strncat.c 1.7 KB

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  1. /* Copyright (C) 1991, 1997 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(strncat)
  18. char *strncat (char *s1, const char *s2, size_t n)
  19. {
  20. reg_char c;
  21. char *s = s1;
  22. /* Find the end of S1. */
  23. do
  24. c = *s1++;
  25. while (c != '\0');
  26. /* Make S1 point before next character, so we can increment
  27. it while memory is read (wins on pipelined cpus). */
  28. s1 -= 2;
  29. if (n >= 4)
  30. {
  31. size_t n4 = n >> 2;
  32. do
  33. {
  34. c = *s2++;
  35. *++s1 = c;
  36. if (c == '\0')
  37. return s;
  38. c = *s2++;
  39. *++s1 = c;
  40. if (c == '\0')
  41. return s;
  42. c = *s2++;
  43. *++s1 = c;
  44. if (c == '\0')
  45. return s;
  46. c = *s2++;
  47. *++s1 = c;
  48. if (c == '\0')
  49. return s;
  50. } while (--n4 > 0);
  51. n &= 3;
  52. }
  53. while (n > 0)
  54. {
  55. c = *s2++;
  56. *++s1 = c;
  57. if (c == '\0')
  58. return s;
  59. n--;
  60. }
  61. if (c != '\0')
  62. *++s1 = '\0';
  63. return s;
  64. }
  65. libc_hidden_def(strncat)