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 Tokenizer 学习笔记
三步搞定phpwind的静态化部署
DEDE5.3把tag标签逗号改成空格的方法分享
实例解析:从IIS的ASP迁移到APACHE的PHP
PHP读取Excel 之 Spreadsheet_Excel_Reader
PHP导出Excel 之 Spreadsheet_Excel_Writer
PDO不推广,PHP得不到发展
勇于创新,激情开拓新的未来
PHPCMS开发文档里看到PHP编码规范
一个模版引擎的诞生 开发者的思考
关于PHP开发框架
开发框架的选择和设计经验谈
框架带给我们什么(浅谈PHP框架对PHP发展的影响)
通过PHP实现DataGrid功能
php curl函数应用方法之模拟浏览器
单汉字转UNICODE
php在线打包/解包
listdir($dir) 目录读取函数
使用Apache的rewrite技术
php正则

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: 158 ::
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