ralloc_adopt() reparents all children from one context to another.
Conceptually, ralloc_adopt(new_ctx, old_ctx) behaves like this
pseudocode:
foreach child of old_ctx:
ralloc_steal(new_ctx, child)
However, ralloc provides no way to iterate over a memory context's
children, and ralloc_adopt does this task more efficiently anyway.
One potential use of this is to implement a memory-sweeper pass: first,
steal all of a context's memory to a temporary context. Then, walk over
anything that should be kept, and ralloc_steal it back to the original
context. Finally, free the temporary context. This works when the
context is something that can't be freed (i.e. an important structure).
Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
---
src/util/ralloc.c | 26 ++++++++++++++++++++++++++
src/util/ralloc.h | 7 +++++++
2 files changed, 33 insertions(+)
diff --git a/src/util/ralloc.c b/src/util/ralloc.c
index 36bc61f..01719c8 100644
--- a/src/util/ralloc.c
+++ b/src/util/ralloc.c
@@ -271,6 +271,32 @@ ralloc_steal(const void *new_ctx, void *ptr)
add_child(parent, info);
}
+void
+ralloc_adopt(const void *new_ctx, void *old_ctx)
+{
+ ralloc_header *new_info, *old_info, *child;
+
+ if (unlikely(old_ctx == NULL))
+ return;
+
+ old_info = get_header(old_ctx);
+ new_info = get_header(new_ctx);
+
+ /* If there are no children, bail. */
+ if (unlikely(old_info->child == NULL))
+ return;
+
+ /* Set all the children's parent to new_ctx; get a pointer to the last
child. */
+ for (child = old_info->child; child->next != NULL; child = child->next) {
+ child->parent = new_info;
+ }
+
+ /* Connect the two lists together; parent them to new_ctx; make old_ctx
empty. */
+ child->next = new_info->child;
+ new_info->child = old_info->child;
+ old_info->child = NULL;
+}
+
void *
ralloc_parent(const void *ptr)
{
diff --git a/src/util/ralloc.h b/src/util/ralloc.h
index f088a36..01f102b 100644
--- a/src/util/ralloc.h
+++ b/src/util/ralloc.h
@@ -235,6 +235,13 @@ void ralloc_free(void *ptr);
void ralloc_steal(const void *new_ctx, void *ptr);
/**
+ * Reparent all children from one context to another.
+ *
+ * This effectively calls ralloc_steal(new_ctx, child) for all children of \p
old_ctx.
+ */
+void ralloc_adopt(const void *new_ctx, void *old_ctx);
+
+/**
* Return the given pointer's ralloc context.
*/
void *ralloc_parent(const void *ptr);
--
2.3.4
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