443 lines
13 KiB
C
443 lines
13 KiB
C
/* An expandable hash tables datatype.
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Copyright (C) 1999-2016 Free Software Foundation, Inc.
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Contributed by Vladimir Makarov <vmakarov@cygnus.com>.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA. */
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/* The hash table code copied from include/hashtab.[hc] and adjusted,
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so that the hash table entries are in the flexible array at the end
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of the control structure, no callbacks are used and the elements in the
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table are of the hash_entry_type type.
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Before including this file, define hash_entry_type type and
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htab_alloc and htab_free functions. After including it, define
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htab_hash and htab_eq inline functions. */
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/* This package implements basic hash table functionality. It is possible
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to search for an entry, create an entry and destroy an entry.
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Elements in the table are generic pointers.
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The size of the table is not fixed; if the occupancy of the table
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grows too high the hash table will be expanded.
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The abstract data implementation is based on generalized Algorithm D
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from Knuth's book "The art of computer programming". Hash table is
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expanded by creation of new hash table and transferring elements from
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the old table to the new table. */
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/* The type for a hash code. */
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typedef unsigned int hashval_t;
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static inline hashval_t htab_hash (hash_entry_type);
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static inline bool htab_eq (hash_entry_type, hash_entry_type);
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/* This macro defines reserved value for empty table entry. */
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#define HTAB_EMPTY_ENTRY ((hash_entry_type) 0)
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/* This macro defines reserved value for table entry which contained
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a deleted element. */
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#define HTAB_DELETED_ENTRY ((hash_entry_type) 1)
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/* Hash tables are of the following type. The structure
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(implementation) of this type is not needed for using the hash
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tables. All work with hash table should be executed only through
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functions mentioned below. The size of this structure is subject to
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change. */
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struct htab {
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/* Current size (in entries) of the hash table. */
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size_t size;
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/* Current number of elements including also deleted elements. */
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size_t n_elements;
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/* Current number of deleted elements in the table. */
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size_t n_deleted;
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/* Current size (in entries) of the hash table, as an index into the
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table of primes. */
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unsigned int size_prime_index;
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/* Table itself. */
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hash_entry_type entries[];
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};
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typedef struct htab *htab_t;
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/* An enum saying whether we insert into the hash table or not. */
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enum insert_option {NO_INSERT, INSERT};
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/* Table of primes and multiplicative inverses.
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Note that these are not minimally reduced inverses. Unlike when generating
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code to divide by a constant, we want to be able to use the same algorithm
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all the time. All of these inverses (are implied to) have bit 32 set.
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For the record, the function that computed the table is in
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libiberty/hashtab.c. */
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struct prime_ent
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{
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hashval_t prime;
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hashval_t inv;
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hashval_t inv_m2; /* inverse of prime-2 */
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hashval_t shift;
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};
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static struct prime_ent const prime_tab[] = {
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{ 7, 0x24924925, 0x9999999b, 2 },
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{ 13, 0x3b13b13c, 0x745d1747, 3 },
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{ 31, 0x08421085, 0x1a7b9612, 4 },
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{ 61, 0x0c9714fc, 0x15b1e5f8, 5 },
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{ 127, 0x02040811, 0x0624dd30, 6 },
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{ 251, 0x05197f7e, 0x073260a5, 7 },
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{ 509, 0x01824366, 0x02864fc8, 8 },
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{ 1021, 0x00c0906d, 0x014191f7, 9 },
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{ 2039, 0x0121456f, 0x0161e69e, 10 },
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{ 4093, 0x00300902, 0x00501908, 11 },
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{ 8191, 0x00080041, 0x00180241, 12 },
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{ 16381, 0x000c0091, 0x00140191, 13 },
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{ 32749, 0x002605a5, 0x002a06e6, 14 },
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{ 65521, 0x000f00e2, 0x00110122, 15 },
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{ 131071, 0x00008001, 0x00018003, 16 },
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{ 262139, 0x00014002, 0x0001c004, 17 },
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{ 524287, 0x00002001, 0x00006001, 18 },
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{ 1048573, 0x00003001, 0x00005001, 19 },
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{ 2097143, 0x00004801, 0x00005801, 20 },
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{ 4194301, 0x00000c01, 0x00001401, 21 },
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{ 8388593, 0x00001e01, 0x00002201, 22 },
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{ 16777213, 0x00000301, 0x00000501, 23 },
