Add log instruction, for inserting debug information into the protocol stream.

src/libguac/guacamole/protocol.h

@@ -37,6 +37,8 @@
 #include "stream.h"
 #include "timestamp.h"
 
+#include <stdarg.h>
+
 #include <cairo/cairo.h>
 
 /**
@@ -280,6 +282,35 @@ int guac_protocol_send_disconnect(guac_socket* socket);
 int guac_protocol_send_error(guac_socket* socket, const char* error,
         guac_protocol_status status);
 
+/**
+ * Sends a log instruction over the given guac_socket connection. This is
+ * mainly useful in debugging.
+ *
+ * If an error occurs sending the instruction, a non-zero value is
+ * returned, and guac_error is set appropriately.
+ *
+ * @param socket The guac_socket connection to use.
+ * @param format A printf-style format string to log.
+ * @param ... Arguments to use when filling the format string for printing.
+ * @return Zero on success, non-zero on error.
+ */
+int guac_protocol_send_log(guac_socket* socket, const char* format, ...);
+
+/**
+ * Sends a log instruction over the given guac_socket connection. This is
+ * mainly useful in debugging.
+ *
+ * If an error occurs sending the instruction, a non-zero value is
+ * returned, and guac_error is set appropriately.
+ *
+ * @param socket The guac_socket connection to use.
+ * @param format A printf-style format string to log.
+ * @param ap The va_list containing the arguments to be used when filling the
+ *           format string for printing.
+ */
+int vguac_protocol_send_log(guac_socket* socket, const char* format,
+        va_list args);
+
 /**
  * Sends a nest instruction over the given guac_socket connection.
  *

src/libguac/protocol.c

@@ -31,6 +31,7 @@
 
 #include <errno.h>
 #include <inttypes.h>
+#include <stdarg.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -774,6 +775,40 @@ int guac_protocol_send_error(guac_socket* socket, const char* error,
 
 }
 
+int vguac_protocol_send_log(guac_socket* socket, const char* format,
+        va_list args) {
+
+    int ret_val;
+
+    /* Copy log message into buffer */
+    char message[4096];
+    vsnprintf(message, sizeof(message), format, args);
+
+    /* Log to instruction */
+    guac_socket_instruction_begin(socket);
+    ret_val =
+           guac_socket_write_string(socket, "3.log,")
+        || __guac_socket_write_length_string(socket, message)
+        || guac_socket_write_string(socket, ";");
+
+    guac_socket_instruction_end(socket);
+    return ret_val;
+
+}
+
+int guac_protocol_send_log(guac_socket* socket, const char* format, ...) {
+
+    int ret_val;
+
+    va_list args;
+    va_start(args, format);
+    ret_val = vguac_protocol_send_log(socket, format, args);
+    va_end(args);
+
+    return ret_val;
+
+}
+
 int guac_protocol_send_file(guac_socket* socket, const guac_stream* stream,
         const char* mimetype, const char* name) {