StreamDataReader.hpp

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/* 
 * StreamDataReader.hpp 
 *
 * This file is part of the Chemical Data Processing Toolkit
 *
 * Copyright (C) 2003 Thomas Seidel <thomas.seidel@univie.ac.at>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; see the file COPYING. If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */
 
#ifndef CDPL_UTIL_STREAMDATAREADER_HPP
#define CDPL_UTIL_STREAMDATAREADER_HPP
 
#include <istream>
#include <vector>
 
#include "CDPL/Base/DataReader.hpp"
#include "CDPL/Base/Exceptions.hpp"
 
 
namespace CDPL
{
 
    namespace Util
    {
 
        template <typename DataType, typename ReaderImpl>
        class StreamDataReader : public Base::DataReader<DataType>
        {
 
          public:
            Base::DataReader<DataType>& read(DataType& obj, bool overwrite = true);
            Base::DataReader<DataType>& read(std::size_t idx, DataType& obj, bool overwrite = true);
 
            Base::DataReader<DataType>& skip();
 
            bool hasMoreData();
 
            std::size_t getRecordIndex() const;
            void setRecordIndex(std::size_t idx);
 
            std::size_t getNumRecords();
 
            operator const void*() const;
            bool operator!() const;
 
          protected:
            StreamDataReader(std::istream& is):
                input(is), recordIndex(0), initStreamPos(is.tellg()), state(is.good()), streamScanned(false) {}
 
          private:
            StreamDataReader(const StreamDataReader& reader);
 
            void scanDataStream();
 
            typedef std::vector<std::istream::pos_type> RecordStreamPosTable;
 
            std::istream&          input;
            std::size_t            recordIndex;
            std::istream::pos_type initStreamPos;
            bool                   state;
            bool                   streamScanned;
            RecordStreamPosTable   recordPositions;
        };
    } // namespace Util
} // namespace CDPL
 
 
// Implementation
 
template <typename DataType, typename ReaderImpl>
CDPL::Base::DataReader<DataType>&
CDPL::Util::StreamDataReader<DataType, ReaderImpl>::read(DataType& obj, bool overwrite)
{
    state = false;
 
    if ((state = static_cast<ReaderImpl*>(this)->readData(input, obj, overwrite))) {
        recordIndex++;
        this->invokeIOCallbacks(1.0);
    }
 
    return *this;
}
 
template <typename DataType, typename ReaderImpl>
CDPL::Base::DataReader<DataType>&
CDPL::Util::StreamDataReader<DataType, ReaderImpl>::read(std::size_t idx, DataType& obj, bool overwrite)
{
    setRecordIndex(idx);
 
    return read(obj, overwrite);
}
 
template <typename DataType, typename ReaderImpl>
CDPL::Base::DataReader<DataType>&
CDPL::Util::StreamDataReader<DataType, ReaderImpl>::skip()
{
    state = false;
 
    if ((state = static_cast<ReaderImpl*>(this)->skipData(input))) {
        recordIndex++;
        this->invokeIOCallbacks(1.0);
    }
 
    return *this;
}
 
template <typename DataType, typename ReaderImpl>
bool CDPL::Util::StreamDataReader<DataType, ReaderImpl>::hasMoreData()
{
    return static_cast<ReaderImpl*>(this)->moreData(input);
}
 
template <typename DataType, typename ReaderImpl>
std::size_t CDPL::Util::StreamDataReader<DataType, ReaderImpl>::getRecordIndex() const
{
    return recordIndex;
}
 
template <typename DataType, typename ReaderImpl>
void CDPL::Util::StreamDataReader<DataType, ReaderImpl>::setRecordIndex(std::size_t idx)
{
    scanDataStream();
 
    if (idx > recordPositions.size())
        throw Base::IndexError("StreamDataReader: record index out of bounds");
 
    input.clear();
    
    if (idx == recordPositions.size())
        input.seekg(0, std::ios_base::end);
    else
        input.seekg(recordPositions[idx]);
 
    recordIndex = idx;
}
 
template <typename DataType, typename ReaderImpl>
std::size_t CDPL::Util::StreamDataReader<DataType, ReaderImpl>::getNumRecords()
{
    scanDataStream();
 
    return recordPositions.size();
}
 
template <typename DataType, typename ReaderImpl>
CDPL::Util::StreamDataReader<DataType, ReaderImpl>::operator const void*() const
{
    return (state ? this : 0);
}
 
template <typename DataType, typename ReaderImpl>
bool CDPL::Util::StreamDataReader<DataType, ReaderImpl>::operator!() const
{
    return !state;
}
 
template <typename DataType, typename ReaderImpl>
void CDPL::Util::StreamDataReader<DataType, ReaderImpl>::scanDataStream()
{
    if (streamScanned)
        return;
 
    streamScanned = true;
 
    std::size_t saved_rec_index = recordIndex;
 
    recordIndex = 0;
 
    input.clear();
    input.seekg(0, std::ios_base::end);
 
    std::istream::pos_type end_pos = input.tellg();
 
    input.seekg(initStreamPos);
 
    while (hasMoreData()) {
        std::istream::pos_type record_pos = input.tellg();
        state                             = false;
 
        if (!(state = static_cast<ReaderImpl*>(this)->skipData(input)))
            break;
 
        recordPositions.push_back(record_pos);
        recordIndex++;
 
        this->invokeIOCallbacks(record_pos / double(end_pos));
    }
 
    this->invokeIOCallbacks(1.0);
 
    if (saved_rec_index < recordPositions.size()) {
        recordIndex = saved_rec_index;
 
        input.clear();
        input.seekg(recordPositions[recordIndex]);
    }
}
 
#endif // CDPL_UTIL_STREAMDATAREADER_HPP