base64.hh

来自「open lattice boltzmann project www.open」· HH 代码 · 共 190 行

/*  This file is part of the OpenLB library
 *
 *  Copyright (C) 2007 Jonas Latt
 *  Address: Rue General Dufour 24,  1211 Geneva 4, Switzerland 
 *  E-mail: [e-mail]
 *
 *  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., 51 Franklin Street, Fifth Floor,
 *  Boston, MA  02110-1301, USA.
*/

/* 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 "base64.h"
#include "core/olbDebug.h"
#include <ostream>
#include <istream>


namespace olb {

////////////// class Base64Encoder ////////////////////////////////////////////

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

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

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

    size_t 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, size_t charLength, size_t& 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 (int 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, int 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) ( '=' );
}


////////////// struct Base64Decoder ////////////////////////////////////////////

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


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

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

    size_t 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, size_t charLength, size_t& 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 olb

#endif