Organizing a Virtual Filesystem - Android NDK Game Development - page 92

4. Read a continuous block of data from this stream and return the number of bytes

actually read:
virtual uint64 BlockRead( void* Buf, const uint64 Size )
{
uint64 RealSize =
( Size > GetBytesLeft() ) ? GetBytesLeft() : Size;

5. Return zero if we have already read everything:

if ( RealSize < 0 ) { return 0; }
memcpy( Buf, ( FFile->GetFileData() + FPosition ),
static_cast<size_t>( RealSize ) );

6. Advance the current position and return the number of copied bytes:

FPosition += RealSize;
return RealSize;
}

virtual void Seek( const uint64 Position )
{ FPosition = Position; }
virtual uint64 GetFileSize() const
{ return FFile->GetFileSize(); }
virtual uint64 GetFilePos() const
{ return FPosition; }
virtual bool Eof() const
{ return ( FPosition >= GetFileSize() ); }

virtual const ubyte* MapStream() const
{ return FFile->GetFileData(); }
virtual const ubyte* MapStreamFromCurrentPos() const
{ return ( FFile->GetFileData() + FPosition ); }
private:
clPtr<iRawFile> FFile;
uint64 FPosition;
};

7. The FileMapper uses the following iRawFile interface to abstract the data

access:

class iRawFile: public iObject
{
public:
iRawFile() {};
virtual ~iRawFile() {};
void SetVirtualFileName( const std::string& VFName );
void SetFileName( const std::string& FName );
std::string GetVirtualFileName() const;
std::string GetFileName();