assimp/code/MemoryIOWrapper.h

/*
Open Asset Import Library (ASSIMP)
----------------------------------------------------------------------

Copyright (c) 2006-2010, 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 conditions are met:

* 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
  materials provided with the distribution.

* 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 
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

----------------------------------------------------------------------
*/

/** @file MemoryIOWrapper.h
 *  Handy IOStream/IOSystem implemetation to read directly from a memory buffer */
#ifndef AI_MEMORYIOSTREAM_H_INC
#define AI_MEMORYIOSTREAM_H_INC
namespace Assimp	{
#define AI_MEMORYIO_MAGIC_FILENAME "$$$___magic___$$$"
#define AI_MEMORYIO_MAGIC_FILENAME_LENGTH 17

// ----------------------------------------------------------------------------------
/** Implementation of IOStream to read directly from a memory buffer */
class MemoryIOStream : public IOStream	{
	friend class MemoryIOSystem;
protected:
	MemoryIOStream (const uint8_t* buff, size_t len) 
		: buffer (buff), length(len), pos((size_t)0) {
	}

public:
	~MemoryIOStream ()	{
	}

	// -------------------------------------------------------------------
	// Read from stream
    size_t Read(void* pvBuffer, size_t pSize, size_t pCount)	{
		const size_t cnt = std::min(pCount,(length-pos)/pSize),ofs = pSize*cnt;
		
		memcpy(pvBuffer,buffer+pos,ofs);
		pos += ofs;

		return cnt;
	}

	// -------------------------------------------------------------------
	// Write to stream
    size_t Write(const void* pvBuffer, size_t pSize,size_t pCount)	{
		ai_assert(false); // won't be needed
		return 0;
	}

	// -------------------------------------------------------------------
	// Seek specific position
	aiReturn Seek(size_t pOffset, aiOrigin pOrigin) {
		if (aiOrigin_SET == pOrigin) {
			if (pOffset >= length) {
				return AI_FAILURE;
			}
			pos = pOffset;
		}
		else if (aiOrigin_END == pOrigin) {
			if (pOffset >= length) {
				return AI_FAILURE;
			}
			pos = length-pOffset;
		}
		else {
			if (pOffset+pos >= length) {
				return AI_FAILURE;
			}
			pos += pOffset;
		}
		return AI_SUCCESS;
	}

	// -------------------------------------------------------------------
	// Get current seek position
	size_t Tell() const {
		return pos;
	}

	// -------------------------------------------------------------------
	// Get size of file
	size_t FileSize() const {
		return length;
	}

	// -------------------------------------------------------------------
	// Flush file contents
	void Flush() {
		ai_assert(false); // won't be needed
	}

private:
	const uint8_t* buffer;
	size_t length,pos;
};

// ---------------------------------------------------------------------------
/** Dummy IO system to read from a memory buffer */
class MemoryIOSystem : public IOSystem
{
public:
	/** Constructor. */
    MemoryIOSystem (const uint8_t* buff, size_t len) 
		: buffer (buff), length(len) {
	}

	/** Destructor. */
	~MemoryIOSystem() {
	}

	// -------------------------------------------------------------------
	/** Tests for the existence of a file at the given path. */
	bool Exists( const char* pFile) const {
		return !strncmp(pFile,AI_MEMORYIO_MAGIC_FILENAME,AI_MEMORYIO_MAGIC_FILENAME_LENGTH);
	}

	// -------------------------------------------------------------------
	/** Returns the directory separator. */
	char getOsSeparator() const {
		return '/'; // why not? it doesn't care
	}

	// -------------------------------------------------------------------
	/** Open a new file with a given path. */
	IOStream* Open( const char* pFile, const char* pMode = "rb") {
		if (strncmp(pFile,AI_MEMORYIO_MAGIC_FILENAME,AI_MEMORYIO_MAGIC_FILENAME_LENGTH)) {
			return NULL;
		}
		return new MemoryIOStream(buffer,length);
	}

	// -------------------------------------------------------------------
	/** Closes the given file and releases all resources associated with it. */
	void Close( IOStream* pFile) {
	}

	// -------------------------------------------------------------------
	/** Compare two paths */
	bool ComparePaths (const char* one, const char* second) const {
		return false;
	}

private:
	const uint8_t* buffer;
	size_t length;
};
} // end namespace Assimp

#endif