Add a hash table for holding packages

Signed-off-by: Allan McRae <allan@archlinux.org>

1 files changed, 292 insertions, 0 deletions

diff --git a/lib/libalpm/pkghash.c b/lib/libalpm/pkghash.c
new file mode 100644
index 00000000..3ed6453f
--- /dev/null
+++ b/lib/libalpm/pkghash.c
@@ -0,0 +1,292 @@
+/*
+ *  pkghash.c
+ *
+ *  Copyright (c) 2011 Pacman Development Team <pacman-dev@archlinux.org>
+ *
+ *  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 2 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "pkghash.h"
+#include "util.h"
+#include "log.h"
+
+/* List of primes for possible sizes of hash tables.
+ *
+ * The maximum table size is the last prime under 1,000,000.  That is
+ * more than an order of magnitude greater than the number of packages
+ * in any Linux distribution.
+ */
+static const size_t prime_list[] =
+{
+	11ul, 13ul, 17ul, 19ul, 23ul, 29ul, 31ul, 37ul, 41ul, 43ul, 47ul,
+	53ul, 59ul, 61ul, 67ul, 71ul, 73ul, 79ul, 83ul, 89ul, 97ul, 103ul,
+	109ul, 113ul, 127ul, 137ul, 139ul, 149ul, 157ul, 167ul, 179ul, 193ul,
+	199ul, 211ul, 227ul, 241ul, 257ul, 277ul, 293ul, 313ul, 337ul, 359ul,
+	383ul, 409ul, 439ul, 467ul, 503ul, 541ul, 577ul, 619ul, 661ul, 709ul,
+	761ul, 823ul, 887ul, 953ul, 1031ul, 1109ul, 1193ul, 1289ul, 1381ul,
+	1493ul, 1613ul, 1741ul, 1879ul, 2029ul, 2179ul, 2357ul, 2549ul,
+	2753ul, 2971ul, 3209ul, 3469ul, 3739ul, 4027ul, 4349ul, 4703ul,
+	5087ul, 5503ul, 5953ul, 6427ul, 6949ul, 7517ul, 8123ul, 8783ul,
+	9497ul, 10273ul, 11113ul, 12011ul, 12983ul, 14033ul, 15173ul,
+	16411ul, 17749ul, 19183ul, 20753ul, 22447ul, 24281ul, 26267ul,
+	28411ul, 30727ul, 33223ul, 35933ul, 38873ul, 42043ul, 45481ul,
+	49201ul, 53201ul, 57557ul, 62233ul, 67307ul, 72817ul, 78779ul,
+	85229ul, 92203ul, 99733ul, 107897ul, 116731ul, 126271ul, 136607ul,
+	147793ul, 159871ul, 172933ul, 187091ul, 202409ul, 218971ul, 236897ul,
+	256279ul, 277261ul, 299951ul, 324503ul, 351061ul, 379787ul, 410857ul,
+	444487ul, 480881ul, 520241ul, 562841ul, 608903ul, 658753ul, 712697ul,
+	771049ul, 834181ul, 902483ul, 976369ul
+};
+
+/* Allocate a hash table with at least "size" buckets */
+pmpkghash_t *_alpm_pkghash_create(size_t size)
+{
+	pmpkghash_t *hash = NULL;
+	size_t i, loopsize;
+
+	MALLOC(hash, sizeof(pmpkghash_t), RET_ERR(PM_ERR_MEMORY, NULL));
+
+	hash->list = NULL;
+	hash->entries = 0;
+
+	loopsize = sizeof(prime_list) / sizeof(*prime_list);
+	for(i = 0; i < loopsize; i++) {
+		if(prime_list[i] > size) {
+			hash->buckets = prime_list[i];
+			break;
+		}
+	}
+
+	CALLOC(hash->hash_table, hash->buckets, sizeof(alpm_list_t*), \
+				free(hash); RET_ERR(PM_ERR_MEMORY, NULL));
+
+	return(hash);
+}
+
+/* Expand the hash table size to the next increment and rebin the entries */
+static pmpkghash_t *rehash(pmpkghash_t *oldhash)
+{
+	//pmpkghash_t *newhash;
+
+	/* TODO - calculate size of newhash */
+	/* Hash tables will need resized in two cases:
+	 *  - adding packages to the local database
+	 *  - poor estimation of the number of packages in sync database
+	 *
+	 * For small hash tables sizes (<500) the increase in size is by a
+	 * minimum of a factor of 2 for optimal rehash efficiency.  For
+	 * larger database sizes, this increase is reduced to avoid excess
+	 * memory allocation as both scenarios requiring a rehash should not
+	 * require a table size increase that large. */
+
+	//newhash = _alpm_pkghash_create(oldhash->buckets);
+
+	/* TODO - rebin entries */
+
+	//_alpm_pkghash_free(oldhash);
+
+	//return newhash;
+
+	printf("rehash needed!!!\n");
+	return(oldhash);
+}
+
+pmpkghash_t *_alpm_pkghash_add(pmpkghash_t *hash, pmpkg_t *pkg)
+{
+	alpm_list_t *ptr;
+	size_t position;
+
+	if(pkg == NULL || hash == NULL) {
+		return(hash);
+	}
+
+	if((hash->entries + 1) / MAX_HASH_LOAD > hash->buckets) {
+		hash = rehash(hash);
+	}
+
+	position = pkg->name_hash % hash->buckets;
+
