当前位置: 首页 > 图文教程 > 网络编程 > PHP > php natsort内核函数浅析

PHP
PHP实时显示输出
php生成缩略图的类代码
php相当简单的分页类
smarty section简介与用法分析
php优化及高效提速问题的实现方法
php下实现在指定目录搜索指定类型文件的函数
PHP base64+gzinflate压缩编码和解码代码
脚本安全的本质_PHP+MYSQL
使用eAccelerator加密PHP程序
PHP注释实例技巧
php 友好URL的实现(吐血推荐)
关于DISCUZ不用通行证登陆得内容介绍
不用mod_rewrite直接用php实现伪静态化页面代码
Cannot modify header information错误解决方法
php获取地址栏信息的代码
php email邮箱正则
php preg_match_all结合str_replace替换内容中所有img
PHP中str_replace函数使用小结
Zend studio for eclipse中使php可以调用mysql相关函数的设置方法
php flush类输出缓冲剖析

PHP 中的 php natsort内核函数浅析


出处:互联网   整理: 软晨网(RuanChen.com)   发布: 2009-09-13   浏览: 90 ::
收藏到网摘: n/a

今天发现了php有个自然排序的函数----natsort,第一次听说了原来还有一种叫做“自然排序”的算法,很好奇

官方手册(http://us.php.net/manual/en/function.natsort.php

复制代码 代码如下:
复制代码 代码如下:

/* {{{ compare_right
*/
static int
compare_right(char const **a, char const *aend, char const **b, char const *bend)
{
int bias = 0;
/* The longest run of digits wins. That aside, the greatest
value wins, but we can't know that it will until we've scanned
both numbers to know that they have the same magnitude, so we
remember it in BIAS. */
for(;; (*a)++, (*b)++) {
if ((*a == aend || !isdigit((int)(unsigned char)**a)) &&
(*b == bend || !isdigit((int)(unsigned char)**b)))
return bias;
else if (*a == aend || !isdigit((int)(unsigned char)**a))
return -1;
else if (*b == bend || !isdigit((int)(unsigned char)**b))
return +1;
else if (**a < **b) {
if (!bias)
bias = -1;
} else if (**a > **b) {
if (!bias)
bias = +1;
}
}
return 0;
}
/* }}} */
/* {{{ compare_left
*/
static int
compare_left(char const **a, char const *aend, char const **b, char const *bend)
{
/* Compare two left-aligned numbers: the first to have a
different value wins. */
for(;; (*a)++, (*b)++) {
if ((*a == aend || !isdigit((int)(unsigned char)**a)) &&
(*b == bend || !isdigit((int)(unsigned char)**b)))
return 0;
else if (*a == aend || !isdigit((int)(unsigned char)**a))
return -1;
else if (*b == bend || !isdigit((int)(unsigned char)**b))
return +1;
else if (**a < **b)
return -1;
else if (**a > **b)
return +1;
}
return 0;
}
/* }}} */
/* {{{ strnatcmp_ex
* call in array.c: strnatcmp_ex(Z_STRVAL(first), Z_STRLEN(first), Z_STRVAL(second), Z_STRLEN(second), fold_case);
*/
PHPAPI int strnatcmp_ex(char const *a, size_t a_len, char const *b, size_t b_len, int fold_case)
{
char ca, cb;
char const *ap, *bp;
char const *aend = a + a_len,
*bend = b + b_len;
int fractional, result;
if (a_len == 0 || b_len == 0)
return a_len - b_len;
ap = a;
bp = b;
while (1) {
ca = *ap; cb = *bp;
/* skip over leading spaces or zeros */
while (isspace((int)(unsigned char)ca) || (ca == '0' && (ap+1 < aend) && (*(ap+1)!='.')))
ca = *++ap;
while (isspace((int)(unsigned char)cb) || (cb == '0' && (bp+1 < bend) && (*(bp+1)!='.')))
cb = *++bp;
/* process run of digits */
if (isdigit((int)(unsigned char)ca) && isdigit((int)(unsigned char)cb)) {
fractional = (ca == '0' || cb == '0');
if (fractional)
result = compare_left(&ap, aend, &bp, bend);
else
result = compare_right(&ap, aend, &bp, bend);
if (result != 0)
return result;
else if (ap == aend && bp == bend)
/* End of the strings. Let caller sort them out. */
return 0;
else {
/* Keep on comparing from the current point. */
ca = *ap; cb = *bp;
}
}
if (fold_case) {
ca = toupper((int)(unsigned char)ca);
cb = toupper((int)(unsigned char)cb);
}
if (ca < cb)
return -1;
else if (ca > cb)
return +1;
++ap; ++bp;
if (ap >= aend && bp >= bend)
/* The strings compare the same. Perhaps the caller
will want to call strcmp to break the tie. */
return 0;
else if (ap >= aend)
return -1;
else if (bp >= bend)
return 1;
}
}
/* }}} */

从strnatcmp_ex函数中的:
复制代码 代码如下:

while (isspace((int)(unsigned char)ca) || (ca == '0' && (ap+1 < aend) && (*(ap+1)!='.')))
ca = *++ap;
while (isspace((int)(unsigned char)cb) || (cb == '0' && (bp+1 < bend) && (*(bp+1)!='.')))
cb = *++bp;

所以,我觉得应该字符串(当前位置开始)中前面的空字符和数字前面的‘0'不会参与比较,比较的结果应该和

http://us.php.net/manual/en/function.natsort.php

http://sourcefrog.net/projects/natsort/example-out.txt

所说的一样,但是在我的php5.2.9中对于“0”的处理结果却不一样(例如“img002.png”与“img1.png”,我的理解应该是前者大于后者,不过在我的5.2.9中却是前者小于后者),原因还没想清楚,可能是5.2.9的一个bug,也可能是自己还没有理解清楚源码的意思。下次配置好环境再好好测试,好好消化~~

在array.c中有两个重要的数据结构很值得我们关注