realloc.c 2.3 KB

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  1. /*
  2. * libc/stdlib/malloc/realloc.c -- realloc function
  3. *
  4. * Copyright (C) 2002 NEC Corporation
  5. * Copyright (C) 2002 Miles Bader <miles@gnu.org>
  6. *
  7. * This file is subject to the terms and conditions of the GNU Lesser
  8. * General Public License. See the file COPYING.LIB in the main
  9. * directory of this archive for more details.
  10. *
  11. * Written by Miles Bader <miles@gnu.org>
  12. */
  13. #include <stdlib.h>
  14. #include <string.h>
  15. #include <errno.h>
  16. #include "malloc.h"
  17. #include "heap.h"
  18. void *
  19. realloc (void *mem, size_t new_size)
  20. {
  21. size_t size;
  22. char *base_mem;
  23. /* Check for special cases. */
  24. if (! mem)
  25. return malloc (new_size);
  26. if (! new_size)
  27. {
  28. free (mem);
  29. return malloc (new_size);
  30. }
  31. /* Normal realloc. */
  32. base_mem = MALLOC_BASE (mem);
  33. size = MALLOC_SIZE (mem);
  34. /* Include extra space to record the size of the allocated block.
  35. Also make sure that we're dealing in a multiple of the heap
  36. allocation unit (SIZE is already guaranteed to be so).*/
  37. new_size = HEAP_ADJUST_SIZE (new_size + MALLOC_HEADER_SIZE);
  38. MALLOC_DEBUG (1, "realloc: 0x%lx, %d (base = 0x%lx, total_size = %d)",
  39. (long)mem, new_size, (long)base_mem, size);
  40. if (new_size > size)
  41. /* Grow the block. */
  42. {
  43. size_t extra = new_size - size;
  44. __heap_lock (&__malloc_heap);
  45. extra = __heap_alloc_at (&__malloc_heap, base_mem + size, extra);
  46. __heap_unlock (&__malloc_heap);
  47. if (extra)
  48. /* Record the changed size. */
  49. MALLOC_SET_SIZE (base_mem, size + extra);
  50. else
  51. /* Our attempts to extend MEM in place failed, just
  52. allocate-and-copy. */
  53. {
  54. void *new_mem = malloc (new_size - MALLOC_HEADER_SIZE);
  55. if (new_mem)
  56. {
  57. __memcpy (new_mem, mem, size - MALLOC_HEADER_SIZE);
  58. free (mem);
  59. }
  60. mem = new_mem;
  61. }
  62. }
  63. else if (new_size + MALLOC_REALLOC_MIN_FREE_SIZE <= size)
  64. /* Shrink the block. */
  65. {
  66. __heap_lock (&__malloc_heap);
  67. __heap_free (&__malloc_heap, base_mem + new_size, size - new_size);
  68. __heap_unlock (&__malloc_heap);
  69. MALLOC_SET_SIZE (base_mem, new_size);
  70. }
  71. if (mem)
  72. MALLOC_DEBUG (-1, "realloc: returning 0x%lx (base:0x%lx, total_size:%d)",
  73. (long)mem, (long)MALLOC_BASE(mem), (long)MALLOC_SIZE(mem));
  74. else
  75. MALLOC_DEBUG (-1, "realloc: returning 0");
  76. return mem;
  77. }