Add audio stream duplication

libs/audio/include/psemek/audio/duplicate.hpp

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <psemek/audio/stream.hpp>
+
+#include <utility>
+
+namespace psemek::audio
+{
+
+	std::pair<stream_ptr, stream_ptr> duplicate(stream_ptr stream);
+
+}

libs/audio/source/duplicate.cpp

@@ -0,0 +1,58 @@
+#include <psemek/audio/duplicate.hpp>
+
+#include <vector>
+
+namespace psemek::audio
+{
+
+	namespace
+	{
+
+		struct duplicate_common
+		{
+			duplicate_common(stream_ptr stream)
+				: stream(std::move(stream))
+			{}
+
+			stream_ptr stream;
+			std::vector<float> buffer;
+			std::size_t counter = 0;
+			std::size_t read = 0;
+		};
+
+		struct duplicate_impl
+			: stream
+		{
+			duplicate_impl(std::shared_ptr<duplicate_common> common)
+				: common_(std::move(common))
+			{}
+
+			std::size_t read(float * data, std::size_t sample_count) override
+			{
+				if (counter_ == common_->counter)
+				{
+					++common_->counter;
+					if (common_->buffer.size() < sample_count)
+						common_->buffer.resize(sample_count);
+					common_->read = common_->stream->read(common_->buffer.data(), sample_count);
+				}
+
+				std::copy(common_->buffer.data(), common_->buffer.data() + common_->read, data);
+				++counter_;
+				return common_->read;
+			}
+
+		private:
+			std::shared_ptr<duplicate_common> common_;
+			std::size_t counter_ = 0;
+		};
+
+	}
+
+	std::pair<stream_ptr, stream_ptr> duplicate(stream_ptr stream)
+	{
+		auto common = std::make_shared<duplicate_common>(std::move(stream));
+		return {std::make_shared<duplicate_impl>(common), std::make_shared<duplicate_impl>(common)};
+	}
+
+}