Import talloc_stack into util library.

1 files changed, 130 insertions, 0 deletions

diff --git a/lib/util/talloc_stack.c b/lib/util/talloc_stack.c
new file mode 100644
index 0000000000..2722fb9676
--- /dev/null
+++ b/lib/util/talloc_stack.c
@@ -0,0 +1,130 @@
+/*
+   Unix SMB/CIFS implementation.
+   Implement a stack of talloc contexts
+   Copyright (C) Volker Lendecke 2007
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+/*
+ * Implement a stack of talloc frames.
+ *
+ * When a new talloc stackframe is allocated with talloc_stackframe(), then
+ * the TALLOC_CTX returned with talloc_tos() is reset to that new
+ * frame. Whenever that stack frame is TALLOC_FREE()'ed, then the reverse
+ * happens: The previous talloc_tos() is restored.
+ *
+ * This API is designed to be robust in the sense that if someone forgets to
+ * TALLOC_FREE() a stackframe, then the next outer one correctly cleans up and
+ * resets the talloc_tos().
+ *
+ * This robustness feature means that we can't rely on a linked list with
+ * talloc destructors because in a hierarchy of talloc destructors the parent
+ * destructor is called before its children destructors. The child destructor
+ * called after the parent would set the talloc_tos() to the wrong value.
+ */
+
+#include "includes.h"
+
+static int talloc_stacksize;
+static int talloc_stack_arraysize;
+static TALLOC_CTX **talloc_stack;
+
+static int talloc_pop(TALLOC_CTX *frame)
+{
+	int i;
+
+	for (i=talloc_stacksize-1; i>0; i--) {
+		if (frame == talloc_stack[i]) {
+			break;
+		}
+		talloc_free(talloc_stack[i]);
+	}
+
+	talloc_stacksize = i;
+	return 0;
+}
+
+/*
+ * Create a new talloc stack frame.
+ *
+ * When free'd, it frees all stack frames that were created after this one and
+ * not explicitly freed.
+ */
+
+static TALLOC_CTX *talloc_stackframe_internal(size_t poolsize)
+{
+	TALLOC_CTX **tmp, *top, *parent;
+
+	if (talloc_stack_arraysize < talloc_stacksize + 1) {
+		tmp = TALLOC_REALLOC_ARRAY(NULL, talloc_stack, TALLOC_CTX *,
+					   talloc_stacksize + 1);
+		if (tmp == NULL) {
+			goto fail;
+		}
+		talloc_stack = tmp;
+		talloc_stack_arraysize = talloc_stacksize + 1;
+        }
+
+	if (talloc_stacksize == 0) {
+		parent = talloc_stack;
+	}
+	else {
+		parent = talloc_stack[talloc_stacksize-1];
+	}
+
+	if (poolsize) {
+		top = talloc_pool(parent, poolsize);
+	} else {
+		top = talloc_new(parent);
+	}
+
+	if (top == NULL) {
+		goto fail;
+	}
+
+	talloc_set_destructor(top, talloc_pop);
+
+	talloc_stack[talloc_stacksize++] = top;
+	return top;
+
+ fail:
+	smb_panic("talloc_stackframe failed");
+	return NULL;
+}
+
+TALLOC_CTX *talloc_stackframe(void)
+{
+	return talloc_stackframe_internal(0);
+}
+
+TALLOC_CTX *talloc_stackframe_pool(size_t poolsize)
+{
+	return talloc_stackframe_internal(poolsize);
+}
+
+/*
+ * Get us the current top of the talloc stack.
+ */
+
+TALLOC_CTX *talloc_tos(void)
+{
+	if (talloc_stacksize == 0) {
+		talloc_stackframe();
+		DEBUG(0, ("no talloc stackframe around, leaking memory\n"));
+	}
+
+	return talloc_stack[talloc_stacksize-1];
+}