2009-03-15 02:29:12 +01:00
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/*
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2011-01-29 10:13:54 +01:00
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* Copyright (C) 2003-2011 The Music Player Daemon Project
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2009-03-15 02:29:12 +01:00
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* http://www.musicpd.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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/** \file
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*
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* This is a library which manages reference counted buffers.
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*/
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2013-01-30 09:18:52 +01:00
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#ifndef MPD_PAGE_HXX
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#define MPD_PAGE_HXX
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#include "util/RefCount.hxx"
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#include <algorithm>
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2009-03-15 02:29:12 +01:00
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#include <stddef.h>
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/**
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* A dynamically allocated buffer which keeps track of its reference
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* count. This is useful for passing buffers around, when several
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* instances hold references to one buffer.
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*/
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2013-01-30 09:18:52 +01:00
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class Page {
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2009-03-15 02:29:12 +01:00
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/**
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* The number of references to this buffer. This library uses
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* atomic functions to access it, i.e. no locks are required.
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* As soon as this attribute reaches zero, the buffer is
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* freed.
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*/
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2013-01-30 09:18:52 +01:00
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RefCount ref;
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2009-03-15 02:29:12 +01:00
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2013-01-30 09:18:52 +01:00
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public:
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2009-03-15 02:29:12 +01:00
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/**
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* The size of this buffer in bytes.
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*/
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2013-01-30 09:18:52 +01:00
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const size_t size;
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2009-03-15 02:29:12 +01:00
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/**
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* Dynamic array containing the buffer data.
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*/
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unsigned char data[sizeof(long)];
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2013-01-30 09:18:52 +01:00
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protected:
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Page(size_t _size):size(_size) {}
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~Page() = default;
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2013-01-15 18:58:02 +01:00
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2013-01-30 09:18:52 +01:00
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/**
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* Allocates a new #Page object, without filling the data
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* element.
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*/
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static Page *Create(size_t size);
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2009-03-15 02:29:12 +01:00
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2013-01-30 09:18:52 +01:00
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public:
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/**
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* Creates a new #page object, and copies data from the
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* specified buffer. It is initialized with a reference count
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* of 1.
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*
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* @param data the source buffer
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* @param size the size of the source buffer
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*/
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static Page *Copy(const void *data, size_t size);
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2009-03-17 20:51:33 +01:00
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2013-01-30 09:18:52 +01:00
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/**
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* Concatenates two pages to a new page.
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*
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* @param a the first page
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* @param b the second page, which is appended
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*/
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static Page *Concat(const Page &a, const Page &b);
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2009-03-15 02:29:12 +01:00
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2013-01-30 09:18:52 +01:00
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/**
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* Increases the reference counter.
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*/
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void Ref() {
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ref.Increment();
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}
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2009-03-15 02:29:12 +01:00
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2013-01-30 09:18:52 +01:00
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/**
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* Decreases the reference counter. If it reaches zero, the #page is
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* freed.
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*
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* @return true if the #page has been freed
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*/
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bool Unref();
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};
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2013-01-15 18:58:02 +01:00
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2009-03-15 02:29:12 +01:00
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#endif
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