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 // Copyright (c) 2017-2019 OPEN CASCADE SAS
 //
 // This file is part of Open CASCADE Technology software library.
 //
 // This library is free software; you can redistribute it and/or modify it under
 // the terms of the GNU Lesser General Public License version 2.1 as published
 // by the Free Software Foundation, with special exception defined in the file
 // OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
 // distribution for complete text of the license and disclaimer of any warranty.
 //
 // Alternatively, this file may be used under the terms of Open CASCADE
 // commercial license or contractual agreement..
 
 #ifndef _Standard_ReadBuffer_HeaderFile
 #define _Standard_ReadBuffer_HeaderFile
 
 #include <Standard_ProgramError.hxx>
 
 #include <iostream>
 
 //! Auxiliary tool for buffered reading from input stream within chunks of constant size.
 class Standard_ReadBuffer
 {
 public:
   //! Constructor with initialization.
   Standard_ReadBuffer(int64_t theDataLen, size_t theChunkLen, bool theIsPartialPayload = false)
       : myBufferPtr(nullptr),
         myBufferEnd(nullptr),
         myDataLen(0),
         myDataRead(0),
         myChunkLen(0),
         myNbChunks(0),
         myBufferLen(0)
   {
     Init(theDataLen, theChunkLen, theIsPartialPayload);
   }
 
   //! Initialize the buffer.
   //! @param[in] theDataLen   the full length of input data to read from stream.
   //! @param[in] theChunkLen  the length of single chunk to read
   //! @param[in] theIsPartialPayload  when FALSE, theDataLen will be automatically aligned to the
   //! multiple of theChunkLen;
   //!                                 when TRUE, last chunk will be read from stream exactly till
   //!                                 theDataLen allowing portion of chunk to be uninitialized
   //!                                 (useful for interleaved data)
   void Init(int64_t theDataLen, size_t theChunkLen, bool theIsPartialPayload = false)
   {
     myDataRead = 0;
     if (theIsPartialPayload)
     {
       myDataLen = theDataLen;
     }
     else
     {
       myDataLen = theDataLen - theDataLen % int64_t(theChunkLen);
     }
     myChunkLen  = theChunkLen;
     myNbChunks  = sizeof(myBuffer) / theChunkLen;
     myBufferLen = theChunkLen * myNbChunks;
 
     myBufferEnd = myBuffer + sizeof(myBuffer);
     myBufferPtr = myBuffer + sizeof(myBuffer);
     memset(myBuffer, 0, sizeof(myBuffer));
 
     if (theChunkLen > sizeof(myBuffer))
     {
       throw Standard_ProgramError(
         "Internal error - chunk size is greater then preallocated buffer");
     }
   }
 
   //! Return TRUE if amount of read bytes is equal to requested length of entire data.
   bool IsDone() const { return myDataRead == myDataLen; }
 
   //! Read next chunk.
   //! @return pointer to the chunk or NULL on error / end of reading buffer
   template <typename Chunk_T, typename Stream_T>
   Chunk_T* ReadChunk(Stream_T& theStream)
   {
     return reinterpret_cast<Chunk_T*>(readRawDataChunk(theStream));
   }
 
   //! Read next chunk.
   //! @return pointer to the chunk or NULL on error / end of reading buffer
   template <typename Stream_T>
   char* ReadDataChunk(Stream_T& theStream)
   {
     return readRawDataChunk(theStream);
   }
 
 private:
   //! Read next chunk.
   //! @return pointer to the chunk or NULL on error / end of reading buffer
   template <typename Stream_T>
   char* readRawDataChunk(Stream_T& theStream)
   {
     if (myBufferPtr == nullptr)
     {
       return nullptr;
     }
 
     myBufferPtr += myChunkLen;
     if (myBufferPtr < myBufferEnd)
     {
       return myBufferPtr;
     }
 
     const int64_t aDataLeft = myDataLen - myDataRead;
     if (aDataLeft <= 0) // myDataLen is normally multiple of myChunkLen, but can be smaller in
                         // interleaved data
     {
       myBufferPtr = nullptr;
       return nullptr;
     }
 
     const size_t aDataToRead = int64_t(myBufferLen) > aDataLeft ? size_t(aDataLeft) : myBufferLen;
     if (!readStream(theStream, aDataToRead))
     {
       myBufferPtr = nullptr;
       return nullptr;
     }
 
     myBufferPtr = myBuffer;
     myBufferEnd = myBuffer + aDataToRead;
     myDataRead += aDataToRead;
     return myBufferPtr;
   }
 
   //! Read from stl stream.
   bool readStream(std::istream& theStream, size_t theLen)
   {
     theStream.read(myBuffer, theLen);
     return theStream.good();
   }
 
   //! Read from FILE stream.
   bool readStream(FILE* theStream, size_t theLen)
   {
     return ::fread(myBuffer, 1, theLen, theStream) == theLen;
   }
 
 private:
   char        myBuffer[4096]; //!< data cache
   char*       myBufferPtr;    //!< current position within the buffer
   const char* myBufferEnd;    //!< end of the buffer
   int64_t     myDataLen;      //!< length of entire data to read
   int64_t     myDataRead;     //!< amount of data already processed
   // clang-format off
   size_t      myChunkLen;     //!< length of single chunk that caller would like to read (e.g. iterator increment)
   size_t      myNbChunks;     //!< number of cached chunks
   size_t      myBufferLen;    //!< effective length of the buffer to be read at once (multiple of chunk length)
   // clang-format on
 };
 
 #endif // _Standard_ReadBuffer_HeaderFile

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