Renames what didn't end up being a whole SerialPort.

Components/Serial/Line.cpp

@@ -0,0 +1,140 @@
+//
+//  SerialPort.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 12/10/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#include "Line.hpp"
+
+using namespace Serial;
+
+void Line::set_writer_clock_rate(HalfCycles clock_rate) {
+	clock_rate_ = clock_rate;
+}
+
+void Line::advance_writer(HalfCycles cycles) {
+	if(cycles == HalfCycles(0)) return;
+
+	const auto integral_cycles = cycles.as_integral();
+	remaining_delays_ = std::max(remaining_delays_ - integral_cycles, Cycles::IntType(0));
+	if(events_.empty()) {
+		write_cycles_since_delegate_call_ += integral_cycles;
+		if(transmission_extra_) {
+			transmission_extra_ -= integral_cycles;
+			if(transmission_extra_ <= 0) {
+				transmission_extra_ = 0;
+				update_delegate(level_);
+			}
+		}
+	} else {
+		while(!events_.empty()) {
+			if(events_.front().delay <= integral_cycles) {
+				cycles -= events_.front().delay;
+				write_cycles_since_delegate_call_ += events_.front().delay;
+				const auto old_level = level_;
+
+				auto iterator = events_.begin() + 1;
+				while(iterator != events_.end() && iterator->type != Event::Delay) {
+					level_ = iterator->type == Event::SetHigh;
+					++iterator;
+				}
+				events_.erase(events_.begin(), iterator);
+
+				if(old_level != level_) {
+					update_delegate(old_level);
+				}
+
+				// Book enough extra time for the read delegate to be posted
+				// the final bit if one is attached.
+				if(events_.empty()) {
+					transmission_extra_ = minimum_write_cycles_for_read_delegate_bit();
+				}
+			} else {
+				events_.front().delay -= integral_cycles;
+				write_cycles_since_delegate_call_ += integral_cycles;
+				break;
+			}
+		}
+	}
+}
+
+void Line::write(bool level) {
+	if(!events_.empty()) {
+		events_.emplace_back();
+		events_.back().type = level ? Event::SetHigh : Event::SetLow;
+	} else {
+		level_ = level;
+		transmission_extra_ = minimum_write_cycles_for_read_delegate_bit();
+	}
+}
+
+void Line::write(HalfCycles cycles, int count, int levels) {
+	remaining_delays_ += count * cycles.as_integral();
+
+	auto event = events_.size();
+	events_.resize(events_.size() + size_t(count)*2);
+	while(count--) {
+		events_[event].type = Event::Delay;
+		events_[event].delay = int(cycles.as_integral());
+		events_[event+1].type = (levels&1) ? Event::SetHigh : Event::SetLow;
+		levels >>= 1;
+		event += 2;
+	}
+}
+
+void Line::reset_writing() {
+	remaining_delays_ = 0;
+	events_.clear();
+}
+
+bool Line::read() {
+	return level_;
+}
+
+void Line::set_read_delegate(ReadDelegate *delegate, Storage::Time bit_length) {
+	read_delegate_ = delegate;
+	read_delegate_bit_length_ = bit_length;
+	read_delegate_bit_length_.simplify();
+	write_cycles_since_delegate_call_ = 0;
+}
+
+void Line::update_delegate(bool level) {
+	// Exit early if there's no delegate, or if the delegate is waiting for
+	// zero and this isn't zero.
+	if(!read_delegate_) return;
+
+	const int cycles_to_forward = write_cycles_since_delegate_call_;
+	write_cycles_since_delegate_call_ = 0;
+	if(level && read_delegate_phase_ == ReadDelegatePhase::WaitingForZero) return;
+
+	// Deal with a transition out of waiting-for-zero mode by seeding time left
+	// in bit at half a bit.
+	if(read_delegate_phase_ == ReadDelegatePhase::WaitingForZero) {
+		time_left_in_bit_ = read_delegate_bit_length_;
+		time_left_in_bit_.clock_rate <<= 1;
+		read_delegate_phase_ = ReadDelegatePhase::Serialising;
+	}
+
+	// Forward as many bits as occur.
+	Storage::Time time_left(cycles_to_forward, int(clock_rate_.as_integral()));
+	const int bit = level ? 1 : 0;
+	int bits = 0;
+	while(time_left >= time_left_in_bit_) {
+		++bits;
+		if(!read_delegate_->serial_line_did_produce_bit(this, bit)) {
+			read_delegate_phase_ = ReadDelegatePhase::WaitingForZero;
+			if(bit) return;
+		}
+
+		time_left -= time_left_in_bit_;
+		time_left_in_bit_ = read_delegate_bit_length_;
+	}
+	time_left_in_bit_ -= time_left;
+}
+
+Cycles::IntType Line::minimum_write_cycles_for_read_delegate_bit() {
+	if(!read_delegate_) return 0;
+	return 1 + (read_delegate_bit_length_ * static_cast<unsigned int>(clock_rate_.as_integral())).get<int>();
+}