MemoryBufferStream.h

/*
 * MemoryBufferStream.h
 *
 *  Created on: Oct 22, 2012
 *      Author: regan
 */
/*****************

Kmernator Copyright (c) 2012, The Regents of the University of California,
through Lawrence Berkeley National Laboratory (subject to receipt of any
required approvals from the U.S. Dept. of Energy).  All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

(1) Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.

(2) 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.

(3) Neither the name of the University of California, Lawrence Berkeley
National Laboratory, U.S. Dept. of Energy nor the names of its contributors may
be used to endorse or promote products derived from this software without
specific prior written permission.

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, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY 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.

You are under no obligation whatsoever to provide any bug fixes, patches, or
upgrades to the features, functionality or performance of the source code
("Enhancements") to anyone; however, if you choose to make your Enhancements
available either publicly, or directly to Lawrence Berkeley National
Laboratory, without imposing a separate written license agreement for such
Enhancements, then you hereby grant the following license: a  non-exclusive,
royalty-free perpetual license to install, use, modify, prepare derivative
works, incorporate into other computer software, distribute, and sublicense
such enhancements or derivative works thereof, in binary and source code form.

*****************/

#ifndef MEMORY_BUFFER_STREAM_H_
#define MEMORY_BUFFER_STREAM_H_

#include <string>
#include <iostream>
#include <deque>
#include <algorithm>

#include <boost/iostreams/filter/symmetric.hpp>
#include <boost/iostreams/filtering_stream.hpp>
#include <boost/iostreams/categories.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>
#include <boost/lexical_cast.hpp>

template< std::streamsize BUFFER_SIZE = 131072 >
class memory_buffer_detail {
public:
	class Buffer {
	public:
		Buffer() : readOffset(0), writeOffset(0), buf(new char[BUFFER_SIZE]) {}
		~Buffer() { delete [] buf; }
		volatile std::streamsize readOffset, writeOffset;
		char * buf;
	};
	typedef boost::shared_ptr< Buffer > BufferType;

	memory_buffer_detail(bool _setExplicitWriteClose = false)
	: writeCount(0), readCount(0),
	  setExplicitWriteClose(_setExplicitWriteClose), writeClosed(false), blocked(false) {
		addBuffer();
		LOG_DEBUG_OPTIONAL(2, true, "memory_buffer_detail(): " << this);
	}
	virtual ~memory_buffer_detail() {
		LOG_DEBUG_OPTIONAL(2, true, "~memory_buffer_detail(): " << this << " readCount: " << readCount << " writeCount: " << writeCount << " buffers:" << buffers.size());
		clear();
	}
	// returns true if reading while write is still open and buffer is empty
	bool isBlocked() {
		return blocked;
	}

	// signals write is complete so last reads can complete too
	void writeClose() {
		writeClosed = true;
		if (setExplicitWriteClose == true) {
			boost::mutex::scoped_lock mylock(writeCloseLock);
			readReady.notify_one();
		}
		LOG_DEBUG_OPTIONAL(2, true, "memory_buffer_detail::writeClose(): " << this << " at " << writeCount);
	}

	// never returns less than n
	std::streamsize write(const char* s, std::streamsize n) {
		assert(!writeClosed);
		std::streamsize wrote = 0, remaining = n;
		while (remaining > 0) {
			wrote = writeSome(s, remaining);
			s+=wrote;
			remaining -= wrote;
		}
		return n;
	}
	// returning less than n signifies EOF
	// so only do so if writing has stopped
	std::streamsize read(char *s, std::streamsize n) {
		std::streamsize totalReadSize = 0, remaining = n;
		while (remaining > 0) {
			std::streamsize readSize = readSome(s, remaining);
			s+=readSize;
			remaining -= readSize;
			totalReadSize += readSize;
			if (readSize == 0) {
				if (setExplicitWriteClose && !writeClosed) {
					blocked = true;
					boost::mutex::scoped_lock mylock(writeCloseLock);
					readReady.timed_wait(mylock, boost::get_system_time() + boost::posix_time::milliseconds(500));
				} else {
					break;
				}
			}
		}
		blocked = false;
		return totalReadSize;
	}
	std::streamsize tellp() const {
		return writeCount;
	}
	std::streamsize tellg() const {
		return readCount;
	}

	std::streamsize writeSome(const char* s, std::streamsize n) {
		BufferType b = back;
		volatile std::streamsize &writeOffset = b->writeOffset;
		std::streamsize wrote = std::min(BUFFER_SIZE - writeOffset, n);

