From 5e08d7db3975d6dca5fadd255dd7dede9d10a09c Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 25 Apr 2021 20:46:49 -0400
Subject: [PATCH] Carries through paging state; avoids file rereads.

---
 Machines/Sinclair/ZXSpectrum/State.hpp      | 14 ++++++++++++++
 Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp | 14 ++++++++++----
 Storage/State/Z80.cpp                       | 20 +++++++++++++-------
 3 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/Machines/Sinclair/ZXSpectrum/State.hpp b/Machines/Sinclair/ZXSpectrum/State.hpp
index 1333c8d62..ae9632ecd 100644
--- a/Machines/Sinclair/ZXSpectrum/State.hpp
+++ b/Machines/Sinclair/ZXSpectrum/State.hpp
@@ -20,13 +20,27 @@ namespace ZXSpectrum {
 struct State: public Reflection::StructImpl<State> {
 	CPU::Z80::State z80;
 	Video::State video;
+
+	// In 16kb or 48kb mode, RAM will be 16kb or 48kb and represent
+	// memory in standard linear order. In 128kb mode, RAM will be
+	// 128kb with the first 16kb representing bank 0, the next bank 1, etc.
 	std::vector<uint8_t> ram;
 
+	// Meaningful for 128kb machines only.
+	uint8_t last_7ffd = 0;
+	uint8_t last_fffd = 0;
+
+	// Meaningful for the +2a and +3 only.
+	uint8_t last_1ffd = 0;
+
 	State() {
 		if(needs_declare()) {
 			DeclareField(z80);
 			DeclareField(video);
 			DeclareField(ram);
+			DeclareField(last_7ffd);
+			DeclareField(last_fffd);
+			DeclareField(last_1ffd);
 		}
 	}
 };
diff --git a/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp b/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
index bde983d91..2632f5295 100644
--- a/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
+++ b/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
@@ -138,6 +138,12 @@ template<Model model> class ConcreteMachine:
 					}
 				} else {
 					memcpy(ram_.data(), state->ram.data(), std::min(ram_.size(), state->ram.size()));
+
+					port1ffd_ = state->last_1ffd;
+					port7ffd_ = state->last_7ffd;
+					update_memory_map();
+
+					GI::AY38910::Utility::select_register(ay_, state->last_fffd);
 				}
 			}
 		}
@@ -400,10 +406,6 @@ template<Model model> class ConcreteMachine:
 
 						// Set the proper video base pointer.
 						set_video_address();
-
-						// Potentially lock paging, _after_ the current
-						// port values have taken effect.
-						disable_paging_ |= *cycle.value & 0x20;
 					}
 
 					// Test for +2a/+3 paging (i.e. port 1ffd).
@@ -729,6 +731,10 @@ template<Model model> class ConcreteMachine:
 				set_memory(2, 2);
 				set_memory(3, port7ffd_ & 7);
 			}
+
+			// Potentially lock paging, _after_ the current
+			// port values have taken effect.
+			disable_paging_ = port7ffd_ & 0x20;
 		}
 
 		void set_memory(int bank, uint8_t source) {
diff --git a/Storage/State/Z80.cpp b/Storage/State/Z80.cpp
index d676b6248..9cf63eeee 100644
--- a/Storage/State/Z80.cpp
+++ b/Storage/State/Z80.cpp
@@ -28,20 +28,25 @@ std::vector<uint8_t> read_memory(Storage::FileHolder &file, size_t size, bool is
 	while(cursor != size) {
 		const uint8_t next = file.get8();
 
-		if(next != 0xed) {
+		// If the next byte definitely doesn't, or can't,
+		// start an ED ED sequence then just take it.
+		if(next != 0xed || cursor == size - 1) {
 			result[cursor] = next;
 			++cursor;
 			continue;
 		}
 
+		// Grab the next byte. If it's not ED then write
+		// both and continue.
 		const uint8_t after = file.get8();
 		if(after != 0xed) {
 			result[cursor] = next;
-			++cursor;
-			file.seek(-1, SEEK_CUR);
+			result[cursor+1] = after;
+			cursor += 2;
 			continue;
 		}
 
+		// An ED ED has begun, so grab the RLE sequence.
 		const uint8_t count = file.get8();
 		const uint8_t value = file.get8();
 
@@ -112,7 +117,8 @@ std::unique_ptr<Analyser::Static::Target> Z80::load(const std::string &file_name
 	}
 
 	state->z80.registers.program_counter = file.get16le();
-	switch(file.get8()) {
+	const uint8_t model = file.get8();
+	switch(model) {
 		default: return nullptr;
 		case 0:		result->model = Target::Model::FortyEightK;		break;
 		case 3:		result->model = Target::Model::OneTwoEightK;	break;
@@ -122,7 +128,7 @@ std::unique_ptr<Analyser::Static::Target> Z80::load(const std::string &file_name
 		case 13:	result->model = Target::Model::Plus2a;			break;
 	}
 
-	const uint8_t last7ffd = file.get8();	(void)last7ffd;	// TODO
+	state->last_7ffd = file.get8();
 
 	file.seek(1, SEEK_CUR);
 	if(file.get8() & 0x80) {
@@ -135,7 +141,7 @@ std::unique_ptr<Analyser::Static::Target> Z80::load(const std::string &file_name
 		}
 	}
 
-	const uint8_t lastfffd = file.get8();	(void)lastfffd;	// TODO
+	state->last_fffd = file.get8();
 	file.seek(16, SEEK_CUR);	// Sound chip registers: TODO.
 
 	if(bonus_header_size != 23) {
@@ -165,7 +171,7 @@ std::unique_ptr<Analyser::Static::Target> Z80::load(const std::string &file_name
 		file.seek(3, SEEK_CUR);
 
 		if(bonus_header_size == 55) {
-			const uint8_t last1ffd = file.get8();	(void)last1ffd;	// TODO
+			state->last_1ffd = file.get8();
 		}
 	}