gallium: Unify reference counting.

The core reference counting code is centralized in p_refcnt.h.

This has some consequences related to struct pipe_buffer:

* The screen member of struct pipe_buffer must be initialized, or
  pipe_buffer_reference() will crash trying to destroy a buffer with reference
  count 0. u_simple_screen takes care of this, but I may have missed some of
  the drivers not using it.
* Except for rare exceptions deep in winsys code, buffers must always be
  allocated via pipe_buffer_create() or via screen->*buffer_create() rather
  than via winsys->*buffer_create().

1 files changed, 84 insertions, 0 deletions

diff --git a/src/gallium/include/pipe/p_refcnt.h b/src/gallium/include/pipe/p_refcnt.h
new file mode 100644
index 0000000000..50b7aa90ef
--- /dev/null
+++ b/src/gallium/include/pipe/p_refcnt.h
@@ -0,0 +1,84 @@
+/**************************************************************************
+ * 
+ * Copyright 2009 VMware, Inc.
+ * All Rights Reserved.
+ * 
+ * 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, sub license, 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 (including the
+ * next paragraph) 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 NON-INFRINGEMENT.
+ * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS 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.
+ * 
+ **************************************************************************/
+
+#ifndef P_REFCNT_H
+#define P_REFCNT_H
+
+
+#include "p_defines.h"
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+struct pipe_reference
+{
+   unsigned count;
+};
+
+
+static INLINE void
+pipe_reference_init(struct pipe_reference *reference, unsigned count)
+{
+   reference->count = count;
+}
+
+
+/**
+ * Set 'ptr' to point to 'reference' and update reference counting.
+ * The old thing pointed to, if any, will be unreferenced first.
+ * 'reference' may be NULL.
+ *
+ * XXX: thread safety issues!
+ */
+static INLINE bool
+pipe_reference(struct pipe_reference **ptr, struct pipe_reference *reference)
+{
+   bool destroy = FALSE;
+
+   /* bump the reference.count first */
+   if (reference) {
+      assert(reference->count);
+      reference->count++;
+   }
+
+   if (*ptr) {
+      assert((*ptr)->count);
+      if (--(*ptr)->count == 0) {
+         destroy = TRUE;
+      }
+   }
+
+   *ptr = reference;
+
+   return destroy;
+}
+
+
+#endif /* P_REFCNT_H */