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.cpp

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2021, kleines Filmröllchen <malu.bertsch@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "Clip.h"
+
+namespace LibDSP {
+
+Sample AudioClip::sample_at(u32 time)
+{
+    VERIFY(time < m_length);
+    return m_samples[time];
+}
+
+void NoteClip::set_note(RollNote note)
+{
+    VERIFY(note.pitch >= 0 && note.pitch < note_count);
+    VERIFY(note.off_sample < m_length);
+    VERIFY(note.length() >= 2);
+
+    auto& notes = m_notes[note.pitch];
+    for (auto it = notes.begin(); !it.is_end();) {
+        auto iterated_note = *it;
+        if (iterated_note.on_sample > note.off_sample) {
+            notes.insert_before(it, note);
+            return;
+        }
+        if (iterated_note.on_sample <= note.on_sample && iterated_note.off_sample >= note.on_sample) {
+            notes.remove(it);
+            return;
+        }
+        if ((note.on_sample == 0 || iterated_note.on_sample >= note.on_sample - 1) && iterated_note.on_sample <= note.off_sample) {
+            notes.remove(it);
+            it = notes.begin();
+            continue;
+        }
+        ++it;
+    }
+
+    notes.append(note);
+}
+
+}