strspn.S 4.1 KB

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  1. /* strspn (str, ss) -- Return the length of the initial segment of STR
  2. which contains only 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. .text
  24. ENTRY (strspn)
  25. movq %rdi, %rdx /* Save SRC. */
  26. /* First we create a table with flags for all possible characters.
  27. For the ASCII (7bit/8bit) or ISO-8859-X character sets which are
  28. supported by the C string functions we have 256 characters.
  29. Before inserting marks for the stop characters we clear the whole
  30. table. */
  31. movq %rdi, %r8 /* Save value. */
  32. subq $256, %rsp /* Make space for 256 bytes. */
  33. movl $32, %ecx /* 32*8 bytes = 256 bytes. */
  34. movq %rsp, %rdi
  35. xorl %eax, %eax /* We store 0s. */
  36. cld
  37. rep
  38. stosq
  39. movq %rsi, %rax /* Setup stopset. */
  40. /* For understanding the following code remember that %rcx == 0 now.
  41. Although all the following instruction only modify %cl we always
  42. have a correct zero-extended 64-bit value in %rcx. */
  43. .p2align 4
  44. L(2): movb (%rax), %cl /* get byte from stopset */
  45. testb %cl, %cl /* is NUL char? */
  46. jz L(1) /* yes => start compare loop */
  47. movb %cl, (%rsp,%rcx) /* set corresponding byte in stopset table */
  48. movb 1(%rax), %cl /* get byte from stopset */
  49. testb $0xff, %cl /* is NUL char? */
  50. jz L(1) /* yes => start compare loop */
  51. movb %cl, (%rsp,%rcx) /* set corresponding byte in stopset table */
  52. movb 2(%rax), %cl /* get byte from stopset */
  53. testb $0xff, %cl /* is NUL char? */
  54. jz L(1) /* yes => start compare loop */
  55. movb %cl, (%rsp,%rcx) /* set corresponding byte in stopset table */
  56. movb 3(%rax), %cl /* get byte from stopset */
  57. addq $4, %rax /* increment stopset pointer */
  58. movb %cl, (%rsp,%rcx) /* set corresponding byte in stopset table */
  59. testb $0xff, %cl /* is NUL char? */
  60. jnz L(2) /* no => process next dword from stopset */
  61. L(1): leaq -4(%rdx), %rax /* prepare loop */
  62. /* We use a neat trick for the following loop. Normally we would
  63. have to test for two termination conditions
  64. 1. a character in the stopset was found
  65. and
  66. 2. the end of the string was found
  67. But as a sign that the character is in the stopset we store its
  68. value in the table. But the value of NUL is NUL so the loop
  69. terminates for NUL in every case. */
  70. .p2align 4
  71. L(3): addq $4, %rax /* adjust pointer for full loop round */
  72. movb (%rax), %cl /* get byte from string */
  73. testb %cl, (%rsp,%rcx) /* is it contained in skipset? */
  74. jz L(4) /* no => return */
  75. movb 1(%rax), %cl /* get byte from string */
  76. testb %cl, (%rsp,%rcx) /* is it contained in skipset? */
  77. jz L(5) /* no => return */
  78. movb 2(%rax), %cl /* get byte from string */
  79. testb %cl, (%rsp,%rcx) /* is it contained in skipset? */
  80. jz L(6) /* no => return */
  81. movb 3(%rax), %cl /* get byte from string */
  82. testb %cl, (%rsp,%rcx) /* is it contained in skipset? */
  83. jnz L(3) /* yes => start loop again */
  84. incq %rax /* adjust pointer */
  85. L(6): incq %rax
  86. L(5): incq %rax
  87. L(4): addq $256, %rsp /* remove stopset */
  88. subq %rdx, %rax /* we have to return the number of valid
  89. characters, so compute distance to first
  90. non-valid character */
  91. ret
  92. END (strspn)
  93. libc_hidden_def(strspn)