[script] Allow commands following a script label

Allow commands to be placed on the same line as a label.  This allows
for improved legibility of loop constructions by incorporating the
loop check condition into the same line as the loop label.  For
example, to iterate over network devices using the forthcoming "inc"
command:

  set idx:int16 0
  :loop isset ${net${idx}/mac} || goto loop_done
    echo net${idx} is a ${net${idx}/chip} with MAC ${net${idx}/mac}
    inc idx && goto loop
  :loop_done

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/image/script.c

  * @ret rc		Return status code
  */
 static int process_script ( struct image *image,
-			    int ( * process_line ) ( const char *line ),
+			    int ( * process_line ) ( struct image *image,
+						     size_t offset,
+						     const char *label,
+						     const char *command ),
 			    int ( * terminate ) ( int rc ) ) {
 	size_t len = 0;
 	char *line = NULL;
+	size_t line_offset;
+	char *label;
+	char *command;
 	off_t eol;
 	size_t frag_len;
 	char *tmp;
 	int rc;
 
+	/* Initialise script and line offsets */
 	script_offset = 0;
+	line_offset = 0;
 
 	do {
-	
+
 		/* Find length of next line, excluding any terminating '\n' */
 		eol = memchr_user ( image->data, script_offset, '\n',
 				    ( image->len - script_offset ) );
 
 		/* Terminate line */
 		line[len] = '\0';
-		DBG ( "$ %s\n", line );
+
+		/* Split line into (optional) label and command */
+		command = line;
+		while ( isspace ( *command ) )
+			command++;
+		if ( *command == ':' ) {
+			label = ++command;
+			while ( *command && ! isspace ( *command ) )
+				command++;
+			if ( *command )
+				*(command++) = '\0';
+		} else {
+			label = NULL;
+		}
 
 		/* Process line */
-		rc = process_line ( line );
+		rc = process_line ( image, line_offset, label, command );
 		if ( terminate ( rc ) )
 			goto err_process;
 
 		line = NULL;
 		len = 0;
 
+		/* Update line offset */
+		line_offset = script_offset;
+
 	} while ( script_offset < image->len );
 
  err_process:
 		 ( rc != 0 ) );
 }
 
-/**
- * Find label within script line
- *
- * @v line		Line of script
- * @ret label		Start of label name, or NULL if not found
- */
-static const char * find_label ( const char *line ) {
-
-	/* Skip any leading whitespace */
-	while ( isspace ( *line ) )
-		line++;
-
-	/* If first non-whitespace character is a ':', then we have a label */
-	if ( *line == ':' ) {
-		return ( line + 1 );
-	} else {
-		return NULL;
-	}
-}
-
 /**
  * Execute script line
  *
- * @v line		Line of script
+ * @v image		Script
+ * @v offset		Offset within script
+ * @v label		Label, or NULL
+ * @v command		Command
  * @ret rc		Return status code
  */
-static int script_exec_line ( const char *line ) {
+static int script_exec_line ( struct image *image, size_t offset,
+			      const char *label __unused,
+			      const char *command ) {
 	int rc;
 
-	/* Skip label lines */
-	if ( find_label ( line ) != NULL )
-		return 0;
+	DBGC ( image, "[%04zx] $ %s\n", offset, command );
 
 	/* Execute command */
-	if ( ( rc = system ( line ) ) != 0 )
+	if ( ( rc = system ( command ) ) != 0 )
 		return rc;
 
 	return 0;
 
 	/* Sanity check */
 	if ( image->len < sizeof ( test ) ) {
-		DBG ( "Too short to be a script\n" );
+		DBGC ( image, "Too short to be a script\n" );
 		return -ENOEXEC;
 	}
 
 	if ( ! ( ( ( memcmp ( test, ipxe_magic, sizeof ( test ) - 1 ) == 0 ) ||
 		   ( memcmp ( test, gpxe_magic, sizeof ( test ) - 1 ) == 0 )) &&
 		 isspace ( test[ sizeof ( test ) - 1 ] ) ) ) {
-		DBG ( "Invalid magic signature\n" );
+		DBGC ( image, "Invalid magic signature\n" );
 		return -ENOEXEC;
 	}
 
 /**
  * Check for presence of label
  *
- * @v line		Script line
+ * @v image		Script
+ * @v offset		Offset within script
+ * @v label		Label
+ * @v command		Command
  * @ret rc		Return status code
  */
-static int goto_find_label ( const char *line ) {
-	size_t len = strlen ( goto_label );
-	const char *label;
+static int goto_find_label ( struct image *image, size_t offset,
+			     const char *label, const char *command __unused ) {
 
-	/* Find label */
-	label = find_label ( line );
+	/* Check label exists */
 	if ( ! label )
 		return -ENOENT;
 
-	/* Check if label matches */
-	if ( strncmp ( goto_label, label, len ) != 0 )
+	/* Check label matches */
+	if ( strcmp ( goto_label, label ) != 0 )
 		return -ENOENT;
 
-	/* Check label is terminated by a NUL or whitespace */
-	if ( label[len] && ! isspace ( label[len] ) )
-		return -ENOENT;
+	/* Update script offset */
+	script_offset = offset;
+	DBGC ( image, "[%04zx] Gone to :%s\n", offset, label );
 
 	return 0;
 }
 	if ( ( rc = process_script ( current_image, goto_find_label,
 				     terminate_on_label_found ) ) != 0 ) {
 		script_offset = saved_offset;
+		DBGC ( current_image, "[%04zx] No such label :%s\n",
+		       script_offset, goto_label );
 		return rc;
 	}