For regression test, add srs-bench to 3rdparty

trunk/3rdparty/srs-bench/vendor/github.com/pion/stun/fingerprint.go

@@ -0,0 +1,67 @@
+package stun
+
+import (
+	"errors"
+	"hash/crc32"
+)
+
+// FingerprintAttr represents FINGERPRINT attribute.
+//
+// RFC 5389 Section 15.5
+type FingerprintAttr struct{}
+
+// ErrFingerprintMismatch means that computed fingerprint differs from expected.
+var ErrFingerprintMismatch = errors.New("fingerprint check failed")
+
+// Fingerprint is shorthand for FingerprintAttr.
+//
+// Example:
+//
+//  m := New()
+//  Fingerprint.AddTo(m)
+var Fingerprint FingerprintAttr
+
+const (
+	fingerprintXORValue uint32 = 0x5354554e //nolint:staticcheck
+	fingerprintSize            = 4          // 32 bit
+)
+
+// FingerprintValue returns CRC-32 of b XOR-ed by 0x5354554e.
+//
+// The value of the attribute is computed as the CRC-32 of the STUN message
+// up to (but excluding) the FINGERPRINT attribute itself, XOR'ed with
+// the 32-bit value 0x5354554e (the XOR helps in cases where an
+// application packet is also using CRC-32 in it).
+func FingerprintValue(b []byte) uint32 {
+	return crc32.ChecksumIEEE(b) ^ fingerprintXORValue // XOR
+}
+
+// AddTo adds fingerprint to message.
+func (FingerprintAttr) AddTo(m *Message) error {
+	l := m.Length
+	// length in header should include size of fingerprint attribute
+	m.Length += fingerprintSize + attributeHeaderSize // increasing length
+	m.WriteLength()                                   // writing Length to Raw
+	b := make([]byte, fingerprintSize)
+	val := FingerprintValue(m.Raw)
+	bin.PutUint32(b, val)
+	m.Length = l
+	m.Add(AttrFingerprint, b)
+	return nil
+}
+
+// Check reads fingerprint value from m and checks it, returning error if any.
+// Can return *AttrLengthErr, ErrAttributeNotFound, and *CRCMismatch.
+func (FingerprintAttr) Check(m *Message) error {
+	b, err := m.Get(AttrFingerprint)
+	if err != nil {
+		return err
+	}
+	if err = CheckSize(AttrFingerprint, len(b), fingerprintSize); err != nil {
+		return err
+	}
+	val := bin.Uint32(b)
+	attrStart := len(m.Raw) - (fingerprintSize + attributeHeaderSize)
+	expected := FingerprintValue(m.Raw[:attrStart])
+	return checkFingerprint(val, expected)
+}