xref: /netbsd-src/external/lgpl3/gmp/dist/tal-notreent.c (revision 72c7faa4dbb41dbb0238d6b4a109da0d4b236dd4)
1 /* Stack allocation routines.  This is intended for machines without support
2    for the `alloca' function.
3 
4 Copyright 1996, 1997, 1999-2001, 2006 Free Software Foundation, Inc.
5 
6 This file is part of the GNU MP Library.
7 
8 The GNU MP Library is free software; you can redistribute it and/or modify
9 it under the terms of either:
10 
11   * the GNU Lesser General Public License as published by the Free
12     Software Foundation; either version 3 of the License, or (at your
13     option) any later version.
14 
15 or
16 
17   * the GNU General Public License as published by the Free Software
18     Foundation; either version 2 of the License, or (at your option) any
19     later version.
20 
21 or both in parallel, as here.
22 
23 The GNU MP Library is distributed in the hope that it will be useful, but
24 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
25 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
26 for more details.
27 
28 You should have received copies of the GNU General Public License and the
29 GNU Lesser General Public License along with the GNU MP Library.  If not,
30 see https://www.gnu.org/licenses/.  */
31 
32 #include "gmp-impl.h"
33 
34 
35 struct tmp_stack
36 {
37   void *end;
38   void *alloc_point;
39   struct tmp_stack *prev;
40 };
41 typedef struct tmp_stack tmp_stack;
42 
43 
44 static unsigned long max_total_allocation = 0;
45 static unsigned long current_total_allocation = 0;
46 
47 static tmp_stack xxx = {&xxx, &xxx, 0};
48 static tmp_stack *current = &xxx;
49 
50 /* The rounded size of the header of each allocation block.  */
51 #define HSIZ   ROUND_UP_MULTIPLE (sizeof (tmp_stack), __TMP_ALIGN)
52 
53 
54 /* Allocate a block of exactly <size> bytes.  This should only be called
55    through the TMP_ALLOC macro, which takes care of rounding/alignment.  */
56 void *
__gmp_tmp_alloc(unsigned long size)57 __gmp_tmp_alloc (unsigned long size)
58 {
59   void *that;
60 
61   ASSERT ((size % __TMP_ALIGN) == 0);
62   ASSERT (((unsigned) current->alloc_point % __TMP_ALIGN) == 0);
63 
64   if (size > (char *) current->end - (char *) current->alloc_point)
65     {
66       void *chunk;
67       tmp_stack *header;
68       unsigned long chunk_size;
69       unsigned long now;
70 
71       /* Allocate a chunk that makes the total current allocation somewhat
72 	 larger than the maximum allocation ever.  If size is very large, we
73 	 allocate that much.  */
74 
75       now = current_total_allocation + size;
76       if (now > max_total_allocation)
77 	{
78 	  /* We need more temporary memory than ever before.  Increase
79 	     for future needs.  */
80 	  now = (now * 3 / 2 + __TMP_ALIGN - 1) & -__TMP_ALIGN;
81 	  chunk_size = now - current_total_allocation + HSIZ;
82 	  current_total_allocation = now;
83 	  max_total_allocation = current_total_allocation;
84 	}
85       else
86 	{
87 	  chunk_size = max_total_allocation - current_total_allocation + HSIZ;
88 	  current_total_allocation = max_total_allocation;
89 	}
90 
91       chunk = (*__gmp_allocate_func) (chunk_size);
92       header = (tmp_stack *) chunk;
93       header->end = (char *) chunk + chunk_size;
94       header->alloc_point = (char *) chunk + HSIZ;
95       header->prev = current;
96       current = header;
97     }
98 
99   that = current->alloc_point;
100   current->alloc_point = (char *) that + size;
101   ASSERT (((unsigned) that % __TMP_ALIGN) == 0);
102   return that;
103 }
104 
105 /* Typically called at function entry.  <mark> is assigned so that
106    __gmp_tmp_free can later be used to reclaim all subsequently allocated
107    storage.  */
108 void
__gmp_tmp_mark(struct tmp_marker * mark)109 __gmp_tmp_mark (struct tmp_marker *mark)
110 {
111   mark->which_chunk = current;
112   mark->alloc_point = current->alloc_point;
113 }
114 
115 /* Free everything allocated since <mark> was assigned by __gmp_tmp_mark */
116 void
__gmp_tmp_free(struct tmp_marker * mark)117 __gmp_tmp_free (struct tmp_marker *mark)
118 {
119   while (mark->which_chunk != current)
120     {
121       tmp_stack *tmp;
122 
123       tmp = current;
124       current = tmp->prev;
125       current_total_allocation -= (((char *) (tmp->end) - (char *) tmp) - HSIZ);
126       (*__gmp_free_func) (tmp, (char *) tmp->end - (char *) tmp);
127     }
128   current->alloc_point = mark->alloc_point;
129 }
130