Encoder.cpp

Go to the documentation of this file.

/* 
 * Copyright (C) 2006-2010 Jacek Sieka, arnetheduck on gmail point com
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include "adchpp.h"

#include "Encoder.h"
#include "common.h"

namespace adchpp {

using namespace std;

const int8_t Encoder::base32Table[256] = {
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,26,27,28,29,30,31,-1,-1,-1,-1,-1,-1,-1,-1,
    -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,
    15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1,
    -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,
    15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
};

const char Encoder::base32Alphabet[32] = { 
    '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', '2', '3', '4', '5', '6', '7'
};

string& Encoder::toBase32(const uint8_t* src, size_t len, string& dst) {
    // Code snagged from the bitzi bitcollider
    size_t i, index;
    uint8_t word;
    dst.reserve(((len * 8) / 5) + 1);

    for(i = 0, index = 0; i < len;) {
        /* Is the current word going to span a byte boundary? */
        if (index > 3) {
            word = (uint8_t)(src[i] & (0xFF >> index));
            index = (index + 5) % 8;
            word <<= index;
            if ((i + 1) < len)
                word |= src[i + 1] >> (8 - index);

            i++;
        } else {
            word = (uint8_t)(src[i] >> (8 - (index + 5))) & 0x1F;
            index = (index + 5) % 8;
            if (index == 0)
                i++;
        }

        dcassert(word < 32);
        dst += base32Alphabet[word];
    }
    return dst;
}

void Encoder::fromBase32(const char* src, uint8_t* dst, size_t len) {
    size_t i, index, offset;

    memset(dst, 0, len);
    for(i = 0, index = 0, offset = 0; src[i]; i++) {
        // Skip what we don't recognise
        int8_t tmp = base32Table[(unsigned char)src[i]];

        if(tmp == -1)
            continue;

        if (index <= 3) {
            index = (index + 5) % 8;
            if (index == 0) {
                dst[offset] |= tmp;
                offset++;
                if(offset == len)
                    break;
            } else {
                dst[offset] |= tmp << (8 - index);
            }
        } else {
            index = (index + 5) % 8;
            dst[offset] |= (tmp >> index);
            offset++;
            if(offset == len)
                break;
            dst[offset] |= tmp << (8 - index);
        }
    }
}

}