From a030d9935e9a3e66635db9d25cf5bce5db742dce Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 18 Jul 2021 20:25:04 -0400
Subject: [PATCH] Adds port input.

---
 Components/6526/6526.hpp                              | 8 +++++++-
 Components/6526/Implementation/6526Implementation.hpp | 8 ++++++++
 Components/6526/Implementation/6526Storage.hpp        | 1 -
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/Components/6526/6526.hpp b/Components/6526/6526.hpp
index c4408a16c..c4edc7e4e 100644
--- a/Components/6526/6526.hpp
+++ b/Components/6526/6526.hpp
@@ -22,7 +22,12 @@ enum Port {
 };
 
 struct PortHandler {
-	/// Sets the current output value of @c port and provides @c direction_mask, indicating which pins are marked as output.
+	/// Requests the current input value of @c port from the port handler.
+	uint8_t get_port_input([[maybe_unused]] Port port) {
+		return 0xff;
+	}
+
+	/// Sets the current output value of @c port; any bits marked as input will be supplied as 1s.
 	void set_port_output([[maybe_unused]] Port port, [[maybe_unused]] uint8_t value) {}
 };
 
@@ -53,6 +58,7 @@ template <typename PortHandlerT, Personality personality> class MOS6526:
 		PortHandlerT &port_handler_;
 
 		template <int port> void set_port_output();
+		template <int port> uint8_t get_port_input();
 };
 
 }
diff --git a/Components/6526/Implementation/6526Implementation.hpp b/Components/6526/Implementation/6526Implementation.hpp
index 83d6ff744..008b9c1ac 100644
--- a/Components/6526/Implementation/6526Implementation.hpp
+++ b/Components/6526/Implementation/6526Implementation.hpp
@@ -21,6 +21,12 @@ template <int port> void MOS6526<BusHandlerT, personality>::set_port_output() {
 	port_handler_.set_port_output(Port(port), output);
 }
 
+template <typename BusHandlerT, Personality personality>
+template <int port> uint8_t MOS6526<BusHandlerT, personality>::get_port_input() {
+	const uint8_t input = port_handler_.get_port_input(Port(port));
+	return (input & ~registers_.data_direction[port]) | (registers_.output[port] & registers_.data_direction[port]);
+}
+
 template <typename BusHandlerT, Personality personality>
 void MOS6526<BusHandlerT, personality>::write(int address, uint8_t value) {
 	address &= 0xf;
@@ -56,6 +62,8 @@ template <typename BusHandlerT, Personality personality>
 uint8_t MOS6526<BusHandlerT, personality>::read(int address) {
 	address &= 0xf;
 	switch(address) {
+		case 0:	return get_port_input<0>();
+		case 1:	return get_port_input<1>();
 
 		case 2: case 3:
 			return registers_.data_direction[address - 2];
diff --git a/Components/6526/Implementation/6526Storage.hpp b/Components/6526/Implementation/6526Storage.hpp
index 4442abb2e..fb8cebcb8 100644
--- a/Components/6526/Implementation/6526Storage.hpp
+++ b/Components/6526/Implementation/6526Storage.hpp
@@ -16,7 +16,6 @@ struct MOS6526Storage {
 
 	struct Registers {
 		uint8_t output[2] = {0, 0};
-		uint8_t input[2] = {0, 0};
 		uint8_t data_direction[2] = {0, 0};
 	} registers_;