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/*
Unix SMB/CIFS implementation.
Implement a stack of talloc contexts
Copyright (C) Volker Lendecke 2007
Copyright (C) Jeremy Allison 2009 - made thread safe.
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"
struct talloc_stackframe {
int talloc_stacksize;
int talloc_stack_arraysize;
TALLOC_CTX **talloc_stack;
};
/*
* In the single threaded case this is a pointer
* to the global talloc_stackframe. In the MT-case
* this is the pointer to the thread-specific key
* used to look up the per-thread talloc_stackframe
* pointer.
*/
static void *global_ts;
/* Variable to ensure TLS value is only initialized once. */
static smb_thread_once_t ts_initialized = SMB_THREAD_ONCE_INIT;
static void talloc_stackframe_init(void * unused)
{
if (SMB_THREAD_CREATE_TLS("talloc_stackframe", global_ts)) {
smb_panic("talloc_stackframe_init create_tls failed");
}
}
static struct talloc_stackframe *talloc_stackframe_create(void)
{
#if defined(PARANOID_MALLOC_CHECKER)
#ifdef malloc
#undef malloc
#endif
#endif
struct talloc_stackframe *ts =
(struct talloc_stackframe *)malloc(sizeof(struct talloc_stackframe));
#if defined(PARANOID_MALLOC_CHECKER)
#define malloc(s) __ERROR_DONT_USE_MALLOC_DIRECTLY
#endif
if (!ts) {
smb_panic("talloc_stackframe_init malloc failed");
}
ZERO_STRUCTP(ts);
SMB_THREAD_ONCE(&ts_initialized, talloc_stackframe_init, NULL);
if (SMB_THREAD_SET_TLS(global_ts, ts)) {
smb_panic("talloc_stackframe_init set_tls failed");
}
return ts;
}
static int talloc_pop(TALLOC_CTX *frame)
{
struct talloc_stackframe *ts =
(struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
int i;
for (i=ts->talloc_stacksize-1; i>0; i--) {
if (frame == ts->talloc_stack[i]) {
break;
}
talloc_free(ts->talloc_stack[i]);
ts->talloc_stack[i] = NULL;
}
ts->talloc_stack[i] = NULL;
ts->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;
struct talloc_stackframe *ts =
(struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
if (ts == NULL) {
ts = talloc_stackframe_create();
}
if (ts->talloc_stack_arraysize < ts->talloc_stacksize + 1) {
tmp = talloc_realloc(NULL, ts->talloc_stack, TALLOC_CTX *,
ts->talloc_stacksize + 1);
if (tmp == NULL) {
goto fail;
}
ts->talloc_stack = tmp;
ts->talloc_stack_arraysize = ts->talloc_stacksize + 1;
}
if (ts->talloc_stacksize == 0) {
parent = ts->talloc_stack;
} else {
parent = ts->talloc_stack[ts->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);
ts->talloc_stack[ts->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)
{
struct talloc_stackframe *ts =
(struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
if (ts == NULL || ts->talloc_stacksize == 0) {
talloc_stackframe();
ts = (struct talloc_stackframe *)SMB_THREAD_GET_TLS(global_ts);
DEBUG(0, ("no talloc stackframe around, leaking memory\n"));
}
return ts->talloc_stack[ts->talloc_stacksize-1];
}
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