Merge pull request #218 from TomHarte/6845Factored

Refactors the 6845 to make end-of-line and end-of-frame conditions more explicit and to reduce repetition

Components/6845/CRTC6845.hpp

@@ -44,106 +44,6 @@ template <class T> class CRTC6845 {
 		CRTC6845(Personality p, T &bus_handler) :
 			personality_(p), bus_handler_(bus_handler) {}
 
-		void run_for(Cycles cycles) {
-			int cyles_remaining = cycles.as_int();
-			while(cyles_remaining--) {
-				// check for end of horizontal sync
-				if(hsync_down_counter_) {
-					hsync_down_counter_--;
-					if(!hsync_down_counter_) {
-						bus_state_.hsync = false;
-					}
-				}
-
-				// check for end of line
-				bool is_end_of_line = character_counter_ == registers_[0];
-
-				// increment counter
-				character_counter_++;
-
-				// check for start of horizontal sync
-				if(character_counter_ == registers_[2]) {
-					hsync_down_counter_ = registers_[3] & 15;
-					if(hsync_down_counter_) bus_state_.hsync = true;
-				}
-
-				// update refresh address
-				if(character_is_visible_) {
-					bus_state_.refresh_address++;
-				}
-
-				// check for end of visible characters
-				if(character_counter_ == registers_[1]) {
-					character_is_visible_ = false;
-				}
-
-				// check for end-of-line
-				if(is_end_of_line) {
-					// check for end of vertical sync
-					if(vsync_down_counter_) {
-						vsync_down_counter_--;
-						if(!vsync_down_counter_) {
-							bus_state_.vsync = false;
-						}
-					}
-
-					if(is_in_adjustment_period_) {
-						line_counter_++;
-						if(line_counter_ == registers_[5]) {
-							line_counter_ = 0;
-							is_in_adjustment_period_ = false;
-							line_is_visible_ = true;
-							line_address_ = (uint16_t)((registers_[12] << 8) | registers_[13]);
-							bus_state_.refresh_address = line_address_;
-						}
-					} else {
-						// advance vertical counter
-						if(bus_state_.row_address == registers_[9]) {
-							if(!character_is_visible_)
-								line_address_ = bus_state_.refresh_address;
-							bus_state_.row_address = 0;
-
-							bool is_at_end_of_frame = line_counter_ == registers_[4];
-							line_counter_ = (line_counter_ + 1) & 0x7f;
-
-							// check for end of visible lines
-							if(line_counter_ == registers_[6]) {
-								line_is_visible_ = false;
-							}
-
-							// check for start of vertical sync
-							if(line_counter_ == registers_[7]) {
-								bus_state_.vsync = true;
-								vsync_down_counter_ = registers_[3] >> 4;
-								if(!vsync_down_counter_) vsync_down_counter_ = 16;
-							}
-
-							// check for entry into the overflow area
-							if(is_at_end_of_frame) {
-								if(registers_[5]) {
-									is_in_adjustment_period_ = true;
-								} else {
-									line_is_visible_ = true;
-									line_address_ = (uint16_t)((registers_[12] << 8) | registers_[13]);
-									bus_state_.refresh_address = line_address_;
-								}
-								bus_state_.row_address = 0;
-								line_counter_ = 0;
-							}
-						} else {
-							bus_state_.row_address = (bus_state_.row_address + 1) & 0x1f;
-						}
-						bus_state_.refresh_address = line_address_;
-					}
-
-					character_counter_ = 0;
-					character_is_visible_ = (registers_[1] != 0);
-				}
-
-				perform_bus_cycle();
-			}
-		}
-
 		void select_register(uint8_t r) {
 			selected_register_ = r;
 		}
@@ -172,6 +72,48 @@ template <class T> class CRTC6845 {
 			registers_[16] = bus_state_.refresh_address >> 8;
 		}
 
