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 *
      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
     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
     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  }