Separates state transitions and tests.

Machines/Amiga/Audio.cpp

@@ -83,93 +83,8 @@ void Audio::output() {
 	}
 }
 
-bool Audio::Channel::output() {
-	// The following attempts to reproduce the audio state diagram provided in
-	// Commodore's Hardware Reference Manual.
-	//
-	// See big comment at the foot of this file.
-
-	switch(state) {
-		case State::Disabled:
-			// Test for top loop of Commodore's state diagram,
-			// which permits CPU-driven audio output.
-			if(has_data && !dma_enabled && !interrupt_pending) {
-				state = State::PlayingHigh;
-
-				data_latch = data;			// i.e. pbufld1
-				has_data = false;
-				period_counter = period;	// i.e. percntrld
-				// TODO: volcntrld (see above).
-
-				// Request an interrupt.
-				return true;
-			}
-
-			// Test for DMA-style transition.
-			if(dma_enabled) {
-				state = State::WaitingForDummyDMA;
-
-				period_counter = period;	// i.e. percntrld
-				length_counter = length;	// i.e. lenctrld
-
-				break;
-			}
-		break;
-
-		case State::WaitingForDummyDMA:
-			if(!dma_enabled) {
-				state = State::Disabled;
-				break;
-			}
-
-			if(dma_enabled && has_data) {
-				has_data = false;
-				state = State::WaitingForDMA;
-				if(length == 1) {
-					length_counter = length;
-					return true;
-				}
-				break;
-			}
-		break;
-
-		case State::WaitingForDMA:
-			if(!dma_enabled) {
-				state = State::Disabled;
-				break;
-			}
-
-			if(dma_enabled && has_data) {
-				data_latch = data;
-				has_data = false;
-				period_counter = period;	// i.e. percntrld
-
-				state = State::PlayingHigh;
-				break;
-			}
-		break;
-
-		case State::PlayingHigh:
-			// TODO: penhi (i.e. output high byte).
-			-- period_counter;
-
-			// This is a reasonable guess as to the exit condition for this node;
-			// Commodore doesn't document.
-			if(period_counter == 1) {
-				state = State::PlayingLow;
-
-				// TODO: if attach period, reload output buffer.
-			}
-		break;
-
-		default: break;
-	}
-
-	return false;
-}
-
 /*
-	Big spiel on the state machine implemented above:
+	Big spiel on the state machine:
 
 	Commodore's Hardware Rerefence Manual provides the audio subsystem's state
 	machine, so I've just tried to reimplement it verbatim. It's depicted
@@ -225,7 +140,7 @@ bool Audio::Channel::output() {
 			if: AUDxON, and AUDxDAT
 			action:
 				1. volcntrld, percentrld, pbufid1
-				2. if napnav, AUDxDR
+				2. if napnav, then AUDxDR
 
 
 
