1 files changed, 112 insertions, 0 deletions
diff --git a/vendor/github.com/go-asn1-ber/asn1-ber/identifier.go b/vendor/github.com/go-asn1-ber/asn1-ber/identifier.go
new file mode 100644
index 00000000..e8c43574
--- /dev/null
+++ b/vendor/github.com/go-asn1-ber/asn1-ber/identifier.go
@@ -0,0 +1,112 @@
+package ber
+
+import (
+	"errors"
+	"fmt"
+	"io"
+)
+
+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
+
+		b = append(b, encodeHighTag(tag)...)
+	}
+	return b
+}
+
+func encodeHighTag(tag Tag) []byte {
+	// set cap=4 to hopefully avoid additional allocations
+	b := make([]byte, 0, 4)
+	for tag != 0 {
+		// t := last 7 bits of tag (HighTagValueBitmask = 0x7F)
+		t := tag & HighTagValueBitmask
+
+		// right shift tag 7 to remove what was just pulled off
+		tag >>= 7
+
+		// if b already has entries this entry needs a continuation bit (0x80)
+		if len(b) != 0 {
+			t |= HighTagContinueBitmask
+		}
+
+		b = append(b, byte(t))
+	}
+	// reverse
+	// since bits were pulled off 'tag' small to high the byte slice is in reverse order.
+	// example: tag = 0xFF results in {0x7F, 0x01 + 0x80 (continuation bit)}
+	// this needs to be reversed into 0x81 0x7F
+	for i, j := 0, len(b)-1; i < len(b)/2; i++ {
+		b[i], b[j-i] = b[j-i], b[i]
+	}
+	return b
+}