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/* strspn (str, ss) -- Return the length of the initial segment of STR
which contains only characters from SS.
For AMD x86-64.
Copyright (C) 1994-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
.text
ENTRY (strspn)
movq %rdi, %rdx /* Save SRC. */
/* First we create a table with flags for all possible characters.
For the ASCII (7bit/8bit) or ISO-8859-X character sets which are
supported by the C string functions we have 256 characters.
Before inserting marks for the stop characters we clear the whole
table. */
movq %rdi, %r8 /* Save value. */
subq $256, %rsp /* Make space for 256 bytes. */
cfi_adjust_cfa_offset(256)
movl $32, %ecx /* 32*8 bytes = 256 bytes. */
movq %rsp, %rdi
xorl %eax, %eax /* We store 0s. */
cld
rep
stosq
movq %rsi, %rax /* Setup stopset. */
/* For understanding the following code remember that %rcx == 0 now.
Although all the following instruction only modify %cl we always
have a correct zero-extended 64-bit value in %rcx. */
.p2align 4
L(2): movb (%rax), %cl /* get byte from stopset */
testb %cl, %cl /* is NUL char? */
jz L(1) /* yes => start compare loop */
movb %cl, (%rsp,%rcx) /* set corresponding byte in stopset table */
movb 1(%rax), %cl /* get byte from stopset */
testb $0xff, %cl /* is NUL char? */
jz L(1) /* yes => start compare loop */
movb %cl, (%rsp,%rcx) /* set corresponding byte in stopset table */
movb 2(%rax), %cl /* get byte from stopset */
testb $0xff, %cl /* is NUL char? */
jz L(1) /* yes => start compare loop */
movb %cl, (%rsp,%rcx) /* set corresponding byte in stopset table */
movb 3(%rax), %cl /* get byte from stopset */
addq $4, %rax /* increment stopset pointer */
movb %cl, (%rsp,%rcx) /* set corresponding byte in stopset table */
testb $0xff, %cl /* is NUL char? */
jnz L(2) /* no => process next dword from stopset */
L(1): leaq -4(%rdx), %rax /* prepare loop */
/* We use a neat trick for the following loop. Normally we would
have to test for two termination conditions
1. a character in the stopset was found
and
2. the end of the string was found
But as a sign that the character is in the stopset we store its
value in the table. But the value of NUL is NUL so the loop
terminates for NUL in every case. */
.p2align 4
L(3): addq $4, %rax /* adjust pointer for full loop round */
movb (%rax), %cl /* get byte from string */
testb %cl, (%rsp,%rcx) /* is it contained in skipset? */
jz L(4) /* no => return */
movb 1(%rax), %cl /* get byte from string */
testb %cl, (%rsp,%rcx) /* is it contained in skipset? */
jz L(5) /* no => return */
movb 2(%rax), %cl /* get byte from string */
testb %cl, (%rsp,%rcx) /* is it contained in skipset? */
jz L(6) /* no => return */
movb 3(%rax), %cl /* get byte from string */
testb %cl, (%rsp,%rcx) /* is it contained in skipset? */
jnz L(3) /* yes => start loop again */
incq %rax /* adjust pointer */
L(6): incq %rax
L(5): incq %rax
L(4): addq $256, %rsp /* remove stopset */
cfi_adjust_cfa_offset(-256)
subq %rdx, %rax /* we have to return the number of valid
characters, so compute distance to first
non-valid character */
ret
END (strspn)
libc_hidden_builtin_def (strspn)
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