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LibDSP: Add Envelope abstraction

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For the upcoming synthesizer, having an abstracted ADSR envelope concept
is highly desirable. Additionally, Envelope is mostly constexpr and
therefore super fast :^)
This commit is contained in:
kleines Filmröllchen 2021-09-28 17:58:21 +02:00 • committed by Andreas Kling
parent a1093abe26
commit cc9aab7462
2 changed files with 103 additions and 0 deletions
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70
Userland/Libraries/LibDSP/Envelope.h Normal file
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/*
* Copyright (c) 2021, kleines Filmröllchen <malu.bertsch@gmail.com>.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/StdLibExtras.h>
namespace LibDSP {
enum class EnvelopeState : u8 {
Off,
Attack,
Decay,
Sustain,
Release,
};
struct Envelope {
constexpr Envelope() = default;
constexpr Envelope(double envelope)
: envelope(envelope)
{
}
constexpr bool is_attack() const { return 0 <= envelope && envelope < 1; }
constexpr double attack() const { return clamp(envelope, 0, 1); }
constexpr void set_attack(double offset) { envelope = offset; }
static constexpr Envelope from_attack(double attack) { return Envelope(attack); }
constexpr bool is_decay() const { return 1 <= envelope && envelope < 2; }
constexpr double decay() const { return clamp(envelope, 1, 2) - 1; }
constexpr void set_decay(double offset) { envelope = 1 + offset; }
static constexpr Envelope from_decay(double decay) { return Envelope(decay + 1); }
constexpr bool is_sustain() const { return 2 <= envelope && envelope < 3; }
constexpr double sustain() const { return clamp(envelope, 2, 3) - 2; }
constexpr void set_sustain(double offset) { envelope = 2 + offset; }
static constexpr Envelope from_sustain(double decay) { return Envelope(decay + 2); }
constexpr bool is_release() const { return 3 <= envelope && envelope < 4; }
constexpr double release() const { return clamp(envelope, 3, 4) - 3; }
constexpr void set_release(double offset) { envelope = 3 + offset; }
static constexpr Envelope from_release(double decay) { return Envelope(decay + 3); }
constexpr bool is_active() const { return 0 <= envelope && envelope < 4; }
constexpr void reset() { envelope = -1; }
constexpr operator EnvelopeState()
{
if (!is_active())
return EnvelopeState::Off;
if (is_attack())
return EnvelopeState::Attack;
if (is_decay())
return EnvelopeState::Decay;
if (is_sustain())
return EnvelopeState::Sustain;
if (is_release())
return EnvelopeState::Release;
VERIFY_NOT_REACHED();
}
double envelope { -1 };
};
}