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{ 33554393, 0x00001381, 0x00001481, 24 },
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{ 67108859, 0x00000141, 0x000001c1, 25 },
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{ 134217689, 0x000004e1, 0x00000521, 26 },
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{ 268435399, 0x00000391, 0x000003b1, 27 },
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{ 536870909, 0x00000019, 0x00000029, 28 },
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{ 1073741789, 0x0000008d, 0x00000095, 29 },
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{ 2147483647, 0x00000003, 0x00000007, 30 },
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/* Avoid "decimal constant so large it is unsigned" for 4294967291. */
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{ 0xfffffffb, 0x00000006, 0x00000008, 31 }
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};
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/* The following function returns an index into the above table of the
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nearest prime number which is greater than N, and near a power of two. */
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static unsigned int
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higher_prime_index (unsigned long n)
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{
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unsigned int low = 0;
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unsigned int high = sizeof(prime_tab) / sizeof(prime_tab[0]);
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while (low != high)
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{
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unsigned int mid = low + (high - low) / 2;
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if (n > prime_tab[mid].prime)
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low = mid + 1;
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else
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high = mid;
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}
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/* If we've run out of primes, abort. */
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if (n > prime_tab[low].prime)
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abort ();
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return low;
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}
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/* Return the current size of given hash table. */
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static inline size_t
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htab_size (htab_t htab)
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{
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return htab->size;
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}
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/* Return the current number of elements in given hash table. */
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static inline size_t
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htab_elements (htab_t htab)
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{
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return htab->n_elements - htab->n_deleted;
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}
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/* Return X % Y. */
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static inline hashval_t
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htab_mod_1 (hashval_t x, hashval_t y, hashval_t inv, int shift)
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{
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/* The multiplicative inverses computed above are for 32-bit types, and
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requires that we be able to compute a highpart multiply. */
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if (sizeof (hashval_t) * __CHAR_BIT__ <= 32)
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{
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hashval_t t1, t2, t3, t4, q, r;
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t1 = ((unsigned long long)x * inv) >> 32;
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t2 = x - t1;
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t3 = t2 >> 1;
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t4 = t1 + t3;
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q = t4 >> shift;
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r = x - (q * y);
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return r;
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}
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/* Otherwise just use the native division routines. */
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return x % y;
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}
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/* Compute the primary hash for HASH given HTAB's current size. */
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static inline hashval_t
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htab_mod (hashval_t hash, htab_t htab)
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{
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const struct prime_ent *p = &prime_tab[htab->size_prime_index];
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return htab_mod_1 (hash, p->prime, p->inv, p->shift);
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}
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/* Compute the secondary hash for HASH given HTAB's current size. */
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static inline hashval_t
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htab_mod_m2 (hashval_t hash, htab_t htab)
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{
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const struct prime_ent *p = &prime_tab[htab->size_prime_index];
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return 1 + htab_mod_1 (hash, p->prime - 2, p->inv_m2, p->shift);
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}
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/* Create hash table of size SIZE. */
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static htab_t
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htab_create (size_t size)
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{
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htab_t result;
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unsigned int size_prime_index;
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size_prime_index = higher_prime_index (size);
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size = prime_tab[size_prime_index].prime;
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result = (htab_t) htab_alloc (sizeof (struct htab)
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+ size * sizeof (hash_entry_type));
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result->size = size;
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result->n_elements = 0;
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result->n_deleted = 0;
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result->size_prime_index = size_prime_index;
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memset (result->entries, 0, size * sizeof (hash_entry_type));
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return result;
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}
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/* Similar to htab_find_slot, but without several unwanted side effects:
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- Does not call htab_eq when it finds an existing entry.
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- Does not change the count of elements in the hash table.
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This function also assumes there are no deleted entries in the table.
