add scaffolding around calling vbEmulate in a loop

main.c

@@ -1,14 +1,24 @@
 #include <cmdbuf.h>
+#include <errno.h>
+#include <netinet/in.h>
 #include <request.h>
 #include <response.h>
 #include <server.h>
 #include <stdio.h>
 #include <string.h>
-#include <netinet/in.h>
+#include <time.h>
 #include <unistd.h>
 #include <vb.h>
 
 #define BUFLEN 8096
+#define MAX_STEP_CYCLES 20000
+
+int sleep_nanos(long int ns) {
+    struct timespec time;
+    time.tv_sec = ns / 1000000000;
+    time.tv_nsec = ns % 1000000000;
+    return nanosleep(&time, NULL);
+}
 
 int server(int connfd, VB *sim) {
     RdbRequest req;
@@ -26,6 +36,8 @@ int server(int connfd, VB *sim) {
 
     while (1) {
         CommandBuf cmd;
+        int brk;
+        uint32_t cycles;
         read_result = rdb_request_read(&req, &cmd);
         if (read_result == read_result_error) {
             return -1;
@@ -34,8 +46,17 @@ int server(int connfd, VB *sim) {
             return 0;
         } else if (read_result == read_result_pending) {
             if (running) {
-                printf("pretend the emulator is running now\n");
+                /*
-                sleep(1);
+                cycles = MAX_STEP_CYCLES;
+                brk = vbEmulate(sim, &cycles);
+                */
+                cycles = 0;
+                brk = 0;
+                if (brk) {
+                    /* We hit a breakpoint */ 
+                } else {
+                    sleep_nanos((MAX_STEP_CYCLES - cycles) * 50);
+                }
             }
             continue;
         } else {
@@ -115,7 +136,10 @@ int main(int argc, char** argv) {
     if (readROM(sim, argv[1])) {
         return 1;
     }
-    vbSetProgramCounter(sim, 0x07000000);
+    /* relevant state at the start of the physics sim's main */
+    vbSetProgramCounter(sim, 0x070002ba);
+    vbSetProgramRegister(sim, 3, 0x0500ffc0);
+    vbSetProgramRegister(sim, 4, 0x05008000);
 
     if (argc > 2) {
         char *end;

makefile

@@ -4,6 +4,7 @@ build:
 	-I include -I ../vbtest \
 	-Werror -std=c90 -Wall -Wextra -Wpedantic \
 	-Wno-unused-parameter -Wno-unused-function \
+	-D _POSIX_C_SOURCE=199309L \
 	-o ./build/rdb
 clean:
 	@rm -rf build