source/lib/talloc.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 3.0
   4    Samba temporary memory allocation functions
   5    Copyright (C) Andrew Tridgell 2000
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 */
  21
  22 /* this is a very simple temporary memory allocator. To use it do the following:
  23
  24    1) when you first want to allocate a pool of meomry use
  25    talloc_init() and save the resulting context pointer somewhere
  26
  27    2) to allocate memory use talloc()
  28
  29    3) when _all_ of the memory allocated using this context is no longer needed
  30    use talloc_destroy()
  31
  32    talloc does not zero the memory. It guarantees memory of a
  33    TALLOC_ALIGN alignment
  34 */
  35
  36 #include "includes.h"
  37
  38 #define TALLOC_ALIGN 32
  39 #define TALLOC_CHUNK_SIZE (0x2000)
  40
  41 /* initialissa talloc context. */
  42 TALLOC_CTX *talloc_init(void)
  43 {
  44         TALLOC_CTX *t;
  45
  46         t = (TALLOC_CTX *)malloc(sizeof(*t));
  47         if (!t) return NULL;
  48
  49         t->list = NULL;
  50
  51         return t;
  52 }
  53
  54 /* allocate a bit of memory from the specified pool */
  55 void *talloc(TALLOC_CTX *t, size_t size)
  56 {
  57         void *p;
  58
  59         size = (size + TALLOC_ALIGN) & (~TALLOC_ALIGN-1);
  60
  61         if (!t->list || (t->list->total_size - t->list->alloc_size) < size) {
  62                 struct talloc_chunk *c;
  63                 size_t asize = (size + TALLOC_CHUNK_SIZE) & ~(TALLOC_CHUNK_SIZE-1);
  64
  65                 c = (struct talloc_chunk *)malloc(sizeof(*c));
  66                 if (!c) return NULL;
  67                 c->next = t->list;
  68                 c->ptr = (void *)malloc(asize);
  69                 if (!c->ptr) {
  70                         free(c);
  71                         return NULL;
  72                 }
  73                 c->alloc_size = 0;
  74                 c->total_size = asize;
  75                 t->list = c;
  76         }
  77
  78         p = ((char *)t->list->ptr) + t->list->alloc_size;
  79         t->list->alloc_size += size;
  80         return p;
  81 }
  82
  83 /* destroy a whole pool */
  84 void talloc_destroy(TALLOC_CTX *t)
  85 {
  86         struct talloc_chunk *c;
  87
  88         while (t->list) {
  89                 c = t->list->next;
  90                 free(t->list->ptr);
  91                 free(t->list);
  92                 t->list = c;
  93         }
  94
  95         free(t);
  96 }