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HASH is the hash value for the element to be inserted. */
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static hash_entry_type *
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find_empty_slot_for_expand (htab_t htab, hashval_t hash)
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{
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hashval_t index = htab_mod (hash, htab);
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size_t size = htab_size (htab);
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hash_entry_type *slot = htab->entries + index;
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hashval_t hash2;
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if (*slot == HTAB_EMPTY_ENTRY)
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return slot;
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else if (*slot == HTAB_DELETED_ENTRY)
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abort ();
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hash2 = htab_mod_m2 (hash, htab);
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for (;;)
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{
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index += hash2;
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if (index >= size)
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index -= size;
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slot = htab->entries + index;
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if (*slot == HTAB_EMPTY_ENTRY)
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return slot;
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else if (*slot == HTAB_DELETED_ENTRY)
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abort ();
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}
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}
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/* The following function changes size of memory allocated for the
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entries and repeatedly inserts the table elements. The occupancy
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of the table after the call will be about 50%. Naturally the hash
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table must already exist. Remember also that the place of the
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table entries is changed. */
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static htab_t
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htab_expand (htab_t htab)
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{
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htab_t nhtab;
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hash_entry_type *olimit;
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hash_entry_type *p;
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size_t osize, elts;
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osize = htab->size;
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olimit = htab->entries + osize;
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elts = htab_elements (htab);
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/* Resize only when table after removal of unused elements is either
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too full or too empty. */
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if (elts * 2 > osize || (elts * 8 < osize && osize > 32))
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nhtab = htab_create (elts * 2);
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else
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nhtab = htab_create (osize - 1);
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nhtab->n_elements = htab->n_elements - htab->n_deleted;
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p = htab->entries;
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do
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{
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hash_entry_type x = *p;
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if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY)
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*find_empty_slot_for_expand (nhtab, htab_hash (x)) = x;
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p++;
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}
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while (p < olimit);
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htab_free (htab);
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return nhtab;
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}
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/* This function searches for a hash table entry equal to the given
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element. It cannot be used to insert or delete an element. */
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static hash_entry_type
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htab_find (htab_t htab, const hash_entry_type element)
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{
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hashval_t index, hash2, hash = htab_hash (element);
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size_t size;
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hash_entry_type entry;
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size = htab_size (htab);
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index = htab_mod (hash, htab);
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entry = htab->entries[index];
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if (entry == HTAB_EMPTY_ENTRY
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|| (entry != HTAB_DELETED_ENTRY && htab_eq (entry, element)))
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return entry;
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hash2 = htab_mod_m2 (hash, htab);
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for (;;)
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{
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index += hash2;
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if (index >= size)
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index -= size;
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entry = htab->entries[index];
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if (entry == HTAB_EMPTY_ENTRY
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|| (entry != HTAB_DELETED_ENTRY && htab_eq (entry, element)))
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return entry;
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}
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}
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/* This function searches for a hash table slot containing an entry
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equal to the given element. To delete an entry, call this with
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insert=NO_INSERT, then call htab_clear_slot on the slot returned
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(possibly after doing some checks). To insert an entry, call this
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with insert=INSERT, then write the value you want into the returned
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slot. */
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static hash_entry_type *
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htab_find_slot (htab_t *htabp, const hash_entry_type element,
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enum insert_option insert)
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{
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hash_entry_type *first_deleted_slot;
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hashval_t index, hash2, hash = htab_hash (element);
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size_t size;
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hash_entry_type entry;
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htab_t htab = *htabp;
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size = htab_size (htab);
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if (insert == INSERT && size * 3 <= htab->n_elements * 4)
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{
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htab = *htabp = htab_expand (htab);
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size = htab_size (htab);
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}
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index = htab_mod (hash, htab);
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first_deleted_slot = NULL;
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entry = htab->entries[index];
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if (entry == HTAB_EMPTY_ENTRY)
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goto empty_entry;
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else if (entry == HTAB_DELETED_ENTRY)
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first_deleted_slot = &htab->entries[index];
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else if (htab_eq (entry, element))
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return &htab->entries[index];
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hash2 = htab_mod_m2 (hash, htab);
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for (;;)
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{
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index += hash2;
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if (index >= size)
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index -= size;
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entry = htab->entries[index];
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if (entry == HTAB_EMPTY_ENTRY)
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goto empty_entry;
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else if (entry == HTAB_DELETED_ENTRY)
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{
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if (!first_deleted_slot)
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first_deleted_slot = &htab->entries[index];
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}
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else if (htab_eq (entry, element))
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return &htab->entries[index];
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}
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empty_entry:
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if (insert == NO_INSERT)
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return NULL;
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if (first_deleted_slot)
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{
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htab->n_deleted--;
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*first_deleted_slot = HTAB_EMPTY_ENTRY;
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return first_deleted_slot;
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}
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htab->n_elements++;
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return &htab->entries[index];
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}
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/* This function clears a specified slot in a hash table. It is
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useful when you've already done the lookup and don't want to do it
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again. */
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static inline void
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htab_clear_slot (htab_t htab, hash_entry_type *slot)
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{
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if (slot < htab->entries || slot >= htab->entries + htab_size (htab)
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|| *slot == HTAB_EMPTY_ENTRY || *slot == HTAB_DELETED_ENTRY)
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abort ();
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*slot = HTAB_DELETED_ENTRY;
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htab->n_deleted++;
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}
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/* Returns a hash code for pointer P. Simplified version of evahash */
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static inline hashval_t
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hash_pointer (const void *p)
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{
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uintptr_t v = (uintptr_t) p;
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if (sizeof (v) > sizeof (hashval_t))
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v ^= v >> (sizeof (uintptr_t) / 2 * __CHAR_BIT__);
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return v;
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}
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