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Annotation of embedaddon/rsync/hashtable.c, revision 1.1

1.1     ! misho       1: /*
        !             2:  * Routines to provide a memory-efficient hashtable.
        !             3:  *
        !             4:  * Copyright (C) 2007-2009 Wayne Davison
        !             5:  *
        !             6:  * This program is free software; you can redistribute it and/or modify
        !             7:  * it under the terms of the GNU General Public License as published by
        !             8:  * the Free Software Foundation; either version 3 of the License, or
        !             9:  * (at your option) any later version.
        !            10:  *
        !            11:  * This program is distributed in the hope that it will be useful,
        !            12:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
        !            13:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        !            14:  * GNU General Public License for more details.
        !            15:  *
        !            16:  * You should have received a copy of the GNU General Public License along
        !            17:  * with this program; if not, visit the http://fsf.org website.
        !            18:  */
        !            19: 
        !            20: #include "rsync.h"
        !            21: 
        !            22: #define HASH_LOAD_LIMIT(size) ((size)*3/4)
        !            23: 
        !            24: struct hashtable *hashtable_create(int size, int key64)
        !            25: {
        !            26:        struct hashtable *tbl;
        !            27:        int node_size = key64 ? sizeof (struct ht_int64_node)
        !            28:                              : sizeof (struct ht_int32_node);
        !            29: 
        !            30:        /* Pick a power of 2 that can hold the requested size. */
        !            31:        if (size & (size-1) || size < 16) {
        !            32:                int req = size;
        !            33:                size = 16;
        !            34:                while (size < req)
        !            35:                        size *= 2;
        !            36:        }
        !            37: 
        !            38:        if (!(tbl = new(struct hashtable))
        !            39:         || !(tbl->nodes = new_array0(char, size * node_size)))
        !            40:                out_of_memory("hashtable_create");
        !            41:        tbl->size = size;
        !            42:        tbl->entries = 0;
        !            43:        tbl->node_size = node_size;
        !            44:        tbl->key64 = key64 ? 1 : 0;
        !            45: 
        !            46:        return tbl;
        !            47: }
        !            48: 
        !            49: void hashtable_destroy(struct hashtable *tbl)
        !            50: {
        !            51:        free(tbl->nodes);
        !            52:        free(tbl);
        !            53: }
        !            54: 
        !            55: /* This returns the node for the indicated key, either newly created or
        !            56:  * already existing.  Returns NULL if not allocating and not found. */
        !            57: void *hashtable_find(struct hashtable *tbl, int64 key, int allocate_if_missing)
        !            58: {
        !            59:        int key64 = tbl->key64;
        !            60:        struct ht_int32_node *node;
        !            61:        uint32 ndx;
        !            62: 
        !            63:        if (key64 ? key == 0 : (int32)key == 0) {
        !            64:                rprintf(FERROR, "Internal hashtable error: illegal key supplied!\n");
        !            65:                exit_cleanup(RERR_MESSAGEIO);
        !            66:        }
        !            67: 
        !            68:        if (allocate_if_missing && tbl->entries > HASH_LOAD_LIMIT(tbl->size)) {
        !            69:                void *old_nodes = tbl->nodes;
        !            70:                int size = tbl->size * 2;
        !            71:                int i;
        !            72: 
        !            73:                if (!(tbl->nodes = new_array0(char, size * tbl->node_size)))
        !            74:                        out_of_memory("hashtable_node");
        !            75:                tbl->size = size;
        !            76:                tbl->entries = 0;
        !            77: 
        !            78:                for (i = size / 2; i-- > 0; ) {
        !            79:                        struct ht_int32_node *move_node = HT_NODE(tbl, old_nodes, i);
        !            80:                        int64 move_key = HT_KEY(move_node, key64);
        !            81:                        if (move_key == 0)
        !            82:                                continue;
        !            83:                        node = hashtable_find(tbl, move_key, 1);
        !            84:                        node->data = move_node->data;
        !            85:                }
        !            86: 
        !            87:                free(old_nodes);
        !            88:        }
        !            89: 
        !            90:        if (!key64) {
        !            91:                /* Based on Jenkins One-at-a-time hash. */
        !            92:                uchar buf[4], *keyp = buf;
        !            93:                int i;
        !            94: 
        !            95:                SIVALu(buf, 0, key);
        !            96:                for (ndx = 0, i = 0; i < 4; i++) {
        !            97:                        ndx += keyp[i];
        !            98:                        ndx += (ndx << 10);
        !            99:                        ndx ^= (ndx >> 6);
        !           100:                }
        !           101:                ndx += (ndx << 3);
        !           102:                ndx ^= (ndx >> 11);
        !           103:                ndx += (ndx << 15);
        !           104:        } else {
        !           105:                /* Based on Jenkins hashword() from lookup3.c. */
        !           106:                uint32 a, b, c;
        !           107: 
        !           108:                /* Set up the internal state */
        !           109:                a = b = c = 0xdeadbeef + (8 << 2);
        !           110: 
        !           111: #define rot(x,k) (((x)<<(k)) ^ ((x)>>(32-(k))))
        !           112: #if SIZEOF_INT64 >= 8
        !           113:                b += (uint32)(key >> 32);
        !           114: #endif
        !           115:                a += (uint32)key;
        !           116:                c ^= b; c -= rot(b, 14);
        !           117:                a ^= c; a -= rot(c, 11);
        !           118:                b ^= a; b -= rot(a, 25);
        !           119:                c ^= b; c -= rot(b, 16);
        !           120:                a ^= c; a -= rot(c, 4);
        !           121:                b ^= a; b -= rot(a, 14);
        !           122:                c ^= b; c -= rot(b, 24);
        !           123: #undef rot
        !           124:                ndx = c;
        !           125:        }
        !           126: 
        !           127:        /* If it already exists, return the node.  If we're not
        !           128:         * allocating, return NULL if the key is not found. */
        !           129:        while (1) {
        !           130:                int64 nkey;
        !           131: 
        !           132:                ndx &= tbl->size - 1;
        !           133:                node = HT_NODE(tbl, tbl->nodes, ndx);
        !           134:                nkey = HT_KEY(node, key64);
        !           135: 
        !           136:                if (nkey == key)
        !           137:                        return node;
        !           138:                if (nkey == 0) {
        !           139:                        if (!allocate_if_missing)
        !           140:                                return NULL;
        !           141:                        break;
        !           142:                }
        !           143:                ndx++;
        !           144:        }
        !           145: 
        !           146:        /* Take over this empty spot and then return the node. */
        !           147:        if (key64)
        !           148:                ((struct ht_int64_node*)node)->key = key;
        !           149:        else
        !           150:                node->key = (int32)key;
        !           151:        tbl->entries++;
        !           152:        return node;
        !           153: }