input/buffered: move basic buffering code to class BufferingInputStream

Prepare to reuse it in another class.

src/input/BufferedInputStream.cxx

@@ -1,5 +1,5 @@
 /*
- * Copyright 2003-2018 The Music Player Daemon Project
+ * Copyright 2003-2019 The Music Player Daemon Project
  * http://www.musicpd.org
  *
  * This program is free software; you can redistribute it and/or modify
@@ -25,212 +25,51 @@
 
 BufferedInputStream::BufferedInputStream(InputStreamPtr _input)
 	:InputStream(_input->GetURI(), _input->mutex),
-	 input(std::move(_input)),
-	 thread(BIND_THIS_METHOD(RunThread)),
-	 buffer(input->GetSize())
+	 BufferingInputStream(std::move(_input))
 {
-	assert(IsEligible(*input));
+	assert(IsEligible(GetInput()));
 
-	input->SetHandler(this);
+	if (GetInput().HasMimeType())
+		SetMimeType(GetInput().GetMimeType());
 
-	if (input->HasMimeType())
-		SetMimeType(input->GetMimeType());
-
-	size = input->GetSize();
-	seekable = input->IsSeekable();
-	offset = input->GetOffset();
+	InputStream::size = BufferingInputStream::size();
+	InputStream::seekable = GetInput().IsSeekable();
+	InputStream::offset = GetInput().GetOffset();
 
 	SetReady();
-
-	thread.Start();
-}
-
-BufferedInputStream::~BufferedInputStream() noexcept
-{
-	{
-		const std::lock_guard<Mutex> lock(mutex);
-		stop = true;
-		wake_cond.notify_one();
-	}
-
-	thread.Join();
 }
 
 void
 BufferedInputStream::Check()
 {
-	if (input)
-		input->Check();
+	BufferingInputStream::Check();
 }
 
 void
 BufferedInputStream::Seek(std::unique_lock<Mutex> &lock,
 			  offset_type new_offset)
 {
-	if (new_offset >= size) {
-		offset = size;
-		return;
-	}
-
-	auto r = buffer.Read(new_offset);
-	if (r.HasData()) {
-		/* nice, we already have some data at the desired
-		   offset and this method call is a no-op */
-		offset = new_offset;
-		return;
-	}
-
-	seek_offset = new_offset;
-	seek = true;
-	wake_cond.notify_one();
-
-	client_cond.wait(lock, [this]{ return !seek; });
-
-	if (seek_error)
-		std::rethrow_exception(std::exchange(seek_error, {}));
-
-	offset = new_offset;
+	BufferingInputStream::Seek(lock, new_offset);
+	InputStream::offset = new_offset;
 }
 
 bool
 BufferedInputStream::IsEOF() noexcept
 {
-	return offset == size;
+	return InputStream::offset == BufferingInputStream::size();
 }
 
 bool
 BufferedInputStream::IsAvailable() noexcept
 {
-	return IsEOF() || buffer.Read(offset).HasData();
+	return BufferingInputStream::IsAvailable();
 }
 
