/*
Reads and returns the next DER encoded SEQUENCE from r,
which may optionally be base64 encoded and may be preceded
by "garbage". The returned data will always be DER bytes
without preceding garbage and NOT base64 encoded.
The SEQUENCE will only be recognized as valid if
it does not contain APPLICATION or PRIVATE tags or
tags >= 31.
This function takes care not to read more bytes than
necessary which allows the function to be called
multiple times on a stream of concatenated SEQUENCEs.
*/
func ReadNextSEQUENCE(r io.Reader) ([]byte, error) {
b := []byte{0}
var err error
var n int
space := true
var eaters deque.Deque
for {
n, err = r.Read(b)
if err != nil {
return nil, err
}
if n == 0 {
return nil, io.EOF
}
if b[0] == 0x30 { // SEQUENCE
eaters.Push(newRawEater())
}
if b[0] > ' ' {
if space {
eaters.Push(newBase64Eater())
}
space = false
} else {
space = true
}
for i := 0; i < eaters.Count(); {
result := eaters.At(i).(eater).Eat(b[0])
switch result {
case -1: // error
eaters.RemoveAt(i)
case 0: // ok, need more data
i++
case 1: // done
return eaters.At(i).(eater).Data(), nil
}
}
}
}
