From a32a2f36be6369478bc18fac78ff50b6398d9882 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Fri, 12 Mar 2021 19:15:35 -0500
Subject: [PATCH] Advances to correctly reading bytes.

Something is still amiss though. Maybe I'm supposed to update the checksum?
---
 Machines/AmstradCPC/AmstradCPC.cpp | 11 ++++++++++-
 Storage/Tape/Parsers/Spectrum.hpp  |  7 ++++++-
 Storage/Tape/Tape.cpp              |  8 ++++++++
 Storage/Tape/Tape.hpp              |  3 +++
 4 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/Machines/AmstradCPC/AmstradCPC.cpp b/Machines/AmstradCPC/AmstradCPC.cpp
index 6595fa47e..4ed228ace 100644
--- a/Machines/AmstradCPC/AmstradCPC.cpp
+++ b/Machines/AmstradCPC/AmstradCPC.cpp
@@ -919,12 +919,21 @@ template <bool has_fdc> class ConcreteMachine:
 					if(address == tape_read_byte_address && read_pointers_[0] == roms_[ROMType::OS].data()) {
 						using Parser = Storage::Tape::ZXSpectrum::Parser;
 						Parser parser(Parser::MachineType::AmstradCPC);
-						parser.set_cpc_read_speed(read_pointers_[tape_speed_value_address >> 14][tape_speed_value_address & 16383]);
 
+						const auto speed = read_pointers_[tape_speed_value_address >> 14][tape_speed_value_address & 16383];
+						parser.set_cpc_read_speed(speed);
+
+						// Seed with the current pulse; the CPC will have finished the
+						// preceding symbol and be a short way into the pulse that should determine the
+						// first bit of this byte.
+						parser.process_pulse(tape_player_.get_current_pulse());
 						const auto byte = parser.get_byte(tape_player_.get_tape());
 						auto flags = z80_.get_value_of_register(CPU::Z80::Register::Flags);
 
 						if(byte) {
+							// In A ROM-esque fashion, begin the first pulse after the final one
+							// that was just consumed.
+							tape_player_.complete_pulse();
 							z80_.set_value_of_register(CPU::Z80::Register::A, *byte);
 							flags |= CPU::Z80::Flag::Carry;
 						} else {
diff --git a/Storage/Tape/Parsers/Spectrum.hpp b/Storage/Tape/Parsers/Spectrum.hpp
index 2b99fcbfb..db51c8f1b 100644
--- a/Storage/Tape/Parsers/Spectrum.hpp
+++ b/Storage/Tape/Parsers/Spectrum.hpp
@@ -94,6 +94,12 @@ class Parser: public Storage::Tape::PulseClassificationParser<WaveType, SymbolTy
 		*/
 		void seed_checksum(uint8_t value = 0x00);
 
+		/*!
+			Push a pulse; primarily provided for Storage::Tape::PulseClassificationParser but also potentially useful
+			for picking up fast loading from an ongoing tape.
+		*/
+		void process_pulse(const Storage::Tape::Tape::Pulse &pulse) override;
+
 	private:
 		const MachineType machine_type_;
 		constexpr bool should_flip_bytes() {
@@ -103,7 +109,6 @@ class Parser: public Storage::Tape::PulseClassificationParser<WaveType, SymbolTy
 			return machine_type_ != MachineType::ZXSpectrum;
 		}
 
-		void process_pulse(const Storage::Tape::Tape::Pulse &pulse) override;
 		void inspect_waves(const std::vector<WaveType> &waves) override;
 
 		uint8_t checksum_ = 0;
diff --git a/Storage/Tape/Tape.cpp b/Storage/Tape/Tape.cpp
index 95d57346a..d2f440e1c 100644
--- a/Storage/Tape/Tape.cpp
+++ b/Storage/Tape/Tape.cpp
@@ -97,6 +97,14 @@ void TapePlayer::get_next_pulse() {
 	set_next_event_time_interval(current_pulse_.length);
 }
 
+Tape::Pulse TapePlayer::get_current_pulse() {
+	return current_pulse_;
+}
+
+void TapePlayer::complete_pulse() {
+	jump_to_next_event();
+}
+
 void TapePlayer::run_for(const Cycles cycles) {
 	if(has_tape()) {
 		TimedEventLoop::run_for(cycles);
diff --git a/Storage/Tape/Tape.hpp b/Storage/Tape/Tape.hpp
index d506e8851..005225d71 100644
--- a/Storage/Tape/Tape.hpp
+++ b/Storage/Tape/Tape.hpp
@@ -110,6 +110,9 @@ class TapePlayer: public TimedEventLoop, public ClockingHint::Source {
 
 		ClockingHint::Preference preferred_clocking() const override;
 
+		Tape::Pulse get_current_pulse();
+		void complete_pulse();
+
 	protected:
 		virtual void process_next_event() override;
 		virtual void process_input_pulse(const Tape::Pulse &pulse) = 0;