Truncating unicode so it fits a maximum size when encoded for wire transfer

Question

Given a Unicode string and these requirements:

• The string be encoded into some byte-sequence format (e.g. UTF-8 or JSON unicode escape)
• The encoded st

Answer 1

Check the last character of the string. If high bit set, then it is not the last byte in a UTF-8 character, so back up and try again until you find one that is.

mxlen=255        
while( toolong.encode("utf8")[mxlen-1] & 0xc0 == 0xc0 ):
    mxlen -= 1

truncated_string = toolong.encode("utf8")[0:mxlen].decode("utf8")