1 /* strcspn (str, ss) -- Return the length of the initial segment of STR
2 which contains no characters from SS.
4 Copyright (C) 1994-1997,2000,2002,2003,2004 Free Software Foundation, Inc.
5 This file is part of the GNU C Library.
6 Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>.
7 Bug fixes by Alan Modra <Alan@SPRI.Levels.UniSA.Edu.Au>.
8 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.
15 The GNU C Library is distributed in the hope that it will be useful,
16 but WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 Lesser General Public License for more details.
20 You should have received a copy of the GNU Lesser General Public
21 License along with the GNU C Library; if not, write to the Free
22 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
26 #include "asm-syntax.h"
28 /* BEWARE: `#ifdef strcspn' means that strcspn is redefined as `strpbrk' */
29 #define STRPBRK_P (defined strcspn)
34 movq %rdi, %rdx /* Save SRC. */
36 /* First we create a table with flags for all possible characters.
37 For the ASCII (7bit/8bit) or ISO-8859-X character sets which are
38 supported by the C string functions we have 256 characters.
39 Before inserting marks for the stop characters we clear the whole
41 movq %rdi, %r8 /* Save value. */
42 subq $256, %rsp /* Make space for 256 bytes. */
43 cfi_adjust_cfa_offset(256)
44 movq $32, %rcx /* 32*8 bytes = 256 bytes. */
46 xorq %rax, %rax /* We store 0s. */
51 movq %rsi, %rax /* Setup skipset. */
53 /* For understanding the following code remember that %rcx == 0 now.
54 Although all the following instruction only modify %cl we always
55 have a correct zero-extended 64-bit value in %rcx. */
58 L(2): movb (%rax), %cl /* get byte from skipset */
59 testb %cl, %cl /* is NUL char? */
60 jz L(1) /* yes => start compare loop */
61 movb %cl, (%rsp,%rcx) /* set corresponding byte in skipset table */
63 movb 1(%rax), %cl /* get byte from skipset */
64 testb $0xff, %cl /* is NUL char? */
65 jz L(1) /* yes => start compare loop */
66 movb %cl, (%rsp,%rcx) /* set corresponding byte in skipset table */
68 movb 2(%rax), %cl /* get byte from skipset */
69 testb $0xff, %cl /* is NUL char? */
70 jz L(1) /* yes => start compare loop */
71 movb %cl, (%rsp,%rcx) /* set corresponding byte in skipset table */
73 movb 3(%rax), %cl /* get byte from skipset */
74 addq $4, %rax /* increment skipset pointer */
75 movb %cl, (%rsp,%rcx) /* set corresponding byte in skipset table */
76 testb $0xff, %cl /* is NUL char? */
77 jnz L(2) /* no => process next dword from skipset */
79 L(1): leaq -4(%rdx), %rax /* prepare loop */
81 /* We use a neat trick for the following loop. Normally we would
82 have to test for two termination conditions
83 1. a character in the skipset was found
85 2. the end of the string was found
86 But as a sign that the character is in the skipset we store its
87 value in the table. But the value of NUL is NUL so the loop
88 terminates for NUL in every case. */
91 L(3): addq $4, %rax /* adjust pointer for full loop round */
93 movb (%rax), %cl /* get byte from string */
94 cmpb %cl, (%rsp,%rcx) /* is it contained in skipset? */
95 je L(4) /* yes => return */
97 movb 1(%rax), %cl /* get byte from string */
98 cmpb %cl, (%rsp,%rcx) /* is it contained in skipset? */
99 je L(5) /* yes => return */
101 movb 2(%rax), %cl /* get byte from string */
102 cmpb %cl, (%rsp,%rcx) /* is it contained in skipset? */
103 jz L(6) /* yes => return */
105 movb 3(%rax), %cl /* get byte from string */
106 cmpb %cl, (%rsp,%rcx) /* is it contained in skipset? */
107 jne L(3) /* no => start loop again */
109 incq %rax /* adjust pointer */
113 L(4): addq $256, %rsp /* remove skipset */
114 cfi_adjust_cfa_offset(-256)
117 orb %cl, %cl /* was last character NUL? */
118 cmovzq %rdx, %rax /* Yes: return NULL */
120 subq %rdx, %rax /* we have to return the number of valid
121 characters, so compute distance to first
122 non-valid character */
126 libc_hidden_builtin_def (strcspn)