memset.c 2.3 KB

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  1. /* Copyright (C) 1991,1993,1995,1997,1998,2003,2004
  2. Free Software Foundation, Inc.
  3. This file is part of the GNU C Library.
  4. Contributed by Torbjorn Granlund (tege@sics.se).
  5. The GNU C Library is free software; you can redistribute it and/or
  6. modify it under the terms of the GNU Lesser General Public
  7. License as published by the Free Software Foundation; either
  8. version 2.1 of the License, or (at your option) any later version.
  9. The GNU C Library is distributed in the hope that it will be useful,
  10. but WITHOUT ANY WARRANTY; without even the implied warranty of
  11. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  12. Lesser General Public License for more details.
  13. You should have received a copy of the GNU Lesser General Public
  14. License along with the GNU C Library; if not, write to the Free
  15. Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  16. 02111-1307 USA. */
  17. #include "api.h"
  18. #define op_t unsigned long int
  19. #define OPSIZ (sizeof(op_t))
  20. typedef unsigned char byte;
  21. void *
  22. memset (void *dstpp, int c, size_t len)
  23. {
  24. long int dstp = (long int) dstpp;
  25. if (len >= 8)
  26. {
  27. int xlen;
  28. op_t cccc;
  29. cccc = (unsigned char) c;
  30. cccc |= cccc << 8;
  31. cccc |= cccc << 16;
  32. if (OPSIZ > 4)
  33. /* Do the shift in two steps to avoid warning if long has 32 bits. */
  34. cccc |= (cccc << 16) << 16;
  35. /* There are at least some bytes to set.
  36. No need to test for LEN == 0 in this alignment loop. */
  37. while (dstp % OPSIZ != 0)
  38. {
  39. ((byte *) dstp)[0] = c;
  40. dstp += 1;
  41. len -= 1;
  42. }
  43. /* Write 8 `op_t' per iteration until less than 8 `op_t' remain. */
  44. xlen = len / (OPSIZ * 8);
  45. while (xlen > 0)
  46. {
  47. ((op_t *) dstp)[0] = cccc;
  48. ((op_t *) dstp)[1] = cccc;
  49. ((op_t *) dstp)[2] = cccc;
  50. ((op_t *) dstp)[3] = cccc;
  51. ((op_t *) dstp)[4] = cccc;
  52. ((op_t *) dstp)[5] = cccc;
  53. ((op_t *) dstp)[6] = cccc;
  54. ((op_t *) dstp)[7] = cccc;
  55. dstp += 8 * OPSIZ;
  56. xlen -= 1;
  57. }
  58. len %= OPSIZ * 8;
  59. /* Write 1 `op_t' per iteration until less than OPSIZ bytes remain. */
  60. xlen = len / OPSIZ;
  61. while (xlen > 0)
  62. {
  63. ((op_t *) dstp)[0] = cccc;
  64. dstp += OPSIZ;
  65. xlen -= 1;
  66. }
  67. len %= OPSIZ;
  68. }
  69. /* Write the last few bytes. */
  70. while (len > 0)
  71. {
  72. ((byte *) dstp)[0] = c;
  73. dstp += 1;
  74. len -= 1;
  75. }
  76. return dstpp;
  77. }