ibrcommon/ibrcommon/data/Base64Reader.cpp

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/*
 * Base64Reader.cpp
 *
 *  Created on: 21.06.2011
 *      Author: morgenro
 */

#include "ibrcommon/data/Base64Reader.h"

namespace ibrcommon
{
        const char Base64Reader::decodeCharacterTable[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
        ,-1,62,-1,-1,-1,63,52,53,54,55,56,57,58,59,60,61,-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,-1,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,-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};

        Base64Reader::Base64Reader(std::istream &stream, const size_t limit, const size_t buffer)
         : std::istream(this), _stream(stream), data_buf_(new char[buffer]), data_size_(buffer), _base64_state(0), _char_counter(0), _base64_padding(0), _byte_read(0), _byte_limit(limit)
        {
                setg(0, 0, 0);
                _base64_buf[0] = '\0';
                _base64_buf[1] = '\0';
                _base64_buf[2] = '\0';
                _base64_buf[3] = '\0';
        }

        Base64Reader::~Base64Reader()
        {
                delete[] data_buf_;
        }

        int Base64Reader::underflow()
        {
                // signal EOF if end of stream is reached
                if (_stream.eof())
                        return std::char_traits<char>::eof();

                if ((_byte_limit > 0) && (_byte_read >= _byte_limit))
                {
                        return std::char_traits<char>::eof();
                }

                // read some data
                char buffer[data_size_];

                if (_byte_limit > 0)
                {
                        // get the remaining bytes
                        size_t bytes_to_read = _byte_limit - _byte_read;

                        if (bytes_to_read > data_size_) bytes_to_read = data_size_;

                        // read at least one byte
                        if (bytes_to_read == 0) bytes_to_read = 1;

                        _stream.read((char*)&buffer, bytes_to_read);
                }
                else
                {
                        _stream.read((char*)&buffer, data_size_);
                }

                size_t len = _stream.gcount();

                // position in array
                size_t decoded_bytes = 0;

                for (size_t i = 0; i < len; i++)
                {
                        // skip newline chars
                        if (buffer[i] == '\n') continue;

                        // put char into the decode buffer
                        if (buffer[i] == '=')
                        {
                                _base64_buf[_base64_state] = decodeCharacterTable[ (int)'\0' ];
                                _base64_padding++;
                        }
                        else
                        {
                                _base64_buf[_base64_state] = decodeCharacterTable[ (int)buffer[i] ];
                        }

                        if (_base64_state == 3)
                        {
                                _base64_buf[0] = (char)((_base64_buf[0] << 2) + ((_base64_buf[1] & 0x30) >> 4));
                                _base64_buf[1] = (char)(((_base64_buf[1] & 0xf) << 4) + ((_base64_buf[2] & 0x3c) >> 2));
                                _base64_buf[2] = (char)(((_base64_buf[2] & 0x3) << 6) + _base64_buf[3]);

                                for (int j = 0; j < (3 - _base64_padding); j++)
                                {
                                        data_buf_[decoded_bytes] = _base64_buf[j];
                                        decoded_bytes++;
                                }

                                _base64_state = 0;
                                _base64_padding = 0;
                        }
                        else
                        {
                                _base64_state++;
                        }
                }

                // Since the input buffer content is now valid (or is new)
                // the get pointer should be initialized (or reset).
                setg(data_buf_, data_buf_, data_buf_ + decoded_bytes);

                if (_byte_limit > 0)
                {
                        _byte_read += decoded_bytes;
                }

                return std::char_traits<char>::not_eof(data_buf_[0]);
        }
}