 32)) |
{ |
nindex = higher_prime_index (elts * 2); |
nsize = prime_tab[nindex].prime; |
} |
else |
{ |
nindex = oindex; |
nsize = osize; |
} |
|
if (htab->alloc_with_arg_f != NULL) |
nentries = (PTR *) (*htab->alloc_with_arg_f) (htab->alloc_arg, nsize, |
sizeof (PTR *)); |
else |
nentries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR *)); |
if (nentries == NULL) |
return 0; |
htab->entries = nentries; |
htab->size = nsize; |
htab->size_prime_index = nindex; |
htab->n_elements -= htab->n_deleted; |
htab->n_deleted = 0; |
|
p = oentries; |
do |
{ |
PTR x = *p; |
|
if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY) |
{ |
PTR *q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x)); |
|
*q = x; |
} |
|
p++; |
} |
while (p < olimit); |
|
if (htab->free_f != NULL) |
(*htab->free_f) (oentries); |
else if (htab->free_with_arg_f != NULL) |
(*htab->free_with_arg_f) (htab->alloc_arg, oentries); |
return 1; |
} |
|
/* This function searches for a hash table entry equal to the given |
element. It cannot be used to insert or delete an element. */ |
|
PTR |
htab_find_with_hash (htab_t htab, const PTR element, hashval_t hash) |
{ |
hashval_t index, hash2; |
size_t size; |
PTR entry; |
|
htab->searches++; |
size = htab_size (htab); |
index = htab_mod (hash, htab); |
|
entry = htab->entries[index]; |
if (entry == HTAB_EMPTY_ENTRY |
|| (entry != HTAB_DELETED_ENTRY && (*htab->eq_f) (entry, element))) |
return entry; |
|
hash2 = htab_mod_m2 (hash, htab); |
for (;;) |
{ |
htab->collisions++; |
index += hash2; |
if (index >= size) |
index -= size; |
|
entry = htab->entries[index]; |
if (entry == HTAB_EMPTY_ENTRY |
|| (entry != HTAB_DELETED_ENTRY && (*htab->eq_f) (entry, element))) |
return entry; |
} |
} |
|
/* Like htab_find_slot_with_hash, but compute the hash value from the |
element. */ |
|
PTR |
htab_find (htab_t htab, const PTR element) |
{ |
return htab_find_with_hash (htab, element, (*htab->hash_f) (element)); |
} |
|
/* This function searches for a hash table slot containing an entry |
equal to the given element. To delete an entry, call this with |
insert=NO_INSERT, then call htab_clear_slot on the slot returned |
(possibly after doing some checks). To insert an entry, call this |
with insert=INSERT, then write the value you want into the returned |
slot. When inserting an entry, NULL may be returned if memory |
allocation fails. */ |
|
PTR * |
htab_find_slot_with_hash (htab_t htab, const PTR element, |
hashval_t hash, enum insert_option insert) |
{ |
PTR *first_deleted_slot; |
hashval_t index, hash2; |
size_t size; |
PTR entry; |
|
size = htab_size (htab); |
if (insert == INSERT && size * 3 <= htab->n_elements * 4) |
{ |
if (htab_expand (htab) == 0) |
return NULL; |
size = htab_size (htab); |
} |
|
index = htab_mod (hash, htab); |
|
htab->searches++; |
first_deleted_slot = NULL; |
|
entry = htab->entries[index]; |
if (entry == HTAB_EMPTY_ENTRY) |
goto empty_entry; |
else if (entry == HTAB_DELETED_ENTRY) |
first_deleted_slot = &htab->entries[index]; |
else if ((*htab->eq_f) (entry, element)) |
return &htab->entries[index]; |
|
hash2 = htab_mod_m2 (hash, htab); |
for (;;) |
{ |
htab->collisions++; |
index += hash2; |
if (index >= size) |
index -= size; |
|
entry = htab->entries[index]; |
if (entry == HTAB_EMPTY_ENTRY) |
goto empty_entry; |
else if (entry == HTAB_DELETED_ENTRY) |
{ |
if (!first_deleted_slot) |
first_deleted_slot = &htab->entries[index]; |
} |
else if ((*htab->eq_f) (entry, element)) |
return &htab->entries[index]; |
} |
|
empty_entry: |
if (insert == NO_INSERT) |
return NULL; |
|
if (first_deleted_slot) |
{ |
htab->n_deleted--; |
*first_deleted_slot = HTAB_EMPTY_ENTRY; |
return first_deleted_slot; |
} |
|
htab->n_elements++; |
return &htab->entries[index]; |
} |
|
/* Like htab_find_slot_with_hash, but compute the hash value from the |
element. */ |
|
PTR * |
htab_find_slot (htab_t htab, const PTR element, enum insert_option insert) |
{ |
return htab_find_slot_with_hash (htab, element, (*htab->hash_f) (element), |
insert); |
} |
|
/* This function deletes an element with the given value from hash |
table (the hash is computed from the element). If there is no matching |
element in the hash table, this function does nothing. */ |
|
void |
htab_remove_elt (htab_t htab, PTR element) |
{ |
htab_remove_elt_with_hash (htab, element, (*htab->hash_f) (element)); |
} |
|
|
/* This function deletes an element with the given value from hash |
table. If there is no matching element in the hash table, this |
function does nothing. */ |
|
void |
