FIFOBuffer implementation and tests

Foundation/include/Poco/FIFOBuffer.h

@@ -0,0 +1,211 @@
+//
+// FIFOBuffer.h
+//
+// $Id: //poco/1.4/Foundation/include/Poco/FIFOBuffer.h#2 $
+//
+// Library: Foundation
+// Package: Core
+// Module:  FIFOBuffer
+//
+// Definition of the FIFOBuffer class.
+//
+// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
+// and Contributors.
+//
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+// 
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+//
+
+
+#ifndef Foundation_FIFOBuffer_INCLUDED
+#define Foundation_FIFOBuffer_INCLUDED
+
+
+#include "Poco/Foundation.h"
+#include "Poco/Exception.h"
+#include "Poco/Buffer.h"
+#include "Poco/Mutex.h"
+#include "Poco/Format.h"
+
+
+namespace Poco {
+
+
+template <class T>
+class FIFOBuffer
+	/// A simple buffer class with support for re-entrant,
+	/// FIFO-style read/write operations as well as 
+	/// introspection into the size of buffer, amount of unread data
+	/// and available space.
+	///
+	/// This class is useful everywhere where a FIFO functionality
+	/// is needed.
+{
+public:
+	FIFOBuffer(std::size_t size):
+		_buffer(size),
+		_used(0)
+		/// Creates and allocates the FIFOBuffer.
+	{
+	}
+	
+	~FIFOBuffer()
+		/// Destroys the FIFOBuffer.
+	{
+	}
+	
+	void resize(std::size_t newSize, bool preserveContent = true)
+		/// Resizes the buffer. If preserveContent is true,
+		/// the content of the old buffer is preserved.
+		/// New size can be larger or smaller than
+		/// the current size, but it must not be 0.
+		/// Additionally, if the new length is smaller
+		/// than currently used length and preserveContent
+		/// is true, InvalidAccessException is thrown.
+	{
+		Mutex::ScopedLock lock(_mutex);
+
+		if (preserveContent && (newSize < _used))
+			throw InvalidAccessException("Can not resize FIFO without data loss.");
+		
+		_buffer.resize(newSize, preserveContent);
+		if (_used > _buffer.size())
+			_used = _buffer.size();
+	}
+	
+	Buffer<T>& peek(Poco::Buffer<T>& buffer, std::size_t length = 0) const
+		/// Peeks into the data currently in the FIFO
+		/// without actually extracting it.
+		/// Resizes the supplied buffer to the size of
+		///.data written to it. If length is not
+		/// supplied by the caller, the current FIFO used length
+		/// is substituted for it.
+		/// 
+		/// Returns the reference to the buffer.
+	{
+		Mutex::ScopedLock lock(_mutex);
+
+		if (0 == length || length > _used) length = _used;
+		poco_assert (length <= _buffer.size());
+		buffer.resize(length);
+		std::memcpy(buffer.begin(), _buffer.begin(), length * sizeof(T));
+		return buffer;
+	}
+	
+	Buffer<T>& read(Poco::Buffer<T>& buffer, std::size_t length = 0)
+		/// Copies the data currently in the FIFO
+		/// into the supplied buffer.
+		/// Resizes the supplied buffer to the size of
+		///.data written to it.
+		/// 
+		/// Returns the reference to the buffer.
+	{
+		Mutex::ScopedLock lock(_mutex);
+
+		std::size_t usedBefore = _used;
+		peek(buffer, length);
+		_used -= buffer.size();
+		if (_used)
+			std::memmove(_buffer.begin(), _buffer.begin() + usedBefore - _used, _used);
+
+		return buffer;
+	}
+
+	std::size_t write(const Buffer<T>& buffer)
+		/// Writes data.size() to the FIFO buffer.
+		/// If there is no sufficient space for the whole
+		/// buffer to be written, data up to available 
+		/// length is written.
+		/// 
+		/// Returns the length of data written.
+	{
+		Mutex::ScopedLock lock(_mutex);
+		poco_assert (_used <= _buffer.size());
+		std::size_t available =  _buffer.size() - _used;
+		std::size_t len = buffer.size() > available ? available : buffer.size();
+		std::memcpy(_buffer.begin() + _used, buffer.begin(), len * sizeof(T));
+		_used += len;
+		poco_assert (_used <= _buffer.size());
+		return len;
+	}
+
+	std::size_t size() const
+		/// Returns the size of the buffer.
+	{
+		return _buffer.size();
+	}
+	
+	std::size_t used() const
+		/// Returns the size of the used portion of the buffer.
+	{
+		return _used;
+	}
+	
+	std::size_t available() const
+		/// Returns the size of the available portion of the buffer.
+	{
+		return _buffer.size() - _used;
+	}
+
+	T& operator [] (std::size_t index)
+		/// Returns value at index position.
+		/// Throws InvalidAccessException if index is larger than 
+		/// the last valid (used) buffer position.
+	{
+		if (index >= _used)
+			throw InvalidAccessException(format("Index out of bounds: %z (max index allowed: %z)", index, _used - 1));
+
+		return _buffer[index];
+	}
+
+	const T& operator [] (std::size_t index) const
+		/// Returns value at index position.
+		/// Throws InvalidAccessException if index is larger than 
+		/// the last valid (used) buffer position.
+	{
+		if (index >= _used)
+			throw InvalidAccessException(format("Index out of bounds: %z (max index allowed: %z)", index, _used - 1));
+
+		return _buffer[index];
+	}
+
+	bool isEmpty() const
+		/// Returns true is buffer is empty, flase otherwise.
+	{
+		return 0 == _used;
+	}
+
+private:
+	FIFOBuffer();
+	FIFOBuffer(const FIFOBuffer&);
+	FIFOBuffer& operator = (const FIFOBuffer&);
+
+	Buffer<T>     _buffer;
+	std::size_t   _used;
+	mutable Mutex _mutex;
+};
+
+
+} // namespace Poco
+
+
+#endif // Foundation_FIFOBuffer_INCLUDED