go-utf8/runescanner.go

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package utf8
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import (
"io"
)
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var _ io.RuneScanner = NewRuneScanner(nil)
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// A utf8.RuneScanner implements the io.RuneScanner interface by reading from an io.Reader.
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type RuneScanner struct {
reader io.Reader
prevRune rune
prevSize int
prevErr error
peeked bool
}
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func WrapRuneScanner(reader io.Reader) RuneScanner {
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return RuneScanner{
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reader: reader,
}
}
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func NewRuneScanner(reader io.Reader) *RuneScanner {
var runescanner RuneScanner = WrapRuneScanner(reader)
return &runescanner
}
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// Buffered returns the number of bytes the UTF-8 encoding of the current buffered rune takes up, if there is a buffered rune.
//
// A buffered rune would come from someone calleding .UnreadRune().
//
// If there is not buffered rune then .Buffered() returns zero (0).
//
// So, for example, if .UnreadRune() was called for the rune 'A' (U+0041), then .Buffered() would return 1.
//
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// Also, for example, if .UnreadRune() was called for the rune '۵' (U+06F5), then .Buffered() would return 2.
//
// And, for example, if .UnreadRune() was called for the rune '≡' (U+2261), then .Buffered() would return 3.
//
// And also, for example, if .UnreadRune() was called for the rune '🙂' (U+1F642), then .Buffered() would return 4.
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//
// This method has been made to be semantically the same as bufio.Reader.Buffered()
func (receiver *RuneScanner) Buffered() int {
if !receiver.peeked {
return 0
}
return receiver.prevSize
}
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func (receiver *RuneScanner) ReadRune() (rune, int, error) {
if nil == receiver {
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return RuneError, 0, errNilReceiver
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}
reader := receiver.reader
if nil == reader {
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return RuneError, 0, errNilReader
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}
if receiver.peeked {
receiver.peeked = false
} else {
receiver.prevRune, receiver.prevSize, receiver.prevErr = ReadRune(reader)
}
return receiver.prevRune, receiver.prevSize, receiver.prevErr
}
func (receiver *RuneScanner) UnreadRune() error {
if nil == receiver {
return errNilReceiver
}
receiver.peeked = true
return nil
}