GLib.convert_with_fallback

function convert_with_fallback(str: String, len: Number(gssize), to_codeset: String, from_codeset: String, fallback: String, bytes_read: Number(gsize), bytes_written: Number(gsize)): String {
    // Gjs wrapper for g_convert_with_fallback()
}

Converts a string from one character set to another, possibly including fallback sequences for characters not representable in the output. Note that it is not guaranteed that the specification for the fallback sequences in fallback will be honored. Some systems may do an approximate conversion from from_codeset to to_codeset in their iconv() functions, in which case GLib will simply return that approximate conversion.

Note that you should use GLib.iconv for streaming conversions. Despite the fact that @byes_read can return information about partial characters, the g_convert_... functions are not generally suitable for streaming. If the underlying converter maintains internal state, then this won't be preserved across successive calls to GLib.convert, GLib.convert_with_iconv or GLib.convert_with_fallback. (An example of this is the GNU C converter for CP1255 which does not emit a base character until it knows that the next character is not a mark that could combine with the base character.)

str: the string to convert
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)
to_codeset: name of character set into which to convert str
from_codeset: character set of str.
fallback: UTF-8 string to use in place of character not present in the target encoding. (The string must be representable in the target encoding). If null, characters not in the target encoding will be represented as Unicode escapes \uxxxx or \Uxxxxyyyy.
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.
bytes_written: the number of bytes stored in the output buffer (not including the terminating nul).
Returns: If the conversion was successful, a newly allocated nul-terminated string, which must be freed with GLib.free. Otherwise null and @error will be set.