c++ 版本url encode 和url decode 代码

#include <iostream>
#include <assert.h>

using namespace std;

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;
}

int main(int argc,char *argv[])
{

string unencode_url(argv[1]);
cout << "unencode_url: " << unencode_url << endl;
string   encode_url = UrlEncode(unencode_url);
cout << "encode_url: " << encode_url << endl;
string   decode_url = UrlDecode(encode_url);
cout << "decode_url: " << decode_url << endl;
}