assimp.assimp/code/StreamReader.h

/*
---------------------------------------------------------------------------
Open Asset Import Library (ASSIMP)
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Copyright (c) 2006-2010, 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 attempt to instance the template directly. Use 
 *  StreamReaderLE to read from a little-endian stream and StreamReaderBE to read from a 
 *  BE stream. The class expects that the endianess of any input data is known at 
 *  compile-time, which should usually be true (#BaseImporter::ConvertToUTF8 implements
 *  runtime endianess conversions for text files). 
 *
 *  XXX switch from unsigned int for size types to size_t? or ptrdiff_t?*/
// --------------------------------------------------------------------------------------------
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 DeadlyImportError("StreamReader: Unable to open file");
		}
		stream = _stream;

		const size_t s = stream->FileSize();
		if (!s) {
			throw DeadlyImportError("StreamReader: File is empty");
		}

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

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

public:

	// deprecated, use overloaded operator>> instead

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

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

	// ---------------------------------------------------------------------
	/** Read a signed 16 bit integer from the stream */
	int16_t GetI2()	{
		return Get<int16_t>();
	}

	// ---------------------------------------------------------------------
	/** Read a signed 8 bit integer from the stream */
	int8_t GetI1()	{
		return Get<int8_t>();
	}

	// ---------------------------------------------------------------------
	/** Read an signed 32 bit integer from the stream */
	int32_t GetI4()	{
		return Get<int32_t>();
	}

	// ---------------------------------------------------------------------
	/** Read a signed 64 bit integer from the stream */
	int64_t GetI8()	{
		return Get<int64_t>();
	}

	// ---------------------------------------------------------------------
	/** Read a unsigned 16 bit integer from the stream */
	uint16_t GetU2()	{
		return Get<uint16_t>();
	}

	// ---------------------------------------------------------------------
	/** Read a unsigned 8 bit integer from the stream */
	uint8_t GetU1()	{
		return Get<uint8_t>();
	}

	// ---------------------------------------------------------------------
	/** Read an unsigned 32 bit integer from the stream */
	uint32_t GetU4()	{
		return Get<uint32_t>();
	}

	// ---------------------------------------------------------------------
	/** Read a unsigned 64 bit integer from the stream */
	uint64_t GetU8()	{
		return Get<uint64_t>();
	}

public:

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


	// ---------------------------------------------------------------------
	/** Get the remaining stream size (to the current read limit). The
	 *  return value is the remaining size of the stream if no custom
	 *  read limit has been set. */
	unsigned int GetRemainingSizeToLimit() const {
		return (unsigned int)(limit - current);
	}


	// ---------------------------------------------------------------------
	/** Increase the file pointer (relative seeking)  */
	void IncPtr(int plus)	{
		current += plus;
		if (current > end) {
			throw DeadlyImportError("End of file was reached");
		}
	}

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


	// ---------------------------------------------------------------------
	/** Set current file pointer (Get it from #GetPtr). This is if you
	 *  prefer to do pointer arithmetics on your own or want to copy 
	 *  large chunks of data at once. 
	 *  @param p The new pointer, which is validated against the size
	 *    limit and buffer boundaries. */
	void SetPtr(int8_t* p)	{

		current = p;
		if (current > end || current < buffer) {
			throw DeadlyImportError("End of file was reached");
		}
	}

	// ---------------------------------------------------------------------
	/** Copy n bytes to an external buffer
	 *  @param out Destination for copying
	 *  @param bytes Number of bytes to copy */
	void CopyAndAdvance(void* out, size_t bytes)	{

		int8_t* ur = GetPtr();
		SetPtr(ur+bytes); // fire exception if eof

		memcpy(out,ur,bytes);
	}


	// ---------------------------------------------------------------------
	/** 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 to the original end of the stream. */
	void SetReadLimit(unsigned int _limit)	{

		if (0xffffffff == _limit) {
			limit = end;
			return;
		}

		limit = buffer + _limit;
		if (limit > end) {
			throw DeadlyImportError("StreamReader: Invalid read limit");
		}
	}

	// ---------------------------------------------------------------------
	/** Get the current read limit in bytes. Reading over this limit
	 *  accidentially raises an exception.  */
	int GetReadLimit() const	{
		return (unsigned int)(limit - buffer);
	}

	// ---------------------------------------------------------------------
	/** Skip to the read limit in bytes. Reading over this limit
	 *  accidentially raises an exception. */
	void SkipToReadLimit()	{
		current = limit;
	}

	// ---------------------------------------------------------------------
	/** overload operator>> and allow chaining of >> ops. */
	template <typename T>
	StreamReader& operator >> (T& f) {
		f = Get<T>(); 
		return *this;
	}

private:

	template <typename T, bool doit>
	struct ByteSwapper	{
		void operator() (T* inout) {
			ByteSwap::Swap(inout);
		}
	};

	template <typename T>
	struct ByteSwapper<T,false>	{
		void operator() (T*) {
		}
	};

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

		T f = *((const T*)current);
		ByteSwapper<T,(SwapEndianess && sizeof(T)>1)> swapper;
		swapper(&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