Libraries: Add LibDSP

LibDSP is a library for digital signal processing, and is primarily
intended to support the future DAW version of Piano.

Userland/Libraries/LibDSP/Clip.h

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2021, kleines Filmröllchen <malu.bertsch@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include "Music.h"
+#include <AK/SinglyLinkedList.h>
+#include <AK/Types.h>
+#include <LibCore/Object.h>
+
+namespace LibDSP {
+
+// A clip is a self-contained snippet of notes or audio that can freely move inside and in between tracks.
+class Clip : public Core::Object {
+    C_OBJECT_ABSTRACT(Clip)
+public:
+    Clip(u32 start, u32 length)
+        : m_start(start)
+        , m_length(length)
+    {
+    }
+    virtual ~Clip() = default;
+
+    u32 start() const { return m_start; }
+    u32 length() const { return m_length; }
+    u32 end() const { return m_start + m_length; }
+
+protected:
+    u32 m_start;
+    u32 m_length;
+};
+
+class AudioClip final : public Clip {
+public:
+    Sample sample_at(u32 time);
+
+    Vector<Sample> const& samples() const { return m_samples; }
+
+private:
+    Vector<Sample> m_samples;
+};
+
+class NoteClip final : public Clip {
+public:
+    void set_note(RollNote note);
+
+    Array<SinglyLinkedList<RollNote>, note_count>& notes() { return m_notes; }
+
+private:
+    Array<SinglyLinkedList<RollNote>, note_count> m_notes;
+};
+
+}