| 1 | package com.rox.apu; | |
| 2 | ||
| 3 | import com.rox.clock.ClockWatcher; | |
| 4 | ||
| 5 | /** | |
| 6 | * NES triangle channel ($4008 / $400A / $400B). Composes a {@link LinearCounter} and | |
| 7 | * {@link LengthCounter} with an 11-bit timer and a 32-step sequencer that produces a stepped | |
| 8 | * triangle waveform. | |
| 9 | * | |
| 10 | * Unlike the pulse/noise timers, the triangle's timer is clocked every CPU cycle rather than every | |
| 11 | * APU cycle (no parity gating) - this is what gives the triangle its doubled effective frequency | |
| 12 | * range relative to pulse/noise for the same timer period. | |
| 13 | * | |
| 14 | * The sequencer only advances while both the length counter and linear counter are nonzero; the | |
| 15 | * output is always whatever the current sequence step holds regardless - real hardware doesn't | |
| 16 | * silence the channel outright when either counter hits 0, it just freezes the waveform at | |
| 17 | * whichever step it was on (a documented quirk, not a bug). | |
| 18 | */ | |
| 19 | public class TriangleChannel implements ClockWatcher { | |
| 20 | static final int[] SEQUENCE = { | |
| 21 | 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, | |
| 22 | 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 | |
| 23 | }; | |
| 24 | private static final int SEQUENCE_LENGTH = 32; | |
| 25 | ||
| 26 | private static final int CONTROL_FLAG_BIT = 0x80; //shared: linear-counter control / length-counter halt | |
| 27 | ||
| 28 | private static final int TIMER_LOW_MASK = 0xFF; | |
| 29 | private static final int TIMER_HIGH_MASK = 0x07; | |
| 30 | private static final int TIMER_HIGH_SHIFT = 8; | |
| 31 | private static final int LENGTH_LOAD_SHIFT = 3; | |
| 32 | private static final int LENGTH_LOAD_MASK = 0x1F; | |
| 33 | ||
| 34 | private final LinearCounter linearCounter; | |
| 35 | private final LengthCounter lengthCounter; | |
| 36 | ||
| 37 | private int timerPeriod; | |
| 38 | private int timerCounter; | |
| 39 | private int sequencePosition; | |
| 40 | ||
| 41 | public TriangleChannel(){ | |
| 42 | this(new LinearCounter(), new LengthCounter()); | |
| 43 | } | |
| 44 | ||
| 45 | TriangleChannel(final LinearCounter linearCounter, final LengthCounter lengthCounter){ | |
| 46 | this.linearCounter = linearCounter; | |
| 47 | this.lengthCounter = lengthCounter; | |
| 48 | } | |
| 49 | ||
| 50 | /** | |
| 51 | * Handle a $4008 write. | |
| 52 | * | |
| 53 | * Register: CRRR RRRR | |
| 54 | * C (bit 7): linear-counter control flag / length-counter halt (shared bit) | |
| 55 | * R (bits 0-6): linear counter reload value | |
| 56 | */ | |
| 57 | public void writeLinearCounterRegister(final int value){ | |
| 58 |
3
1. writeLinearCounterRegister : negated conditional → KILLED 2. writeLinearCounterRegister : Replaced bitwise AND with OR → KILLED 3. writeLinearCounterRegister : removed call to com/rox/apu/LengthCounter::setHalt → KILLED |
lengthCounter.setHalt((value & CONTROL_FLAG_BIT) != 0); |
| 59 |
1
1. writeLinearCounterRegister : removed call to com/rox/apu/LinearCounter::writeControlRegister → KILLED |
linearCounter.writeControlRegister(value); |
| 60 | } | |
| 61 | ||
| 62 | /** Handle a $400A write: low 8 bits of the 11-bit timer period. */ | |
| 63 | public void writeTimerLow(final int value){ | |
| 64 |
3
1. writeTimerLow : Replaced bitwise AND with OR → KILLED 2. writeTimerLow : Replaced bitwise OR with AND → KILLED 3. writeTimerLow : Replaced bitwise AND with OR → KILLED |
timerPeriod = (timerPeriod & (TIMER_HIGH_MASK << TIMER_HIGH_SHIFT)) | (value & TIMER_LOW_MASK); |
| 65 | } | |
| 66 | ||
| 67 | /** | |
| 68 | * Handle a $400B write. | |
| 69 | * | |
| 70 | * Register: LLLL LHHH | |
| 71 | * L (bits 3-7): length-counter table index | |
| 72 | * H (bits 0-2): high 3 bits of the 11-bit timer period | |
| 73 | */ | |
| 74 | public void writeTimerHighAndLengthLoad(final int value){ | |
| 75 |
4
1. writeTimerHighAndLengthLoad : Replaced Shift Left with Shift Right → KILLED 2. writeTimerHighAndLengthLoad : Replaced bitwise AND with OR → KILLED 3. writeTimerHighAndLengthLoad : Replaced bitwise OR with AND → KILLED 4. writeTimerHighAndLengthLoad : Replaced bitwise AND with OR → KILLED |
timerPeriod = (timerPeriod & TIMER_LOW_MASK) | ((value & TIMER_HIGH_MASK) << TIMER_HIGH_SHIFT); |
| 76 |
3
1. writeTimerHighAndLengthLoad : removed call to com/rox/apu/LengthCounter::load → KILLED 2. writeTimerHighAndLengthLoad : Replaced Shift Right with Shift Left → KILLED 3. writeTimerHighAndLengthLoad : Replaced bitwise AND with OR → KILLED |
lengthCounter.load((value >> LENGTH_LOAD_SHIFT) & LENGTH_LOAD_MASK); |
| 77 |
1
1. writeTimerHighAndLengthLoad : removed call to com/rox/apu/LinearCounter::requestReload → KILLED |
linearCounter.requestReload(); |
| 78 | } | |
| 79 | ||
| 80 | /** Handle a $4015 enable-bit change - see {@link LengthCounter#setEnabled}. */ | |
| 81 | public void setEnabled(final boolean enabled){ | |
| 82 |
1
1. setEnabled : removed call to com/rox/apu/LengthCounter::setEnabled → KILLED |
