Add throttling to posix

Author: phire

Diff for: Makefile

@@ -36,7 +36,7 @@ cbin_load.o: cpu6.h cbin.h
 
 math128.o: math128.h
 
-mux.o : centurion.h mux.h
+mux.o : centurion.h mux.h console.h cpu6.h
 
 clean:
 	rm -f centurion *.o *~

Diff for: centurion.c

@@ -807,6 +807,9 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	throttle_init();
+	throttle_set_speed(1.0);
+
 	while (!emulator_done) {
 		cpu6_execute_one(trace & TRACE_CPU);
 		if (cpu6_halted())
@@ -846,6 +849,8 @@ int main(int argc, char *argv[])
 		/* Update peripherals state */
 		mux_poll(trace & TRACE_MUX);
 
+		throttle_emulation(cpu_timestamp_ns);
+
 		instruction_count++;
 		if (terminate_at && instruction_count >= terminate_at) {
 			printf("\nTerminated after %lli instructions\n", instruction_count);

Diff for: console.c

@@ -8,10 +8,12 @@
 #include <sys/select.h>
 #include <sys/socket.h>
 #include <arpa/inet.h>
+#include <time.h>
 
 #include "centurion.h"
 #include "console.h"
 #include "mux.h"
+#include "scheduler.h"
 
 static struct termios saved_term, term;
 
@@ -109,7 +111,7 @@ void mux_poll_fds(unsigned trace)
 		int ifd = mux_get_in_poll_fd(unit);
 
 		if (ifd == -1)
-			continue;		
+			continue;
 		FD_SET(ifd, &i);
 		if (ifd >= max_fd)
 			max_fd = ifd + 1;
@@ -127,3 +129,43 @@ void mux_poll_fds(unsigned trace)
 			mux_set_read_ready(unit, trace);
 	}
 }
+
+
+// Get's the current time from the OS (in nanoseconds)
+uint64_t monotonic_time_ns() {
+	struct timespec ts;
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	return ts.tv_sec * 1000000000ULL + ts.tv_nsec;
+}
+
+
+static uint64_t throttle_start_time;
+static float throttle_speed;
+
+void throttle_init() {
+	throttle_start_time = monotonic_time_ns();
+}
+
+void throttle_set_speed(float speed) {
+	throttle_speed = speed;
+}
+
+// Stall emulation if running faster than realtime
+void throttle_emulation(uint64_t expected_time_ns) {
+	uint64_t now = monotonic_time_ns();
+	uint64_t adjusted_target = expected_time_ns / throttle_speed;
+	int64_t delta_ns = (throttle_start_time + adjusted_target) - now;
+
+	// We don't want to sleep if the delta is less than 5ms
+	if (delta_ns > (5 * ONE_MILISECOND_NS)) {
+		struct timespec delta;
+		delta.tv_sec = delta_ns / 1000000000ULL;
+		delta.tv_nsec = delta_ns % 1000000000ULL;
+
+		// sometimes nanosecond returns early, so loop until it finishs
+		while (nanosleep(&delta, &delta));
+	} else if (delta_ns < -(50 * ONE_MILISECOND_NS)) {
+		// If have lagged by too much, we forgive the time
+		//throttle_start_time += delta_ns;
+	}
+}

Diff for: console.h

@@ -1,2 +1,10 @@
+#pragma once
+
+#include <stdint.h>
+
 void tty_init(void);
 void net_init(unsigned short port);
+
+void throttle_emulation(uint64_t expected_time_ns);
+void throttle_init();
+void throttle_set_speed(float speed);

Diff for: console_win32.c

@@ -103,3 +103,16 @@ void mux_poll_fds(unsigned trace)
                         mux_set_read_ready(unit, trace);
 	}
 }
+
+
+void throttle_emulation(uint64_t expected_time_ns) {
+        // Unimplemented
+}
+
+void throttle_init() {
+        // Unimplemented
+}
+
+void throttle_set_speed(float speed) {
+        // Unimplemented
+}