1 package ber
2
3 import (
4 "errors"
5 "fmt"
6 "io"
7 )
8
9 func readHeader(reader io.Reader) (identifier Identifier, length int, read int, err error) {
10 var (
11 c, l int
12 i Identifier
13 )
14
15 if i, c, err = readIdentifier(reader); err != nil {
16 return Identifier{}, 0, read, err
17 }
18 identifier = i
19 read += c
20
21 if l, c, err = readLength(reader); err != nil {
22 return Identifier{}, 0, read, err
23 }
24 length = l
25 read += c
26
27
28 if length == LengthIndefinite && identifier.TagType == TypePrimitive {
29 return Identifier{}, 0, read, errors.New("indefinite length used with primitive type")
30 }
31
32 if length < LengthIndefinite {
33 err = fmt.Errorf("length cannot be less than %d", LengthIndefinite)
34 return
35 }
36
37 return identifier, length, read, nil
38 }
39
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