From 4636d8dfb7c70260c455c339b9f4504cc6053b62 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 30 Jan 2021 19:38:19 -0500
Subject: [PATCH] Adds support for installing the AP6 ROM and/or sideways RAM.

---
 Analyser/Static/Acorn/Target.hpp |  4 ++++
 Machines/Electron/Electron.cpp   | 39 +++++++++++++++++++++++++++++++-
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/Analyser/Static/Acorn/Target.hpp b/Analyser/Static/Acorn/Target.hpp
index 1ef46c291..f415f4b30 100644
--- a/Analyser/Static/Acorn/Target.hpp
+++ b/Analyser/Static/Acorn/Target.hpp
@@ -20,6 +20,8 @@ namespace Acorn {
 struct Target: public ::Analyser::Static::Target, public Reflection::StructImpl<Target> {
 	bool has_adfs = false;
 	bool has_dfs = false;
+	bool has_ap6_rom = false;
+	bool has_sideways_ram = false;
 	bool should_shift_restart = false;
 	std::string loading_command;
 
@@ -27,6 +29,8 @@ struct Target: public ::Analyser::Static::Target, public Reflection::StructImpl<
 		if(needs_declare()) {
 			DeclareField(has_adfs);
 			DeclareField(has_dfs);
+			DeclareField(has_ap6_rom);
+			DeclareField(has_sideways_ram);
 		}
 	}
 };
diff --git a/Machines/Electron/Electron.cpp b/Machines/Electron/Electron.cpp
index 53fb9b028..80bc3ccf7 100644
--- a/Machines/Electron/Electron.cpp
+++ b/Machines/Electron/Electron.cpp
@@ -72,6 +72,10 @@ class ConcreteMachine:
 			if(target.has_dfs) {
 				required_roms.emplace_back(machine_name, "the 1770 DFS ROM", "DFS-1770-2.20.rom", 16*1024, 0xf3dc9bc5);
 			}
+			const size_t ap6_rom_position = required_roms.size();
+			if(target.has_ap6_rom) {
+				required_roms.emplace_back(machine_name, "the 8kb Advanced Plus 6 ROM", "AP6v133.rom", 8*1024, 0xe0013cfc);
+			}
 			const auto roms = rom_fetcher(required_roms);
 
 			for(const auto &rom: roms) {
@@ -82,6 +86,15 @@ class ConcreteMachine:
 			set_rom(ROM::BASIC, *roms[0], false);
 			set_rom(ROM::OS, *roms[1], false);
 
+			/*
+				ROM slot mapping applied:
+
+					* the keyboard and BASIC ROMs occupy slots 8, 9, 10 and 11;
+					* the DFS, if in use, occupies slot 1;
+					* the ADFS, if in use, occupies slots 4 and 5;
+					* the AP6, if in use, occupies slot 15; and
+					* if sideways RAM was asked for, all otherwise unused slots are populated with sideways RAM.
+			*/
 			if(target.has_dfs || target.has_adfs) {
 				plus3_ = std::make_unique<Plus3>();
 
@@ -94,6 +107,18 @@ class ConcreteMachine:
 				}
 			}
 
+			if(target.has_ap6_rom) {
+				set_rom(ROM::Slot15, *roms[ap6_rom_position], true);
+			}
+
+			if(target.has_sideways_ram) {
+				for(int c = 0; c < 16; c++) {
+					if(rom_inserted_[c]) continue;
+					if(c >= int(ROM::Keyboard) && c < int(ROM::BASIC)+1) continue;
+					set_sideways_ram(ROM(c));
+				}
+			}
+
 			insert_media(target.media);
 
 			if(!target.loading_command.empty()) {
@@ -517,8 +542,20 @@ class ConcreteMachine:
 				rom_ptr += size_to_copy;
 			}
 
-			if(int(slot) < 16)
+			if(int(slot) < 16) {
 				rom_inserted_[int(slot)] = true;
+			}
+		}
+
+		/*!
+			Enables @c slot as sideways RAM; ensures that it does not currently contain a valid ROM signature.
+		*/
+		void set_sideways_ram(ROM slot) {
+			std::memset(roms_[int(slot)], 0xff, 16*1024);
+			if(int(slot) < 16) {
+				rom_inserted_[int(slot)] = true;
+				rom_write_masks_[int(slot)] = true;
+			}
 		}
 
 		// MARK: - Work deferral updates.