159 lines
3.9 KiB
C++
159 lines
3.9 KiB
C++
/*
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* Copyright 2003-2020 The Music Player Daemon Project
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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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#ifndef MPD_THREAD_INPUT_STREAM_HXX
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#define MPD_THREAD_INPUT_STREAM_HXX
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#include "InputStream.hxx"
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#include "thread/Thread.hxx"
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#include "thread/Cond.hxx"
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#include "util/HugeAllocator.hxx"
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#include "util/CircularBuffer.hxx"
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#include <exception>
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#include <assert.h>
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#include <stdint.h>
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/**
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* Helper class for moving InputStream implementations with blocking
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* backend library implementation to a dedicated thread. Data is
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* being read into a ring buffer, and that buffer is then consumed by
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* another thread using the regular #InputStream API. This class
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* manages the thread and the buffer.
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*
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* This works only for "streams": unknown length, no seeking, no tags.
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*
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* The implementation must call Stop() before its destruction
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* completes. This cannot be done in ~ThreadInputStream() because at
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* this point, the class has been morphed back to #ThreadInputStream
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* and the still-running thread will crash due to pure method call.
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*/
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class ThreadInputStream : public InputStream {
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const char *const plugin;
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Thread thread;
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/**
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* Signalled when the thread shall be woken up: when data from
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* the buffer has been consumed and when the stream shall be
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* closed.
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*/
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Cond wake_cond;
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std::exception_ptr postponed_exception;
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HugeArray<uint8_t> allocation;
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CircularBuffer<uint8_t> buffer;
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/**
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* Shall the stream be closed?
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*/
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bool close = false;
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/**
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* Has the end of the stream been seen by the thread?
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*/
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bool eof = false;
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public:
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ThreadInputStream(const char *_plugin,
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const char *_uri, Mutex &_mutex,
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size_t _buffer_size) noexcept;
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#ifndef NDEBUG
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~ThreadInputStream() override {
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/* Stop() must have been called already */
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assert(!thread.IsDefined());
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}
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#endif
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/**
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* Initialize the object and start the thread.
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*/
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void Start();
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/* virtual methods from InputStream */
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void Check() final;
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bool IsEOF() const noexcept final;
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bool IsAvailable() const noexcept final;
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size_t Read(std::unique_lock<Mutex> &lock,
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void *ptr, size_t size) override final;
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protected:
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/**
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* Stop the thread and free the buffer. This must be called
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* before destruction of this object completes.
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*/
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void Stop() noexcept;
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void SetMimeType(const char *_mime) noexcept {
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assert(thread.IsInside());
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InputStream::SetMimeType(_mime);
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}
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/* to be implemented by the plugin */
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/**
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* Optional initialization after entering the thread. After
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* this returns with success, the InputStream::ready flag is
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* set.
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*
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* The #InputStream is locked. Unlock/relock it if you do a
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* blocking operation.
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*
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* Throws std::runtime_error on error.
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*/
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virtual void Open() {
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}
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/**
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* Read from the stream.
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*
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* The #InputStream is not locked.
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*
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* Throws std::runtime_error on error.
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*
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* @return 0 on end-of-file
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*/
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virtual size_t ThreadRead(void *ptr, size_t size) = 0;
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/**
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* Optional deinitialization before leaving the thread.
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*
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* The #InputStream is not locked.
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*/
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virtual void Close() noexcept {}
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/**
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* Called from the client thread to cancel a Read() inside the
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* thread.
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*
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* The #InputStream is not locked.
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*/
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virtual void Cancel() noexcept {}
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private:
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void ThreadFunc() noexcept;
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};
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#endif
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