strnlen.c 1.7 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. #ifdef __USE_GNU
  32. libc_hidden_proto(strnlen)
  33. size_t strnlen(const char *s, size_t count)
  34. {
  35. int d0;
  36. register int __res;
  37. __asm__ __volatile__(
  38. "movl %2,%0\n\t"
  39. "incl %1\n"
  40. "jmp 2f\n"
  41. "1:\tcmpb $0,(%0)\n\t"
  42. "je 3f\n\t"
  43. "incl %0\n"
  44. "2:\tdecl %1\n\t"
  45. "jne 1b\n"
  46. "3:\tsubl %2,%0"
  47. :"=a" (__res), "=&d" (d0)
  48. :"c" (s),"1" (count));
  49. return __res;
  50. }
  51. libc_hidden_def(strnlen)
  52. #endif