From 1ba3f262a2fad6ccafbb206fa95369fe8a43bba7 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 22 Jul 2017 21:46:50 -0400
Subject: [PATCH] Sketched out a template for clock-receiving components to
 allow them to be implemented in terms of either half or whole cycles.

---
 Components/ClockReceiver.hpp                  | 55 +++++++++++++++++++
 .../Clock Signal.xcodeproj/project.pbxproj    |  2 +
 2 files changed, 57 insertions(+)
 create mode 100644 Components/ClockReceiver.hpp

diff --git a/Components/ClockReceiver.hpp b/Components/ClockReceiver.hpp
new file mode 100644
index 000000000..2e2a0501d
--- /dev/null
+++ b/Components/ClockReceiver.hpp
@@ -0,0 +1,55 @@
+//
+//  ClockReceiver.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 22/07/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#ifndef ClockReceiver_hpp
+#define ClockReceiver_hpp
+
+/*! Describes an integer number of whole cycles — pairs of clock signal transitions. */
+class Cycles {
+	public:
+		Cycles(int l) : length_(l) {}
+		operator int() const { return length_; }
+
+	private:
+		int length_;
+};
+
+/*! Describes an integer number of half cycles — single clock signal transitions. */
+class HalfCycles {
+	public:
+		HalfCycles(int l) : length_(l) {}
+		HalfCycles(const Cycles &cycles) : length_(int(cycles) << 1) {}
+		operator int() const { return length_; }
+
+	private:
+		int length_;
+};
+
+/*!
+	ClockReceiver is a template for components that receove a clock, measured either
+	in cycles or in half cycles. They are expected to implement either of the run_for
+	methods; buying into the template means that the other run_for will automatically
+	map appropriately to the implemented one, so callers may use either.
+*/
+template <class T> class ClockReceiver {
+	public:
+		void run_for(const Cycles &cycles) {
+			static_cast<T *>(this)->run_for(HalfCycles(cycles));
+		}
+
+		void run_for(const HalfCycles &half_cycles) {
+			int cycles = int(half_cycles) + half_cycle_carry;
+			half_cycle_carry = cycles & 1;
+			run_for(Cycles(cycles >> 1));
+		}
+
+	private:
+		int half_cycle_carry;
+};
+
+#endif /* ClockReceiver_hpp */
diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index 2925ec984..3970d170e 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -563,6 +563,7 @@
 		4B4DC8271D2C2470003C5BF8 /* C1540.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = C1540.hpp; sourceTree = "<group>"; };
 		4B4DC8291D2C27A4003C5BF8 /* SerialBus.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = SerialBus.cpp; sourceTree = "<group>"; };
 		4B4DC82A1D2C27A4003C5BF8 /* SerialBus.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = SerialBus.hpp; sourceTree = "<group>"; };
+		4B4EA7E01F24349400C216B4 /* ClockReceiver.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = ClockReceiver.hpp; sourceTree = "<group>"; };
 		4B5073051DDD3B9400C48FBD /* ArrayBuilder.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = ArrayBuilder.cpp; sourceTree = "<group>"; };
 		4B5073061DDD3B9400C48FBD /* ArrayBuilder.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = ArrayBuilder.hpp; sourceTree = "<group>"; };
 		4B5073091DDFCFDF00C48FBD /* ArrayBuilderTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = ArrayBuilderTests.mm; sourceTree = "<group>"; };
@@ -1988,6 +1989,7 @@
 		4BC9DF4A1D04691600F44158 /* Components */ = {
 			isa = PBXGroup;
 			children = (
+				4B4EA7E01F24349400C216B4 /* ClockReceiver.hpp */,
 				4BD468F81D8DF4290084958B /* 1770 */,
 				4BC9DF4B1D04691600F44158 /* 6522 */,
 				4B1E85791D174DEC001EF87D /* 6532 */,