178 lines
4.5 KiB
C
178 lines
4.5 KiB
C
/* -*- mode: c; c-file-style: "k&r" -*-
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strnatcmp.c -- Perform 'natural order' comparisons of strings in C.
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Copyright (C) 2000, 2004 by Martin Pool <mbp sourcefrog net>
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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*/
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/* partial change history:
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*
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* 2004-10-10 mbp: Lift out character type dependencies into macros.
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*
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* Eric Sosman pointed out that ctype functions take a parameter whose
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* value must be that of an unsigned int, even on platforms that have
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* negative chars in their default char type.
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*/
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#include <stddef.h> /* size_t */
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#include <ctype.h>
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#include "strnatcmp.h"
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/* These are defined as macros to make it easier to adapt this code to
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* different characters types or comparison functions. */
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static inline int
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nat_isdigit(nat_char a)
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{
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return isdigit((unsigned char) a);
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}
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static inline int
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nat_isspace(nat_char a)
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{
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return isspace((unsigned char) a);
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}
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static inline nat_char
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nat_toupper(nat_char a)
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{
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return toupper((unsigned char) a);
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}
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static int
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compare_right(nat_char const *a, nat_char const *b)
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{
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int bias = 0;
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/* The longest run of digits wins. That aside, the greatest
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value wins, but we can't know that it will until we've scanned
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both numbers to know that they have the same magnitude, so we
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remember it in BIAS. */
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for (;; a++, b++) {
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if (!nat_isdigit(*a) && !nat_isdigit(*b))
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return bias;
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if (!nat_isdigit(*a))
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return -1;
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if (!nat_isdigit(*b))
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return +1;
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if (*a < *b) {
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if (!bias)
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bias = -1;
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} else if (*a > *b) {
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if (!bias)
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bias = +1;
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} else if (!*a && !*b)
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return bias;
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}
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return 0;
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}
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static int
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compare_left(nat_char const *a, nat_char const *b)
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{
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/* Compare two left-aligned numbers: the first to have a
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different value wins. */
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for (;; a++, b++) {
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if (!nat_isdigit(*a) && !nat_isdigit(*b))
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return 0;
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if (!nat_isdigit(*a))
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return -1;
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if (!nat_isdigit(*b))
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return +1;
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if (*a < *b)
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return -1;
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if (*a > *b)
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return +1;
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}
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return 0;
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}
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static int
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strnatcmp0(nat_char const *a, nat_char const *b, int fold_case)
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{
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int ai, bi;
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nat_char ca, cb;
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int fractional, result;
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ai = bi = 0;
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while (1) {
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ca = a[ai]; cb = b[bi];
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/* skip over leading spaces or zeros */
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while (nat_isspace(ca))
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ca = a[++ai];
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while (nat_isspace(cb))
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cb = b[++bi];
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/* process run of digits */
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if (nat_isdigit(ca) && nat_isdigit(cb)) {
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fractional = (ca == '0' || cb == '0');
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if (fractional) {
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if ((result = compare_left(a+ai, b+bi)) != 0)
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return result;
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} else {
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if ((result = compare_right(a+ai, b+bi)) != 0)
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return result;
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}
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}
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if (!ca && !cb) {
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/* The strings compare the same. Perhaps the caller
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will want to call strcmp to break the tie. */
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return 0;
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}
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if (fold_case) {
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ca = nat_toupper(ca);
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cb = nat_toupper(cb);
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}
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if (ca < cb)
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return -1;
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if (ca > cb)
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return +1;
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++ai; ++bi;
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}
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}
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int
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strnatcmp(nat_char const *a, nat_char const *b) {
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return strnatcmp0(a, b, 0);
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}
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/* Compare, recognizing numeric string and ignoring case. */
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int
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strnatcasecmp(nat_char const *a, nat_char const *b) {
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return strnatcmp0(a, b, 1);
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}
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