Add audio stereo aggregator

libs/audio/include/psemek/audio/stereo.hpp

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <psemek/audio/stream.hpp>
+
+#include <memory>
+
+namespace psemek::audio
+{
+
+	stream_ptr stereo(stream_ptr left, stream_ptr right);
+
+}

libs/audio/source/stereo.cpp

@@ -0,0 +1,51 @@
+#include <psemek/audio/stereo.hpp>
+
+#include <vector>
+
+namespace psemek::audio
+{
+
+	namespace
+	{
+
+		struct stereo_impl
+			: stream
+		{
+			stereo_impl(stream_ptr left, stream_ptr right)
+				: left_(std::move(left))
+				, right_(std::move(right))
+			{}
+
+			std::size_t read(float * data, std::size_t sample_count) override
+			{
+				if (buffer_.size() < sample_count)
+					buffer_.resize(sample_count);
+
+				auto right_result = right_->read(data, sample_count);
+				auto left_result = left_->read(buffer_.data(), sample_count);
+
+				auto result = std::min(right_result, left_result);
+
+				{
+					auto begin = buffer_.data();
+					auto end = buffer_.data() + result;
+					auto dst = data;
+					for (; begin < end; begin += 2, dst += 2)
+						*dst = *begin;
+				}
+				return result;
+			}
+
+		private:
+			stream_ptr left_, right_;
+			std::vector<float> buffer_;
+		};
+
+	}
+
+	stream_ptr stereo(stream_ptr left, stream_ptr right)
+	{
+		return std::make_shared<stereo_impl>(std::move(left), std::move(right));
+	}
+
+}