+		void run_for(Cycles cycles) {
+			static int c = 0;
+			c++;
+
+			int cyles_remaining = cycles.as_int();
+			while(cyles_remaining--) {
+				// check for end of horizontal sync
+				if(hsync_down_counter_) {
+					hsync_down_counter_--;
+					if(!hsync_down_counter_) {
+						bus_state_.hsync = false;
+					}
+				}
+
+				// check for start of horizontal sync
+				if(character_counter_ == registers_[2]) {
+					hsync_down_counter_ = registers_[3] & 15;
+					if(hsync_down_counter_) bus_state_.hsync = true;
+				}
+
+				// check for end of visible characters
+				if(character_counter_ == registers_[1]) {
+					// TODO: consider skew in character_is_visible_. Or maybe defer until perform_bus_cycle?
+					character_is_visible_ = false;
+					end_of_line_address_ = bus_state_.refresh_address;
+				}
+
+				perform_bus_cycle();
+				bus_state_.refresh_address++;
+
+				// check for end-of-line
+				if(character_counter_ == registers_[0]) {
+					character_counter_ = 0;
+					do_end_of_line();
+					character_is_visible_ = true;
+				} else {
+					// increment counter
+					character_counter_++;
+				}
+			}
+		}
+
 	private:
 		inline void perform_bus_cycle() {
 			bus_state_.display_enable = character_is_visible_ && line_is_visible_;
@@ -179,6 +121,67 @@ template <class T> class CRTC6845 {
 			bus_handler_.perform_bus_cycle(bus_state_);
 		}
 
+		inline void do_end_of_line() {
+			// check for end of vertical sync
+			if(vsync_down_counter_) {
+				vsync_down_counter_--;
+				if(!vsync_down_counter_) {
+					bus_state_.vsync = false;
+				}
+			}
+
+			if(is_in_adjustment_period_) {
+				line_counter_++;
+				if(line_counter_ == registers_[5]) {
+					is_in_adjustment_period_ = false;
+					do_end_of_frame();
+				}
+			} else {
+				// advance vertical counter
+				if(bus_state_.row_address == registers_[9]) {
+					bus_state_.row_address = 0;
+					line_address_ = end_of_line_address_;
+
+					// check for entry into the overflow area
+					if(line_counter_ == registers_[4]) {
+						if(registers_[5]) {
+							line_counter_ = 0;
+							is_in_adjustment_period_ = true;
+						} else {
+							do_end_of_frame();
+						}
+					} else {
+						line_counter_ = (line_counter_ + 1) & 0x7f;
+
+						// check for start of vertical sync
+						if(line_counter_ == registers_[7]) {
+							bus_state_.vsync = true;
+							vsync_down_counter_ = registers_[3] >> 4;
+							if(!vsync_down_counter_) vsync_down_counter_ = 16;
+						}
+
+						// check for end of visible lines
+						if(line_counter_ == registers_[6]) {
+							line_is_visible_ = false;
+						}
+					}
+				} else {
+					bus_state_.row_address = (bus_state_.row_address + 1) & 0x1f;
+				}
+			}
+
+			bus_state_.refresh_address = line_address_;
+			character_counter_ = 0;
+			character_is_visible_ = (registers_[1] != 0);
+		}
+
+		inline void do_end_of_frame() {
+			line_counter_ = 0;
+			line_is_visible_ = true;
+			line_address_ = (uint16_t)((registers_[12] << 8) | registers_[13]);
+			bus_state_.refresh_address = line_address_;
+		}
+
 		Personality personality_;
 		T &bus_handler_;
 		BusState bus_state_;
@@ -194,7 +197,9 @@ template <class T> class CRTC6845 {
 		int hsync_down_counter_;
 		int vsync_down_counter_;
 		bool is_in_adjustment_period_;
+
 		uint16_t line_address_;
+		uint16_t end_of_line_address_;
 };
 
 }

Outputs/Speaker.hpp

@@ -91,7 +91,7 @@ class Speaker {
 			std::shared_ptr<std::list<std::function<void(void)>>> queued_functions = queued_functions_;
 			queued_functions_.reset();
 			_queue->enqueue([queued_functions] {
-				for(auto function : *queued_functions) {
+				for(auto &function : *queued_functions) {
 					function();
 				}
 			});