DataReader.h

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/*
    This software is Copyright by the Board of Trustees of Michigan
    State University (c) Copyright 2017.

    You may use this software under the terms of the GNU public license
    (GPL).  The terms of this license are described at:

     http://www.gnu.org/licenses/gpl.txt

     Authors:
             Ron Fox
             Giordano Cerriza
         FRIB
         Michigan State University
         East Lansing, MI 48824-1321
*/

#ifndef DATAREADER_H
#define DATAREADER_H

#include <cstddef>

namespace frib {
    namespace analysis {
        class CDataReader {
        private:
            std::size_t m_nBytes;                   // bytes in the buffer.
            void*  m_pBuffer;                  // buffer itself.
            std::size_t m_nBufferSize;              // Size of the buffer.
            bool   m_eof;
            
            int    m_nFd;                      // Data source.
            
            // State of the last 'read':
            
            bool   m_fReleased;               // A new read is allowed.
            std::size_t m_nUserBytes;              // Bytes we gave to the user.
            std::size_t m_nUserItems;              // items we gave to the user.
            
        public:           // Exported data types:
            
            // What a read returns:
            
            typedef struct _Result {
                std::size_t s_nbytes;
                std::size_t s_nItems;
                const void* s_pData;
            } Result, *pResult;
        public:
            CDataReader(const char* pFilename, std::size_t bufferSize);
            CDataReader(int fd,  std::size_t bufferSize);
            virtual ~CDataReader();
            
        private:
            CDataReader(const CDataReader& rhs);
            CDataReader& operator=(const CDataReader& rhs);
            int operator==(const CDataReader& rhs);
            int operator!=(const CDataReader& rhs);
        public:
            Result getBlock(std::size_t maxbytes);
            void done();
        private:
            void allocateBuffer();
            void fillBuffer();
            void probeData(std::size_t maxBytes);
        };
    }
}


#endif