1 /* Stack allocation routines. This is intended for machines without support 2 for the `alloca' function. 3 4 Copyright 1996, 1997, 1999, 2000, 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 the GNU Lesser General Public License as published by 10 the Free Software Foundation; either version 3 of the License, or (at your 11 option) any later version. 12 13 The GNU MP Library is distributed in the hope that it will be useful, but 14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 16 License for more details. 17 18 You should have received a copy of the GNU Lesser General Public License 19 along 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 25 struct tmp_stack 26 { 27 void *end; 28 void *alloc_point; 29 struct tmp_stack *prev; 30 }; 31 typedef struct tmp_stack tmp_stack; 32 33 34 static unsigned long max_total_allocation = 0; 35 static unsigned long current_total_allocation = 0; 36 37 static tmp_stack xxx = {&xxx, &xxx, 0}; 38 static 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. */ 46 void * 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. */ 98 void 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 */ 106 void 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