文章关键字 ‘urlencode函数’

题目好像弄错了，PHP本身就是用C语言写，所以准确来说题目应该是PHP的urlencode函数的C语言源码。在用C语言写某个程序（至于是什么程序，参见其他文章）的时候要用到PHP的urlencode函数。好在PHP是开源的，就搜索了一下PHP的源码，在php-5.3.2\ext\standard\url.c文件中找到了PHP的urlencode函数的C语言源代码，感兴趣的可以下载PHP源码看看。但是因为用到了PHP源码中的其他函数，urlencode的源代码不能直接用到C语言程序中，我参考源码修改了一下，就可以直接使用了。代码如下，s为需要urlencode的字符串，len为字符串的长度，new_length为urlencode后新字符串的长度：

char *php_url_encode(char const *s, int len, int *new_length)
{
	#define safe_emalloc(nmemb, size, offset)	malloc((nmemb) * (size) + (offset))
	static unsigned char hexchars[] = "0123456789ABCDEF";
	register unsigned char c;
	unsigned char *to, *start;
	unsigned char const *from, *end;
	
	from = (unsigned char *)s;
	end = (unsigned char *)s + len;
	start = to = (unsigned char *) safe_emalloc(3, len, 1);

	while (from < end) {
		c = *from++;

		if (c == ' ') {
			*to++ = '+';
#ifndef CHARSET_EBCDIC
		} else if ((c < '0' && c != '-' && c != '.') ||
				   (c < 'A' && c > '9') ||
				   (c > 'Z' && c < 'a' && c != '_') ||
				   (c > 'z')) {
			to[0] = '%';
			to[1] = hexchars[c >> 4];
			to[2] = hexchars[c & 15];
			to += 3;
#else /*CHARSET_EBCDIC*/
		} else if (!isalnum(c) && strchr("_-.", c) == NULL) {
			/* Allow only alphanumeric chars and '_', '-', '.'; escape the rest */
			to[0] = '%';
			to[1] = hexchars[os_toascii[c] >> 4];
			to[2] = hexchars[os_toascii[c] & 15];
			to += 3;
#endif /*CHARSET_EBCDIC*/
		} else {
			*to++ = c;
		}
	}
	*to = 0;
	if (new_length) {
		*new_length = to - start;
	}
	return (char *) start;
}

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