+	/* collision resolution using open addressing with linear probing */
+	while((ptr = hash->hash_table[position]) != NULL) {
+		position = (position + 1) % hash->buckets;
+	}
+
+	ptr = calloc(1, sizeof(alpm_list_t));
+	if(ptr == NULL) {
+		return(hash);
+	}
+
+	ptr->data = pkg;
+	ptr->next = NULL;
+	ptr->prev = ptr;
+
+	hash->hash_table[position] = ptr;
+	hash->list = alpm_list_join(hash->list, ptr);
+	hash->entries += 1;
+
+	return(hash);
+}
+
+pmpkghash_t *_alpm_pkghash_add_sorted(pmpkghash_t *hash, pmpkg_t *pkg)
+{
+	if(!hash) {
+		return(_alpm_pkghash_add(hash, pkg));
+	}
+
+	alpm_list_t *ptr;
+	size_t position;
+
+	if((hash->entries + 1) / MAX_HASH_LOAD > hash->buckets) {
+		hash = rehash(hash);
+	}
+
+	position = pkg->name_hash % hash->buckets;
+
+	/* collision resolution using open addressing with linear probing */
+	while((ptr = hash->hash_table[position]) != NULL) {
+		position = (position + 1) % hash->buckets;
+	}
+
+	ptr = calloc(1, sizeof(alpm_list_t));
+	if(ptr == NULL) {
+		return(hash);
+	}
+
+	ptr->data = pkg;
+	ptr->next = NULL;
+	ptr->prev = ptr;
+
+	hash->hash_table[position] = ptr;
+	hash->list = alpm_list_mmerge(hash->list, ptr, _alpm_pkg_cmp);
+	hash->entries += 1;
+
+	return(hash);
+}
+
+/**
+ * @brief Remove a package from a pkghash.
+ *
+ * @param hash     the hash to remove the package from
+ * @param pkg      the package we are removing
+ * @param data     output parameter containing the removed item
+ *
+ * @return the resultant hash
+ */
+pmpkghash_t *_alpm_pkghash_remove(pmpkghash_t *hash, pmpkg_t *pkg, pmpkg_t *data)
+{
+	alpm_list_t *i;
+	size_t position;
+
+	if(pkg == NULL || hash == NULL) {
+		return(hash);
+	}
+
+	position = pkg->name_hash % hash->buckets;
+	while((i = hash->hash_table[position]) != NULL) {
+		pmpkg_t *info = i->data;
+
+		if(info->name_hash == pkg->name_hash &&
+					strcmp(info->name, pkg->name) == 0) {
+
+#if 0  /* Actually removing items is not a good idea with linear probing...  */
+			/* remove from list */
+			/* TODO - refactor with alpm_list_remove */
+			if(i == hash->list) {
+				/* Special case: removing the head node which has a back reference to
+				 * the tail node */
+				hash->list = i->next;
+				if(hash->list) {
+					hash->list->prev = i->prev;
+				}
+				i->prev = NULL;
+			} else if(i == hash->list->prev) {
+				/* Special case: removing the tail node, so we need to fix the back
+				 * reference on the head node. We also know tail != head. */
+				if(i->prev) {
+					/* i->next should always be null */
+					i->prev->next = i->next;
+					hash->list->prev = i->prev;
+					i->prev = NULL;
+				}
+			} else {
+				/* Normal case, non-head and non-tail node */
+				if(i->next) {
+					i->next->prev = i->prev;
+				}
+				if(i->prev) {
+					i->prev->next = i->next;
+				}
+			}
+
+			/* remove from hash */
+			data = info;
+			info = NULL;
+			free(i);
+			i = NULL;
+
+			hash->entries -= 1;
+#endif
+
+			/* fake removal - pkgname can not be blank so 0 hash is impossible */
+			info->name_hash = 0;
+
+			return(hash);
+		}
+
+		position = (position + 1) % hash->buckets;
+	}
+
+	return(hash);
+}
+
+void _alpm_pkghash_free(pmpkghash_t *hash)
+{
+	size_t i;
+	if(hash != NULL) {
+		for(i = 0; i < hash->buckets; i++) {
+			free(hash->hash_table[i]);
+		}
+		free(hash->hash_table);
+	}
+	free(hash);
+}
+
+pmpkg_t *_alpm_pkghash_find(pmpkghash_t *hash, const char *name)
+{
+	alpm_list_t *lp;
+	unsigned long name_hash;
+	size_t position;
+
+	ALPM_LOG_FUNC;
+
+	if(name == NULL || hash == NULL) {
+		return(NULL);
+	}
+
+	name_hash = _alpm_hash_sdbm(name);
+
+	position = name_hash % hash->buckets;
+
+	while((lp = hash->hash_table[position]) != NULL) {
+		pmpkg_t *info = lp->data;
+
+		if(info->name_hash == name_hash && strcmp(info->name, name) == 0) {
+			return(info);
+		}
+
+		position = (position + 1) % hash->buckets;
+	}
+
+	return(NULL);
+}