57 lines
1 KiB
Go
57 lines
1 KiB
Go
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package dns
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// Implement a simple scanner, return a byte stream from an io reader.
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import (
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"bufio"
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"context"
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"io"
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"text/scanner"
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)
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type scan struct {
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src *bufio.Reader
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position scanner.Position
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eof bool // Have we just seen a eof
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ctx context.Context
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}
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func scanInit(r io.Reader) (*scan, context.CancelFunc) {
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s := new(scan)
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s.src = bufio.NewReader(r)
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s.position.Line = 1
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ctx, cancel := context.WithCancel(context.Background())
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s.ctx = ctx
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return s, cancel
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}
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// tokenText returns the next byte from the input
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func (s *scan) tokenText() (byte, error) {
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c, err := s.src.ReadByte()
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if err != nil {
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return c, err
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}
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select {
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case <-s.ctx.Done():
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return c, context.Canceled
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default:
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break
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}
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// delay the newline handling until the next token is delivered,
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// fixes off-by-one errors when reporting a parse error.
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if s.eof == true {
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s.position.Line++
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s.position.Column = 0
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s.eof = false
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}
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if c == '\n' {
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s.eof = true
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return c, nil
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}
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s.position.Column++
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return c, nil
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}
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