memchr.c 2.5 KB

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  1. /*
  2. * This string-include defines all string functions as inline
  3. * functions. Use gcc. It also assumes ds=es=data space, this should be
  4. * normal. Most of the string-functions are rather heavily hand-optimized,
  5. * see especially strtok,strstr,str[c]spn. They should work, but are not
  6. * very easy to understand. Everything is done entirely within the register
  7. * set, making the functions fast and clean. String instructions have been
  8. * used through-out, making for "slightly" unclear code :-)
  9. *
  10. * NO Copyright (C) 1991, 1992 Linus Torvalds,
  11. * consider these trivial functions to be PD.
  12. */
  13. /*
  14. * Copyright (C) 2000-2005 Erik Andersen <andersen@uclibc.org>
  15. *
  16. * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
  17. */
  18. /*
  19. * Modified for uClibc by Erik Andersen <andersen@codepoet.org>
  20. * These make no attempt to use nifty things like mmx/3dnow/etc.
  21. * These are not inline, and will therefore not be as fast as
  22. * modifying the headers to use inlines (and cannot therefore
  23. * do tricky things when dealing with const memory). But they
  24. * should (I hope!) be faster than their generic equivalents....
  25. *
  26. * More importantly, these should provide a good example for
  27. * others to follow when adding arch specific optimizations.
  28. * -Erik
  29. */
  30. #include <string.h>
  31. #undef memchr
  32. //#define memchr TESTING
  33. void *memchr(const void *s, int c, size_t count)
  34. {
  35. void *edi;
  36. int ecx;
  37. __asm__ __volatile__(
  38. " jecxz 1f\n"
  39. " repne; scasb\n"
  40. " leal -1(%%edi), %%edi\n"
  41. " je 2f\n"
  42. "1:\n"
  43. " xorl %%edi, %%edi\n" /* NULL */
  44. "2:\n"
  45. : "=&D" (edi), "=&c" (ecx)
  46. : "a" (c), "0" (s), "1" (count)
  47. /* : no clobbers */
  48. );
  49. return edi;
  50. }
  51. #ifndef memchr
  52. libc_hidden_def(memchr)
  53. #else
  54. /* Uncomment TESTING, gcc -D_GNU_SOURCE -m32 -Os memchr.c -o memchr
  55. * and run ./memchr
  56. */
  57. int main()
  58. {
  59. static const char str[] = "abc.def";
  60. printf((char*)memchr(str, '.',-2) - str == 3 ? "ok\n" : "BAD!\n");
  61. printf((char*)memchr(str, '.',-1) - str == 3 ? "ok\n" : "BAD!\n");
  62. printf((char*)memchr(str, '.', 0) == NULL ? "ok\n" : "BAD!\n");
  63. printf((char*)memchr(str, '.', 1) == NULL ? "ok\n" : "BAD!\n");
  64. printf((char*)memchr(str, '.', 2) == NULL ? "ok\n" : "BAD!\n");
  65. printf((char*)memchr(str, '.', 3) == NULL ? "ok\n" : "BAD!\n");
  66. printf((char*)memchr(str, '.', 4) - str == 3 ? "ok\n" : "BAD!\n");
  67. printf((char*)memchr(str, '.', 5) - str == 3 ? "ok\n" : "BAD!\n");
  68. printf((char*)memchr(str+3, '.', 0) == NULL ? "ok\n" : "BAD!\n");
  69. printf((char*)memchr(str+3, '.', 5) - str == 3 ? "ok\n" : "BAD!\n");
  70. }
  71. #endif