@@ -326,3 +241,175 @@ bool Audio::Channel::output() {
 		napnav		/AUDxAV * /AUDxAP + AUDxAV -- no attach stuff or else attach
 					volume. Condition for normal DMA and interrupt requests.
 */
+
+
+//
+// Non-action fallback transition.
+//
+
+template <
+	Audio::Channel::State begin,
+	Audio::Channel::State end> bool Audio::Channel::transit() {
+	state = end;
+	return false;
+}
+
+//
+//	Audio::Channel::State::Disabled
+//
+
+template <> bool Audio::Channel::transit<
+	Audio::Channel::State::Disabled,
+	Audio::Channel::State::WaitingForDummyDMA>() {
+	state = State::WaitingForDummyDMA;
+
+	period_counter = period;	// i.e. percntrld
+	length_counter = length;	// i.e. lenctrld
+
+	return false;
+}
+
+template <> bool Audio::Channel::transit<
+	Audio::Channel::State::Disabled,
+	Audio::Channel::State::PlayingHigh>() {
+	state = State::PlayingHigh;
+
+	data_latch = data;			// i.e. pbufld1
+	has_data = false;
+	period_counter = period;	// i.e. percntrld
+	// TODO: volcntrld (see above).
+
+	// Request an interrupt.
+	return true;
+}
+
+template <> bool Audio::Channel::output<Audio::Channel::State::Disabled>() {
+	if(has_data && !dma_enabled && !interrupt_pending) {
+		return transit<State::Disabled, State::PlayingHigh>();
+	}
+
+	// Test for DMA-style transition.
+	if(dma_enabled) {
+		return transit<State::Disabled, State::WaitingForDummyDMA>();
+	}
+
+	return false;
+}
+
+//
+//	Audio::Channel::State::WaitingForDummyDMA
+//
+
+template <> bool Audio::Channel::transit<
+	Audio::Channel::State::WaitingForDummyDMA,
+	Audio::Channel::State::WaitingForDMA>() {
+	state = State::WaitingForDMA;
+
+	has_data = false;
+	if(length == 1) {
+		length_counter = length;
+		return true;
+	}
+
+	return false;
+}
+
+template <> bool Audio::Channel::output<Audio::Channel::State::WaitingForDummyDMA>() {
+	if(!dma_enabled) {
+		return transit<State::WaitingForDummyDMA, State::Disabled>();
+	}
+
+	if(dma_enabled && has_data) {
+		return transit<State::WaitingForDummyDMA, State::WaitingForDMA>();
+	}
+
+	return false;
+}
+
+//
+//	Audio::Channel::State::WaitingForDMA
+//
+
+template <> bool Audio::Channel::transit<
+	Audio::Channel::State::WaitingForDMA,
+	Audio::Channel::State::PlayingHigh>() {
+	state = State::PlayingHigh;
+
+	data_latch = data;
+	has_data = false;
+	period_counter = period;	// i.e. percntrld
+
+	return false;
+}
+
+template <> bool Audio::Channel::output<Audio::Channel::State::WaitingForDMA>() {
+	if(!dma_enabled) {
+		return transit<State::WaitingForDummyDMA, State::Disabled>();
+	}
+
+	if(dma_enabled && has_data) {
+		return transit<State::WaitingForDummyDMA, State::PlayingHigh>();
+	}
+
+	return false;
+}
+
+//
+//	Audio::Channel::State::PlayingHigh
+//
+
+template <> bool Audio::Channel::output<Audio::Channel::State::PlayingHigh>() {
+	-- period_counter;
+
+	// This is a reasonable guess as to the exit condition for this node;
+	// Commodore doesn't document.
+	if(!period_counter) {
+		return transit<State::PlayingHigh, State::PlayingLow>();
+	}
+
+	// TODO: penhi (i.e. output high byte).
+
+	return false;
+}
+
+//
+//	Audio::Channel::State::PlayingLow
+//
+
+template <> bool Audio::Channel::output<Audio::Channel::State::PlayingLow>() {
+	-- period_counter;
+
+	const bool dma_and_not_done = dma_enabled && !interrupt_pending;
+
+	if(!period_counter && !dma_and_not_done) {
+		return transit<State::PlayingLow, State::Disabled>();
+	}
+
+	if(!period_counter && dma_and_not_done) {
+		return transit<State::PlayingLow, State::PlayingHigh>();
+	}
+
+	// TODO: not penhi (i.e. output low byte).
+
+	return false;
+}
+
+//
+// Dispatcher
+//
+
+bool Audio::Channel::output() {
+	switch(state) {
+		case State::Disabled:			return output<State::Disabled>();
+		case State::WaitingForDummyDMA:	return output<State::WaitingForDummyDMA>();
+		case State::WaitingForDMA:		return output<State::WaitingForDMA>();
+		case State::PlayingHigh:		return output<State::PlayingHigh>();
+		case State::PlayingLow:			return output<State::PlayingLow>();
+
+		default:
+			assert(false);
+		break;
+	}
+
+	return false;
+}

Machines/Amiga/Audio.hpp

@@ -94,6 +94,8 @@ class Audio: public DMADevice<4> {
 			} state = State::Disabled;
 
 			bool output();
+			template <State state> bool output();
+			template <State begin, State end> bool transit();
 		} channels_[4];
 };