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, 
with or without modification, are permitted provided that the following 
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* Redistributions of source code must retain the above
  copyright notice, this list of conditions and the
  following disclaimer.

* Redistributions in binary form must reproduce the above
  copyright notice, this list of conditions and the
  following disclaimer in the documentation and/or other
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* Neither the name of the ASSIMP team, nor the names of its
  contributors may be used to endorse or promote products
  derived from this software without specific prior
  written permission of the ASSIMP Development Team.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
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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)
	{
		ai_assert(NULL != stream);
		this->stream = stream;

		size_t s = stream->FileSize();
		if (!s)throw new ImportErrorException("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