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runereader.go
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/
runereader.go
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package iointernal
import (
"io"
"unicode/utf8"
"github.com/srlehn/termimg/internal/errors"
)
type RuneReader interface {
ReadRune() (r rune, size int, err error)
}
func NewRuneReader(rdr io.Reader) RuneReader {
if rdr == nil {
return nil
}
var readRuneFunc func() (rn rune, size int, err error)
if rnRdr, ok := rdr.(RuneReader); ok {
readRuneFunc = rnRdr.ReadRune
}
return &runeReader{
reader: rdr,
readRuneFunc: readRuneFunc,
}
}
var _ RuneReader = (*runeReader)(nil)
type runeReader struct {
reader io.Reader
buf []byte
readRuneFunc func() (rn rune, size int, err error)
}
func (r *runeReader) ReadRune() (rn rune, size int, err error) {
rn = utf8.RuneError // '\uFFFD'
defer func() {
}()
if r == nil {
return rn, len(string(rn)), errors.NilReceiver()
}
if r.readRuneFunc != nil {
return r.readRuneFunc()
}
if r.reader == nil {
return rn, len(string(rn)), errors.New(`nil tty`)
}
rb := make([]byte, 4) // 4 is the max bytes for UTF-8 character code points
l := min(len(r.buf), cap(rb))
copy(rb, r.buf[:l])
i := 0
for ; i < cap(rb); i++ {
if i >= len(r.buf) {
b := make([]byte, 1)
_, err := r.reader.Read(b)
if err != nil {
if i > 0 {
r.buf = rb[1:i]
}
return rn, i + 1, errors.New(err)
}
rb[i] = b[0]
}
if utf8.Valid(rb[:i+1]) {
rb = rb[:i+1]
r.buf = nil
break
} else if i == cap(rb)-1 {
r.buf = rb[1:]
return rn, i + 1, errors.New(err)
}
}
rn, _ = utf8.DecodeRune(rb)
if rn == utf8.RuneError {
rn = utf8.RuneError
return rn, i + 1, errors.New(err)
}
return rn, i + 1, nil
}