htab_remove_elt_with_hash (htab_t htab, PTR element, hashval_t hash) |
{ |
PTR *slot; |
|
slot = htab_find_slot_with_hash (htab, element, hash, NO_INSERT); |
if (*slot == HTAB_EMPTY_ENTRY) |
return; |
|
if (htab->del_f) |
(*htab->del_f) (*slot); |
|
*slot = HTAB_DELETED_ENTRY; |
htab->n_deleted++; |
} |
|
/* This function clears a specified slot in a hash table. It is |
useful when you've already done the lookup and don't want to do it |
again. */ |
|
void |
htab_clear_slot (htab_t htab, PTR *slot) |
{ |
if (slot < htab->entries || slot >= htab->entries + htab_size (htab) |
|| *slot == HTAB_EMPTY_ENTRY || *slot == HTAB_DELETED_ENTRY) |
abort (); |
|
if (htab->del_f) |
(*htab->del_f) (*slot); |
|
*slot = HTAB_DELETED_ENTRY; |
htab->n_deleted++; |
} |
|
/* This function scans over the entire hash table calling |
CALLBACK for each live entry. If CALLBACK returns false, |
the iteration stops. INFO is passed as CALLBACK's second |
argument. */ |
|
void |
htab_traverse_noresize (htab_t htab, htab_trav callback, PTR info) |
{ |
PTR *slot; |
PTR *limit; |
|
slot = htab->entries; |
limit = slot + htab_size (htab); |
|
do |
{ |
PTR x = *slot; |
|
if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY) |
if (!(*callback) (slot, info)) |
break; |
} |
while (++slot < limit); |
} |
|
/* Like htab_traverse_noresize, but does resize the table when it is |
too empty to improve effectivity of subsequent calls. */ |
|
void |
htab_traverse (htab_t htab, htab_trav callback, PTR info) |
{ |
size_t size = htab_size (htab); |
if (htab_elements (htab) * 8 < size && size > 32) |
htab_expand (htab); |
|
htab_traverse_noresize (htab, callback, info); |
} |
|
/* Return the fraction of fixed collisions during all work with given |
hash table. */ |
|
double |
htab_collisions (htab_t htab) |
{ |
if (htab->searches == 0) |
return 0.0; |
|
return (double) htab->collisions / (double) htab->searches; |
} |
|
/* Hash P as a null-terminated string. |
|
Copied from gcc/hashtable.c. Zack had the following to say with respect |
to applicability, though note that unlike hashtable.c, this hash table |
implementation re-hashes rather than chain buckets. |
|
http://gcc.gnu.org/ml/gcc-patches/2001-08/msg01021.html |
From: Zack Weinberg <zackw@panix.com> |
Date: Fri, 17 Aug 2001 02:15:56 -0400 |
|
I got it by extracting all the identifiers from all the source code |
I had lying around in mid-1999, and testing many recurrences of |
the form "H_n = H_{n-1} * K + c_n * L + M" where K, L, M were either |
prime numbers or the appropriate identity. This was the best one. |
I don't remember exactly what constituted "best", except I was |
looking at bucket-length distributions mostly. |
|
So it should be very good at hashing identifiers, but might not be |
as good at arbitrary strings. |
|
I'll add that it thoroughly trounces the hash functions recommended |
for this use at http://burtleburtle.net/bob/hash/index.html, both |
on speed and bucket distribution. I haven't tried it against the |
function they just started using for Perl's hashes. */ |
|
hashval_t |
htab_hash_string (const PTR p) |
{ |
const unsigned char *str = (const unsigned char *) p; |
hashval_t r = 0; |
unsigned char c; |
|
while ((c = *str++) != 0) |
r = r * 67 + c - 113; |
|
return r; |
} |
|
/* DERIVED FROM: |
-------------------------------------------------------------------- |
lookup2.c, by Bob Jenkins, December 1996, Public Domain. |
hash(), hash2(), hash3, and mix() are externally useful functions. |
Routines to test the hash are included if SELF_TEST is defined. |
You can use this free for any purpose. It has no warranty. |
-------------------------------------------------------------------- |
*/ |
|
/* |
-------------------------------------------------------------------- |
mix -- mix 3 32-bit values reversibly. |
For every delta with one or two bit set, and the deltas of all three |
high bits or all three low bits, whether the original value of a,b,c |
is almost all zero or is uniformly distributed, |
* If mix() is run forward or backward, at least 32 bits in a,b,c |
have at least 1/4 probability of changing. |
* If mix() is run forward, every bit of c will change between 1/3 and |
2/3 of the time. (Well, 22/100 and 78/100 for some 2-bit deltas.) |
mix() was built out of 36 single-cycle latency instructions in a |
structure that could supported 2x parallelism, like so: |
a -= b; |
a -= c; x = (c>>13); |
b -= c; a ^= x; |
b -= a; x = (a<<8); |
c -= a; b ^= x; |
c -= b; x = (b>>13); |
... |
Unfortunately, superscalar Pentiums and Sparcs can't take advantage |
