base64.hh

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/* This file is part of the Palabos library.
 *
 * Copyright (C) 2011 FlowKit Sarl
 * Avenue de Chailly 23
 * 1012 Lausanne, Switzerland
 * E-mail contact: contact@flowkit.com
 *
 * The most recent release of Palabos can be downloaded at 
 * <http://www.palabos.org/>
 *
 * The library Palabos is free software: you can redistribute it and/or
 * modify it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * The library 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/* Acknowledgment: The strategy adopted here to encode
 * and decode Base64, and in particular the expression of the
 * arrays Base64Encoder::enc64 and Base64Decoder::dec64, 
 * is inspired by the open source library b64 by Bob Trower,
 * which is distributed with a MIT license at the address
 * http://base64.sourceforge.net/b64.c
 */

#ifndef BASE64_HH
#define BASE64_HH

#include "io/base64.h"
#include "core/plbDebug.h"
#include <ostream>
#include <istream>


namespace plb {


template<typename T>
const char Base64Encoder<T>::enc64[65]=
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
    "abcdefghijklmnopqrstuvwxyz0123456789+/";

template<typename T>
Base64Encoder<T>::Base64Encoder(std::ostream& ostr_, pluint fullLength_)
    : ostr(ostr_),
      charFullLength(fullLength_ * sizeof(T)),
      numWritten(0),
      numOverflow(0)
{ }

template<typename T>
void Base64Encoder<T>::encode(const T* data, pluint length) {
    const unsigned char* charData = reinterpret_cast<const unsigned char*>(data);
    pluint charLength = length * sizeof(T);
    PLB_PRECONDITION( numWritten+charLength <= charFullLength );

    pluint pos=0;
    fillOverflow(charData, charLength, pos);
    while (pos+3 <= charLength) {
        encodeBlock(charData+pos);
        pos += 3;
    }
    fillOverflow(charData, charLength, pos);
    numWritten += charLength;
    if (numWritten == charFullLength) {
        flushOverflow();
    }
}

template<typename T>
void Base64Encoder<T>::fillOverflow(const unsigned char* charData, pluint charLength, pluint& pos) {
    while (numOverflow < 3 && pos < charLength) {
        overflow[numOverflow] = charData[pos];
        ++numOverflow;
        ++pos;
    }
    if (numOverflow == 3) {
        encodeBlock(overflow);
        numOverflow = 0;
    }
}

template<typename T>
void Base64Encoder<T>::flushOverflow() {
    if (numOverflow > 0) {
        for (plint iOverflow = numOverflow; iOverflow<3; ++iOverflow) {
            overflow[iOverflow] = 0;
        }
        encodeUnfinishedBlock(overflow, numOverflow);
        numOverflow = 0;
    }
}

template<typename T>
void Base64Encoder<T>::encodeBlock( const unsigned char* data) {
    ostr << enc64[ data[0] >> 2 ];
    ostr << enc64[ ((data[0] & 0x03) << 4) | ((data[1] & 0xf0) >> 4) ];
    ostr << (unsigned char) (enc64[ ((data[1] & 0x0f) << 2) | ((data[2] & 0xc0) >> 6) ]);
    ostr << (unsigned char) (enc64[ data[2] & 0x3f ]);
}

template<typename T>
void Base64Encoder<T>::encodeUnfinishedBlock( const unsigned char* data, plint length ) {
    ostr << enc64[ data[0] >> 2 ];
    ostr << enc64[ ((data[0] & 0x03) << 4) | ((data[1] & 0xf0) >> 4) ];
    ostr << (unsigned char) (
                length == 2 ?
                    enc64[ ((data[1] & 0x0f) << 2) | ((data[2] & 0xc0) >> 6) ] :
                    '='
             );
    ostr << (unsigned char) ( '=' );
}



template<typename T>
const char Base64Decoder<T>::dec64[82]=
    "|###}rstuvwxyz{#######>?@"\
    "ABCDEFGHIJKLMNOPQRSTUVW######XYZ"\
    "[\\]^_`abcdefghijklmnopq";


template<typename T>
Base64Decoder<T>::Base64Decoder(std::istream& istr_, pluint fullLength_)
    : istr(istr_),
      charFullLength(fullLength_ * sizeof(T)),
      numRead(0),
      posOverflow(3)
{ }

template<typename T>
void Base64Decoder<T>::decode(T* data, pluint length) {
    unsigned char* charData = reinterpret_cast<unsigned char*>(data);
    pluint charLength = length * sizeof(T);
    PLB_PRECONDITION( numRead+charLength <= charFullLength );

    pluint pos = 0;
    flushOverflow(charData, charLength, pos);
    while (pos+3 <= charLength) {
        decodeBlock(charData+pos);
        pos += 3;
    }
    if (pos < charLength) {
        decodeBlock(overflow); posOverflow=0;
        flushOverflow(charData, charLength, pos);
    }
    numRead += charLength;
}

template<typename T>
void Base64Decoder<T>::flushOverflow(unsigned char* charData, pluint charLength, pluint& pos) {
    while (posOverflow < 3 && pos < charLength) {
        charData[pos] = overflow[posOverflow];
        ++pos;
        ++posOverflow;
    }
}

template<typename T>
unsigned char Base64Decoder<T>::getNext() {
    unsigned char nextChar;
    istr >> nextChar;
    return (unsigned char) (dec64[nextChar - 43] - 62);
}

template<typename T>
void Base64Decoder<T>::decodeBlock(unsigned char* data) {
    unsigned char input[4];
    input[0] = getNext(); 
    input[1] = getNext(); 
    input[2] = getNext(); 
    input[3] = getNext(); 
    data[0] = (unsigned char) (input[0] << 2 | input[1] >> 4);
    data[1] = (unsigned char) (input[1] << 4 | input[2] >> 2);
    data[2] = (unsigned char) (((input[2] << 6) & 0xc0) | input[3]);
}

}  // namespace plb

#endif  // BASE64_HH