CoolVLViewer/indra/llmessage/llcorebufferstream.h

/**
 * @file llcorebufferstream.h
 * @brief Public-facing declaration for the BufferStream adapter class
 *
 * $LicenseInfo:firstyear=2012&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2012, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#ifndef	_LLCORE_BUFFER_STREAM_H_
#define	_LLCORE_BUFFER_STREAM_H_

#include <sstream>
#include <cstdlib>

#include "llcorebufferarray.h"

// std::streambuf and std::iostream adapters for BufferArray objects.
//
// BufferArrayStreamBuf inherits std::streambuf and implements an unbuffered
// interface for streambuf. This may or may not be the most time efficient
// implementation and it is a little challenging.
//
// BufferArrayStream inherits std::iostream and will be the adapter object most
// callers will be interested in (though it uses BufferArrayStreamBuf
// internally). Instances allow for the usual streaming operators ('<<', '>>')
// and serialization methods.
//
// Example of LLSD serialization to a BufferArray:
//
//   BufferArray * ba = new BufferArray;
//   BufferArrayStream bas(ba);
//   LLSDSerialize::toXML(llsd, bas);
//   operationOnBufferArray(ba);
//   ba->release();
//   ba = NULL;
//   // operationOnBufferArray and bas are each holding
//   // references to the ba instance at this point.

namespace LLCore
{

// =====================================================
// BufferArrayStreamBuf
// =====================================================

// Adapter class to put a std::streambuf interface on a BufferArray
//
// Application developers will rarely be interested in anything other than the
// constructor and even that will rarely be used except indirectly via the
// @BufferArrayStream class. The choice of interfaces implemented yields a
// bufferless adapter that doesn't used either the input or output pointer
// triplets of the more common buffered implementations. This may or may not be
// faster and that question could stand to be looked at sometime.

class BufferArrayStreamBuf : public std::streambuf
{
public:
	// Constructor increments the reference count on the
	// BufferArray argument and calls release() on destruction.
	BufferArrayStreamBuf(BufferArray* array);
	~BufferArrayStreamBuf() override;

	BufferArrayStreamBuf(const BufferArrayStreamBuf&) = delete;
	void operator=(const BufferArrayStreamBuf&) = delete;

	// Input interfaces from std::streambuf
	int_type underflow() override;
	int_type uflow() override;
	int_type pbackfail(int_type ch) override;
	std::streamsize showmanyc() override;

	// Output interfaces from std::streambuf
	int_type overflow(int c) override;
	std::streamsize xsputn(const char* src, std::streamsize count) override;

	// Common/misc interfaces from std::streambuf
	std::streampos seekoff(std::streamoff off, std::ios_base::seekdir way,
						   std::ios_base::openmode which) override;

protected:
	BufferArray*	mBufferArray;	// Ref counted
	const char*		mReadBegin;
	const char*		mReadCur;
	const char*		mReadEnd;
	size_t			mReadCurPos;
	S32				mReadCurBlock;
	size_t			mWriteCurPos;
};

// =====================================================
// BufferArrayStream
// =====================================================

// Adapter class that supplies streaming operators to BufferArray
//
// Provides a streaming adapter to an existing BufferArray instance so that the
// convenient '<<' and '>>' conversions can be applied to a BufferArray. Very
// convenient for LLSD serialization and parsing as well.

class BufferArrayStream : public std::iostream
{
public:
	// Constructor increments the reference count on the BufferArray argument
	// and calls release() on destruction.
	BufferArrayStream(BufferArray* ba);

protected:
	BufferArrayStream(const BufferArrayStream&);
	void operator=(const BufferArrayStream&);

protected:
	BufferArrayStreamBuf	mStreamBuf;
};

}  // End namespace LLCore

#endif	// _LLCORE_BUFFER_STREAM_H_