of that parallelism. They've also turned some of those single-cycle |
latency instructions into multi-cycle latency instructions. Still, |
this is the fastest good hash I could find. There were about 2^^68 |
to choose from. I only looked at a billion or so. |
-------------------------------------------------------------------- |
*/ |
/* same, but slower, works on systems that might have 8 byte hashval_t's */ |
#define mix(a,b,c) \ |
{ \ |
a -= b; a -= c; a ^= (c>>13); \ |
b -= c; b -= a; b ^= (a<< 8); \ |
c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \ |
a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \ |
b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \ |
c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \ |
a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \ |
b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \ |
c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \ |
} |
|
/* |
-------------------------------------------------------------------- |
hash() -- hash a variable-length key into a 32-bit value |
k : the key (the unaligned variable-length array of bytes) |
len : the length of the key, counting by bytes |
level : can be any 4-byte value |
Returns a 32-bit value. Every bit of the key affects every bit of |
the return value. Every 1-bit and 2-bit delta achieves avalanche. |
About 36+6len instructions. |
|
The best hash table sizes are powers of 2. There is no need to do |
mod a prime (mod is sooo slow!). If you need less than 32 bits, |
use a bitmask. For example, if you need only 10 bits, do |
h = (h & hashmask(10)); |
In which case, the hash table should have hashsize(10) elements. |
|
If you are hashing n strings (ub1 **)k, do it like this: |
for (i=0, h=0; i<n; ++i) h = hash( k[i], len[i], h); |
|
By Bob Jenkins, 1996. bob_jenkins@burtleburtle.net. You may use this |
code any way you wish, private, educational, or commercial. It's free. |
|
See http://burtleburtle.net/bob/hash/evahash.html |
Use for hash table lookup, or anything where one collision in 2^32 is |
acceptable. Do NOT use for cryptographic purposes. |
-------------------------------------------------------------------- |
*/ |
|
hashval_t |
iterative_hash (const PTR k_in /* the key */, |
register size_t length /* the length of the key */, |
register hashval_t initval /* the previous hash, or |
an arbitrary value */) |
{ |
register const unsigned char *k = (const unsigned char *)k_in; |
register hashval_t a,b,c,len; |
|
/* Set up the internal state */ |
len = length; |
a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */ |
c = initval; /* the previous hash value */ |
|
/*---------------------------------------- handle most of the key */ |
#ifndef WORDS_BIGENDIAN |
/* On a little-endian machine, if the data is 4-byte aligned we can hash |
by word for better speed. This gives nondeterministic results on |
big-endian machines. */ |
if (sizeof (hashval_t) == 4 && (((size_t)k)&3) == 0) |
while (len >= 12) /* aligned */ |
{ |
a += *(hashval_t *)(k+0); |
b += *(hashval_t *)(k+4); |
c += *(hashval_t *)(k+8); |
mix(a,b,c); |
k += 12; len -= 12; |
} |
else /* unaligned */ |
#endif |
while (len >= 12) |
{ |
a += (k[0] +((hashval_t)k[1]<<8) +((hashval_t)k[2]<<16) +((hashval_t)k[3]<<24)); |
b += (k[4] +((hashval_t)k[5]<<8) +((hashval_t)k[6]<<16) +((hashval_t)k[7]<<24)); |
c += (k[8] +((hashval_t)k[9]<<8) +((hashval_t)k[10]<<16)+((hashval_t)k[11]<<24)); |
mix(a,b,c); |
k += 12; len -= 12; |
} |
|
/*------------------------------------- handle the last 11 bytes */ |
c += length; |
switch(len) /* all the case statements fall through */ |
{ |
case 11: c+=((hashval_t)k[10]<<24); |
case 10: c+=((hashval_t)k[9]<<16); |
case 9 : c+=((hashval_t)k[8]<<8); |
/* the first byte of c is reserved for the length */ |
case 8 : b+=((hashval_t)k[7]<<24); |
case 7 : b+=((hashval_t)k[6]<<16); |
case 6 : b+=((hashval_t)k[5]<<8); |
case 5 : b+=k[4]; |
case 4 : a+=((hashval_t)k[3]<<24); |
case 3 : a+=((hashval_t)k[2]<<16); |
case 2 : a+=((hashval_t)k[1]<<8); |
case 1 : a+=k[0]; |
/* case 0: nothing left to add */ |
} |
mix(a,b,c); |
/*-------------------------------------------- report the result */ |
return c; |
} |
|
/* Returns a hash code for pointer P. Simplified version of evahash */ |
|
static hashval_t |
hash_pointer (const PTR p) |
{ |
intptr_t v = (intptr_t) p; |
unsigned a, b, c; |
|
a = b = 0x9e3779b9; |
a += v >> (sizeof (intptr_t) * CHAR_BIT / 2); |
b += v & (((intptr_t) 1 << (sizeof (intptr_t) * CHAR_BIT / 2)) - 1); |
c = 0x42135234; |
mix (a, b, c); |
return c; |
} |