source/libs/gmp/gmp-src/tal-notreent.c

   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.h"
  33 #include "gmp-impl.h"
  34
  35
  36 struct tmp_stack
  37 {
  38   void *end;
  39   void *alloc_point;
  40   struct tmp_stack *prev;
  41 };
  42 typedef struct tmp_stack tmp_stack;
  43
  44
  45 static unsigned long max_total_allocation = 0;
  46 static unsigned long current_total_allocation = 0;
  47
  48 static tmp_stack xxx = {&xxx, &xxx, 0};
  49 static tmp_stack *current = &xxx;
  50
  51 /* The rounded size of the header of each allocation block.  */
  52 #define HSIZ   ROUND_UP_MULTIPLE (sizeof (tmp_stack), __TMP_ALIGN)
  53
  54
  55 /* Allocate a block of exactly <size> bytes.  This should only be called
  56    through the TMP_ALLOC macro, which takes care of rounding/alignment.  */
  57 void *
  58 __gmp_tmp_alloc (unsigned long size)
  59 {
  60   void *that;
  61
  62   ASSERT ((size % __TMP_ALIGN) == 0);
  63   ASSERT (((unsigned) current->alloc_point % __TMP_ALIGN) == 0);
  64
  65   if (size > (char *) current->end - (char *) current->alloc_point)
  66     {
  67       void *chunk;
  68       tmp_stack *header;
  69       unsigned long chunk_size;
  70       unsigned long now;
  71
  72       /* Allocate a chunk that makes the total current allocation somewhat
  73          larger than the maximum allocation ever.  If size is very large, we
  74          allocate that much.  */
  75
  76       now = current_total_allocation + size;
  77       if (now > max_total_allocation)
  78         {
  79           /* We need more temporary memory than ever before.  Increase
  80              for future needs.  */
  81           now = (now * 3 / 2 + __TMP_ALIGN - 1) & -__TMP_ALIGN;
  82           chunk_size = now - current_total_allocation + HSIZ;
  83           current_total_allocation = now;
  84           max_total_allocation = current_total_allocation;
  85         }
  86       else
  87         {
  88           chunk_size = max_total_allocation - current_total_allocation + HSIZ;
  89           current_total_allocation = max_total_allocation;
  90         }
  91
  92       chunk = (*__gmp_allocate_func) (chunk_size);
  93       header = (tmp_stack *) chunk;
  94       header->end = (char *) chunk + chunk_size;
  95       header->alloc_point = (char *) chunk + HSIZ;
  96       header->prev = current;
  97       current = header;
  98     }
  99
 100   that = current->alloc_point;
 101   current->alloc_point = (char *) that + size;
 102   ASSERT (((unsigned) that % __TMP_ALIGN) == 0);
 103   return that;
 104 }
 105
 106 /* Typically called at function entry.  <mark> is assigned so that
 107    __gmp_tmp_free can later be used to reclaim all subsequently allocated
 108    storage.  */
 109 void
 110 __gmp_tmp_mark (struct tmp_marker *mark)
 111 {
 112   mark->which_chunk = current;
 113   mark->alloc_point = current->alloc_point;
 114 }
 115
 116 /* Free everything allocated since <mark> was assigned by __gmp_tmp_mark */
 117 void
 118 __gmp_tmp_free (struct tmp_marker *mark)
 119 {
 120   while (mark->which_chunk != current)
 121     {
 122       tmp_stack *tmp;
 123
 124       tmp = current;
 125       current = tmp->prev;
 126       current_total_allocation -= (((char *) (tmp->end) - (char *) tmp) - HSIZ);
 127       (*__gmp_free_func) (tmp, (char *) tmp->end - (char *) tmp);
 128     }
 129   current->alloc_point = mark->alloc_point;
 130 }