fnmatch源码阅读

源码下载地址如下：

http://web.mit.edu/freebsd/csup/fnmatch.h
http://web.mit.edu/freebsd/csup/fnmatch.c

代码整体不错，但是中有一些地方稍有不足。我没有去改（添加了一些{}，以便结构清晰）。

/*
* Copyright (c) 1989, 1993, 1994
*	The Regents of the University of California.  All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Guido van Rossum.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
*    must display the following acknowledgement:
*	This product includes software developed by the University of
*	California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* From FreeBSD fnmatch.c 1.11
* $Id: fnmatch.c,v 1.3 1997/08/19 02:34:30 jdp Exp $
*/

#ifndef	_FNMATCH_H_
#define	_FNMATCH_H_

#define	FNM_NOMATCH	1	/* Match failed. */

#define	FNM_NOESCAPE	0x01	/* 禁用反斜杠进行转义 */
#define	FNM_PATHNAME	0x02	/* 斜杠只能被斜杠匹配(即不能被*或者?匹配) */
#define	FNM_PERIOD	0x04	/* Period must be matched by period. */
/*如果这个标志设置了，string 里的起始点号必须匹配 pattern 里的点号。
一个点号被认为是起始点号，如果它是string 第一个字符，或者如果同时设
置了 FNM_PATHNAME，紧跟在斜杠后面的点号。
*/
#define	FNM_LEADING_DIR	0x08	/* Ignore /<tail> after Imatch. */
/*如果这个标志(GNU 扩展)设置了，模式必须匹配跟随在斜杠之后的 string
的初始片断。这个标志主要是给 glibc 内部使用并且只在一定条件下实现。
即只匹配目录路径部分，不匹配到具体文件名
*/
#define	FNM_CASEFOLD	0x10	/* 模式匹配忽略大小写. */
#define FNM_PREFIX_DIRS	0x20	/* Directory prefixes of pattern match too. */

/* Make this compile successfully with "gcc -traditional" */
#ifndef __STDC__
#define const	/* empty */
#endif

int	 fnmatch(const char *, const char *, int);

#endif /* !_FNMATCH_H_ */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)fnmatch.c	8.2 (Berkeley) 4/16/94";
#endif /* LIBC_SCCS and not lint */

/*
* 函数fnmatch()，如POSIX 1003.2-1992 B.6节所述。
* 将文件名或者目录名与pattern进行比较
*/

#include <ctype.h>
#include <string.h>
#include <stdio.h>

// 定义字符串结尾标志
#define	EOS	''

static const char *rangematch(const char *, char, int);

int
fnmatch(const char *pattern, const char *string, int flags)
{
	const char *stringstart;
	char c, test;

	for (stringstart = string;;){
        // 逐个取匹配字符串中的成分(分为*?和range三种)
		switch (c = *pattern++) {
		case EOS:   // 没有匹配串的情况
            // 如果忽略'/'后面的部分，则匹配成功
			if ((flags & FNM_LEADING_DIR) && *string == '/'){
				return (0);
			}
			// 如果string也是空串，则匹配成功
			return (*string == EOS ? 0 : FNM_NOMATCH);
		case '?':   // 匹配单个任意字符
			// string为空则不能匹配
			if (*string == EOS){
				return (FNM_NOMATCH);
			}
			// 判断'/'是否只能由'/'进行匹配
			if (*string == '/' && (flags & FNM_PATHNAME)){
				return (FNM_NOMATCH);
			}
			// 判断是否string中的起始'.'必须匹配pattern中的'.'（即'?'不能匹配'.'）
			if (*string == '.' && (flags & FNM_PERIOD) &&
				(string == stringstart ||
				((flags & FNM_PATHNAME) && *(string - 1) == '/'))){
				return (FNM_NOMATCH);
			}
			// 匹配成功则匹配string的下一个字符
			++string;
			break;
		case '*':   // 匹配单个或多个任意字符
			c = *pattern;
			/* 多个'*'当做一个 */
			while (c == '*'){
				c = *++pattern;
			}
			// 判断是否需要对'.'进行处理
			if (*string == '.' && (flags & FNM_PERIOD) &&
				(string == stringstart ||
				((flags & FNM_PATHNAME) && *(string - 1) == '/'))){
				return (FNM_NOMATCH);
			}

			/* 优化 * 在匹配串结尾或者在 /. 之前的匹配*/
			if (c == EOS){  // 在结尾
                // 判断 * 是否不匹配斜杠
				if (flags & FNM_PATHNAME){
                    // 不匹配斜杠，则判断是否忽略'/'之后部分
					return ((flags & FNM_LEADING_DIR) ||
						((strchr(string, '/') == NULL) ? 0 : FNM_NOMATCH));
				}else{
					return (0);
				}
			}
			else if (c == '/' && flags & FNM_PATHNAME) { // 在 /. 之前
                // 如果string后没有 '/'则匹配失败
				if ((string = strchr(string, '/')) == NULL){
					return (FNM_NOMATCH);
				}
				break;
			}

