CoolVLViewer/indra/llcommon/llmemorystream.h

/**
 * @file llmemorystream.h
 * @author Phoenix
 * @date 2005-06-03
 * @brief Implementation of a simple fixed memory stream
 *
 * $LicenseInfo:firstyear=2005&license=viewergpl$
 *
 * Copyright (c) 2005-2009, Linden Research, Inc.
 *
 * Second Life Viewer Source Code
 * The source code in this file ("Source Code") is provided by Linden Lab
 * to you under the terms of the GNU General Public License, version 2.0
 * ("GPL"), unless you have obtained a separate licensing agreement
 * ("Other License"), formally executed by you and Linden Lab.  Terms of
 * the GPL can be found in doc/GPL-license.txt in this distribution, or
 * online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
 *
 * There are special exceptions to the terms and conditions of the GPL as
 * it is applied to this Source Code. View the full text of the exception
 * in the file doc/FLOSS-exception.txt in this software distribution, or
 * online at
 * http://secondlifegrid.net/programs/open_source/licensing/flossexception
 *
 * By copying, modifying or distributing this software, you acknowledge
 * that you have read and understood your obligations described above,
 * and agree to abide by those obligations.
 *
 * ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
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 * $/LicenseInfo$
 */

#ifndef LL_LLMEMORYSTREAM_H
#define LL_LLMEMORYSTREAM_H

// This is a simple but effective optimization when you want to treat a chunk
// of memory as an istream. I wrote this to avoid turning a buffer into a
// string, and then throwing the string into an iostringstream just to parse it
// into another datatype, eg, LLSD.

// The memory passed in is NOT owned by an instance. The caller must be careful
// to always pass in a valid memory location that exists for at least as long
// as this streambuf.

#include <iostream>

#include "llpreprocessor.h"
#include "stdtypes.h"

// LLMemoryStreamBuf class

class LLMemoryStreamBuf : public std::streambuf
{
public:
	LL_INLINE LLMemoryStreamBuf(const U8* start, S32 length)
	{
		reset(start, length);
	}

	LL_INLINE void reset(const U8* start, S32 length)
	{
		setg((char*)start, (char*)start, (char*)start + length);
	}

protected:
	LL_INLINE int underflow()
	{
		if (gptr() >= egptr())
		{
			return EOF;
		}
		return *gptr();
	}
};

// LLMemoryStream class

class LLMemoryStream : public std::istream
{
public:
	LL_INLINE LLMemoryStream(const U8* start, S32 length)
	:	std::istream(&mStreamBuf),
		mStreamBuf(start, length)
	{
	}

protected:
	LLMemoryStreamBuf mStreamBuf;
};

#endif // LL_LLMEMORYSTREAM_H