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/*
* Copyright 2003-2017 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.
*/
#ifndef MPD_THREAD_INPUT_STREAM_HXX
#define MPD_THREAD_INPUT_STREAM_HXX
#include "check.h"
#include "InputStream.hxx"
#include "thread/Thread.hxx"
#include "thread/Cond.hxx"
#include "util/HugeAllocator.hxx"
#include "util/CircularBuffer.hxx"
#include <exception>
#include <assert.h>
#include <stdint.h>
/**
* Helper class for moving InputStream implementations with blocking
* backend library implementation to a dedicated thread. Data is
* being read into a ring buffer, and that buffer is then consumed by
* another thread using the regular #InputStream API. This class
* manages the thread and the buffer.
*
* This works only for "streams": unknown length, no seeking, no tags.
*
* The implementation must call Stop() before its destruction
* completes. This cannot be done in ~ThreadInputStream() because at
* this point, the class has been morphed back to #ThreadInputStream
* and the still-running thread will crash due to pure method call.
*/
class ThreadInputStream : public InputStream {
const char *const plugin;
Thread thread;
/**
* Signalled when the thread shall be woken up: when data from
* the buffer has been consumed and when the stream shall be
* closed.
*/
Cond wake_cond;
std::exception_ptr postponed_exception;
HugeArray<uint8_t> allocation;
CircularBuffer<uint8_t> buffer;
/**
* Shall the stream be closed?
*/
bool close = false;
/**
* Has the end of the stream been seen by the thread?
*/
bool eof = false;
public:
ThreadInputStream(const char *_plugin,
const char *_uri, Mutex &_mutex,
size_t _buffer_size) noexcept;
#ifndef NDEBUG
~ThreadInputStream() override {
/* Stop() must have been called already */
assert(!thread.IsDefined());
}
#endif
/**
* Initialize the object and start the thread.
*/
void Start();
/* virtual methods from InputStream */
void Check() override final;
bool IsEOF() noexcept final;
bool IsAvailable() noexcept final;
size_t Read(void *ptr, size_t size) override final;
protected:
/**
* Stop the thread and free the buffer. This must be called
* before destruction of this object completes.
*/
void Stop() noexcept;
void SetMimeType(const char *_mime) noexcept {
assert(thread.IsInside());
InputStream::SetMimeType(_mime);
}
/* to be implemented by the plugin */
/**
* Optional initialization after entering the thread. After
* this returns with success, the InputStream::ready flag is
* set.
*
* The #InputStream is locked. Unlock/relock it if you do a
* blocking operation.
*
* Throws std::runtime_error on error.
*/
virtual void Open() {
}
/**
* Read from the stream.
*
* The #InputStream is not locked.
*
* Throws std::runtime_error on error.
*
* @return 0 on end-of-file
*/
virtual size_t ThreadRead(void *ptr, size_t size) = 0;
/**
* Optional deinitialization before leaving the thread.
*
* The #InputStream is not locked.
*/
virtual void Close() noexcept {}
/**
* Called from the client thread to cancel a Read() inside the
* thread.
*
* The #InputStream is not locked.
*/
virtual void Cancel() noexcept {}
private:
void ThreadFunc() noexcept;
};
#endif