56 lines
1.7 KiB
C
56 lines
1.7 KiB
C
/* Copyright (C) 1992 Free Software Foundation, Inc.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 675 Mass Ave,
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Cambridge, MA 02139, USA. */
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#include <string.h>
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/* Return the length of the null-terminated string STR. Scan for
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the null terminator quickly by testing eight bytes at a time. */
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size_t
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strlen (const char *str)
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{
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const char *char_ptr;
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const unsigned long int *longword_ptr;
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/* Handle the first few characters by reading one character at a time.
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Do this until STR is aligned on a 8-byte border. */
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for (char_ptr = str; ((unsigned long int) char_ptr & 7) != 0; ++char_ptr)
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if (*char_ptr == '\0')
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return char_ptr - str;
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longword_ptr = (unsigned long int *) char_ptr;
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for (;;)
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{
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const unsigned long int longword = *longword_ptr++;
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int mask;
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/* Set bits in MASK if bytes in LONGWORD are zero. */
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asm ("cmpbge $31, %1, %0" : "=r" (mask) : "r" (longword));
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if (mask)
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{
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/* Which of the bytes was the zero? */
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const char *cp = (const char *) (longword_ptr - 1);
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int i;
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for (i = 0; i < 8; i++)
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if (cp[i] == 0)
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return cp - str + i;
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}
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}
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}
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