diff options
Diffstat (limited to 'vendor/gopkg.in/asn1-ber.v1/identifier.go')
-rw-r--r-- | vendor/gopkg.in/asn1-ber.v1/identifier.go | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/vendor/gopkg.in/asn1-ber.v1/identifier.go b/vendor/gopkg.in/asn1-ber.v1/identifier.go new file mode 100644 index 000000000..f7672a844 --- /dev/null +++ b/vendor/gopkg.in/asn1-ber.v1/identifier.go @@ -0,0 +1,103 @@ +package ber + +import ( + "errors" + "fmt" + "io" + "math" +) + +func readIdentifier(reader io.Reader) (Identifier, int, error) { + identifier := Identifier{} + read := 0 + + // identifier byte + b, err := readByte(reader) + if err != nil { + if Debug { + fmt.Printf("error reading identifier byte: %v\n", err) + } + return Identifier{}, read, err + } + read++ + + identifier.ClassType = Class(b) & ClassBitmask + identifier.TagType = Type(b) & TypeBitmask + + if tag := Tag(b) & TagBitmask; tag != HighTag { + // short-form tag + identifier.Tag = tag + return identifier, read, nil + } + + // high-tag-number tag + tagBytes := 0 + for { + b, err := readByte(reader) + if err != nil { + if Debug { + fmt.Printf("error reading high-tag-number tag byte %d: %v\n", tagBytes, err) + } + return Identifier{}, read, err + } + tagBytes++ + read++ + + // Lowest 7 bits get appended to the tag value (x.690, 8.1.2.4.2.b) + identifier.Tag <<= 7 + identifier.Tag |= Tag(b) & HighTagValueBitmask + + // First byte may not be all zeros (x.690, 8.1.2.4.2.c) + if tagBytes == 1 && identifier.Tag == 0 { + return Identifier{}, read, errors.New("invalid first high-tag-number tag byte") + } + // Overflow of int64 + // TODO: support big int tags? + if tagBytes > 9 { + return Identifier{}, read, errors.New("high-tag-number tag overflow") + } + + // Top bit of 0 means this is the last byte in the high-tag-number tag (x.690, 8.1.2.4.2.a) + if Tag(b)&HighTagContinueBitmask == 0 { + break + } + } + + return identifier, read, nil +} + +func encodeIdentifier(identifier Identifier) []byte { + b := []byte{0x0} + b[0] |= byte(identifier.ClassType) + b[0] |= byte(identifier.TagType) + + if identifier.Tag < HighTag { + // Short-form + b[0] |= byte(identifier.Tag) + } else { + // high-tag-number + b[0] |= byte(HighTag) + + tag := identifier.Tag + + highBit := uint(63) + for { + if tag&(1<<highBit) != 0 { + break + } + highBit-- + } + + tagBytes := int(math.Ceil(float64(highBit) / 7.0)) + for i := tagBytes - 1; i >= 0; i-- { + offset := uint(i) * 7 + mask := Tag(0x7f) << offset + tagByte := (tag & mask) >> offset + if i != 0 { + tagByte |= 0x80 + } + b = append(b, byte(tagByte)) + } + } + return b +} |