Sync message support.

libguac/configure.in

@@ -48,7 +48,7 @@ AC_CHECK_LIB([png], [png_write_png],, AC_MSG_ERROR("libpng is required for writi
 AC_CHECK_LIB([wsock32], [main])
 
 # Checks for header files.
-AC_CHECK_HEADERS([fcntl.h stdlib.h string.h sys/socket.h sys/time.h syslog.h unistd.h pngstruct.h])
+AC_CHECK_HEADERS([fcntl.h stdlib.h string.h sys/socket.h time.h sys/time.h syslog.h unistd.h pngstruct.h])
 
 # Checks for typedefs, structures, and compiler characteristics.
 AC_TYPE_SIZE_T
@@ -57,7 +57,7 @@ AC_TYPE_SSIZE_T
 # Checks for library functions.
 AC_FUNC_MALLOC
 AC_FUNC_REALLOC
-AC_CHECK_FUNCS([gettimeofday memmove memset select strdup png_get_io_ptr])
+AC_CHECK_FUNCS([clock_gettime gettimeofday memmove memset select strdup png_get_io_ptr])
 
 AC_CONFIG_FILES([Makefile])
 AC_OUTPUT

libguac/include/guacio.h

@@ -118,7 +118,7 @@ GUACIO* guac_open(int fd);
  * @param i The unsigned int to write.
  * @return Zero on success, or non-zero if an error occurs while writing.
  */
-ssize_t guac_write_int(GUACIO* io, unsigned int i);
+ssize_t guac_write_int(GUACIO* io, unsigned long i);
 
 /**
  * Writes the given string to the given GUACIO object. The data

libguac/include/protocol.h

@@ -131,6 +131,15 @@ void guac_send_args(GUACIO* io, const char** name);
  */
 void guac_send_name(GUACIO* io, const char* name);
 
+/**
+ * Sends a sync instruction over the given GUACIO connection. The
+ * current time in milliseconds should be passed in as the timestamp.
+ *
+ * @param io The GUACIO connection to use.
+ * @param timestamp The current timestamp (in milliseconds).
+ */
+void guac_send_sync(GUACIO* io, long timestamp);
+
 /**
  * Sends an error instruction over the given GUACIO connection. The
  * error description given will be automatically escaped for

libguac/src/client.c

@@ -37,6 +37,11 @@
 
 #include <stdlib.h>
 #include <stdio.h>
+#ifdef HAVE_CLOCK_GETTIME
+#include <time.h>
+#else
+#include <sys/time.h>
+#endif
 #include <string.h>
 #include <dlfcn.h>
 
@@ -243,11 +248,42 @@ void guac_free_client(guac_client* client) {
 }
 
 
+long __guac_current_timestamp() {
+
+#ifdef HAVE_CLOCK_GETTIME
+
+    struct timespec current;
+
+    /* Get current time */
+    clock_gettime(CLOCK_REALTIME, &current);
+    
+    /* Calculate milliseconds */
+    return current.tv_sec * 1000 + current.tv_nsec / 1000000;
+
+#else
+
+    struct timeval current;
+
+    /* Get current time */
+    gettimeofday(&current, NULL);
+    
+    /* Calculate milliseconds */
+    return current.tv_sec * 1000 + current.tv_usec / 1000;
+
+#endif
+
+}
+
 void guac_start_client(guac_client* client) {
 
     GUACIO* io = client->io;
     guac_instruction instruction;
     int wait_result;
+    long last_received_timestamp;
+    long last_sent_timestamp;
+
+    /* Init timestamps */
+    last_received_timestamp = last_sent_timestamp = __guac_current_timestamp();
 
     /* VNC Client Loop */
     for (;;) {
@@ -255,13 +291,21 @@ void guac_start_client(guac_client* client) {
         /* Handle server messages */
         if (client->handle_messages) {
 
-            int retval = client->handle_messages(client);
+            /* Only handle messages if synced within threshold */
-            if (retval) {
+            if (last_sent_timestamp - last_received_timestamp < 200) {
-                GUAC_LOG_ERROR("Error handling server messages");
-                return;
-            }
 
-            guac_flush(io);
+                int retval = client->handle_messages(client);
+                if (retval) {
+                    GUAC_LOG_ERROR("Error handling server messages");
+                    return;
+                }
+
+                /* Send sync after updates */
+                last_sent_timestamp = __guac_current_timestamp();
+                guac_send_sync(io, last_sent_timestamp);
+
+                guac_flush(io);
+            }
 
         }
 
@@ -275,7 +319,15 @@ void guac_start_client(guac_client* client) {
            
                 do {
 
-                    if (strcmp(instruction.opcode, "mouse") == 0) {
+                    if (strcmp(instruction.opcode, "sync") == 0) {
+                        last_received_timestamp = atol(instruction.argv[0]);
+                        if (last_received_timestamp > last_sent_timestamp) {
+                            guac_send_error(io, "Received sync from future.");
+                            guac_free_instruction_data(&instruction);
+                            return;
+                        }
+                    }
+                    else if (strcmp(instruction.opcode, "mouse") == 0) {
                         if (client->mouse_handler)
                             if (
                                     client->mouse_handler(

libguac/src/guacio.c

@@ -97,7 +97,7 @@ ssize_t __guac_write(GUACIO* io, const char* buf, int count) {
     return retval;
 }
 
-ssize_t guac_write_int(GUACIO* io, unsigned int i) {
+ssize_t guac_write_int(GUACIO* io, unsigned long i) {
 
     char buffer[128];
     char* ptr = &(buffer[127]);

libguac/src/protocol.c

@@ -226,6 +226,14 @@ void guac_send_error(GUACIO* io, const char* error) {
 
 }
 
+void guac_send_sync(GUACIO* io, long timestamp) {
+
+    guac_write_string(io, "sync:");
+    guac_write_int(io, timestamp);
+    guac_write_string(io, ";");
+
+}
+
 void guac_send_copy(GUACIO* io, int srcl, int srcx, int srcy, int w, int h, int dstl, int dstx, int dsty) {
     guac_write_string(io, "copy:");
     guac_write_int(io, srcl);