80 lines
1.7 KiB
Go
80 lines
1.7 KiB
Go
package utf8
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import (
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"io"
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)
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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 {
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reader io.Reader
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prevRune rune
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prevSize int
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prevErr error
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peeked bool
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}
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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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}
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}
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func NewRuneScanner(reader io.Reader) *RuneScanner {
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var runescanner RuneScanner = WrapRuneScanner(reader)
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return &runescanner
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}
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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.
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//
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// A buffered rune would come from someone calleding .UnreadRune().
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//
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// If there is not buffered rune then .Buffered() returns zero (0).
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//
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// So, for example, if .UnreadRune() was called for the rune 'A' (U+0041), then .Buffered() would return 1.
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//
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// And, for example, if .UnreadRune() was called for the rune '🙂' (U+1F642), then .Buffered() would return 4.
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//
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// This method has been made to be semantically the same as bufio.Reader.Buffered()
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func (receiver *RuneScanner) Buffered() int {
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if !receiver.peeked {
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return 0
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}
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return receiver.prevSize
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}
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func (receiver *RuneScanner) ReadRune() (rune, int, error) {
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if nil == receiver {
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return RuneError, 0, errNilReceiver
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}
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reader := receiver.reader
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if nil == reader {
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return RuneError, 0, errNilReader
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}
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if receiver.peeked {
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receiver.peeked = false
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} else {
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receiver.prevRune, receiver.prevSize, receiver.prevErr = ReadRune(reader)
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}
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return receiver.prevRune, receiver.prevSize, receiver.prevErr
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}
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func (receiver *RuneScanner) UnreadRune() error {
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if nil == receiver {
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return errNilReceiver
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}
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receiver.peeked = true
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return nil
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}
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