IMPORT: lru: import simple ebtree-based LRU functions
This will be usable to implement some maps/acl caches for heavy datasets
loaded from files (mostly regex-based but in general anything that cannot
be indexed in a tree).
diff --git a/src/lru.c b/src/lru.c
new file mode 100644
index 0000000..bdb525d
--- /dev/null
+++ b/src/lru.c
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+/*
+ * Copyright (C) 2015 Willy Tarreau <w@1wt.eu>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <import/lru.h>
+
+/* Minimal list manipulation macros for lru64_list */
+#define LIST_ADD(lh, el) ({ (el)->n = (lh)->n; (el)->n->p = (lh)->n = (el); (el)->p = (lh); })
+#define LIST_DEL(el) ({ (el)->n->p = (el)->p; (el)->p->n = (el)->n; })
+
+/* Get key <key> from LRU cache <lru> for use with domain <domain> whose data's
+ * current revision is <revision>. If the key doesn't exist it's first created
+ * with ->domain = NULL. The caller detects this situation by checking ->domain
+ * and must perform the operation to be cached then call lru64_commit() to
+ * complete the operation. A lock (mutex or spinlock) may be added around the
+ * function to permit use in a multi-threaded environment. The function may
+ * return NULL upon memory allocation failure.
+ */
+struct lru64 *lru64_get(unsigned long long key, struct lru64_head *lru,
+ void *domain, unsigned long long revision)
+{
+ struct eb64_node *node;
+ struct lru64 *elem;
+
+ if (!lru->spare) {
+ if (!lru->cache_size)
+ return NULL;
+ lru->spare = malloc(sizeof(*lru->spare));
+ if (!lru->spare)
+ return NULL;
+ lru->spare->domain = NULL;
+ }
+
+ /* Lookup or insert */
+ lru->spare->node.key = key;
+ node = __eb64_insert(&lru->keys, &lru->spare->node);
+ elem = container_of(node, typeof(*elem), node);
+
+ if (elem != lru->spare) {
+ /* Existing entry found, check validity then move it at the
+ * head of the LRU list.
+ */
+ if (elem->domain == domain && elem->revision == revision) {
+ LIST_DEL(&elem->lru);
+ LIST_ADD(&lru->list, &elem->lru);
+ return elem;
+ }
+
+ if (!elem->domain)
+ return NULL; // currently locked
+
+ /* recycle this entry */
+ LIST_DEL(&elem->lru);
+ }
+ else {
+ /* New entry inserted, initialize and move to the head of the
+ * LRU list, and lock it until commit.
+ */
+ lru->cache_usage++;
+ lru->spare = NULL; // used, need a new one next time
+ }
+
+ elem->domain = NULL;
+ LIST_ADD(&lru->list, &elem->lru);
+
+ if (lru->cache_usage > lru->cache_size) {
+ /* try to kill oldest entry */
+ struct lru64 *old;
+
+ old = container_of(lru->list.p, typeof(*old), lru);
+ if (old->domain) {
+ /* not locked */
+ LIST_DEL(&old->lru);
+ __eb64_delete(&old->node);
+ if (!lru->spare)
+ lru->spare = old;
+ else
+ free(old);
+ lru->cache_usage--;
+ }
+ }
+ return elem;
+}
+
+/* Commit element <elem> with data <data>, domain <domain> and revision
+ * <revision>. <elem> is checked for NULL so that it's possible to call it
+ * with the result from a call to lru64_get(). The caller might lock it using a
+ * spinlock or mutex shared with the one around lru64_get().
+ */
+void lru64_commit(struct lru64 *elem, void *data, void *domain, unsigned long long revision)
+{
+ if (!elem)
+ return;
+
+ elem->data = data;
+ elem->revision = revision;
+ elem->domain = domain;
+}
+
+/* Create a new LRU cache of <size> entries. Returns the new cache or NULL in
+ * case of allocation failure.
+ */
+struct lru64_head *lru64_new(int size)
+{
+ struct lru64_head *lru;
+
+ lru = malloc(sizeof(*lru));
+ if (lru) {
+ lru->list.p = lru->list.n = &lru->list;
+ lru->keys = EB_ROOT_UNIQUE;
+ lru->spare = NULL;
+ lru->cache_size = size;
+ lru->cache_usage = 0;
+ }
+ return lru;
+}
+
+/* Tries to destroy the LRU cache <lru>. Returns the number of locked entries
+ * that prevent it from being destroyed, or zero meaning everything was done.
+ */
+int lru64_destroy(struct lru64_head *lru)
+{
+ struct lru64 *elem, *next;
+
+ if (!lru)
+ return 0;
+
+ elem = container_of(lru->list.p, typeof(*elem), lru);
+ while (&elem->lru != &lru->list) {
+ next = container_of(elem->lru.p, typeof(*next), lru);
+ if (elem->domain) {
+ /* not locked */
+ LIST_DEL(&elem->lru);
+ eb64_delete(&elem->node);
+ free(elem);
+ lru->cache_usage--;
+ lru->cache_size--;
+ }
+ elem = next;
+ }
+
+ if (lru->cache_usage)
+ return lru->cache_usage;
+
+ free(lru);
+ return 0;
+}
+
+/* The code below is just for validation and performance testing. It's an
+ * example of a function taking some time to return results that could be
+ * cached.
+ */
+#ifdef STANDALONE
+
+#include <stdio.h>
+
+static unsigned int misses;
+
+static unsigned long long sum(unsigned long long x)
+{
+#ifndef TEST_LRU_FAST_OPERATION
+ if (x < 1)
+ return 0;
+ return x + sum(x * 99 / 100 - 1);
+#else
+ return (x << 16) - (x << 8) - 1;
+#endif
+}
+
+static long get_value(struct lru64_head *lru, long a)
+{
+ struct lru64 *item;
+
+ if (lru) {
+ item = lru64_get(a, lru, lru, 0);
+ if (item && item->domain)
+ return (long)item->data;
+ }
+ misses++;
+ /* do the painful work here */
+ a = sum(a);
+ if (item)
+ lru64_commit(item, (void *)a, lru, 0);
+ return a;
+}
+
+/* pass #of loops in argv[1] and set argv[2] to something to use the LRU */
+int main(int argc, char **argv)
+{
+ struct lru64_head *lru = NULL;
+ long long ret;
+ int total, loops;
+
+ if (argc < 2) {
+ printf("Need a number of rounds and optionally an LRU cache size (0..65536)\n");
+ exit(1);
+ }
+
+ total = atoi(argv[1]);
+
+ if (argc > 2) /* cache size */
+ lru = lru64_new(atoi(argv[2]));
+
+ ret = 0;
+ for (loops = 0; loops < total; loops++) {
+ ret += get_value(lru, rand() & 65535);
+ }
+ /* just for accuracy control */
+ printf("ret=%llx, hits=%d, misses=%d (%d %% hits)\n", ret, total-misses, misses, (int)((float)(total-misses) * 100.0 / total));
+
+ while (lru64_destroy(lru));
+
+ return 0;
+}
+
+#endif