strncat.c 2.7 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. #undef strncat
  32. //#define strncat TESTING
  33. char *strncat(char * dest, const char * src, size_t count)
  34. {
  35. int esi, edi, eax, ecx, edx;
  36. __asm__ __volatile__(
  37. " xorl %%eax, %%eax\n"
  38. " incl %%edx\n"
  39. " pushl %%edi\n" /* save dest */
  40. " repne; scasb\n"
  41. " decl %%edi\n" /* edi => NUL in dest */
  42. /* count-- */
  43. "1: decl %%edx\n"
  44. /* if count reached 0, store NUL and bail out */
  45. " movl %%edx, %%eax\n"
  46. " jz 2f\n"
  47. /* else copy a char */
  48. " lodsb\n"
  49. "2: stosb\n"
  50. " testb %%al, %%al\n"
  51. " jnz 1b\n"
  52. /* end of loop */
  53. " popl %%eax\n" /* restore dest into eax */
  54. : "=&S" (esi), "=&D" (edi), "=&a" (eax), "=&c" (ecx), "=&d" (edx)
  55. : "0" (src), "1" (dest), "3" (0xffffffff), "4" (count)
  56. : "memory"
  57. );
  58. return (char *)eax;
  59. }
  60. #ifndef strncat
  61. libc_hidden_def(strncat)
  62. #else
  63. /* Uncomment TESTING, gcc -m32 -Os strncat.c -o strncat
  64. * and run ./strncat
  65. */
  66. int main()
  67. {
  68. char buf[99];
  69. strcpy(buf, "abc"); buf[4] = '*'; strncat(buf, "def", 0);
  70. printf(strcmp(buf, "abc") == 0 && buf[4] == '*' ? "ok\n" : "BAD!\n");
  71. strcpy(buf, "abc"); buf[6] = 1; buf[7] = '*'; strncat(buf, "def", 50);
  72. printf(strcmp(buf, "abcdef") == 0 && buf[7] == '*' ? "ok\n" : "BAD!\n");
  73. strcpy(buf, "abc"); buf[6] = 1; buf[7] = '*'; strncat(buf, "def", -1);
  74. printf(strcmp(buf, "abcdef") == 0 && buf[7] == '*' ? "ok\n" : "BAD!\n");
  75. strcpy(buf, "abc"); buf[6] = 1; buf[7] = '*'; strncat(buf, "def123", 3);
  76. printf(strcmp(buf, "abcdef") == 0 && buf[7] == '*' ? "ok\n" : "BAD!\n");
  77. }
  78. #endif