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package ber
import (
"errors"
"fmt"
"io"
)
func readHeader(reader io.Reader) (identifier Identifier, length int, read int, err error) {
if i, c, err := readIdentifier(reader); err != nil {
return Identifier{}, 0, read, err
} else {
identifier = i
read += c
}
if l, c, err := readLength(reader); err != nil {
return Identifier{}, 0, read, err
} else {
length = l
read += c
}
// Validate length type with identifier (x.600, 8.1.3.2.a)
if length == LengthIndefinite && identifier.TagType == TypePrimitive {
return Identifier{}, 0, read, errors.New("indefinite length used with primitive type")
}
if length < LengthIndefinite {
err = fmt.Errorf("length cannot be less than %d", LengthIndefinite)
return
}
return identifier, length, read, nil
}
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