The previous implementation revolved around runes instead of bytes, which caused
weird behavior when converting between the two. For example, peekRune would read
the byte 0xff from a buffer, convert it to a rune, then return it. As rune is an
alias of int32, 0xff was 0-padded to int32(255), which is the hex code point for
?. However, peekRune also returned the length of the byte (1). When calling
utf8.EncodeRune, we only allocated 1 byte, but tried the write the 2-byte
character ?.
tl;dr: I apparently didn't understand runes when I wrote this.
PiperOrigin-RevId: 241789081
Change-Id: I14c788af4d9754973137801500ef6af7ab8a8727
82529becae