[readline] Allow a prefilled input string to be provided

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

src/hci/readline.c

  * Read line from console (with history)
  *
  * @v prompt		Prompt string
+ * @v prefill		Prefill string, or NULL for no prefill
  * @v history		History buffer, or NULL for no history
  * @ret line		Line read from console (excluding terminating newline)
  *
  * The returned line is allocated with malloc(); the caller must
  * eventually call free() to release the storage.
  */
-char * readline_history ( const char *prompt,
+char * readline_history ( const char *prompt, const char *prefill,
 			  struct readline_history *history ) {
 	char buf[READLINE_MAX];
 	struct edit_string string;
 	init_editstring ( &string, buf, sizeof ( buf ) );
 	buf[0] = '\0';
 
+	/* Prefill string, if applicable */
+	if ( prefill ) {
+		replace_string ( &string, prefill );
+		sync_console ( &string );
+	}
+
 	while ( 1 ) {
 		/* Handle keypress */
 		key = edit_string ( &string, getkey ( 0 ) );
  * eventually call free() to release the storage.
  */
 char * readline ( const char *prompt ) {
-	return readline_history ( prompt, NULL );
+	return readline_history ( prompt, NULL, NULL );
 }

src/hci/shell.c

 
 	/* Read and execute commands */
 	do {
-		line = readline_history ( shell_prompt, &history );
+		line = readline_history ( shell_prompt, NULL, &history );
 		if ( line ) {
 			rc = system ( line );
 			free ( line );

src/include/readline/readline.h

 
 extern void history_free ( struct readline_history *history );
 extern char * __malloc readline_history ( const char *prompt,
+					  const char *prefill,
 					  struct readline_history *history );
 extern char * __malloc readline ( const char *prompt );