i2pd/base64.cpp

#include <stdlib.h>
#include "base64.h"

namespace i2p
{
namespace data
{

    static void iT64Build(void);

    /*
    *
    * BASE64 Substitution Table
    * -------------------------
    *
    * Direct Substitution Table
    */

    static char T64[64] = { 
               'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
               'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
               'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
               'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
               'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
               'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
               'w', 'x', 'y', 'z', '0', '1', '2', '3',
               '4', '5', '6', '7', '8', '9', '-', '~'
    };

    const char * GetBase64SubstitutionTable ()
    {
        return T64;
    }   
    
    /*
     * Reverse Substitution Table (built in run time)
     */
    static char iT64[256];
    static int isFirstTime = 1;

    /*
    * Padding 
    */
    static char P64 = '='; 


    size_t ByteStreamToBase64(const uint8_t* InBuffer, size_t InCount, char* OutBuffer, size_t len)
    {
        unsigned char * ps;
        unsigned char * pd;
        unsigned char   acc_1;
        unsigned char   acc_2;
        int             i; 
        int             n; 
        int             m; 
        size_t outCount;

        ps = (unsigned char *)InBuffer;
        n = InCount/3;
        m = InCount%3;
        if (!m)
             outCount = 4*n;
        else
             outCount = 4*(n+1);
        if (outCount > len) return 0;
        pd = (unsigned char *)OutBuffer;
        for ( i = 0; i<n; i++ ){
             acc_1 = *ps++;
             acc_2 = (acc_1<<4)&0x30; 
             acc_1 >>= 2;              /* base64 digit #1 */
             *pd++ = T64[acc_1];
             acc_1 = *ps++;
             acc_2 |= acc_1 >> 4;      /* base64 digit #2 */
             *pd++ = T64[acc_2];
             acc_1 &= 0x0f;
             acc_1 <<=2;
             acc_2 = *ps++;
             acc_1 |= acc_2>>6;        /* base64 digit #3 */
             *pd++ = T64[acc_1];
             acc_2 &= 0x3f;            /* base64 digit #4 */
             *pd++ = T64[acc_2];
        } 
        if ( m == 1 ){
             acc_1 = *ps++;
             acc_2 = (acc_1<<4)&0x3f;  /* base64 digit #2 */
             acc_1 >>= 2;              /* base64 digit #1 */
             *pd++ = T64[acc_1];
             *pd++ = T64[acc_2];
             *pd++ = P64;
             *pd++ = P64;

        }
        else if ( m == 2 ){
             acc_1 = *ps++;
             acc_2 = (acc_1<<4)&0x3f; 
             acc_1 >>= 2;              /* base64 digit #1 */
             *pd++ = T64[acc_1];
             acc_1 = *ps++;
             acc_2 |= acc_1 >> 4;      /* base64 digit #2 */
             *pd++ = T64[acc_2];
             acc_1 &= 0x0f;
             acc_1 <<=2;               /* base64 digit #3 */
             *pd++ = T64[acc_1];
             *pd++ = P64;
        }
        
        return outCount;
    }


    size_t Base64ToByteStream(const char * InBuffer, size_t InCount, uint8_t* OutBuffer, size_t len)
    {
        unsigned char * ps;
        unsigned char * pd;
        unsigned char   acc_1;
        unsigned char   acc_2;
        int             i; 
        int             n; 
        int             m; 
        size_t outCount;

        if (isFirstTime) iT64Build();
        n = InCount/4;
        m = InCount%4;
        if(InCount && !m) 
             outCount = 3*n;
        else {
             outCount = 0;
             return 0;
        }
        
        ps = (unsigned char *)(InBuffer + InCount - 1);
        while ( *ps-- == P64 ) outCount--;
        ps = (unsigned char *)InBuffer;
        
        if (outCount > len) return 0;
        pd = OutBuffer;
        auto endOfOutBuffer = OutBuffer + outCount;     
        for ( i = 0; i < n; i++ ){
             acc_1 = iT64[*ps++];
             acc_2 = iT64[*ps++];
             acc_1 <<= 2;
             acc_1 |= acc_2>>4;
             *pd++  = acc_1;
             if (pd >= endOfOutBuffer) break;

             acc_2 <<= 4;
             acc_1 = iT64[*ps++];
             acc_2 |= acc_1 >> 2;
             *pd++ = acc_2;
              if (pd >= endOfOutBuffer) break;  

             acc_2 = iT64[*ps++];
             acc_2 |= acc_1 << 6;
             *pd++ = acc_2;
        }

        return outCount;
    }

    /*
    *
    * iT64
    * ----
    * Reverse table builder. P64 character is replaced with 0
    *
    *
    */
    static void iT64Build()
    {
        int  i;
        isFirstTime = 0;
        for ( i=0; i<256; i++ ) iT64[i] = -1;
        for ( i=0; i<64; i++ ) iT64[(int)T64[i]] = i;
        iT64[(int)P64] = 0;
    }

    size_t Base32ToByteStream (const char * inBuf, size_t len, uint8_t * outBuf, size_t outLen) 
    {
        int tmp = 0, bits = 0;
        size_t ret = 0;
        for (size_t i = 0; i < len; i++)
        {
            char ch = inBuf[i]; 
            if (ch >= '2' && ch <= '7') // digit
                ch = (ch - '2') + 26; // 26 means a-z
            else if (ch >= 'a' && ch <= 'z')
                ch = ch - 'a'; // a = 0
            else
                return 0; // unexpected character
            
            tmp |= ch;
            bits += 5;
            if (bits >= 8)
            {
                if (ret >= outLen) return ret;
                outBuf[ret] = tmp >> (bits - 8);
                bits -= 8;
                ret++;
            }
            tmp <<= 5;
        }
        return ret;
    }

    size_t ByteStreamToBase32 (const uint8_t * inBuf, size_t len, char * outBuf, size_t outLen)
    {
        if(!len)
            return 0; // No data given

        size_t ret = 0, pos = 1;
        int bits = 8, tmp = inBuf[0];
        while (ret < outLen && (bits > 0 || pos < len))
        {   
            if (bits < 5)
            {
                if (pos < len)
                {
                    tmp <<= 8;
                    tmp |= inBuf[pos] & 0xFF;
                    pos++;
                    bits += 8;
                }
                else // last byte
                {
                    tmp <<= (5 - bits);
                    bits = 5;
                }
            }   
        
            bits -= 5;
            int ind = (tmp >> bits) & 0x1F;
            outBuf[ret] = (ind < 26) ? (ind + 'a') : ((ind - 26) + '2');
            ret++;
        }
        return ret;
    }
}
}