input/{async,thread}: move code to ReadFromBuffer()

src/input/AsyncInputStream.cxx

@@ -159,26 +159,12 @@ AsyncInputStream::IsAvailable() const noexcept
 		!buffer.empty();
 }
 
-size_t
-AsyncInputStream::Read(std::unique_lock<Mutex> &lock,
-		       std::span<std::byte> dest)
+inline std::size_t
+AsyncInputStream::ReadFromBuffer(std::span<std::byte> dest) noexcept
 {
-	assert(!GetEventLoop().IsInside());
-
-	/* wait for data */
-	CircularBuffer<std::byte>::Range r;
-	while (true) {
-		Check();
-
-		r = buffer.Read();
-		if (!r.empty())
-			break;
-
-		if (IsEOF())
-			return 0;
-
-		caller_cond.wait(lock);
-	}
+	const auto r = buffer.Read();
+	if (r.empty())
+		return 0;
 
 	const size_t nbytes = std::min(dest.size(), r.size());
 	memcpy(dest.data(), r.data(), nbytes);
@@ -191,13 +177,33 @@ AsyncInputStream::Read(std::unique_lock<Mutex> &lock,
 		buffer.Clear();
 
 	offset += (offset_type)nbytes;
-
-	if (paused && buffer.GetSize() < resume_at)
-		deferred_resume.Schedule();
-
 	return nbytes;
 }
 
+size_t
+AsyncInputStream::Read(std::unique_lock<Mutex> &lock,
+		       std::span<std::byte> dest)
+{
+	assert(!GetEventLoop().IsInside());
+
+	/* wait for data */
+	while (true) {
+		Check();
+
+		if (std::size_t nbytes = ReadFromBuffer(dest); nbytes > 0) {
+			if (paused && buffer.GetSize() < resume_at)
+				deferred_resume.Schedule();
+
+			return nbytes;
+		}
+
+		if (IsEOF())
+			return 0;
+
+		caller_cond.wait(lock);
+	}
+}
+
 void
 AsyncInputStream::CommitWriteBuffer(size_t nbytes) noexcept
 {

src/input/AsyncInputStream.hxx

@@ -152,6 +152,7 @@ protected:
 	void SeekDone() noexcept;
 
 private:
+	std::size_t ReadFromBuffer(std::span<std::byte> dest) noexcept;
 	void Resume();
 
 	/* for InjectEvent */

src/input/ThreadInputStream.cxx

@@ -149,6 +149,27 @@ ThreadInputStream::Seek([[maybe_unused]] std::unique_lock<Mutex> &lock,
 	wake_cond.notify_one();
 }
 
+inline std::size_t
+ThreadInputStream::ReadFromBuffer(std::span<std::byte> dest) noexcept
+{
+	const auto r = buffer.Read();
+	if (r.empty())
+		return 0;
+
+	const size_t nbytes = std::min(dest.size(), r.size());
+	memcpy(dest.data(), r.data(), nbytes);
+	buffer.Consume(nbytes);
+
+	if (buffer.empty())
+		/* when the buffer becomes empty, reset its head and
+		   tail so the next write can fill the whole buffer
+		   and not just the part after the tail */
+		buffer.Clear();
+
+	offset += (offset_type)nbytes;
+	return nbytes;
+}
+
 size_t
 ThreadInputStream::Read(std::unique_lock<Mutex> &lock,
 			std::span<std::byte> dest)
@@ -164,21 +185,8 @@ ThreadInputStream::Read(std::unique_lock<Mutex> &lock,
 			continue;
 		}
 
-		auto r = buffer.Read();
-		if (!r.empty()) {
-			size_t nbytes = std::min(dest.size(), r.size());
-			memcpy(dest.data(), r.data(), nbytes);
-			buffer.Consume(nbytes);
-
-			if (buffer.empty())
-				/* when the buffer becomes empty,
-				   reset its head and tail so the next
-				   write can fill the whole buffer and
-				   not just the part after the tail */
-				buffer.Clear();
-
+		if (std::size_t nbytes = ReadFromBuffer(dest); nbytes > 0) {
 			wake_cond.notify_one();
-			offset += nbytes;
 			return nbytes;
 		}
 

src/input/ThreadInputStream.hxx

@@ -151,6 +151,8 @@ protected:
 	virtual void Cancel() noexcept {}
 
 private:
+	std::size_t ReadFromBuffer(std::span<std::byte> dest) noexcept;
+
 	bool IsSeeking() const noexcept {
 		return seek_offset != UNKNOWN_SIZE;
 	}