strncmp.c 2.0 KB

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  1. /* Copyright (C) 1991, 1996, 1997, 2003 Free Software Foundation, Inc.
  2. This file is part of the GNU C Library.
  3. The GNU C Library is free software; you can redistribute it and/or
  4. modify it under the terms of the GNU Lesser General Public
  5. License as published by the Free Software Foundation; either
  6. version 2.1 of the License, or (at your option) any later version.
  7. The GNU C Library is distributed in the hope that it will be useful,
  8. but WITHOUT ANY WARRANTY; without even the implied warranty of
  9. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  10. Lesser General Public License for more details.
  11. You should have received a copy of the GNU Lesser General Public
  12. License along with the GNU C Library; if not, write to the Free
  13. Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  14. 02111-1307 USA. */
  15. #include <string.h>
  16. #include "memcopy.h"
  17. libc_hidden_proto(strncmp)
  18. /* Compare no more than N characters of S1 and S2,
  19. returning less than, equal to or greater than zero
  20. if S1 is lexicographically less than, equal to or
  21. greater than S2. */
  22. int strncmp (const char *s1, const char *s2, size_t n)
  23. {
  24. unsigned reg_char c1 = '\0';
  25. unsigned reg_char c2 = '\0';
  26. if (n >= 4)
  27. {
  28. size_t n4 = n >> 2;
  29. do
  30. {
  31. c1 = (unsigned char) *s1++;
  32. c2 = (unsigned char) *s2++;
  33. if (c1 == '\0' || c1 != c2)
  34. return c1 - c2;
  35. c1 = (unsigned char) *s1++;
  36. c2 = (unsigned char) *s2++;
  37. if (c1 == '\0' || c1 != c2)
  38. return c1 - c2;
  39. c1 = (unsigned char) *s1++;
  40. c2 = (unsigned char) *s2++;
  41. if (c1 == '\0' || c1 != c2)
  42. return c1 - c2;
  43. c1 = (unsigned char) *s1++;
  44. c2 = (unsigned char) *s2++;
  45. if (c1 == '\0' || c1 != c2)
  46. return c1 - c2;
  47. } while (--n4 > 0);
  48. n &= 3;
  49. }
  50. while (n > 0)
  51. {
  52. c1 = (unsigned char) *s1++;
  53. c2 = (unsigned char) *s2++;
  54. if (c1 == '\0' || c1 != c2)
  55. return c1 - c2;
  56. n--;
  57. }
  58. return c1 - c2;
  59. }
  60. libc_hidden_weak(strncmp)