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. libc_hidden_proto(memcpy)
  17. #include "malloc.h"
  18. #include "heap.h"
  19. void *
  20. realloc (void *mem, size_t new_size)
  21. {
  22. size_t size;
  23. char *base_mem;
  24. /* Check for special cases. */
  25. if (! new_size)
  26. {
  27. free (mem);
  28. return malloc (new_size);
  29. }
  30. if (! mem)
  31. return malloc (new_size);
  32. /* Normal realloc. */
  33. base_mem = MALLOC_BASE (mem);
  34. size = MALLOC_SIZE (mem);
  35. /* Include extra space to record the size of the allocated block.
  36. Also make sure that we're dealing in a multiple of the heap
  37. allocation unit (SIZE is already guaranteed to be so).*/
  38. new_size = HEAP_ADJUST_SIZE (new_size + MALLOC_HEADER_SIZE);
  39. MALLOC_DEBUG (1, "realloc: 0x%lx, %d (base = 0x%lx, total_size = %d)",
  40. (long)mem, new_size, (long)base_mem, size);
  41. if (new_size > size)
  42. /* Grow the block. */
  43. {
  44. size_t extra = new_size - size;
  45. __heap_lock (&__malloc_heap);
  46. extra = __heap_alloc_at (&__malloc_heap, base_mem + size, extra);
  47. __heap_unlock (&__malloc_heap);
  48. if (extra)
  49. /* Record the changed size. */
  50. MALLOC_SET_SIZE (base_mem, size + extra);
  51. else
  52. /* Our attempts to extend MEM in place failed, just
  53. allocate-and-copy. */
  54. {
  55. void *new_mem = malloc (new_size - MALLOC_HEADER_SIZE);
  56. if (new_mem)
  57. {
  58. memcpy (new_mem, mem, size - MALLOC_HEADER_SIZE);
  59. free (mem);
  60. }
  61. mem = new_mem;
  62. }
  63. }
  64. else if (new_size + MALLOC_REALLOC_MIN_FREE_SIZE <= size)
  65. /* Shrink the block. */
  66. {
  67. __heap_lock (&__malloc_heap);
  68. __heap_free (&__malloc_heap, base_mem + new_size, size - new_size);
  69. __heap_unlock (&__malloc_heap);
  70. MALLOC_SET_SIZE (base_mem, new_size);
  71. }
  72. if (mem)
  73. MALLOC_DEBUG (-1, "realloc: returning 0x%lx (base:0x%lx, total_size:%d)",
  74. (long)mem, (long)MALLOC_BASE(mem), (long)MALLOC_SIZE(mem));
  75. else
  76. MALLOC_DEBUG (-1, "realloc: returning 0");
  77. return mem;
  78. }