125 lines
2.6 KiB
C++
125 lines
2.6 KiB
C++
// SPDX-License-Identifier: GPL-2.0-or-later
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// Copyright The Music Player Daemon Project
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#pragma once
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#include "Ptr.hxx"
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#include "Handler.hxx"
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#include "thread/Thread.hxx"
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#include "thread/Mutex.hxx"
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#include "thread/Cond.hxx"
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#include "util/SparseBuffer.hxx"
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#include <cstddef>
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#include <exception>
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/**
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* A "huge" buffer which remembers the (partial) contents of an
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* #InputStream. This works only if the #InputStream is a "file", not
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* a "stream".
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*/
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class BufferingInputStream : InputStreamHandler {
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InputStreamPtr input;
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public:
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Mutex &mutex;
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private:
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Thread thread;
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/**
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* This #Cond wakes up the #Thread. It is used by both the
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* "client" thread (to submit commands) and #input's handler
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* (to notify new data being available).
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*/
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Cond wake_cond;
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/**
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* This #Cond wakes up the client upon command completion.
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*/
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Cond client_cond;
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SparseBuffer<std::byte> buffer;
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bool stop = false;
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/* must be mutable because IsAvailable() acts as a hint to
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modify this attribute */
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mutable size_t want_offset = INVALID_OFFSET;
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std::exception_ptr error, seek_error;
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static constexpr size_t INVALID_OFFSET = ~size_t(0);
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public:
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/**
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* Allocate a buffer which fits the given #InputStream and
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* start a thread reading into the buffer.
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*
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* Throws on error.
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*
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* @param _input a seekable #InputStream with a known size
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*/
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explicit BufferingInputStream(InputStreamPtr _input);
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~BufferingInputStream() noexcept;
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/**
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* Caller must lock the mutex.
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*/
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const auto &GetInput() const noexcept {
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return *input;
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}
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auto size() const noexcept {
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return buffer.size();
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}
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/**
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* Wrapper for InputStream::Check().
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*
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* Throws on error.
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*
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* Caller must lock the mutex.
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*/
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void Check();
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/**
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* Check whether data is available in the buffer at the given
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* offset..
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*/
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bool IsAvailable(size_t offset) const noexcept;
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/**
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* Copy data from the buffer into the given pointer.
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*
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* @return the number of bytes copied into the given pointer.
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*/
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size_t Read(std::unique_lock<Mutex> &lock, size_t offset,
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std::span<std::byte> dest);
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protected:
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/**
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* This virtual method gets called each time data has been
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* added to the buffer. During this method call, the mutex is
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* locked.
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*/
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virtual void OnBufferAvailable() noexcept {}
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private:
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size_t FindFirstHole() const noexcept;
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void RunThreadLocked(std::unique_lock<Mutex> &lock);
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void RunThread() noexcept;
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/* virtual methods from class InputStreamHandler */
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void OnInputStreamReady() noexcept final {
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/* this should never be called, because our input must
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be "ready" already */
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}
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void OnInputStreamAvailable() noexcept final {
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wake_cond.notify_one();
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}
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};
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