62 lines
860 B
Go
62 lines
860 B
Go
package apdu
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import (
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"bytes"
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"fmt"
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"io"
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)
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type ErrTagNotFound struct {
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tag uint8
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}
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func (e *ErrTagNotFound) Error() string {
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return fmt.Sprintf("tag %x not found", e.tag)
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}
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func FindTag(raw []byte, tags ...uint8) ([]byte, error) {
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if len(tags) == 0 {
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return raw, nil
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}
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target := tags[0]
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buf := bytes.NewBuffer(raw)
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var (
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tag uint8
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length uint8
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err error
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)
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for {
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tag, err = buf.ReadByte()
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switch {
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case err == io.EOF:
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return []byte{}, &ErrTagNotFound{target}
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case err != nil:
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return nil, err
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}
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length, err = buf.ReadByte()
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if err != nil {
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return nil, err
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}
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data := make([]byte, length)
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if length != 0 {
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_, err = buf.Read(data)
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if err != nil {
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return nil, err
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}
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}
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if tag == target {
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if len(tags) == 1 {
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return data, nil
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}
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return FindTag(data, tags[1:]...)
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}
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}
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}
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