w-vi

#include <stdio.h>
#include <string.h>

/* UTF-8 character might be encoded in up to 4 bytes according to RFC
 * 3629 so to truncate it correctly care needs to be taken for such
 * characters. ASCII character are in single byte using 7 bits (max is
 * 127) so any multi-byte character has first byte higher then
 * 127. Because first byte in multi-byte sequence is encoding how many
 * bytes this sequence has we can easily check for it looking for the
 * first byte in sequence and see how many bytes more to truncate.