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/*
* Copyright 2003-2016 The Music Player Daemon Project
* http://www.musicpd.org
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
/** \file
*
* This is a library which manages reference counted buffers.
*/
#ifndef MPD_PAGE_HXX
#define MPD_PAGE_HXX
#include "util/RefCount.hxx"
#include <stddef.h>
/**
* A dynamically allocated buffer which keeps track of its reference
* count. This is useful for passing buffers around, when several
* instances hold references to one buffer.
*/
class Page {
/**
* The number of references to this buffer. This library uses
* atomic functions to access it, i.e. no locks are required.
* As soon as this attribute reaches zero, the buffer is
* freed.
*/
RefCount ref;
public:
/**
* The size of this buffer in bytes.
*/
const size_t size;
/**
* Dynamic array containing the buffer data.
*/
unsigned char data[sizeof(long)];
protected:
Page(size_t _size):size(_size) {}
~Page() = default;
/**
* Allocates a new #Page object, without filling the data
* element.
*/
static Page *Create(size_t size);
public:
/**
* Creates a new #page object, and copies data from the
* specified buffer. It is initialized with a reference count
* of 1.
*
* @param data the source buffer
* @param size the size of the source buffer
*/
static Page *Copy(const void *data, size_t size);
/**
* Concatenates two pages to a new page.
*
* @param a the first page
* @param b the second page, which is appended
*/
static Page *Concat(const Page &a, const Page &b);
/**
* Increases the reference counter.
*/
void Ref() {
ref.Increment();
}
/**
* Decreases the reference counter. If it reaches zero, the #page is
* freed.
*
* @return true if the #page has been freed
*/
bool Unref();
};
#endif
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