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LibDSP: Add Envelope abstraction
For the upcoming synthesizer, having an abstracted ADSR envelope concept is highly desirable. Additionally, Envelope is mostly constexpr and therefore super fast :^)
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70
Userland/Libraries/LibDSP/Envelope.h
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70
Userland/Libraries/LibDSP/Envelope.h
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/*
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* Copyright (c) 2021, kleines Filmröllchen <malu.bertsch@gmail.com>.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/StdLibExtras.h>
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namespace LibDSP {
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enum class EnvelopeState : u8 {
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Off,
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Attack,
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Decay,
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Sustain,
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Release,
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};
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struct Envelope {
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constexpr Envelope() = default;
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constexpr Envelope(double envelope)
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: envelope(envelope)
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{
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}
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constexpr bool is_attack() const { return 0 <= envelope && envelope < 1; }
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constexpr double attack() const { return clamp(envelope, 0, 1); }
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constexpr void set_attack(double offset) { envelope = offset; }
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static constexpr Envelope from_attack(double attack) { return Envelope(attack); }
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constexpr bool is_decay() const { return 1 <= envelope && envelope < 2; }
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constexpr double decay() const { return clamp(envelope, 1, 2) - 1; }
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constexpr void set_decay(double offset) { envelope = 1 + offset; }
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static constexpr Envelope from_decay(double decay) { return Envelope(decay + 1); }
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constexpr bool is_sustain() const { return 2 <= envelope && envelope < 3; }
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constexpr double sustain() const { return clamp(envelope, 2, 3) - 2; }
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constexpr void set_sustain(double offset) { envelope = 2 + offset; }
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static constexpr Envelope from_sustain(double decay) { return Envelope(decay + 2); }
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constexpr bool is_release() const { return 3 <= envelope && envelope < 4; }
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constexpr double release() const { return clamp(envelope, 3, 4) - 3; }
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constexpr void set_release(double offset) { envelope = 3 + offset; }
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static constexpr Envelope from_release(double decay) { return Envelope(decay + 3); }
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constexpr bool is_active() const { return 0 <= envelope && envelope < 4; }
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constexpr void reset() { envelope = -1; }
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constexpr operator EnvelopeState()
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{
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if (!is_active())
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return EnvelopeState::Off;
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if (is_attack())
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return EnvelopeState::Attack;
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if (is_decay())
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return EnvelopeState::Decay;
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if (is_sustain())
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return EnvelopeState::Sustain;
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if (is_release())
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return EnvelopeState::Release;
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VERIFY_NOT_REACHED();
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}
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double envelope { -1 };
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};
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}
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