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0001 // Copyright (c) 2016 OPEN CASCADE SAS
0002 //
0003 // This file is part of Open CASCADE Technology software library.
0004 //
0005 // This library is free software; you can redistribute it and/or modify it under
0006 // the terms of the GNU Lesser General Public License version 2.1 as published
0007 // by the Free Software Foundation, with special exception defined in the file
0008 // OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
0009 // distribution for complete text of the license and disclaimer of any warranty.
0010 //
0011 // Alternatively, this file may be used under the terms of Open CASCADE
0012 // commercial license or contractual agreement.
0013 
0014 #ifndef _Standard_ArrayStreamBuffer_HeaderFile
0015 #define _Standard_ArrayStreamBuffer_HeaderFile
0016 
0017 #include <Standard_Type.hxx>
0018 
0019 #include <fstream>
0020 
0021 // Suppress VC9 warning on xsputn() function
0022 #ifdef _MSC_VER
0023   #pragma warning(push)
0024   #pragma warning(disable : 4996)
0025 #endif
0026 
0027 //! Custom buffer object implementing STL interface std::streambuf for streamed reading from
0028 //! allocated memory block. Implements minimal sub-set of methods for passing buffer to
0029 //! std::istream, including seek support.
0030 //!
0031 //! This class can be used for creating a seekable input stream in cases,
0032 //! when the source data does not satisfies Reader requirements (non-seekable stream, compressed
0033 //! data) or represents an in-memory resource.
0034 //!
0035 //! The memory itself is NOT managed by this class - it is up to the caller to ensure that passed
0036 //! memory pointer is not released during Standard_ArrayStreamBuffer lifetime.
0037 //!
0038 //! Usage example:
0039 //! @code
0040 //!   const char*  theBuffer;
0041 //!   const size_t theBufferLength;
0042 //!   Standard_ArrayStreamBuffer aStreamBuffer (theBuffer, theBufferLength);
0043 //!   std::istream aStream (&aStreamBuffer);
0044 //!   TopoDS_Shape aShape;
0045 //!   BRep_Builder aBuilder;
0046 //!   BRepTools::Read (aShape, aStream, aBuilder);
0047 //! @endcode
0048 class Standard_ArrayStreamBuffer : public std::streambuf
0049 {
0050 public:
0051   //! Main constructor.
0052   //! Passed pointer is stored as is (memory is NOT copied nor released with destructor).
0053   //! @param theBegin pointer to the beginning of pre-allocated buffer
0054   //! @param theSize  length of pre-allocated buffer
0055   Standard_EXPORT Standard_ArrayStreamBuffer(const char* theBegin, const size_t theSize);
0056 
0057   //! Destructor.
0058   Standard_EXPORT virtual ~Standard_ArrayStreamBuffer();
0059 
0060   //! (Re)-initialize the stream.
0061   //! Passed pointer is stored as is (memory is NOT copied nor released with destructor).
0062   //! @param theBegin pointer to the beginning of pre-allocated buffer
0063   //! @param theSize  length of pre-allocated buffer
0064   Standard_EXPORT virtual void Init(const char* theBegin, const size_t theSize);
0065 
0066 protected:
0067   //! Get character on underflow.
0068   //! Virtual function called by other member functions to get the current character
0069   //! in the controlled input sequence without changing the current position.
0070   Standard_EXPORT virtual int_type underflow() Standard_OVERRIDE;
0071 
0072   //! Get character on underflow and advance position.
0073   //! Virtual function called by other member functions to get the current character
0074   //! in the controlled input sequence and then advance the position indicator to the next
0075   //! character.
0076   Standard_EXPORT virtual int_type uflow() Standard_OVERRIDE;
0077 
0078   //! Put character back in the case of backup underflow.
0079   //! Virtual function called by other member functions to put a character back
0080   //! into the controlled input sequence and decrease the position indicator.
0081   Standard_EXPORT virtual int_type pbackfail(int_type ch) Standard_OVERRIDE;
0082 
0083   //! Get number of characters available.
0084   //! Virtual function (to be read s-how-many-c) called by other member functions
0085   //! to get an estimate on the number of characters available in the associated input sequence.
0086   Standard_EXPORT virtual std::streamsize showmanyc() Standard_OVERRIDE;
0087 
0088   //! Seek to specified position.
0089   Standard_EXPORT virtual pos_type seekoff(off_type                theOff,
0090                                            std::ios_base::seekdir  theWay,
0091                                            std::ios_base::openmode theWhich) Standard_OVERRIDE;
0092 
0093   //! Change to specified position, according to mode.
0094   Standard_EXPORT virtual pos_type seekpos(pos_type                thePosition,
0095                                            std::ios_base::openmode theWhich) Standard_OVERRIDE;
0096 
0097 public:
0098   //! Read a bunch of bytes at once.
0099   Standard_EXPORT virtual std::streamsize xsgetn(char*           thePtr,
0100                                                  std::streamsize theCount) Standard_OVERRIDE;
0101 
0102 private:
0103   // copying is not allowed
0104   Standard_ArrayStreamBuffer(const Standard_ArrayStreamBuffer&);
0105   Standard_ArrayStreamBuffer& operator=(const Standard_ArrayStreamBuffer&);
0106 
0107 protected:
0108   const char* myBegin;
0109   const char* myEnd;
0110   const char* myCurrent;
0111 };
0112 
0113 #ifdef _MSC_VER
0114   #pragma warning(pop)
0115 #endif
0116 
0117 #endif // _Standard_ArrayStreamBuffer_HeaderFile