			/* 非特殊情况下，递归匹配 */
			while ((test = *string) != EOS) {
                // 不对'.'进行特殊处理，进行匹配（则只需判断'/'匹配情况）
				if (!fnmatch(pattern, string, flags & ~FNM_PERIOD)){
					return (0); // 匹配成功
				}
				// 对 '/'进行处理（斜杠只匹配斜杠，则匹配失败）
				if (test == '/' && flags & FNM_PATHNAME){
					break;
				}
				++string;
			}
			// 返回匹配失败（即*没有匹配成功,'.'和'/'上的匹配没有成功）
			return (FNM_NOMATCH);
		case '[':   // range 范围匹配
			if (*string == EOS){
				return (FNM_NOMATCH);   // 空串匹配失败
			}
			if (*string == '/' && flags & FNM_PATHNAME){
				return (FNM_NOMATCH);   // '/'匹配失败
			}
			if ((pattern =
				rangematch(pattern, *string, flags)) == NULL){
				return (FNM_NOMATCH);   // 范围匹配失败
			}
			++string;
			break;
		case '\':  // 斜杠匹配（判断是否需要转义）
			if (!(flags & FNM_NOESCAPE)) {
				if ((c = *pattern++) == EOS) {
					c = '\';
					--pattern;
				}
			}
			/* 非上述部分，则直接匹配单个字符 */
		default:
			if (c == *string){
                ;   // 直接匹配上了
			}else if ((flags & FNM_CASEFOLD) &&
				(tolower((unsigned char)c) ==
					tolower((unsigned char)*string))){
				;   // 忽略大小写匹配成功
			}
			else if ((flags & FNM_PREFIX_DIRS) && *string == EOS &&
				((c == '/' && string != stringstart) ||
				(string == stringstart + 1 && *stringstart == '/'))){
				return (0); // 匹配成功
			}
			else{
				return (FNM_NOMATCH); // 匹配失败
			}
			string++;
			break;
		}
	}
	/* NOTREACHED */
}

// 字符范围匹配
// pattern传入如 [a-x]*** 形式的字符串
// 匹配失败或匹配到EOS结束(也是失败)，返回NULL
// 成功返回匹配串的下一个匹配成分首地址
static const char *
rangematch(const char *pattern, char test, int flags)
{
    // 此处没有对c进行初始化，可能出问题（栈上变量默认值未定）
	int negate, ok;
	char c, c2;

	/*
	* A bracket expression starting with an unquoted circumflex
	* character produces unspecified results
	* 以无引号 ^ 字符开始的方括号表达式，将产生未指定的结果
	* (IEEE 1003.2-1992,3.13.2).  此实现将其视为 '!',以与正则表达式语法保持一致.
	* J.T. Conklin (conklin@ngai.kaleida.com)
	*/
	// 检测方括号表达式中第一个字符
	// 如果为!或者^，则对后面匹配的结果取反
	if ((negate = (*pattern == '!' || *pattern == '^'))){
		++pattern;
	}

	// 忽略大小写，则转为小写处理
	if (flags & FNM_CASEFOLD){
		test = tolower((unsigned char)test);
	}
	// 循环到方括号表达式结束
	for (ok = 0; (c = *pattern++) != ']';) {
        // 如果没有禁用转义，获取字符
		if (c == '\' && !(flags & FNM_NOESCAPE)){
			c = *pattern++;
		}
		// 匹配结束
		if (c == EOS){
			return (NULL);
		}
        // 忽略大小写，则转为小写
		if (flags & FNM_CASEFOLD){
			c = tolower((unsigned char)c);
        }
        // 如果当前匹配项c 的下一个是'-'，则获取'-'后面的一个字符
        // 例如，匹配串为 [a-x] 当前c为a,则c2为x，表示匹配a-x之间字符
		if (*pattern == '-'
			&& (c2 = *(pattern + 1)) != EOS && c2 != ']') {
			pattern += 2;
			// 判断是否需要转义
			if (c2 == '\' && !(flags & FNM_NOESCAPE)){
				c2 = *pattern++;
			}
			if (c2 == EOS){
				return (NULL);
			}
            // 判断是否区分大小写
			if (flags & FNM_CASEFOLD){
				c2 = tolower((unsigned char)c2);
			}
            // 判断test是否位于 [c,c2]区间
			if ((unsigned char)c <= (unsigned char)test &&
				(unsigned char)test <= (unsigned char)c2){
				ok = 1;
			}
		}
		else if (c == test){
			ok = 1;
		}
	}
	// 返回匹配结果
	return (ok == negate ? NULL : pattern);
}