assimp.assimp/code/StreamReader.h

/*
---------------------------------------------------------------------------
Open Asset Import Library (ASSIMP)
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Copyright (c) 2006-2008, ASSIMP Development Team

All rights reserved.

Redistribution and use of this software in source and binary forms, 
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* Redistributions of source code must retain the above
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  following disclaimer.

* Redistributions in binary form must reproduce the above
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  derived from this software without specific prior
  written permission of the ASSIMP Development Team.

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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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*/

/** @file Defines the StreamReader class which reads data from
 *  a binary stream with a well-defined endianess.
 */

#ifndef AI_STREAMREADER_H_INCLUDED
#define AI_STREAMREADER_H_INCLUDED

#include "ByteSwap.h"

namespace Assimp
{

/** Wrapper class around IOStream to allow for consistent reading
 *  of binary data in both little and big endian format.
 *  Don't use this type directly. Use StreamReaderLE to read
 *  from a little-endian stream and StreamReaderBE to read from a 
 *  BE stream. This class expects that the endianess of the data
 * is known at compile-time.
 */
template <bool SwapEndianess = false>
class StreamReader
{
public:

	/** Construction from a given stream with a well-defined endianess
	 * 
	 *  The stream will be deleted afterwards.
	 *  @param stream Input stream
	 */
	StreamReader(IOStream* _stream)
	{
		if (!_stream)
			throw new ImportErrorException("StreamReader: Unable to open file");
		stream = _stream;

		size_t s = stream->FileSize();
		if (!s)
			throw new ImportErrorException("StreamReader: File is empty");

		current = buffer = new int8_t[s];
		stream->Read(current,s,1);
		end = limit = &buffer[s];
	}

	~StreamReader() 
	{
		delete[] buffer;
		delete stream;
	}


	/** Read a float from the stream 
	 */
	float GetF4()
	{
		return Get<float>();
	}

	/** Read a double from the stream 
	 */
	double GetF8()
	{
		return Get<double>();
	}

	/** Read a short from the stream
	 */
	int16_t GetI2()
	{
		return Get<int16_t>();
	}

	/** Read a char from the stream
	 */
	int8_t GetI1()
	{
		if (current >= end)
			throw new ImportErrorException("End of file was reached");

		return *current++;
	}

	/** Read an int from the stream
	 */
	int32_t GetI4()
	{
		return Get<int32_t>();
	}

	/** Read a long from the stream
	 */
	int64_t GetI8()
	{
		return Get<int64_t>();
	}

	/** Get the remaining stream size (to the end of the srream)
	 */
	unsigned int GetRemainingSize()
	{
		return (unsigned int)(end - current);
	}


	/** Get the remaining stream size (to the current read limit)
	 */
	unsigned int GetRemainingSizeToLimit()
	{
		return (unsigned int)(limit - current);
	}


	/** Increase the file pointer
	 */
	void IncPtr(unsigned int plus)
	{
		current += plus;
		if (current > end)
		{
			throw new ImportErrorException("End of file was reached");
		}
	}

	/** Get the current file pointer
	 */
	int8_t* GetPtr() const
	{
		return current;
	}

	/** Set current file pointer
	 */
	void SetPtr(int8_t* p)
	{
		current = p;
		if (current > end || current < buffer)
		{
			throw new ImportErrorException("End of file was reached");
		}
	}

	/** Get the current offset from the beginning of the file
	 */
	int GetCurrentPos() const
	{
		return (unsigned int)(current - buffer);
	}

	/** Setup a temporary read limit
	 * 
	 *  @param limit Maximum number of bytes to be read from
	 *    the beginning of the file. Passing 0xffffffff
	 *    resets the limit.
	 */
	void SetReadLimit(unsigned int _limit)
	{
		if (0xffffffff == _limit)
		{
			limit = end;
			return;
		}
		limit = buffer + _limit;
		if (limit > end)
			throw new ImportErrorException("StreamReader: Invalid read limit");
	}

	/** Get the current read limit
	 */
	int GetReadLimit() const
	{
		return (unsigned int)(limit - buffer);
	}

	/** Skip to the read limit
	 */
	void SkipToReadLimit()
	{
		current = limit;
	}

	// overload operator>> for those who prefer this way ...
	void operator >> (float& f) 
		{f = GetF4();}

	void operator >> (double& f) 
		{f = GetF8();}

	void operator >> (int16_t& f) 
		{f = GetI2();}

	void operator >> (int32_t& f) 
		{f = GetI4();}

	void operator >> (int64_t& f) 
		{f = GetI8();}

	void operator >> (int8_t& f) 
		{f = GetI1();}

private:

	/** Generic read method. ByteSwap::Swap(T*) must exist.
	 */
	template <typename T>
	T Get()
	{
		if (current + sizeof(T) > limit)
			throw new ImportErrorException("End of file or stream limit was reached");

		T f = *((const T*)current);
		if (SwapEndianess)
		{
			ByteSwap::Swap(&f);
		}
		current += sizeof(T);
		return f;
	}

	IOStream* stream;
	int8_t *buffer, *current, *end, *limit;
};

#ifdef AI_BUILD_BIG_ENDIAN
	typedef StreamReader<true>  StreamReaderLE;
	typedef StreamReader<false> StreamReaderBE;
#else
	typedef StreamReader<true>  StreamReaderBE;
	typedef StreamReader<false> StreamReaderLE;
#endif

} // end namespace Assimp

#endif // !! AI_STREAMREADER_H_INCLUDED