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