C++ 写的UrlEncode和UrlDecode实例

unsigned char ToHex(unsigned char x) 
{ 
 return x > 9 ? x + 55 : x + 48; 
} 
 
unsigned char FromHex(unsigned char x) 
{ 
 unsigned char y; 
 if (x >= 'A' && x <= 'Z') y = x - 'A' + 10; 
 else if (x >= 'a' && x <= 'z') y = x - 'a' + 10; 
 else if (x >= '0' && x <= '9') y = x - '0'; 
 else assert(0); 
 return y; 
} 
 
std::string UrlEncode(const std::string& str) 
{ 
 std::string strTemp = ""; 
 size_t length = str.length(); 
 for (size_t i = 0; i < length; i++) 
 { 
  if (isalnum((unsigned char)str[i]) || 
   (str[i] == '-') || 
   (str[i] == '_') || 
   (str[i] == '.') || 
   (str[i] == '~')) 
   strTemp += str[i]; 
  else if (str[i] == ' ') 
   strTemp += "+"; 
  else 
  { 
   strTemp += '%'; 
   strTemp += ToHex((unsigned char)str[i] >> 4); 
   strTemp += ToHex((unsigned char)str[i] % 16); 
  } 
 } 
 return strTemp; 
} 
 
std::string UrlDecode(const std::string& str) 
{ 
 std::string strTemp = ""; 
 size_t length = str.length(); 
 for (size_t i = 0; i < length; i++) 
 { 
  if (str[i] == '+') strTemp += ' '; 
  else if (str[i] == '%') 
  { 
   assert(i + 2 < length); 
   unsigned char high = FromHex((unsigned char)str[++i]); 
   unsigned char low = FromHex((unsigned char)str[++i]); 
   strTemp += high*16 + low; 
  } 
  else strTemp += str[i]; 
 } 
 return strTemp; 
} 

#include <iostream> 
#include <string>
using namespace std;
 
char dec2hexChar(short int n) {
	if (0 <= n && n <= 9) {
		return char(short('0') + n);
	}
	else if (10 <= n && n <= 15) {
		return char(short('A') + n - 10);
	}
	else {
		return char(0);
	}
}
 
short int hexChar2dec(char c) {
	if ('0' <= c && c <= '9') {
		return short(c - '0');
	}
	else if ('a' <= c && c <= 'f') {
		return (short(c - 'a') + 10);
	}
	else if ('A' <= c && c <= 'F') {
		return (short(c - 'A') + 10);
	}
	else {
		return -1;
	}
}
 
string escapeURL(const string& URL)
{
	string result = "";
	for (unsigned int i = 0; i < URL.length(); i++) {
		char c = URL[i];
		if (
			('0' <= c && c <= '9') ||
			('a' <= c && c <= 'z') ||
			('A' <= c && c <= 'Z') ||
			c == '/' || c == '.'
			) {
			result += c;
		}
		else {
			int j = (short int)c;
			if (j < 0) {
				j += 256;
			}
			int i1, i0;
			i1 = j / 16;
			i0 = j - i1 * 16;
			result += '%';
			result += dec2hexChar(i1);
			result += dec2hexChar(i0);
		}
	}
	return result;
}
 
string deescapeURL(const string& URL) {
	string result = "";
	for (unsigned int i = 0; i < URL.length(); i++) {
		char c = URL[i];
		if (c != '%') {
			result += c;
		}
		else {
			char c1 = URL[++i];
			char c0 = URL[++i];
			int num = 0;
			num += hexChar2dec(c1) * 16 + hexChar2dec(c0);
			result += char(num);
		}
	}
	return result;
}