lengthCounter.setEnabled(enabled); |
| 83 | } | |
| 84 | ||
| 85 | /** Whether the length counter is currently nonzero - for the $4015 status read. */ | |
| 86 | public boolean isLengthCounterActive(){ | |
| 87 |
2
1. isLengthCounterActive : replaced boolean return with true for com/rox/apu/TriangleChannel::isLengthCounterActive → KILLED 2. isLengthCounterActive : negated conditional → KILLED |
return !lengthCounter.isZero(); |
| 88 | } | |
| 89 | ||
| 90 | /** CPU-cycle clock: unlike pulse/noise, runs at full CPU rate (no APU-cycle parity gating). */ | |
| 91 | @Override | |
| 92 | public void tick(){ | |
| 93 |
1
1. tick : negated conditional → KILLED |
if (timerCounter == 0){ |
| 94 | timerCounter = timerPeriod; | |
| 95 |
2
1. tick : negated conditional → KILLED 2. tick : negated conditional → KILLED |
if (!lengthCounter.isZero() && !linearCounter.isZero()){ |
| 96 |
2
1. tick : Replaced integer modulus with multiplication → KILLED 2. tick : Replaced integer addition with subtraction → KILLED |
sequencePosition = (sequencePosition + 1) % SEQUENCE_LENGTH; |
| 97 | } | |
| 98 | } else { | |
| 99 |
1
1. tick : Replaced integer subtraction with addition → KILLED |
timerCounter--; |
| 100 | } | |
| 101 | } | |
| 102 | ||
| 103 | /** Quarter-frame clock: advances the linear counter. */ | |
| 104 | public void quarterFrameTick(){ | |
| 105 |
1
1. quarterFrameTick : removed call to com/rox/apu/LinearCounter::tick → KILLED |
linearCounter.tick(); |
| 106 | } | |
| 107 | ||
| 108 | /** Half-frame clock: advances the length counter. */ | |
| 109 | public void halfFrameTick(){ | |
| 110 |
1
1. halfFrameTick : removed call to com/rox/apu/LengthCounter::tick → KILLED |
lengthCounter.tick(); |
| 111 | } | |
| 112 | ||
| 113 | /** Current output: always the current sequence step (real hardware never silences the channel outright). */ | |
| 114 | public int outputSample(){ | |
| 115 |
1
1. outputSample : replaced int return with 0 for com/rox/apu/TriangleChannel::outputSample → KILLED |
return SEQUENCE[sequencePosition]; |
| 116 | } | |
| 117 | ||
| 118 | int currentSequencePosition(){ | |
| 119 |
1
1. currentSequencePosition : replaced int return with 0 for com/rox/apu/TriangleChannel::currentSequencePosition → KILLED |
return sequencePosition; |
| 120 | } | |
| 121 | ||
| 122 | int currentTimerPeriod(){ | |
| 123 |
1
1. currentTimerPeriod : replaced int return with 0 for com/rox/apu/TriangleChannel::currentTimerPeriod → KILLED |
return timerPeriod; |
| 124 | } | |
| 125 | ||
| 126 | /** Everything a {@link TriangleChannel} needs to carry on exactly where it was, sub-units included. */ | |
| 127 | public record Snapshot(int timerPeriod, int timerCounter, int sequencePosition, | |
| 128 | LinearCounter.Snapshot linearCounter, LengthCounter.Snapshot lengthCounter) { | |
| 129 | } | |
| 130 | ||
| 131 | public Snapshot snapshot(){ | |
| 132 |
1
1. snapshot : replaced return value with null for com/rox/apu/TriangleChannel::snapshot → KILLED |
return new Snapshot(timerPeriod, timerCounter, sequencePosition, linearCounter.snapshot(), |
| 133 | lengthCounter.snapshot()); | |
| 134 | } | |
| 135 | ||
| 136 | public void restore(final Snapshot snapshot){ | |
| 137 | timerPeriod = snapshot.timerPeriod(); | |
| 138 | timerCounter = snapshot.timerCounter(); | |
| 139 | sequencePosition = snapshot.sequencePosition(); | |
| 140 |
1
1. restore : removed call to com/rox/apu/LinearCounter::restore → KILLED |
linearCounter.restore(snapshot.linearCounter()); |
| 141 |
1
1. restore : removed call to com/rox/apu/LengthCounter::restore → KILLED |
lengthCounter.restore(snapshot.lengthCounter()); |
| 142 | } | |
| 143 | } | |
Mutations | ||
| 58 |
1.1 2.2 3.3 |
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| 59 |
1.1 |
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| 64 |
1.1 2.2 3.3 |
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| 75 |
1.1 2.2 3.3 4.4 |
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| 76 |
1.1 2.2 3.3 |
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| 77 |
1.1 |
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| 82 |
1.1 |
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| 87 |
1.1 2.2 |
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| 93 |
1.1 |
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| 95 |
1.1 2.2 |
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| 96 |
1.1 2.2 |
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| 99 |
1.1 |
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| 105 |
1.1 |
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| 110 |
1.1 |
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| 115 |
1.1 |
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| 119 |
1.1 |
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| 123 |
1.1 |
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| 132 |
1.1 |
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| 140 |
1.1 |
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| 141 |
1.1 |