From c630f86f33909d6e4db3914f04840a67104edc26 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 29 May 2023 22:56:36 +0100
Subject: [PATCH] Attempt to generalise out from the 9918's current sense of
 dispatching.

---
 ClockReceiver/Dispatcher.hpp                  | 89 +++++++++++++++++++
 .../Clock Signal.xcodeproj/project.pbxproj    |  4 +-
 2 files changed, 92 insertions(+), 1 deletion(-)
 create mode 100644 ClockReceiver/Dispatcher.hpp

diff --git a/ClockReceiver/Dispatcher.hpp b/ClockReceiver/Dispatcher.hpp
new file mode 100644
index 000000000..2773c6c55
--- /dev/null
+++ b/ClockReceiver/Dispatcher.hpp
@@ -0,0 +1,89 @@
+//
+//  Serialiser.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 29/05/2023.
+//  Copyright © 2023 Thomas Harte. All rights reserved.
+//
+
+#ifndef Dispatcher_hpp
+#define Dispatcherr_hpp
+
+namespace Dispatcher {
+
+/// The unity function; converts n directly to n.
+struct UnitConverter {
+	constexpr int operator ()(int n) {
+		return n;
+	}
+};
+
+template <int max, typename SequencerT, typename ConverterT = UnitConverter>
+struct Dispatcher {
+
+	/// Perform @c target.perform<n>() for the input range [start, end]; @c ConverterT()(n) will be applied to
+	/// each individual step before it becomes the relevant template argument.
+	void dispatch(SequencerT &target, int start, int end) {
+
+		// Minor optimisation: do a comparison with end once outside the loop and if it implies so
+		// then do no further comparisons within the loop. This is somewhat targetted at expected
+		// use cases.
+		if(end < max) {
+			dispatch<true>(target, start, end);
+		} else {
+			dispatch<false>(target, start, end);
+		}
+	}
+
+private:
+	template <bool use_end> void dispatch(SequencerT &target, int start, int end) {
+		static_assert(max < 2048);
+
+		// Yes, macros, yuck. But I want an actual switch statement for the dispatch to start
+		// and to allow a simple [[fallthrough]] through all subsequent steps up until end.
+		// So I don't think I have much in the way of options here.
+		//
+		// Sensible choices by the optimiser are assumed.
+
+#define index(n)							\
+	if constexpr (n == max) return;			\
+	if(use_end && end == n) return;			\
+	[[fallthrough]];						\
+	case n: target.template perform<ConverterT()(n)>();
+
+#define index2(n)		index(n);		index(n+1);
+#define index4(n)		index2(n);		index2(n+2);
+#define index8(n)		index4(n);		index4(n+4);
+#define index16(n)		index8(n);		index8(n+8);
+#define index32(n)		index16(n);		index16(n+16);
+#define index64(n)		index32(n);		index32(n+32);
+#define index128(n)		index64(n);		index64(n+64);
+#define index256(n)		index128(n);	index128(n+128);
+#define index512(n)		index256(n);	index256(n+256);
+#define index1024(n)	index512(n);	index512(n+512);
+#define index2048(n)	index1024(n);	index1024(n+1024);
+
+		switch(start) {
+			default: 	assert(false);
+			index2048(0);
+		}
+
+#undef index
+#undef index2
+#undef index4
+#undef index8
+#undef index16
+#undef index32
+#undef index64
+#undef index128
+#undef index256
+#undef index512
+#undef index1024
+#undef index2048
+	}
+
+};
+
+}
+
+#endif /* Dispatcher_hpp */
diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index 75e1fd830..953a4376f 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -1101,6 +1101,7 @@
 
 /* Begin PBXFileReference section */
 		428168372A16C25C008ECD27 /* LineLayout.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = LineLayout.hpp; sourceTree = "<group>"; };
+		428168382A254FBE008ECD27 /* Dispatcher.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = Dispatcher.hpp; sourceTree = "<group>"; };
 		42AD552E2A0C4D5000ACE410 /* 68000.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = 68000.hpp; sourceTree = "<group>"; };
 		42AD55302A0C4D5000ACE410 /* 68000Storage.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = 68000Storage.hpp; sourceTree = "<group>"; };
 		42AD55312A0C4D5000ACE410 /* 68000Implementation.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = 68000Implementation.hpp; sourceTree = "<group>"; };
@@ -4967,12 +4968,13 @@
 				4BB146C61F49D7D700253439 /* ClockingHintSource.hpp */,
 				4BF6606A1F281573002CB053 /* ClockReceiver.hpp */,
 				4B8A7E85212F988200F2BBC6 /* DeferredQueue.hpp */,
+				4B99EBD026BF2D9F00CA924D /* DeferredValue.hpp */,
 				4BB06B211F316A3F00600C7A /* ForceInline.hpp */,
 				4B80214322EE7C3E00068002 /* JustInTime.hpp */,
 				4B644ED023F0FB55006C0CC5 /* ScanSynchroniser.hpp */,
+				428168382A254FBE008ECD27 /* Dispatcher.hpp */,
 				4B449C942063389900A095C8 /* TimeTypes.hpp */,
 				4B996B2D2496DAC2001660EF /* VSyncPredictor.hpp */,
-				4B99EBD026BF2D9F00CA924D /* DeferredValue.hpp */,
 			);
 			name = ClockReceiver;
 			path = ../../ClockReceiver;