 size_t
 BufferedInputStream::Read(std::unique_lock<Mutex> &lock,
 			  void *ptr, size_t s)
 {
-	if (offset >= size)
-		return 0;
-
-	while (true) {
-		assert(size == buffer.size());
-
-		auto r = buffer.Read(offset);
-		if (r.HasData()) {
-			/* yay, we have some data */
-			size_t nbytes = std::min(s, r.defined_buffer.size);
-			memcpy(ptr, r.defined_buffer.data, nbytes);
-			offset += nbytes;
-
-			if (!IsAvailable()) {
-				/* wake up the sleeping thread */
-				idle = false;
-				wake_cond.notify_one();
-			}
-
+	size_t nbytes = BufferingInputStream::Read(lock, ptr, s);
+	InputStream::offset += nbytes;
 	return nbytes;
 }
-
-		if (read_error) {
-			wake_cond.notify_one();
-			std::rethrow_exception(std::exchange(read_error, {}));
-		}
-
-		if (idle) {
-			/* wake up the sleeping thread */
-			idle = false;
-			wake_cond.notify_one();
-		}
-
-		client_cond.wait(lock);
-	}
-}
-
-void
-BufferedInputStream::RunThread() noexcept
-{
-	SetThreadName("input_buffered");
-
-	std::unique_lock<Mutex> lock(mutex);
-
-	while (!stop) {
-		assert(size == buffer.size());
-
-		if (seek) {
-			try {
-				input->Seek(lock, seek_offset);
-			} catch (...) {
-				seek_error = std::current_exception();
-			}
-
-			idle = false;
-			seek = false;
-			client_cond.notify_one();
-		} else if (!idle && !read_error &&
-			   offset != input->GetOffset() &&
-			   !IsAvailable()) {
-			/* a past Seek() call was a no-op because data
-			   was already available at that position, but
-			   now we've reached a new position where
-			   there is no more data in the buffer, and
-			   our input is reading somewhere else (maybe
-			   stuck at the end of the file); to find a
-			   way out, we now seek our input to our
-			   reading position to be able to fill our
-			   buffer */
-
-			try {
-				input->Seek(lock, offset);
-			} catch (...) {
-				/* this is really a seek error, but we
-				   register it as a read_error,
-				   because seek_error is only checked
-				   by Seek(), and at our frontend (our
-				   own InputStream interface) is in
-				   "read" mode */
-				read_error = std::current_exception();
-			}
-		} else if (!idle && !read_error &&
-			   input->IsAvailable() && !input->IsEOF()) {
-			const auto read_offset = input->GetOffset();
-			auto w = buffer.Write(read_offset);
-
-			if (w.empty()) {
-				if (IsAvailable()) {
-					/* we still have enough data
-					   for the next Read() - sleep
-					   until we need more data */
-					idle = true;
-				} else {
-					/* we need more data at our
-					   current position, because
-					   the next Read() will stall
-					   - seek our input to our
-					   offset to prepare filling
-					   the buffer from there */
-					try {
-						input->Seek(lock, offset);
-					} catch (...) {
-						read_error = std::current_exception();
-						client_cond.notify_one();
-						InvokeOnAvailable();
-					}
-				}
-
-				continue;
-			}
-
-			try {
-				size_t nbytes = input->Read(lock,
-							    w.data, w.size);
-				buffer.Commit(read_offset,
-					      read_offset + nbytes);
-			} catch (...) {
-				read_error = std::current_exception();
-			}
-
-			client_cond.notify_one();
-			InvokeOnAvailable();
-		} else
-			wake_cond.wait(lock);
-	}
-}

src/input/BufferedInputStream.hxx

@@ -1,5 +1,5 @@
 /*
- * Copyright 2003-2018 The Music Player Daemon Project
+ * Copyright 2003-2019 The Music Player Daemon Project
  * http://www.musicpd.org
  *
  * This program is free software; you can redistribute it and/or modify
@@ -21,13 +21,7 @@
 #define MPD_BUFFERED_INPUT_STREAM_BUFFER_HXX
 
 #include "InputStream.hxx"
-#include "Ptr.hxx"
-#include "Handler.hxx"
-#include "thread/Thread.hxx"
-#include "thread/Cond.hxx"
-#include "util/SparseBuffer.hxx"
-
-#include <exception>
+#include "BufferingInputStream.hxx"
 
 #include <assert.h>
 
@@ -36,37 +30,12 @@
  * #InputStream.  This works only if the #InputStream is a "file", not
  * a "stream"; see IsEligible() for details.
  */
-class BufferedInputStream final : public InputStream, InputStreamHandler {
-	InputStreamPtr input;
-
-	Thread thread;
-
-	/**
-	 * This #Cond wakes up the #Thread.  It is used by both the
-	 * "client" thread (to submit commands) and #input's handler
-	 * (to notify new data being available).
-	 */
-	Cond wake_cond;
-
-	/**
-	 * This #Cond wakes up the client upon command completion.
-	 */
-	Cond client_cond;
-
-	SparseBuffer<uint8_t> buffer;
-
-	bool stop = false, seek = false, idle = false;
-
-	offset_type seek_offset;
-
-	std::exception_ptr read_error, seek_error;
-
+class BufferedInputStream final : public InputStream, BufferingInputStream {
 	// TODO: make configurable
 	static constexpr offset_type MAX_SIZE = 128 * 1024 * 1024;
 
 public:
 	BufferedInputStream(InputStreamPtr _input);
-	~BufferedInputStream() noexcept override;
 