		memcpy(b->buf + writeOffset, s, wrote);
		{
			// make copies to prevent race between read & write threads
			std::streamsize tmp = writeOffset + wrote;
			writeOffset = tmp;
		}
		writeCount += wrote;
		if (writeOffset == BUFFER_SIZE)
			addBuffer();
		if (setExplicitWriteClose == true)
			readReady.notify_one();
		return wrote;
	}

	std::streamsize readSome(char *s, std::streamsize n) {
		int readSize;
		BufferType b = front;
		if (b.get() == NULL)
			return 0;
		else {
			std::streamsize writeOffset = b->writeOffset; // make a copy
			volatile std::streamsize &readOffset = b->readOffset;  // direct reference
			readSize = std::min(n, writeOffset - readOffset);
			memcpy(s, b->buf + readOffset, readSize);
			readOffset += readSize;
			readCount += readSize;
			if (readOffset == BUFFER_SIZE || (readOffset == b->writeOffset && writeClosed))
				removeFirstBuffer();
		}
		return readSize;
	}

	void concat(memory_buffer_detail &src) {
		assert(writeClosed && src.writeClosed);
		readCount += src.readCount;
		writeCount += src.writeCount;
		buffers.insert(buffers.end(), src.buffers.begin(), src.buffers.end());
		front = buffers.front();
		back = buffers.back();
		src.clear();
	}

protected:
	void clear() {
		{
			writeCount = readCount = 0;
			buffers.clear();
			front.reset();
			back.reset();
		}
	}

	void addBuffer() {
		BufferType p( new Buffer() );
		{
			buffers.push_back( p );
			if (front.get() != buffers.front().get())
				front = buffers.front();
			back = p;
		}
	}
	void removeFirstBuffer() {
		assert(!buffers.empty());
		{
			buffers.pop_front();
			if (!buffers.empty()) {
				front = buffers.front();
				if (back.get() != buffers.back().get())
					back = buffers.back();
			} else {
				front.reset();
				back.reset();
			}
		}
	}

private:
	std::streamsize writeCount, readCount;
	std::deque< BufferType > buffers;
	bool setExplicitWriteClose, writeClosed, blocked;
	BufferType front, back;
	boost::mutex writeCloseLock;
	boost::condition_variable readReady;
};


template< typename Impl >
class stream_impl_template {
public:
	typedef char char_type;
	typedef boost::iostreams::bidirectional_device_tag category;
	typedef boost::shared_ptr< Impl > ImplPtr;

	stream_impl_template() : _impl( new Impl() ) {}

	template<typename U1>
	stream_impl_template(U1 &u1) : _impl( new Impl(u1) ) {};

	template<typename U1, typename U2>
	stream_impl_template(U1 &u1, U2 &u2) : _impl( new Impl(u1, u2) ) {};

	template<typename U1, typename U2, typename U3>
	stream_impl_template(U1 &u1, U2 &u2, U3 &u3) : _impl( new Impl(u1, u2, u3) ) {};

	~stream_impl_template() {}
	stream_impl_template &operator=(const stream_impl_template &copy) {
		_impl = copy._impl;
		return *this;
	}
	std::streamsize write(const char* s, std::streamsize n) {
		return _impl->write(s, n);
	}
	std::streamsize read(char *s, std::streamsize n) {
		return _impl->read(s, n);
	}
	std::streamsize tellp() const {
		return _impl->tellp();
	}
	std::streamsize tellg() const {
		return _impl->tellg();
	}

	template<typename U>
	stream_impl_template &operator<<(U u) {
		std::string s = boost::lexical_cast<std::string>(u);
		write(s.c_str(), s.length());
		return *this;
	}

	// specialized for memory_buffer_detail
	bool isBlocked() {
		return _impl->isBlocked();
	}
	void writeClose() {
		_impl->writeClose();
	}
	void concat(stream_impl_template &src) {
		_impl->concat(*src._impl);
	}

	class ostream : public boost::iostreams::filtering_ostream
	{
	public:
		ostream(stream_impl_template &_os) {
			this->push(_os);
		}
/*
		template<typename U>
		ostream(U &u, stream_impl_template &_os) {
			this->push(u);
			this->push(_os);
		};
*/
		virtual ~ostream() {}
	};

	class istream : public boost::iostreams::filtering_istream
	{
	public:
		istream(stream_impl_template &_is) {
			this->push(_is);
		}
/*
		template<typename U>
		istream(U &u, stream_impl_template &_is) {
			this->push(u);
			this->push(_is);
		};
*/
		virtual ~istream() {}
	};

private:
	ImplPtr _impl;
};

typedef stream_impl_template< memory_buffer_detail< > > MemoryBuffer;
typedef boost::shared_ptr< MemoryBuffer > MemoryBufferPtr;
typedef std::vector< MemoryBufferPtr > MemoryBufferVector;

#endif // MEMORY_BUFFER_STREAM_H_