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GB: Refactor apu envelope code to reduce duplicated code
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,87 @@ | ||
| #pragma once | ||
| #include "pch.h" | ||
|
|
||
| class GbEnvelope | ||
| { | ||
| public: | ||
| template<typename T, typename U> | ||
| static void ClockEnvelope(T& state, U& channel) | ||
| { | ||
| uint8_t timer = state.EnvTimer; | ||
| if(state.EnvTimer == 0 || --state.EnvTimer == 0) { | ||
| if(state.EnvPeriod > 0 && !state.EnvStopped) { | ||
| if(state.EnvRaiseVolume && state.Volume < 0x0F) { | ||
| state.Volume++; | ||
| } else if(!state.EnvRaiseVolume && state.Volume > 0) { | ||
| state.Volume--; | ||
| } else { | ||
| state.EnvStopped = true; | ||
| } | ||
|
|
||
| //Clocking envelope should update output immediately (based on div_trigger_volume/channel_4_volume_div tests) | ||
| channel.UpdateOutput(); | ||
|
|
||
| state.EnvTimer = state.EnvPeriod; | ||
| if(timer == 0) { | ||
| //When the timer was already 0 (because period was 0), it looks like the next | ||
| //clock occurs earlier than expected. | ||
| //This fixes the last test result in channel_1_nrx2_glitch (but may be incorrect) | ||
| state.EnvTimer--; | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| template<typename T, typename U> | ||
| static void WriteRegister(T& state, uint8_t value, U& channel) | ||
| { | ||
| bool raiseVolume = (value & 0x08) != 0; | ||
| uint8_t period = value & 0x07; | ||
|
|
||
| if((value & 0xF8) == 0) { | ||
| state.Enabled = false; | ||
| } else { | ||
| //This implementation of the Zombie mode behavior differs from the description | ||
| //found here: https://gbdev.gg8.se/wiki/articles/Gameboy_sound_hardware | ||
| //Instead, it's based on the behavior of the channel_1_nrx2_glitch test and | ||
| //and SameBoy's implementation of the glitch | ||
| bool preventIncrement = false; | ||
| if(raiseVolume != state.EnvRaiseVolume) { | ||
| if(raiseVolume) { | ||
| if(!state.EnvStopped && state.EnvPeriod == 0) { | ||
| state.Volume ^= 0x0F; | ||
| } else { | ||
| state.Volume = 14 - state.Volume; | ||
| } | ||
| preventIncrement = true; | ||
| } else { | ||
| //"If the mode was changed (add to subtract or subtract to add), volume is set to 16 - volume." | ||
| state.Volume = 16 - state.Volume; | ||
| } | ||
|
|
||
| //"Only the low 4 bits of volume are kept" | ||
| state.Volume &= 0xF; | ||
| } | ||
|
|
||
| if(!state.EnvStopped && !preventIncrement) { | ||
| if(state.EnvPeriod == 0 && (period || raiseVolume)) { | ||
| if(raiseVolume) { | ||
| //"If the old envelope period was zero and the envelope is still doing automatic updates, volume is incremented by 1" | ||
| state.Volume++; | ||
| } else { | ||
| state.Volume--; | ||
| } | ||
|
|
||
| //"Only the low 4 bits of volume are kept" | ||
| state.Volume &= 0xF; | ||
| } | ||
| } | ||
| } | ||
|
|
||
| state.EnvPeriod = period; | ||
| state.EnvRaiseVolume = raiseVolume; | ||
| state.EnvVolume = (value & 0xF0) >> 4; | ||
|
|
||
| channel.UpdateOutput(); | ||
| } | ||
| }; |
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