From fd725b9471dc760ee07325bfe6d15d2894f6df3c Mon Sep 17 00:00:00 2001 From: Roland McGrath Date: Wed, 25 Nov 1992 19:02:14 +0000 Subject: [PATCH] Initial revision --- sysdeps/alpha/strchr.c | 85 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) create mode 100644 sysdeps/alpha/strchr.c diff --git a/sysdeps/alpha/strchr.c b/sysdeps/alpha/strchr.c new file mode 100644 index 0000000000..8cf20245c2 --- /dev/null +++ b/sysdeps/alpha/strchr.c @@ -0,0 +1,85 @@ +/* Copyright (C) 1992 Free Software Foundation, Inc. + +The GNU C Library is free software; you can redistribute it and/or +modify it under the terms of the GNU Library General Public License as +published by the Free Software Foundation; either version 2 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 +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + +#include + +/* Return the length of the null-terminated string STR. Scan for + the null terminator quickly by testing eight bytes at a time. */ + +char * +strchr (const char *str, int c) +{ + const char *char_ptr; + const unsigned long int *longword_ptr; + unsigned long int charmask; + + c = (unsigned char) c; + + /* Handle the first few characters by reading one character at a time. + Do this until STR is aligned on a 8-byte border. */ + for (char_ptr = str; ((unsigned long int) char_ptr & 7) != 0; ++char_ptr) + if (*char_ptr == '\0') + return NULL; + else if (*char_ptr == c) + return char_ptr; + + longword_ptr = (unsigned long int *) char_ptr; + + /* Set up a longword, each of whose bytes is C. */ + charmask = c | (c << 8); + charmask |= charmask << 16; + charmask |= charmask << 32; + + for (;;) + { + const unsigned long int longword = *longword_ptr++; + int ge, le, zero; + + /* Set bits in ZERO if bytes in LONGWORD are zero. */ + asm ("cmpbge $31, %1, %0" : "=r" (zero) : "r" (longword)); + + /* Set bits in GE if bytes in CHARMASK are >= bytes in LONGWORD. */ + asm ("cmpbge %1, %2, %0" : "=r" (ge) : "r" (charmask), "r" (longword)); + + /* Set bits in LE if bytes in CHARMASK are <= bytes in LONGWORD. */ + asm ("cmpbge %2, %1, %0" : "=r" (le) : "r" (charmask), "r" (longword)); + + /* Bytes that are both <= and >= are == to C. */ + if (zero || (ge & le)) + { + /* Which of the bytes was the C? */ + + const char *cp = (const char *) (longword_ptr - 1); + + if (cp[0] == c) + return cp; + if (cp[0] == 0) + return NULL; + if (cp[1] == c) + return &cp[1]; + if (cp[1] == 0) + return NULL; + if (cp[2] == c) + return &cp[2]; + if (cp[2] == 0) + return NULL; + if (cp[3] == c) + return &cp[3]; + return NULL; + } + } +} -- 2.43.5