1 files changed, 81 insertions, 0 deletions
diff --git a/vendor/github.com/go-asn1-ber/asn1-ber/length.go b/vendor/github.com/go-asn1-ber/asn1-ber/length.go
new file mode 100644
index 00000000..750e8f44
--- /dev/null
+++ b/vendor/github.com/go-asn1-ber/asn1-ber/length.go
@@ -0,0 +1,81 @@
+package ber
+
+import (
+	"errors"
+	"fmt"
+	"io"
+)
+
+func readLength(reader io.Reader) (length int, read int, err error) {
+	// length byte
+	b, err := readByte(reader)
+	if err != nil {
+		if Debug {
+			fmt.Printf("error reading length byte: %v\n", err)
+		}
+		return 0, 0, err
+	}
+	read++
+
+	switch {
+	case b == 0xFF:
+		// Invalid 0xFF (x.600, 8.1.3.5.c)
+		return 0, read, errors.New("invalid length byte 0xff")
+
+	case b == LengthLongFormBitmask:
+		// Indefinite form, we have to decode packets until we encounter an EOC packet (x.600, 8.1.3.6)
+		length = LengthIndefinite
+
+	case b&LengthLongFormBitmask == 0:
+		// Short definite form, extract the length from the bottom 7 bits (x.600, 8.1.3.4)
+		length = int(b) & LengthValueBitmask
+
+	case b&LengthLongFormBitmask != 0:
+		// Long definite form, extract the number of length bytes to follow from the bottom 7 bits (x.600, 8.1.3.5.b)
+		lengthBytes := int(b) & LengthValueBitmask
+		// Protect against overflow
+		// TODO: support big int length?
+		if lengthBytes > 8 {
+			return 0, read, errors.New("long-form length overflow")
+		}
+
+		// Accumulate into a 64-bit variable
+		var length64 int64
+		for i := 0; i < lengthBytes; i++ {
+			b, err = readByte(reader)
+			if err != nil {
+				if Debug {
+					fmt.Printf("error reading long-form length byte %d: %v\n", i, err)
+				}
+				return 0, read, err
+			}
+			read++
+
+			// x.600, 8.1.3.5
+			length64 <<= 8
+			length64 |= int64(b)
+		}
+
+		// Cast to a platform-specific integer
+		length = int(length64)
+		// Ensure we didn't overflow
+		if int64(length) != length64 {
+			return 0, read, errors.New("long-form length overflow")
+		}
+
+	default:
+		return 0, read, errors.New("invalid length byte")
+	}
+
+	return length, read, nil
+}
+
+func encodeLength(length int) []byte {
+	length_bytes := encodeUnsignedInteger(uint64(length))
+	if length > 127 || len(length_bytes) > 1 {
+		longFormBytes := []byte{(LengthLongFormBitmask | byte(len(length_bytes)))}
+		longFormBytes = append(longFormBytes, length_bytes...)
+		length_bytes = longFormBytes
+	}
+	return length_bytes
+}