Add a simple scheduler

Author: phire

Makefile

@@ -14,9 +14,12 @@ all: centurion
 CFLAGS = -g3 -Wall -pedantic
 
 centurion: centurion.o cpu6.o disassemble.o dsk.o hawk.o math128.o mux.o \
-           cbin.o cbin_load.o $(SYS_OBJS)
+           cbin.o cbin_load.o scheduler.o $(SYS_OBJS)
 
-centurion.o: centurion.c centurion.h console.h cpu6.h disassemble.h dma.h dsk.h math128.o mux.h
+centurion.o: centurion.c centurion.h console.h cpu6.h disassemble.h dma.h \
+            dsk.h math128.o mux.h scheduler.h
+
+scheduler.o: scheduler.c scheduler.h cpu6.h
 
 console.o : console.c console.h mux.h
 
@@ -26,17 +29,17 @@ cpu6.o : cpu6.c cpu6.h
 
 disassemble.o: disassemble.c disassemble.h cpu6.h
 
-dsk.o: dsk.c dsk.h hawk.h dma.h
+dsk.o: dsk.c dsk.h hawk.h dma.h scheduler.h cpu6.h
 
-hawk.o: hawk.c hawk.h
+hawk.o: hawk.c hawk.h scheduler.h
 
 cbin.o: cbin.h
 
 cbin_load.o: cpu6.h cbin.h
 
 math128.o: math128.h
 
-mux.o : centurion.h mux.h console.h cpu6.h
+mux.o : centurion.h mux.h console.h cpu6.h scheduler.h
 
 clean:
 	rm -f centurion *.o *~

centurion.c

@@ -17,6 +17,7 @@
 #include "dsk.h"
 #include "mux.h"
 #include "cbin_load.h"
+#include "scheduler.h"
 
 static unsigned finch;		/* Finch or original FDC */
 
@@ -849,6 +850,7 @@ int main(int argc, char *argv[])
 		/* Update peripherals state */
 		mux_poll(trace & TRACE_MUX);
 
+		run_scheduler(cpu_timestamp_ns);
 		throttle_emulation(cpu_timestamp_ns);
 
 		instruction_count++;

cpu6.h

@@ -26,8 +26,6 @@
 #define C		12	/* Flags ? */
 #define P		14	/* PC */
 
-#define ONE_SECOND_NS 1000000000.0
-
 extern uint8_t mem_read8(uint32_t addr);
 extern uint8_t mem_read8_debug(uint32_t addr);
 extern uint16_t mem_read16_debug(uint32_t addr);

dsk.c

@@ -7,6 +7,7 @@
 #include "dma.h"
 #include "dsk.h"
 #include "hawk.h"
+#include "scheduler.h"
 
 #ifndef O_BINARY
 #define O_BINARY 0

mux.c

@@ -8,6 +8,7 @@
 #include "console.h"
 #include "cpu6.h"
 #include "mux.h"
+#include "scheduler.h"
 
 struct MuxUnit mux[NUM_MUX_UNITS];
  // 0 disables interrupts

scheduler.c

@@ -0,0 +1,72 @@
+#include "scheduler.h"
+#include "cpu6.h"
+
+#include <stdlib.h>
+#include <assert.h>
+
+static struct event_t* event_list = NULL;
+static uint64_t next_event = UINT64_MAX;
+
+void schedule_event(struct event_t *event)
+{
+    uint64_t now = get_current_time();
+    int64_t scheduled = get_current_time() + event->delta_ns;
+    assert(scheduled > now);
+
+    if (event->next != NULL)
+        cancel_event(event);
+
+    event->scheduled_ns = scheduled;
+
+    if (!event_list) {
+        event->next = NULL;
+        event_list = event;
+        next_event = scheduled;
+        return;
+    }
+
+    struct event_t* item = event_list;
+
+    while (item && item->scheduled_ns < scheduled) {
+        item = item->next;
+    }
+    event->next = item->next;
+    item->next = event;
+}
+
+void run_scheduler(uint64_t current_time)
+{
+    if (next_event > current_time)
+        return;
+
+    assert(event_list);
+
+    while (next_event <= current_time) {
+        // Pop event
+        struct event_t* event = event_list;
+        event_list = event_list->next;
+        event->next = NULL;
+
+        // Update next_event
+        next_event = (event_list == NULL) ? UINT64_MAX : event_list->scheduled_ns;
+
+        // Run callback
+        event->callback(event, current_time - event->scheduled_ns);
+    }
+}
+
+
+void cancel_event(struct event_t *event)
+{
+    struct event_t** next_ptr = &event_list;
+
+    while(*next_ptr != NULL) {
+        struct event_t* next = *next_ptr;
+        if (next == event) {
+            *next_ptr = next->next;
+            event->next = NULL;
+            return;
+        }
+        next_ptr = &next->next;
+    }
+}

scheduler.h

@@ -0,0 +1,29 @@
+
+#pragma once
+
+#include <stdint.h>
+
+#define ONE_SECOND_NS 1000000000.0
+#define ONE_MILISECOND_NS 1000000.0
+
+
+struct event_t;
+
+// event callbacks get called with their event and how many ns have passed
+// since their scheduled event time.
+// If event was dynamically allocated, the callback should free it.
+typedef void (*callback_t)(struct event_t *event, int64_t late_ns);
+
+struct event_t {
+    int64_t delta_ns;
+    callback_t callback;
+
+    // internal state
+    struct event_t *next;
+    int64_t scheduled_ns;
+};
+
+void schedule_event(struct event_t *event);
+void cancel_event(struct event_t *event);
+void run_scheduler(uint64_t current_time);
+uint64_t get_current_time();