55 lines
1.6 KiB
Go
55 lines
1.6 KiB
Go
package tape
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import "fmt"
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// Skim uses up data from a decoder to "skim" over one value (and all else
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// contained within it) without actually putting the data anywhere.
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func Skim(decoder *Decoder, tag Tag) (n int, err error) {
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switch tag.WithoutCN() {
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case SI:
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// SI: (none)
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return n, nil
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case LI, LSI, FP:
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// LI: <value: IntN>
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// LSI: <value: IntN>
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// FP: <value: FloatN>
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nn, err := decoder.Discard(tag.CN() + 1)
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n += nn; if err != nil { return n, err }
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case SBA:
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// SBA: <data: U8>*
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nn, err := decoder.Discard(tag.CN())
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n += nn; if err != nil { return n, err }
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case LBA:
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// LBA: <length: UN> <data: U8>*
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length, nn, err := decoder.ReadUintN(tag.CN() + 1)
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n += nn; if err != nil { return n, err }
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nn, err = decoder.Discard(int(length))
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n += nn; if err != nil { return n, err }
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case OTA:
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// OTA: <length: UN> <elementTag: tape.Tag> <values>*
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length, nn, err := decoder.ReadUintN(tag.CN() + 1)
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n += nn; if err != nil { return n, err }
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oneTag, nn, err := decoder.ReadTag()
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n += nn; if err != nil { return n, err }
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for _ = range length {
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nn, err := Skim(decoder, oneTag)
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n += nn; if err != nil { return n, err }
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}
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case KTV:
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// KTV: <length: UN> (<key: U16> <tag: Tag> <value>)*
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length, nn, err := decoder.ReadUintN(tag.CN() + 1)
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n += nn; if err != nil { return n, err }
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for _ = range length {
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nn, err := decoder.Discard(2)
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n += nn; if err != nil { return n, err }
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itemTag, nn, err := decoder.ReadTag()
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n += nn; if err != nil { return n, err }
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nn, err = Skim(decoder, itemTag)
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n += nn; if err != nil { return n, err }
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}
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default:
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return n, fmt.Errorf("unknown TN %d", tag.TN())
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}
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return n, nil
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}
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