mizu-core 1.3.0

The core library implementation of all Gameboy emulation for Mizu
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170

use save_state::Savable;

pub trait ApuChannel {
    fn output(&self) -> u8;
    fn muted(&self) -> bool;
    fn set_enable(&mut self, enabled: bool);
    fn enabled(&self) -> bool;
    fn set_dac_enable(&mut self, enabled: bool);
    fn dac_enabled(&self) -> bool;
    fn trigger(&mut self);
}

#[derive(Savable)]
pub struct LengthCountedChannel<C: ApuChannel> {
    // FIXME: re-order the organization of apu channels,
    //  `dac_enable`, should not be here like this
    //dac_enable: bool,
    max_length: u16,
    length: u16,
    current_counter: u16,
    counter_decrease_enable: bool,
    channel: C,
}

impl<C: ApuChannel> LengthCountedChannel<C> {
    pub fn new(channel: C, max_length: u16) -> Self {
        Self {
            // dac_enable: true,
            max_length,
            length: 0,
            current_counter: 0,
            counter_decrease_enable: false,
            channel,
        }
    }
    pub fn channel(&self) -> &C {
        &self.channel
    }

    pub fn channel_mut(&mut self) -> &mut C {
        &mut self.channel
    }

    pub fn write_sound_length(&mut self, data: u8) {
        self.length = self.max_length - data as u16;
        self.current_counter = self.length;
    }

    pub fn write_length_enable(&mut self, data: bool) {
        self.counter_decrease_enable = data;
    }

    pub fn read_length_enable(&self) -> bool {
        self.counter_decrease_enable
    }

    pub fn clock_length_counter(&mut self) {
        if self.counter_decrease_enable {
            if self.current_counter == 0 {
                self.set_enable(false);
            } else {
                self.current_counter -= 1;
                if self.current_counter == 0 {
                    self.set_enable(false);
                }
            }
        }
    }

    // The code needs imporovements :(
    //
    /// A wrapper around `trigger` to account for the special case where the current
    /// counter is clocked after reloading to the max length
    pub fn trigger_length(&mut self, is_not_length_clock_next: bool) {
        if self.current_counter == 0 {
            self.current_counter =
                self.max_length - (is_not_length_clock_next && self.counter_decrease_enable) as u16;
        }
        self.trigger();
    }

    pub fn reset_length_counter(&mut self) {
        self.length = self.max_length;
        self.current_counter = self.length;
    }
}

impl<C: ApuChannel> ApuChannel for LengthCountedChannel<C> {
    fn output(&self) -> u8 {
        if !self.channel.enabled() {
            0
        } else {
            self.channel.output()
        }
    }

    fn muted(&self) -> bool {
        !self.channel.enabled() || self.channel.muted()
    }

    fn trigger(&mut self) {
        if self.dac_enabled() {
            self.set_enable(true);
        }

        self.channel.trigger();
    }

    fn set_enable(&mut self, enabled: bool) {
        self.channel.set_enable(enabled);
    }

    fn enabled(&self) -> bool {
        self.channel.enabled()
    }

    fn set_dac_enable(&mut self, enabled: bool) {
        self.channel.set_dac_enable(enabled);

        if !enabled {
            self.set_enable(false);
        }
    }

    fn dac_enabled(&self) -> bool {
        self.channel.dac_enabled()
    }
}

#[derive(Savable)]
pub struct Dac<C: ApuChannel> {
    capacitor: f32,
    channel: C,
}

impl<C: ApuChannel> Dac<C> {
    pub fn new(channel: C) -> Self {
        Self {
            capacitor: 0.,
            channel,
        }
    }

    pub fn dac_output(&mut self) -> f32 {
        if self.channel.muted() {
            0.
        } else {
            let dac_in = self.channel.output() as f32 / 15.;
            let dac_out = dac_in - self.capacitor;

            self.capacitor = dac_in - dac_out * 0.996;

            dac_out
        }
    }
}

impl<C: ApuChannel> std::ops::Deref for Dac<C> {
    type Target = C;

    fn deref(&self) -> &Self::Target {
        &self.channel
    }
}

impl<C: ApuChannel> std::ops::DerefMut for Dac<C> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.channel
    }
}