shared: split mempool implementation from hashmaps

1 files changed, 94 insertions, 0 deletions

diff --git a/src/shared/mempool.c b/src/shared/mempool.c
new file mode 100644
index 0000000000..b39a37f2db
--- /dev/null
+++ b/src/shared/mempool.c
@@ -0,0 +1,94 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010-2014 Lennart Poettering
+  Copyright 2014 Michal Schmidt
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd 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
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "mempool.h"
+#include "macro.h"
+#include "util.h"
+
+struct pool {
+        struct pool *next;
+        unsigned n_tiles;
+        unsigned n_used;
+};
+
+void* mempool_alloc_tile(struct mempool *mp) {
+        unsigned i;
+
+        /* When a tile is released we add it to the list and simply
+         * place the next pointer at its offset 0. */
+
+        assert(mp->tile_size >= sizeof(void*));
+        assert(mp->at_least > 0);
+
+        if (mp->freelist) {
+                void *r;
+
+                r = mp->freelist;
+                mp->freelist = * (void**) mp->freelist;
+                return r;
+        }
+
+        if (_unlikely_(!mp->first_pool) ||
+            _unlikely_(mp->first_pool->n_used >= mp->first_pool->n_tiles)) {
+                unsigned n;
+                size_t size;
+                struct pool *p;
+
+                n = mp->first_pool ? mp->first_pool->n_tiles : 0;
+                n = MAX(mp->at_least, n * 2);
+                size = PAGE_ALIGN(ALIGN(sizeof(struct pool)) + n*mp->tile_size);
+                n = (size - ALIGN(sizeof(struct pool))) / mp->tile_size;
+
+                p = malloc(size);
+                if (!p)
+                        return NULL;
+
+                p->next = mp->first_pool;
+                p->n_tiles = n;
+                p->n_used = 0;
+
+                mp->first_pool = p;
+        }
+
+        i = mp->first_pool->n_used++;
+
+        return ((uint8_t*) mp->first_pool) + ALIGN(sizeof(struct pool)) + i*mp->tile_size;
+}
+
+void mempool_free_tile(struct mempool *mp, void *p) {
+        * (void**) p = mp->freelist;
+        mp->freelist = p;
+}
+
+#ifdef VALGRIND
+
+void mempool_drop(struct mempool *mp) {
+        struct pool *p = mp->first_pool;
+        while (p) {
+                struct pool *n;
+                n = p->next;
+                free(p);
+                p = n;
+        }
+}
+
+#endif