std::string UrlEncode(const std::string& szToEncode)
{
	std::string src = szToEncode;
	char hex[] = "0123456789ABCDEF";
	string dst;


	for (size_t i = 0; i < src.size(); ++i)
	{
		unsigned char cc = src[i];
		if ( cc >= ‘A‘ && cc <= ‘Z‘ 
                 || cc >=‘a‘ && cc <= ‘z‘
                 || cc >=‘0‘ && cc <= ‘9‘
                 || cc == ‘.‘
                 || cc == ‘_‘
                 || cc == ‘-‘
                 || cc == ‘*‘)
		{
			if (cc == ‘ ‘)
			{
				dst += "+";
			}
			else
				dst += cc;
		}
		else
		{
			unsigned char c = static_cast<unsigned char>(src[i]);
			dst += ‘%‘;
			dst += hex[c / 16];
			dst += hex[c % 16];
		}
	}
	return dst;
}

std::string UrlDecode(const std::string& szToDecode)
{
	std::string result;
	int hex = 0;
	for (size_t i = 0; i < szToDecode.length(); ++i)
	{
		switch (szToDecode[i])
		{
		case ‘+‘:
			result += ‘ ‘;
			break;
		case ‘%‘:
			if (isxdigit(szToDecode[i + 1]) && isxdigit(szToDecode[i + 2]))
			{
				std::string hexStr = szToDecode.substr(i + 1, 2);
				hex = strtol(hexStr.c_str(), 0, 16);
				//字母和数字[0-9a-zA-Z]、一些特殊符号[$-_.+!*‘(),] 、以及某些保留字[$&+,/:;=?@]
				//可以不经过编码直接用于URL
				if (!((hex >= 48 && hex <= 57) ||	//0-9
					(hex >=97 && hex <= 122) ||	//a-z
					(hex >=65 && hex <= 90) ||	//A-Z
					//一些特殊符号及保留字[$-_.+!*‘(),]  [$&+,/:;=?@]
					hex == 0x21 || hex == 0x24 || hex == 0x26 || hex == 0x27 || hex == 0x28 || hex == 0x29
					|| hex == 0x2a || hex == 0x2b|| hex == 0x2c || hex == 0x2d || hex == 0x2e || hex == 0x2f
					|| hex == 0x3A || hex == 0x3B|| hex == 0x3D || hex == 0x3f || hex == 0x40 || hex == 0x5f
					))
				{
					result += char(hex);
					i += 2;
				}
				else result += ‘%‘;
			}else {
				result += ‘%‘;
			}
			break;
		default:
			result += szToDecode[i];
			break;
		}
	}
	return result;
}

C++语言的url encode 和decode