strncpy.c 1.7 KB

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  1. /* Copyright (C) 1991, 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(strncpy)
  18. char *strncpy (char *s1, const char *s2, size_t n)
  19. {
  20. reg_char c;
  21. char *s = s1;
  22. --s1;
  23. if (n >= 4)
  24. {
  25. size_t n4 = n >> 2;
  26. for (;;)
  27. {
  28. c = *s2++;
  29. *++s1 = c;
  30. if (c == '\0')
  31. break;
  32. c = *s2++;
  33. *++s1 = c;
  34. if (c == '\0')
  35. break;
  36. c = *s2++;
  37. *++s1 = c;
  38. if (c == '\0')
  39. break;
  40. c = *s2++;
  41. *++s1 = c;
  42. if (c == '\0')
  43. break;
  44. if (--n4 == 0)
  45. goto last_chars;
  46. }
  47. n = n - (s1 - s) - 1;
  48. if (n == 0)
  49. return s;
  50. goto zero_fill;
  51. }
  52. last_chars:
  53. n &= 3;
  54. if (n == 0)
  55. return s;
  56. do
  57. {
  58. c = *s2++;
  59. *++s1 = c;
  60. if (--n == 0)
  61. return s;
  62. }
  63. while (c != '\0');
  64. zero_fill:
  65. do
  66. *++s1 = '\0';
  67. while (--n > 0);
  68. return s;
  69. }
  70. libc_hidden_def(strncpy)