 	/**
 	 * Check whether the given #InputStream can be used as input
@@ -93,18 +62,11 @@ public:
 	size_t Read(std::unique_lock<Mutex> &lock,
 		    void *ptr, size_t size) override;
 
-	/* virtual methods from class InputStreamHandler */
-	void OnInputStreamReady() noexcept override {
-		/* this should never be called, because our input must
-		   be "ready" already */
-	}
-
-	void OnInputStreamAvailable() noexcept override {
-		wake_cond.notify_one();
-	}
-
 private:
-	void RunThread() noexcept;
+	/* virtual methods from class BufferingInputStream */
+	void OnBufferAvailable() noexcept override {
+		InvokeOnAvailable();
+	}
 };
 
 #endif

src/input/BufferingInputStream.cxx

@@ -0,0 +1,213 @@
+/*
+ * Copyright 2003-2019 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.
+ */
+
+#include "BufferingInputStream.hxx"
+#include "thread/Cond.hxx"
+#include "thread/Name.hxx"
+
+#include <string.h>
+
+BufferingInputStream::BufferingInputStream(InputStreamPtr _input)
+	:input(std::move(_input)),
+	 mutex(input->mutex),
+	 thread(BIND_THIS_METHOD(RunThread)),
+	 buffer(input->GetSize())
+{
+	input->SetHandler(this);
+
+	thread.Start();
+}
+
+BufferingInputStream::~BufferingInputStream() noexcept
+{
+	{
+		const std::lock_guard<Mutex> lock(mutex);
+		stop = true;
+		wake_cond.notify_one();
+	}
+
+	thread.Join();
+}
+
+void
+BufferingInputStream::Check()
+{
+	if (input)
+		input->Check();
+}
+
+void
+BufferingInputStream::Seek(std::unique_lock<Mutex> &lock, size_t new_offset)
+{
+	if (new_offset >= size()) {
+		offset = new_offset;
+		return;
+	}
+
+	auto r = buffer.Read(new_offset);
+	if (r.HasData()) {
+		/* nice, we already have some data at the desired
+		   offset and this method call is a no-op */
+		offset = new_offset;
+		return;
+	}
+
+	seek_offset = new_offset;
+	seek = true;
+	wake_cond.notify_one();
+
+	client_cond.wait(lock, [this]{ return !seek; });
+
+	if (seek_error)
+		std::rethrow_exception(std::exchange(seek_error, {}));
+
+	offset = new_offset;
+}
+
+bool
+BufferingInputStream::IsAvailable() noexcept
+{
+	return offset == size() || buffer.Read(offset).HasData();
+}
+
+size_t
+BufferingInputStream::Read(std::unique_lock<Mutex> &lock, void *ptr, size_t s)
+{
+	if (offset >= size())
+		return 0;
+
+	while (true) {
+		auto r = buffer.Read(offset);
+		if (r.HasData()) {
+			/* yay, we have some data */
+			size_t nbytes = std::min(s, r.defined_buffer.size);
+			memcpy(ptr, r.defined_buffer.data, nbytes);
+			offset += nbytes;
+
+			if (!IsAvailable()) {
+				/* wake up the sleeping thread */
+				idle = false;
+				wake_cond.notify_one();
+			}
+
+			return nbytes;
+		}
+
+		if (read_error) {
+			wake_cond.notify_one();
+			std::rethrow_exception(std::exchange(read_error, {}));
+		}
+
+		if (idle) {
+			/* wake up the sleeping thread */
+			idle = false;
+			wake_cond.notify_one();
+		}
+
+		client_cond.wait(lock);
+	}
+}
+
+void
+BufferingInputStream::RunThread() noexcept
+{
+	SetThreadName("input_buffered");
+
+	std::unique_lock<Mutex> lock(mutex);
+
+	while (!stop) {
+		if (seek) {
+			try {
+				input->Seek(lock, seek_offset);
+			} catch (...) {
+				seek_error = std::current_exception();
+			}
+
+			idle = false;
+			seek = false;
+			client_cond.notify_one();
+		} else if (!idle && !read_error &&
+			   offset != input->GetOffset() &&
+			   !IsAvailable()) {
+			/* a past Seek() call was a no-op because data
+			   was already available at that position, but
+			   now we've reached a new position where
+			   there is no more data in the buffer, and
+			   our input is reading somewhere else (maybe
+			   stuck at the end of the file); to find a
+			   way out, we now seek our input to our
+			   reading position to be able to fill our
+			   buffer */
+
+			try {
+				input->Seek(lock, offset);
+			} catch (...) {
+				/* this is really a seek error, but we
+				   register it as a read_error,
+				   because seek_error is only checked
+				   by Seek(), and at our frontend (our
+				   own InputStream interface) is in
+				   "read" mode */
+				read_error = std::current_exception();
+			}
+		} else if (!idle && !read_error &&
+			   input->IsAvailable() && !input->IsEOF()) {
+			const auto read_offset = input->GetOffset();
+			auto w = buffer.Write(read_offset);
+
+			if (w.empty()) {
+				if (IsAvailable()) {
+					/* we still have enough data
+					   for the next Read() - sleep
+					   until we need more data */
+					idle = true;
+				} else {
+					/* we need more data at our
+					   current position, because
+					   the next Read() will stall
+					   - seek our input to our
+					   offset to prepare filling
+					   the buffer from there */
+					try {
+						input->Seek(lock, offset);
+					} catch (...) {
+						read_error = std::current_exception();
+						client_cond.notify_one();
+						OnBufferAvailable();
+					}
+				}
+
+				continue;
+			}
+
+			try {
+				size_t nbytes = input->Read(lock,
+							    w.data, w.size);
+				buffer.Commit(read_offset,
+					      read_offset + nbytes);
+			} catch (...) {
+				read_error = std::current_exception();
+			}
+
+			client_cond.notify_one();
+			OnBufferAvailable();
+		} else
+			wake_cond.wait(lock);
+	}
+}

