如何把英文字母等非特殊字符也url編碼

炒雞簡單！上次做到一個CTF的題需要把admin轉化成url編碼（轉化兩次），我網上找半天的網站，都沒有，寫代碼又不想寫，後面看了一下url編碼的介紹發現urlencode其實就是字符的十六進制前面加了個百分號。

0x01
寫代碼太慢了，所以就想着把字符串進行hex編碼再加個%
0x02
再進行一次hex編碼，得到如圖下!：
再加上百分號就好。

0x03
但是如果字符串的量太大的話還是寫代碼，其實代碼也不長。

#include "stdafx.h"
#include <string>

using namespace std;

unsigned int utf8_decode( char *s, unsigned int *pi )
{
    unsigned int c;
    int i = *pi;
    /* one digit utf-8 */
    if ((s[i] & 128)== 0 ) {
        c = (unsigned int) s[i];
        i += 1;
    } else if ((s[i] & 224)== 192 ) { /* 110xxxxx & 111xxxxx == 110xxxxx */
        c = (( (unsigned int) s[i] & 31 ) << 6) +
            ( (unsigned int) s[i+1] & 63 );
        i += 2;
    } else if ((s[i] & 240)== 224 ) { /* 1110xxxx & 1111xxxx == 1110xxxx */
        c = ( ( (unsigned int) s[i] & 15 ) << 12 ) +
            ( ( (unsigned int) s[i+1] & 63 ) << 6 ) +
            ( (unsigned int) s[i+2] & 63 );
        i += 3;
    } else if ((s[i] & 248)== 240 ) { /* 11110xxx & 11111xxx == 11110xxx */
        c =  ( ( (unsigned int) s[i] & 7 ) << 18 ) +
            ( ( (unsigned int) s[i+1] & 63 ) << 12 ) +
            ( ( (unsigned int) s[i+2] & 63 ) << 6 ) +
            ( (unsigned int) s[i+3] & 63 );
        i+= 4;
    } else if ((s[i] & 252)== 248 ) { /* 111110xx & 111111xx == 111110xx */
        c = ( ( (unsigned int) s[i] & 3 ) << 24 ) +
            ( ( (unsigned int) s[i+1] & 63 ) << 18 ) +
            ( ( (unsigned int) s[i+2] & 63 ) << 12 ) +
            ( ( (unsigned int) s[i+3] & 63 ) << 6 ) +
            ( (unsigned int) s[i+4] & 63 );
        i += 5;
    } else if ((s[i] & 254)== 252 ) { /* 1111110x & 1111111x == 1111110x */
        c = ( ( (unsigned int) s[i] & 1 ) << 30 ) +
            ( ( (unsigned int) s[i+1] & 63 ) << 24 ) +
            ( ( (unsigned int) s[i+2] & 63 ) << 18 ) +
            ( ( (unsigned int) s[i+3] & 63 ) << 12 ) +
            ( ( (unsigned int) s[i+4] & 63 ) << 6 ) +
            ( (unsigned int) s[i+5] & 63 );
        i += 6;
    } else {
        c = '?';
        i++;
    }
    *pi = i;
    return c;
}

std::string UrlEncode(const std::string& src)
{
    static    char hex[] = "0123456789ABCDEF";
    std::string dst;
   
    for (size_t i = 0; i < src.size(); i++)
    {
        unsigned char ch = src[i];
        if (isalnum(ch))
        {
            dst += ch;
        }
        else
            if (src[i] == ' ')
            {
                dst += '+';
            }
            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& src)
{
    std::string dst, dsturl;

    int srclen = src.size();

    for (size_t i = 0; i < srclen; i++)
    {
        if (src[i] == '%')
        {
            if(isxdigit(src[i + 1]) && isxdigit(src[i + 2]))
            {
                char c1 = src[++i];
                char c2 = src[++i];
                c1 = c1 - 48 - ((c1 >= 'A') ? 7 : 0) - ((c1 >= 'a') ? 32 : 0);
                c2 = c2 - 48 - ((c2 >= 'A') ? 7 : 0) - ((c2 >= 'a') ? 32 : 0);
                dst += (unsigned char)(c1 * 16 + c2);
            }
        }
        else
            if (src[i] == '+')
            {
                dst += ' ';
            }
            else
            {
                dst += src[i];
            }
    }

    int len = dst.size();
   
    for(unsigned int pos = 0; pos < len;)
    {
        unsigned int nvalue = utf8_decode((char *)dst.c_str(), &pos);
        dsturl += (unsigned char)nvalue;
    }

    return dsturl;
}

// 測試程序

int main(int argc, char* argv[])
{
    string str1 = "VC知識庫 vckbase.com";
    string str2 = "www.vckbase.com/sql.asp?id=2%20update and sele%%ct%fc%80%80%80%80%af";

    printf("%s ", UrlEncode(str1).c_str());    // URL編碼
    printf("%s ", UrlDecode(str2).c_str());    // URL解碼
   
    return 0;
}

代碼作者：https://www.cctry.com/space-uid-51.html