From cfccdaed9bd68f455c309e17404e9bba4b43fbeb Mon Sep 17 00:00:00 2001
From: Lucas Clemente <lucas@clemente.io>
Date: Wed, 6 Apr 2016 23:10:52 +0200
Subject: [PATCH] add public header parser

---
 public_header.go      | 84 +++++++++++++++++++++++++++++++++++++++++++
 public_header_test.go | 23 ++++++++++++
 quic_suite_test.go    | 13 +++++++
 3 files changed, 120 insertions(+)
 create mode 100644 public_header.go
 create mode 100644 public_header_test.go
 create mode 100644 quic_suite_test.go

diff --git a/public_header.go b/public_header.go
new file mode 100644
index 00000000..02fe67a1
--- /dev/null
+++ b/public_header.go
@@ -0,0 +1,84 @@
+package quic
+
+import "io"
+
+// The PublicHeader of a QUIC packet
+type PublicHeader struct {
+	VersionFlag bool
+	ResetFlag   bool
+
+	ConnectionIDLength uint8
+	ConnectionID       uint64
+
+	QuicVersion uint32
+
+	PacketNumberLength uint8
+	PacketNumber       uint64
+}
+
+// ParsePublicHeader parses a QUIC packet's public header
+func ParsePublicHeader(b io.ByteReader) (*PublicHeader, error) {
+	header := &PublicHeader{}
+
+	// First byte
+	publicFlagByte, err := b.ReadByte()
+	if err != nil {
+		return nil, err
+	}
+	header.VersionFlag = publicFlagByte&0x01 > 0
+	header.ResetFlag = publicFlagByte&0x02 > 0
+	switch publicFlagByte & 0x0C {
+	case 0x0C:
+		header.ConnectionIDLength = 8
+	case 0x08:
+		header.ConnectionIDLength = 4
+	case 0x04:
+		header.ConnectionIDLength = 1
+	}
+	switch publicFlagByte & 0x30 {
+	case 0x30:
+		header.PacketNumberLength = 6
+	case 0x20:
+		header.PacketNumberLength = 4
+	case 0x10:
+		header.PacketNumberLength = 2
+	case 0x00:
+		header.PacketNumberLength = 1
+	}
+
+	// Connection ID
+	header.ConnectionID, err = readUint64(b, header.ConnectionIDLength)
+	if err != nil {
+		return nil, err
+	}
+
+	// Version (optional)
+	if header.VersionFlag {
+		var v uint64
+		v, err = readUint64(b, 4)
+		if err != nil {
+			return nil, err
+		}
+		header.QuicVersion = uint32(v)
+	}
+
+	// Packet number
+	header.PacketNumber, err = readUint64(b, header.PacketNumberLength)
+	if err != nil {
+		return nil, err
+	}
+
+	return header, nil
+}
+
+func readUint64(b io.ByteReader, length uint8) (uint64, error) {
+	var res uint64
+	for i := uint8(0); i < length; i++ {
+		bt, err := b.ReadByte()
+		if err != nil {
+			return 0, err
+		}
+		res = res<<8 + uint64(bt)
+	}
+	return res, nil
+}
diff --git a/public_header_test.go b/public_header_test.go
new file mode 100644
index 00000000..18196505
--- /dev/null
+++ b/public_header_test.go
@@ -0,0 +1,23 @@
+package quic
+
+import (
+	"bytes"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Public Header", func() {
+	It("parses intial client header", func() {
+		b := bytes.NewReader([]byte{0xd, 0xf6, 0x19, 0x86, 0x66, 0x9b, 0x9f, 0xfa, 0x4c, 0x51, 0x30, 0x33, 0x30, 0x1})
+		publicHeader, err := ParsePublicHeader(b)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(publicHeader.VersionFlag).To(BeTrue())
+		Expect(publicHeader.ResetFlag).To(BeFalse())
+		Expect(publicHeader.ConnectionIDLength).To(Equal(uint8(8)))
+		Expect(publicHeader.ConnectionID).ToNot(BeZero())
+		Expect(publicHeader.QuicVersion).To(Equal(uint32(0x51303330)))
+		Expect(publicHeader.PacketNumberLength).To(Equal(uint8(1)))
+		Expect(publicHeader.PacketNumber).To(Equal(uint64(1)))
+	})
+})
diff --git a/quic_suite_test.go b/quic_suite_test.go
new file mode 100644
index 00000000..31e8db1c
--- /dev/null
+++ b/quic_suite_test.go
@@ -0,0 +1,13 @@
+package quic
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"testing"
+)
+
+func TestQuicGo(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "QUIC Suite")
+}