some minor tweaks
This is a C89 UTF-8 library, with an API compatible with that of Plan 9's libutf, but with a number of improvements:
utflen and utfnlen cannot overflow on 32- or 64-bit machines.chartorune treats all invalid codepoints as though Runeerror.fullrune, utfecpy, and utfnlen do not overestimate the length of malformed runes.charntorune(p,s,n), equivalent to fullrune(s,n) ? chartorune(p,s) : 0.Runeerror may be set to an alternative replacement value, such as -1, to be used instead of U+FFFD.Differences to be aware of:
UTFmax is 6, though runetochar will never write more than 4 bytes. Plan 9's UTFmax is 3.chartorune may consume multiple bytes for each illegal rune. Plan 9 always consumes 1.runelen and runetochar return 0 if the rune is too large to print. Plan 9 erroneously returns UTFmax.