1/* Stack allocation routines.  This is intended for machines without support
2   for the `alloca' function.
3
4Copyright 1996, 1997, 1999, 2000, 2001, 2006 Free Software Foundation, Inc.
5
6This file is part of the GNU MP Library.
7
8The GNU MP Library is free software; you can redistribute it and/or modify
9it under the terms of the GNU Lesser General Public License as published by
10the Free Software Foundation; either version 3 of the License, or (at your
11option) any later version.
12
13The GNU MP Library is distributed in the hope that it will be useful, but
14WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
16License for more details.
17
18You should have received a copy of the GNU Lesser General Public License
19along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
20
21#include "gmp.h"
22#include "gmp-impl.h"
23
24
25struct tmp_stack
26{
27  void *end;
28  void *alloc_point;
29  struct tmp_stack *prev;
30};
31typedef struct tmp_stack tmp_stack;
32
33
34static unsigned long max_total_allocation = 0;
35static unsigned long current_total_allocation = 0;
36
37static tmp_stack xxx = {&xxx, &xxx, 0};
38static tmp_stack *current = &xxx;
39
40/* The rounded size of the header of each allocation block.  */
41#define HSIZ   ROUND_UP_MULTIPLE (sizeof (tmp_stack), __TMP_ALIGN)
42
43
44/* Allocate a block of exactly <size> bytes.  This should only be called
45   through the TMP_ALLOC macro, which takes care of rounding/alignment.  */
46void *
47__gmp_tmp_alloc (unsigned long size)
48{
49  void *that;
50
51  ASSERT ((size % __TMP_ALIGN) == 0);
52  ASSERT (((unsigned) current->alloc_point % __TMP_ALIGN) == 0);
53
54  if (size > (char *) current->end - (char *) current->alloc_point)
55    {
56      void *chunk;
57      tmp_stack *header;
58      unsigned long chunk_size;
59      unsigned long now;
60
61      /* Allocate a chunk that makes the total current allocation somewhat
62	 larger than the maximum allocation ever.  If size is very large, we
63	 allocate that much.  */
64
65      now = current_total_allocation + size;
66      if (now > max_total_allocation)
67	{
68	  /* We need more temporary memory than ever before.  Increase
69	     for future needs.  */
70	  now = (now * 3 / 2 + __TMP_ALIGN - 1) & -__TMP_ALIGN;
71	  chunk_size = now - current_total_allocation + HSIZ;
72	  current_total_allocation = now;
73	  max_total_allocation = current_total_allocation;
74	}
75      else
76	{
77	  chunk_size = max_total_allocation - current_total_allocation + HSIZ;
78	  current_total_allocation = max_total_allocation;
79	}
80
81      chunk = (*__gmp_allocate_func) (chunk_size);
82      header = (tmp_stack *) chunk;
83      header->end = (char *) chunk + chunk_size;
84      header->alloc_point = (char *) chunk + HSIZ;
85      header->prev = current;
86      current = header;
87    }
88
89  that = current->alloc_point;
90  current->alloc_point = (char *) that + size;
91  ASSERT (((unsigned) that % __TMP_ALIGN) == 0);
92  return that;
93}
94
95/* Typically called at function entry.  <mark> is assigned so that
96   __gmp_tmp_free can later be used to reclaim all subsequently allocated
97   storage.  */
98void
99__gmp_tmp_mark (struct tmp_marker *mark)
100{
101  mark->which_chunk = current;
102  mark->alloc_point = current->alloc_point;
103}
104
105/* Free everything allocated since <mark> was assigned by __gmp_tmp_mark */
106void
107__gmp_tmp_free (struct tmp_marker *mark)
108{
109  while (mark->which_chunk != current)
110    {
111      tmp_stack *tmp;
112
113      tmp = current;
114      current = tmp->prev;
115      current_total_allocation -= (((char *) (tmp->end) - (char *) tmp) - HSIZ);
116      (*__gmp_free_func) (tmp, (char *) tmp->end - (char *) tmp);
117    }
118  current->alloc_point = mark->alloc_point;
119}
120