91 lines
3.0 KiB
C
91 lines
3.0 KiB
C
/*
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* Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
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* The President and Fellows of Harvard College.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* This file is shared between libc and the kernel, so don't put anything
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* in here that won't work in both contexts.
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*/
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#ifdef _KERNEL
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#include <types.h>
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#include <lib.h>
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#else
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#include <string.h>
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#endif
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/*
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* Standard C string function: compare two strings and return their
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* sort order.
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*/
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int
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strcmp(const char *a, const char *b)
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{
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size_t i;
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/*
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* Walk down both strings until either they're different
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* or we hit the end of A.
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*
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* If A and B strings are not the same length, when the
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* shorter one ends, the two will be different, and we'll
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* stop before running off the end of either.
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*
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* If they *are* the same length, it's sufficient to check
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* that we haven't run off the end of A, because that's the
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* same as checking to make sure we haven't run off the end of
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* B.
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*/
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for (i=0; a[i]!=0 && a[i]==b[i]; i++) {
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/* nothing */
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}
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/*
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* If A is greater than B, return 1. If A is less than B,
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* return -1. If they're the same, return 0. Since we have
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* stopped at the first character of difference (or the end of
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* both strings) checking the character under I accomplishes
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* this.
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*
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* Note that strcmp does not handle accented characters,
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* internationalization, or locale sort order; strcoll() does
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* that.
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*
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* The rules say we compare order in terms of *unsigned* char.
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*/
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if ((unsigned char)a[i] > (unsigned char)b[i]) {
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return 1;
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}
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else if (a[i] == b[i]) {
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return 0;
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}
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return -1;
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}
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