Implement looping effect

libs/audio/include/psemek/audio/effect/loop.hpp

@@ -0,0 +1,10 @@
+#pragma once
+
+#include <psemek/audio/stream.hpp>
+
+namespace psemek::audio
+{
+
+	stream_ptr loop(stream_ptr stream, std::optional<std::size_t> count = {});
+
+}

libs/audio/source/effect/loop.cpp

@@ -0,0 +1,64 @@
+#include <psemek/audio/effect/loop.hpp>
+#include <psemek/audio/duplicate.hpp>
+
+namespace psemek::audio
+{
+
+	namespace
+	{
+
+		struct loop_impl
+			: stream
+		{
+			loop_impl(duplicator dup, std::optional<std::size_t> count)
+				: dup_(std::move(dup))
+				, stream_(dup_())
+				, count_(count)
+			{}
+
+			std::optional<std::size_t> length() const override
+			{
+				if (count_)
+					return (*stream_->length()) * (*count_);
+				return std::nullopt;
+			}
+
+			std::size_t read(float * data, std::size_t sample_count) override
+			{
+				std::size_t result = 0;
+				while (result < sample_count && (!count_ || repeated_ < *count_))
+				{
+					auto need = sample_count - result;
+					auto count = stream_->read(data + result, need);
+					result += count;
+					if (count < need)
+					{
+						++repeated_;
+						stream_ = dup_();
+					}
+				}
+				return result;
+			}
+
+			std::size_t played() const override
+			{
+				return stream_->played() + (*stream_->length()) * repeated_;
+			}
+
+		private:
+			duplicator dup_;
+			stream_ptr stream_;
+			std::optional<std::size_t> count_;
+			std::size_t repeated_ = 0;
+		};
+
+	}
+
+	stream_ptr loop(stream_ptr stream, std::optional<std::size_t> count)
+	{
+		if (!stream->length())
+			return stream;
+		return std::make_shared<loop_impl>(make_duplicator(std::move(stream)), count);
+	}
+
+}