Base64.cpp

// *********************************************************************
// * Base64 - a simple base64 encoder and decoder.
// *
// *     Copyright (c) 1999, Bob Withers - bwit@pobox.com
// *
// * This code may be freely used for any purpose, either personal
// * or commercial, provided the authors copyright notice remains
// * intact.
// *
// * Enhancements by Stanley Yamane:
// *     o reverse lookup table for the decode function 
// *     o reserve string buffer space in advance
// *
// *********************************************************************

#include<ImLib3D/Base64.hpp>


static const char          fillchar = '=';
static const std::string::size_type np = std::string::npos;

// 0000000000111111111122222222223333333333444444444455555555556666
// 0123456789012345678901234567890123456789012345678901234567890123
static const std::string Base64Table("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");

// Decode Table gives the index of any valid base64 character in the Base64 table]
// 65 == A, 97 == a, 48 == 0, 43 == +, 47 == /

                                               // 0  1  2  3  4  5  6  7  8  9 
const std::string::size_type DecodeTable[] = {np,np,np,np,np,np,np,np,np,np,  // 0 - 9
                                              np,np,np,np,np,np,np,np,np,np,  //10 -19
                                              np,np,np,np,np,np,np,np,np,np,  //20 -29
                                              np,np,np,np,np,np,np,np,np,np,  //30 -39
                                              np,np,np,62,np,np,np,63,52,53,  //40 -49
                                              54,55,56,57,58,59,60,61,np,np,  //50 -59
                                              np,np,np,np,np, 0, 1, 2, 3, 4,  //60 -69
                                              5, 6, 7, 8, 9,10,11,12,13,14,  //70 -79
                                              15,16,17,18,19,20,21,22,23,24,  //80 -89
                                              25,np,np,np,np,np,np,26,27,28,  //90 -99
                                              29,30,31,32,33,34,35,36,37,38,  //100 -109
                                              39,40,41,42,43,44,45,46,47,48,  //110 -119
                                              49,50,51,np,np,np,np,np,np,np,  //120 -129
                                              np,np,np,np,np,np,np,np,np,np,  //130 -139
                                              np,np,np,np,np,np,np,np,np,np,  //140 -149
                                              np,np,np,np,np,np,np,np,np,np,  //150 -159
                                              np,np,np,np,np,np,np,np,np,np,  //160 -169
                                              np,np,np,np,np,np,np,np,np,np,  //170 -179
                                              np,np,np,np,np,np,np,np,np,np,  //180 -189
                                              np,np,np,np,np,np,np,np,np,np,  //190 -199
                                              np,np,np,np,np,np,np,np,np,np,  //200 -209
                                              np,np,np,np,np,np,np,np,np,np,  //210 -219
                                              np,np,np,np,np,np,np,np,np,np,  //220 -229
                                              np,np,np,np,np,np,np,np,np,np,  //230 -239
                                              np,np,np,np,np,np,np,np,np,np,  //240 -249
                                              np,np,np,np,np,np               //250 -256
};


std::string 
Base64::Encode(const std::string& data)
{
    std::string::size_type  i;
    char               c;
    std::string::size_type  len = data.length();
    std::string             ret;

    ret.reserve(len * 2);

    for (i = 0; i < len; ++i)
    {
        c = (data[i] >> 2) & 0x3f;
        ret.append(1, Base64Table[c]);
        c = (data[i] << 4) & 0x3f;
        if (++i < len)
            c |= (data[i] >> 4) & 0x0f;

        ret.append(1, Base64Table[c]);
        if (i < len)
        {
            c = (data[i] << 2) & 0x3f;
            if (++i < len)
                c |= (data[i] >> 6) & 0x03;

            ret.append(1, Base64Table[c]);
        }
        else
        {
            ++i;
            ret.append(1, fillchar);
        }

        if (i < len)
        {
            c = data[i] & 0x3f;
            ret.append(1, Base64Table[c]);
        }
        else
        {
            ret.append(1, fillchar);
        }
    }

    return(ret);
}

std::string 
Base64::Decode(const std::string& data)
{
    std::string::size_type  i;
    char               c;
    char               c1;
    std::string::size_type  len = data.length();
    std::string             ret;

    ret.reserve(len);

    for (i = 0; i < len; ++i)
    {
        c = (char) DecodeTable[(unsigned char)data[i]];
        ++i;
        c1 = (char) DecodeTable[(unsigned char)data[i]];
        c = (c << 2) | ((c1 >> 4) & 0x3);
        ret.append(1, c);
        if (++i < len)
        {
            c = data[i];
            if (fillchar == c)
                break;

            c = (char) DecodeTable[(unsigned char)data[i]];
            c1 = ((c1 << 4) & 0xf0) | ((c >> 2) & 0xf);
            ret.append(1, c1);
        }

        if (++i < len)
        {
            c1 = data[i];
            if (fillchar == c1)
                break;

            c1 = (char) DecodeTable[(unsigned char)data[i]];
            c = ((c << 6) & 0xc0) | c1;
            ret.append(1, c);
        }
    }

    return(ret);
}

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