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/*
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(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];
}
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