input/MaybeBuffered: proxy InputStream implementation which auto-uses BufferedInputStream

Makefile.am

@@ -1393,6 +1393,7 @@ libinput_a_SOURCES = \
 	src/input/ProxyInputStream.cxx src/input/ProxyInputStream.hxx \
 	src/input/RewindInputStream.cxx src/input/RewindInputStream.hxx \
 	src/input/BufferedInputStream.cxx src/input/BufferedInputStream.hxx \
+	src/input/MaybeBufferedInputStream.cxx src/input/MaybeBufferedInputStream.hxx \
 	src/input/plugins/FileInputPlugin.cxx src/input/plugins/FileInputPlugin.hxx
 
 libinput_a_CPPFLAGS = $(AM_CPPFLAGS) \

src/input/BufferedInputStream.cxx

@@ -32,6 +32,8 @@ BufferedInputStream::BufferedInputStream(InputStreamPtr _input)
 {
 	assert(IsEligible(*input));
 
+	input->SetHandler(this);
+
 	if (input->HasMimeType())
 		SetMimeType(input->GetMimeType());
 
@@ -66,10 +68,12 @@ void
 BufferedInputStream::Seek(offset_type new_offset)
 {
 	auto r = buffer.Read(new_offset);
-	if (r.HasData())
+	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;
@@ -80,6 +84,8 @@ BufferedInputStream::Seek(offset_type new_offset)
 
 	if (seek_error)
 		std::rethrow_exception(std::exchange(seek_error, {}));
+
+	offset = input->GetOffset();
 }
 
 bool
@@ -101,17 +107,26 @@ BufferedInputStream::Read(void *ptr, size_t s)
 		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.signal();
+			}
+
 			return nbytes;
 		}
 
 		if (read_error) {
-			wake_cond.broadcast();
+			wake_cond.signal();
 			std::rethrow_exception(std::exchange(read_error, {}));
 		}
 
@@ -133,6 +148,8 @@ BufferedInputStream::RunThread() noexcept
 	const std::lock_guard<Mutex> lock(mutex);
 
 	while (!stop) {
+		assert(size == buffer.size());
+
 		if (seek) {
 			try {
 				input->Seek(seek_offset);
@@ -140,8 +157,6 @@ BufferedInputStream::RunThread() noexcept
 				seek_error = std::current_exception();
 			}
 
-			offset = input->GetOffset();
-
 			idle = false;
 			seek = false;
 			client_cond.signal();
@@ -151,8 +166,7 @@ BufferedInputStream::RunThread() noexcept
 			auto w = buffer.Write(read_offset);
 
 			if (w.empty()) {
-				auto r = buffer.Read(offset);
+				if (IsAvailable()) {
-				if (r.HasData()) {
 					/* we still have enough data
 					   for the next Read() - sleep
 					   until we need more data */

src/input/MaybeBufferedInputStream.cxx

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2003-2018 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 "config.h"
+#include "MaybeBufferedInputStream.hxx"
+#include "BufferedInputStream.hxx"
+
+MaybeBufferedInputStream::MaybeBufferedInputStream(InputStreamPtr _input) noexcept
+	:ProxyInputStream(std::move(_input)) {}
+
+void
+MaybeBufferedInputStream::Update() noexcept
+{
+	const bool was_ready = IsReady();
+
+	ProxyInputStream::Update();
+
+	if (!was_ready && IsReady() && BufferedInputStream::IsEligible(*input))
+		/* our input has just become ready - check if we
+		   should buffer it */
+		SetInput(std::make_unique<BufferedInputStream>(std::move(input)));
+}

src/input/MaybeBufferedInputStream.hxx

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2003-2018 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_MAYBE_BUFFERED_INPUT_STREAM_BUFFER_HXX
+#define MPD_MAYBE_BUFFERED_INPUT_STREAM_BUFFER_HXX
+
+#include "check.h"
+#include "ProxyInputStream.hxx"
+
+/**
+ * A proxy which automatically inserts #BufferedInputStream once the
+ * input becomes ready and is "eligible" (see
+ * BufferedInputStream::IsEligible()).
+ */
+class MaybeBufferedInputStream final : public ProxyInputStream {
+public:
+	explicit MaybeBufferedInputStream(InputStreamPtr _input) noexcept;
+
+	/* virtual methods from class InputStream */
+	void Update() noexcept override;
+};
+
+#endif