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runescanner.go
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/
runescanner.go
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package utf8n
import (
"fmt"
"io"
"unicode/utf8"
)
func RuneScanner(readSeeker io.ReadSeeker) io.RuneScanner {
return &internalRuneScanner {
readSeeker:readSeeker,
}
}
type internalRuneScanner struct {
readSeeker io.ReadSeeker
unread bool
previous rune
}
func (receiver *internalRuneScanner) yield(value rune) (r rune, size int, err error) {
receiver.previous = value
return value, utf8.RuneLen(value), nil
}
func (receiver *internalRuneScanner) ReadRune() (r rune, size int, err error) {
if receiver.unread {
receiver.unread = false
r = receiver.previous
return r, utf8.RuneLen(r), nil
}
var readSeeker io.ReadSeeker = receiver.readSeeker
if nil == readSeeker {
return RuneError, 0, errNilReadSeeker
}
// This is UTF8Max*2 (rather than just UTF8Max) because of "\r\n"
var buffer [UTF8Max * 2]byte
var src []byte = buffer[:]
var numRead int
{
numRead, err = readSeeker.Read(src)
if nil != err {
return RuneError, numRead, err
}
if numRead > len(buffer) {
return RuneError, numRead, fmt.Errorf("utf8n: Internal Error: number of bytes read (%d) is larger than the buffer (%d)", numRead, len(buffer))
}
src = src[:numRead]
}
r, size = DecodeRune(src)
{
difference := numRead - size
if 0 < difference {
_, err := readSeeker.Seek(int64(difference * -1), io.SeekCurrent)
if nil != err {
return r, -1, err
}
}
}
return receiver.yield(r)
}
func (receiver *internalRuneScanner) UnreadRune() error {
receiver.unread = true
return nil
}