+/*
+ * Parses a filename in the source list file format. (See the man page for
+ * 'imagex capture' for details on this format and the meaning.) Accepted
+ * formats for filenames are an unquoted string (whitespace-delimited), or a
+ * double or single-quoted string.
+ *
+ * @line_p: Pointer to the pointer to the line of data. Will be updated
+ * to point past the filename iff the return value is
+ * PARSE_FILENAME_SUCCESS. If *len_p > 0, (*line_p)[*len_p - 1] must
+ * be '\0'.
+ *
+ * @len_p: @len_p initially stores the length of the line of data, which may
+ * be 0, and it will be updated to the number of bytes remaining in
+ * the line iff the return value is PARSE_FILENAME_SUCCESS.
+ *
+ * @fn_ret: Iff the return value is PARSE_FILENAME_SUCCESS, a pointer to the
+ * parsed filename will be returned here.
+ *
+ * Returns: PARSE_FILENAME_SUCCESS if a filename was successfully parsed; or
+ * PARSE_FILENAME_FAILURE if the data was invalid due to a missing
+ * closing quote; or PARSE_FILENAME_NONE if the line ended before the
+ * beginning of a filename was found.
+ */
+static int parse_filename(char **line_p, size_t *len_p, char **fn_ret)