// read reads blocks of 4096 bytes from the File, sending lines to the
// channel as it encounters newlines. If EOF is encountered, the partial line
// is returned to be concatenated with on the next call.
func (t *Tailer) read(f afero.File, partialIn string) (partialOut string, err error) {
partial := partialIn
b := make([]byte, 0, 4096)
for {
n, err := f.Read(b[:cap(b)])
b = b[:n]
if err != nil {
return partial, err
}
for i, width := 0, 0; i < len(b) && i < n; i += width {
var rune rune
rune, width = utf8.DecodeRune(b[i:])
switch {
case rune != '\n':
partial += string(rune)
default:
// send off line for processing
t.lines <- partial
// reset accumulator
partial = ""
}
}
}
}
