Amp_Stream.h

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/*
* Copyright 2016 Autodesk, Inc. All rights reserved.
* Use of this software is subject to the terms of the Autodesk license agreement and any attachments or Appendices thereto provided at the time of installation or download,
* or which otherwise accompanies this software in either electronic or hard copy form, or which is signed by you and accepted by Autodesk.
*/

/**************************************************************************

Filename    :   Amp_Stream.h
Content     :   Stream used by AMP to serialize messages
Created     :   December 2009
Authors     :   Alex Mantzaris

**************************************************************************/

#pragma once

#include "gwnavruntime/kernel/SF_File.h"

namespace Kaim {
namespace Net {
namespace AMP {

// Custom stream class used to send messages across the network
// The size of each message precedes the data so we can split messages into
// packets and reconstruct them after they have been received on the other end
//
// The data are stored as a Little-endian array of bytes
// The object normally holds only one message for write operations
// because the first four bytes are used to hold the message size
// For read operations, multiple messages can be contained on the stream
// After a message has been processed, PopFirstMessage is called to remove it
class AmpStream : public File
{
public:
    // Default constructor (for writing a new message)
    AmpStream();
    // Buffer constructor (for parsing a received message)
    AmpStream(const UByte* buffer, UPInt bufferSize);

    // File virtual method overrides
    virtual const char* GetFilePath()   { return ""; }
    virtual bool        IsValid()       { return true; }
    virtual bool        IsWritable()    { return true; }
    virtual int         Tell ();
    virtual SInt64      LTell ()        { return  Tell(); }
    virtual int         GetLength ()    { return static_cast<int>(Data.GetSize()); }
    virtual SInt64      LGetLength ()   { return GetLength(); }
    virtual int         GetErrorCode()  { return 0; }
    virtual bool        Flush()         { return true; }
    virtual bool        Close()         { return false; }
    virtual int         Write(const UByte *pbufer, int numBytes);
    virtual int         Read(UByte *pbufer, int numBytes);
    virtual int         SkipBytes(int numBytes);
    virtual int         BytesAvailable();
    virtual int         Seek(int offset, int origin=Seek_Set);
    virtual SInt64      LSeek(SInt64 offset, int origin=Seek_Set);
    virtual bool        ChangeSize(int newSize);
    virtual int         CopyFromStream(File *pstream, int byteSize);

    // Serialization
    void                Read(File& str);
    void                Write(File& str) const;

    // Append an buffer that is already in the AmpStream format
    void                Append(const UByte* buffer, UPInt bufferSize);

    // Data accessors
    const UByte*        GetBuffer() const;
    UPInt               GetBufferSize() const;

    // Clear the stream
    void                Clear();

    // Set the current read position to the beginning
    void                Rewind();

    // Message retrieval methods
    UPInt               FirstMessageSize();
    bool                PopFirstMessage();

private:
    typedef ArrayConstPolicy<0, 4, true> NeverShrinkPolicy;
    ArrayLH<UByte, Stat_Default_Mem, NeverShrinkPolicy>     Data;
    int                                                     readPosition;  // next location to be read

    // Update the header with the message size
    // Assumes that there is only one message currently in the stream
    void IncreaseMessageSize(UInt32 newSize);
};

} // namespace AMP
} // namespace Net
} // namespace Kaim