Rsync源码——HashTable相关

预定义代码：

struct hashtable {void *nodes;int32 size, entries;uint32 node_size;int key64;};struct ht_int32_node {void *data;int32 key;};struct ht_int64_node {void *data;int64 key;};#define HT_NODE(tbl, bkts, i) ((void*)((char*)(bkts) + (i)*(tbl)->node_size))#define HT_KEY(node, k64) ((k64)? ((struct ht_int64_node*)(node))->key \ : (int64)((struct ht_int32_node*)(node))->key)

hashtable.c:

/* * Routines to provide a memory-efficient hashtable. * * Copyright (C) 2007-2009 Wayne Davison * * This program 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 program 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, visit the http://fsf.org website. */#include "rsync.h"#define HASH_LOAD_LIMIT(size) ((size)*3/4)struct hashtable *hashtable_create(int size, int key64){struct hashtable *tbl;int node_size = key64 ? sizeof (struct ht_int64_node)      : sizeof (struct ht_int32_node);/* Pick a power of 2 that can hold the requested size. */if (size & (size-1) || size < 16) {int req = size;size = 16;while (size < req)size *= 2;}if (!(tbl = new(struct hashtable)) || !(tbl->nodes = new_array0(char, size * node_size)))out_of_memory("hashtable_create");tbl->size = size;tbl->entries = 0;tbl->node_size = node_size;tbl->key64 = key64 ? 1 : 0;return tbl;}void hashtable_destroy(struct hashtable *tbl){free(tbl->nodes);free(tbl);}/* This returns the node for the indicated key, either newly created or * already existing.  Returns NULL if not allocating and not found. */void *hashtable_find(struct hashtable *tbl, int64 key, int allocate_if_missing){int key64 = tbl->key64;struct ht_int32_node *node;uint32 ndx;if (key64 ? key == 0 : (int32)key == 0) {rprintf(FERROR, "Internal hashtable error: illegal key supplied!\n");exit_cleanup(RERR_MESSAGEIO);}if (allocate_if_missing && tbl->entries > HASH_LOAD_LIMIT(tbl->size)) {void *old_nodes = tbl->nodes;int size = tbl->size * 2;int i;if (!(tbl->nodes = new_array0(char, size * tbl->node_size)))out_of_memory("hashtable_node");tbl->size = size;tbl->entries = 0;for (i = size / 2; i-- > 0; ) {struct ht_int32_node *move_node = HT_NODE(tbl, old_nodes, i);int64 move_key = HT_KEY(move_node, key64);if (move_key == 0)continue;node = hashtable_find(tbl, move_key, 1);node->data = move_node->data;}free(old_nodes);}if (!key64) {/* Based on Jenkins One-at-a-time hash. */uchar buf[4], *keyp = buf;int i;SIVALu(buf, 0, key);for (ndx = 0, i = 0; i < 4; i++) {ndx += keyp[i];ndx += (ndx << 10);ndx ^= (ndx >> 6);}ndx += (ndx << 3);ndx ^= (ndx >> 11);ndx += (ndx << 15);} else {/* Based on Jenkins hashword() from lookup3.c. */uint32 a, b, c;/* Set up the internal state */a = b = c = 0xdeadbeef + (8 << 2);#define rot(x,k) (((x)<<(k)) ^ ((x)>>(32-(k))))#if SIZEOF_INT64 >= 8b += (uint32)(key >> 32);#endifa += (uint32)key;c ^= b; c -= rot(b, 14);a ^= c; a -= rot(c, 11);b ^= a; b -= rot(a, 25);c ^= b; c -= rot(b, 16);a ^= c; a -= rot(c, 4);b ^= a; b -= rot(a, 14);c ^= b; c -= rot(b, 24);#undef rotndx = c;}/* If it already exists, return the node.  If we're not * allocating, return NULL if the key is not found. */while (1) {int64 nkey;ndx &= tbl->size - 1;node = HT_NODE(tbl, tbl->nodes, ndx);nkey = HT_KEY(node, key64);if (nkey == key)return node;if (nkey == 0) {if (!allocate_if_missing)return NULL;break;}ndx++;}/* Take over this empty spot and then return the node. */if (key64)((struct ht_int64_node*)node)->key = key;elsenode->key = (int32)key;tbl->entries++;return node;}