1 files changed, 108 insertions, 0 deletions
diff --git a/source3/lib/talloc_stack.c b/source3/lib/talloc_stack.c
new file mode 100644
index 0000000000..baebbd4fac
--- /dev/null
+++ b/source3/lib/talloc_stack.c
@@ -0,0 +1,108 @@
+/*
+   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 TALLOC_CTX **talloc_stack;
+
+static int talloc_pop(int *ptr)
+{
+	int tos = *ptr;
+	int i;
+
+	for (i=talloc_stacksize-1; i>=tos; i--) {
+		talloc_free(talloc_stack[i]);
+	}
+
+	talloc_stacksize = tos;
+	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.
+ */
+
+TALLOC_CTX *talloc_stackframe(void)
+{
+	TALLOC_CTX **tmp, *top;
+	int *cleanup;
+
+	if (!(tmp = TALLOC_REALLOC_ARRAY(NULL, talloc_stack, TALLOC_CTX *,
+					 talloc_stacksize + 1))) {
+		goto fail;
+	}
+
+	talloc_stack = tmp;
+
+	if (!(top = talloc_new(talloc_stack))) {
+		goto fail;
+	}
+
+	if (!(cleanup = talloc(top, int))) {
+		goto fail;
+	}
+
+	*cleanup = talloc_stacksize;
+	talloc_set_destructor(cleanup, talloc_pop);
+
+	talloc_stack[talloc_stacksize++] = top;
+
+	return top;
+
+ fail:
+	smb_panic("talloc_stackframe failed");
+	return NULL;
+}
+
+/*
+ * Get us the current top of the talloc stack.
+ */
+
+TALLOC_CTX *talloc_tos(void)
+{
+	if (talloc_stacksize == 0) {
+		DEBUG(0, ("no talloc stackframe around, leaking memory\n"));
+		talloc_stackframe();
+	}
+
+	return talloc_stack[talloc_stacksize-1];
+}