strcspn.S 4.4 KB

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  1. /* strcspn (str, ss) -- Return the length of the initial segment of STR
  2. which contains no characters from SS.
  3. For AMD x86-64.
  4. Copyright (C) 1994-1997, 2000, 2002, 2003, 2004, 2005
  5. Free Software Foundation, Inc.
  6. This file is part of the GNU C Library.
  7. Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>.
  8. Bug fixes by Alan Modra <Alan@SPRI.Levels.UniSA.Edu.Au>.
  9. Adopted for x86-64 by Andreas Jaeger <aj@suse.de>.
  10. The GNU C Library is free software; you can redistribute it and/or
  11. modify it under the terms of the GNU Lesser General Public
  12. License as published by the Free Software Foundation; either
  13. version 2.1 of the License, or (at your option) any later version.
  14. The GNU C Library is distributed in the hope that it will be useful,
  15. but WITHOUT ANY WARRANTY; without even the implied warranty of
  16. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  17. Lesser General Public License for more details.
  18. You should have received a copy of the GNU Lesser General Public
  19. License along with the GNU C Library; if not, write to the Free
  20. Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  21. 02111-1307 USA. */
  22. #include "_glibc_inc.h"
  23. /* BEWARE: `#ifdef strcspn' means that strcspn is redefined as `strpbrk' */
  24. #define STRPBRK_P (defined strcspn)
  25. .text
  26. ENTRY (strcspn)
  27. movq %rdi, %rdx /* Save SRC. */
  28. /* First we create a table with flags for all possible characters.
  29. For the ASCII (7bit/8bit) or ISO-8859-X character sets which are
  30. supported by the C string functions we have 256 characters.
  31. Before inserting marks for the stop characters we clear the whole
  32. table. */
  33. movq %rdi, %r8 /* Save value. */
  34. subq $256, %rsp /* Make space for 256 bytes. */
  35. movl $32, %ecx /* 32*8 bytes = 256 bytes. */
  36. movq %rsp, %rdi
  37. xorl %eax, %eax /* We store 0s. */
  38. cld
  39. rep
  40. stosq
  41. movq %rsi, %rax /* Setup skipset. */
  42. /* For understanding the following code remember that %rcx == 0 now.
  43. Although all the following instruction only modify %cl we always
  44. have a correct zero-extended 64-bit value in %rcx. */
  45. .p2align 4
  46. L(2): movb (%rax), %cl /* get byte from skipset */
  47. testb %cl, %cl /* is NUL char? */
  48. jz L(1) /* yes => start compare loop */
  49. movb %cl, (%rsp,%rcx) /* set corresponding byte in skipset table */
  50. movb 1(%rax), %cl /* get byte from skipset */
  51. testb $0xff, %cl /* is NUL char? */
  52. jz L(1) /* yes => start compare loop */
  53. movb %cl, (%rsp,%rcx) /* set corresponding byte in skipset table */
  54. movb 2(%rax), %cl /* get byte from skipset */
  55. testb $0xff, %cl /* is NUL char? */
  56. jz L(1) /* yes => start compare loop */
  57. movb %cl, (%rsp,%rcx) /* set corresponding byte in skipset table */
  58. movb 3(%rax), %cl /* get byte from skipset */
  59. addq $4, %rax /* increment skipset pointer */
  60. movb %cl, (%rsp,%rcx) /* set corresponding byte in skipset table */
  61. testb $0xff, %cl /* is NUL char? */
  62. jnz L(2) /* no => process next dword from skipset */
  63. L(1): leaq -4(%rdx), %rax /* prepare loop */
  64. /* We use a neat trick for the following loop. Normally we would
  65. have to test for two termination conditions
  66. 1. a character in the skipset was found
  67. and
  68. 2. the end of the string was found
  69. But as a sign that the character is in the skipset we store its
  70. value in the table. But the value of NUL is NUL so the loop
  71. terminates for NUL in every case. */
  72. .p2align 4
  73. L(3): addq $4, %rax /* adjust pointer for full loop round */
  74. movb (%rax), %cl /* get byte from string */
  75. cmpb %cl, (%rsp,%rcx) /* is it contained in skipset? */
  76. je L(4) /* yes => return */
  77. movb 1(%rax), %cl /* get byte from string */
  78. cmpb %cl, (%rsp,%rcx) /* is it contained in skipset? */
  79. je L(5) /* yes => return */
  80. movb 2(%rax), %cl /* get byte from string */
  81. cmpb %cl, (%rsp,%rcx) /* is it contained in skipset? */
  82. jz L(6) /* yes => return */
  83. movb 3(%rax), %cl /* get byte from string */
  84. cmpb %cl, (%rsp,%rcx) /* is it contained in skipset? */
  85. jne L(3) /* no => start loop again */
  86. incq %rax /* adjust pointer */
  87. L(6): incq %rax
  88. L(5): incq %rax
  89. L(4): addq $256, %rsp /* remove skipset */
  90. #if STRPBRK_P
  91. xorl %edx,%edx
  92. orb %cl, %cl /* was last character NUL? */
  93. cmovzq %rdx, %rax /* Yes: return NULL */
  94. #else
  95. subq %rdx, %rax /* we have to return the number of valid
  96. characters, so compute distance to first
  97. non-valid character */
  98. #endif
  99. ret
  100. END (strcspn)
  101. #if !STRPBRK_P
  102. libc_hidden_def(strcspn)
  103. #endif