src/input/BufferingInputStream.hxx

@@ -0,0 +1,100 @@
+/*
+ * Copyright 2003-2019 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_BUFFERING_INPUT_STREAM_BUFFER_HXX
+#define MPD_BUFFERING_INPUT_STREAM_BUFFER_HXX
+
+#include "InputStream.hxx"
+#include "Ptr.hxx"
+#include "Handler.hxx"
+#include "thread/Thread.hxx"
+#include "thread/Cond.hxx"
+#include "util/SparseBuffer.hxx"
+
+#include <exception>
+
+/**
+ * A "huge" buffer which remembers the (partial) contents of an
+ * #InputStream.  This works only if the #InputStream is a "file", not
+ * a "stream".
+ */
+class BufferingInputStream : InputStreamHandler {
+	InputStreamPtr input;
+
+	Mutex &mutex;
+
+	Thread thread;
+
+	/**
+	 * This #Cond wakes up the #Thread.  It is used by both the
+	 * "client" thread (to submit commands) and #input's handler
+	 * (to notify new data being available).
+	 */
+	Cond wake_cond;
+
+	/**
+	 * This #Cond wakes up the client upon command completion.
+	 */
+	Cond client_cond;
+
+	SparseBuffer<uint8_t> buffer;
+
+	bool stop = false, seek = false, idle = false;
+
+	size_t offset = 0;
+
+	size_t seek_offset;
+
+	std::exception_ptr read_error, seek_error;
+
+public:
+	explicit BufferingInputStream(InputStreamPtr _input);
+	~BufferingInputStream() noexcept;
+
+	const auto &GetInput() const noexcept {
+		return *input;
+	}
+
+	auto size() const noexcept {
+		return buffer.size();
+	}
+
+	void Check();
+	void Seek(std::unique_lock<Mutex> &lock, size_t new_offset);
+	bool IsAvailable() noexcept;
+	size_t Read(std::unique_lock<Mutex> &lock, void *ptr, size_t size);
+
+protected:
+	virtual void OnBufferAvailable() noexcept {}
+
+private:
+	void RunThread() noexcept;
+
+	/* virtual methods from class InputStreamHandler */
+	void OnInputStreamReady() noexcept final {
+		/* this should never be called, because our input must
+		   be "ready" already */
+	}
+
+	void OnInputStreamAvailable() noexcept final {
+		wake_cond.notify_one();
+	}
+};
+
+#endif

src/input/meson.build

@@ -32,6 +32,7 @@ input_glue = static_library(
   'TextInputStream.cxx',
   'ProxyInputStream.cxx',
   'RewindInputStream.cxx',
+  'BufferingInputStream.cxx',
   'BufferedInputStream.cxx',
   'MaybeBufferedInputStream.cxx',
   include_directories: inc,