Make buffer structure sharable

Use stucture offsets instead of pointers so that we can share the buffer
structure between client and server.
We can then pass an fd wrapping the memory of the buffer to the client.
Add beginnings of a memory pool

spa/lib/memory.c

@@ -0,0 +1,141 @@
+/* Simple Plugin API
+ * Copyright (C) 2016 Wim Taymans <wim.taymans@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include <stdio.h>
+
+#include "spa/memory.h"
+
+#define MAX_POOLS       16
+#define MAX_MEMORIES    1024
+
+struct _SpaMemoryPool {
+  bool valid;
+  uint32_t id;
+  SpaMemory memories[MAX_MEMORIES];
+  unsigned int n_free;
+  uint32_t free_mem[MAX_MEMORIES];
+};
+
+static SpaMemoryPool pools[MAX_POOLS];
+
+static void
+spa_memory_pool_init (SpaMemoryPool *pool, uint32_t id)
+{
+  int i;
+
+  for (i = 0; i < MAX_MEMORIES; i++)
+    pool->free_mem[i] = MAX_MEMORIES - 1 - i;
+  pool->n_free = MAX_MEMORIES;
+  pool->id = id;
+  pool->valid = true;
+}
+
+void
+spa_memory_init (void)
+{
+  static bool initialized = false;
+
+  if (!initialized) {
+    spa_memory_pool_init (&pools[0], 0);
+    initialized = true;
+  }
+}
+
+uint32_t
+spa_memory_pool_get (uint32_t type)
+{
+  return pools[type].id;
+}
+
+uint32_t
+spa_memory_pool_new (void)
+{
+  int i;
+
+  for (i = 0; i < MAX_POOLS; i++) {
+    if (!pools[i].valid) {
+      spa_memory_pool_init (&pools[i], i);
+      return i;
+    }
+  }
+  return SPA_ID_INVALID;
+}
+
+void
+spa_memory_pool_free (uint32_t pool_id)
+{
+  pools[pool_id].valid = false;
+}
+
+SpaMemory *
+spa_memory_alloc (uint32_t pool_id)
+{
+  SpaMemory *mem;
+  SpaMemoryPool *pool;
+  uint32_t id;
+
+  if (pool_id >= MAX_POOLS || !pools[pool_id].valid)
+    return NULL;
+
+  pool = &pools[pool_id];
+
+  if (pool->n_free == 0)
+    return NULL;
+
+  id = pool->free_mem[pool->n_free - 1];
+  pool->n_free--;
+
+  mem = &pool->memories[id];
+  mem->refcount = 1;
+  mem->pool_id = pool_id;
+  mem->id = id;
+
+  return mem;
+}
+
+SpaResult
+spa_memory_free (uint32_t pool_id, uint32_t id)
+{
+  SpaMemoryPool *pool;
+
+  if (pool_id >= MAX_POOLS || !pools[pool_id].valid)
+    return SPA_RESULT_INVALID_ARGUMENTS;
+
+  pool = &pools[pool_id];
+  pool->free_mem[pool->n_free] = id;
+  pool->n_free++;
+
+  return SPA_RESULT_OK;
+}
+
+SpaMemory *
+spa_memory_find (uint32_t pool_id, uint32_t id)
+{
+  SpaMemoryPool *pool;
+
+  if (pool_id >= MAX_POOLS || !pools[pool_id].valid)
+    return NULL;
+
+  pool = &pools[pool_id];
+
+  if (id >= MAX_MEMORIES || pool->memories[id].refcount <= 0)
+    return NULL;
+
+  return &pool->memories[id];
+}