GLib.locale_to_utf8

function locale_to_utf8(opsysstring: String, len: Number(gssize), bytes_read: Number(gsize), bytes_written: Number(gsize)): String {
    // Gjs wrapper for g_locale_to_utf8()
}

Converts a string which is in the encoding used for strings by the C runtime (usually the same as that used by the operating system) in the [current locale][setlocale] into a UTF-8 string.

opsysstring: a string in the encoding of the current locale. On Windows this means the system codepage.
len: the length of the string, or -1 if the string is nul-terminated (Note that some encodings may allow nul bytes to occur inside strings. In that case, using -1 for the len parameter is unsafe)
bytes_read: location to store the number of bytes in the input string that were successfully converted, or null. Even if the conversion was successful, this may be less than len if there were partial characters at the end of the input. If the error #G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value stored will the byte offset after the last valid input sequence.
bytes_written: the number of bytes stored in the output buffer (not including the terminating nul).
Returns: A newly-allocated buffer containing the converted string, or null on an error, and error will be set.