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73 lines
1.4 KiB
73 lines
1.4 KiB
package gg
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import (
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"bufio"
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"fmt"
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"io"
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)
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// Decoder reads Value's off of a byte stream.
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type Decoder struct {
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br *bufio.Reader
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brNextLoc Location
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unread []locatableRune
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lastRead locatableRune
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}
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// NewDecoder returns a Decoder which will decode the given stream as a gg
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// formatted stream of a Values.
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func NewDecoder(r io.Reader) *Decoder {
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return &Decoder{
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br: bufio.NewReader(r),
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brNextLoc: Location{Row: 1, Col: 1},
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}
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}
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func (d *Decoder) readRune() (locatableRune, error) {
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if len(d.unread) > 0 {
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d.lastRead = d.unread[len(d.unread)-1]
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d.unread = d.unread[:len(d.unread)-1]
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return d.lastRead, nil
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}
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loc := d.brNextLoc
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r, _, err := d.br.ReadRune()
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if err != nil {
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return d.lastRead, err
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}
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if r == '\n' {
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d.brNextLoc.Row++
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d.brNextLoc.Col = 1
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} else {
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d.brNextLoc.Col++
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}
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d.lastRead = locatableRune{loc, r}
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return d.lastRead, nil
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}
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func (d *Decoder) unreadRune(lr locatableRune) {
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if d.lastRead != lr {
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panic(fmt.Sprintf(
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"unreading rune %#v, but last read rune was %#v", lr, d.lastRead,
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))
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}
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d.unread = append(d.unread, lr)
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}
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func (d *Decoder) nextLoc() Location {
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if len(d.unread) > 0 {
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return d.unread[len(d.unread)-1].Location
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}
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return d.brNextLoc
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}
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// Next returns the next top-level value in the stream, or io.EOF.
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func (d *Decoder) Next() (Value, error) {
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return topLevelTerm.decodeFn(d)
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}
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