Return to hashtable.c CVS log

Up to [ELWIX - Embedded LightWeight unIX -] / embedaddon / rsync

rsync

    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: }