Add hex2pcap

internal/pcap/writer_test.go

@@ -0,0 +1,36 @@
+package pcap
+
+import (
+	"bytes"
+	"encoding/hex"
+	"testing"
+	"time"
+)
+
+func TestWriter(t *testing.T) {
+	var buf bytes.Buffer
+	w, err := NewWriter(&buf, LinkTypeRaw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	ts := time.Unix(0x01020304, 5000)
+	if err := w.WritePacket(ts, []byte{0xaa, 0xbb}); err != nil {
+		t.Fatal(err)
+	}
+
+	want := "d4c3b2a1" + "0200" + "0400" + "00000000" + "00000000" + "00000400" + "65000000" +
+		"04030201" + "05000000" + "02000000" + "02000000" + "aabb"
+	if got := hex.EncodeToString(buf.Bytes()); got != want {
+		t.Errorf("got  %s\nwant %s", got, want)
+	}
+}
+
+func TestWriterRejectsOversizedPacket(t *testing.T) {
+	w, err := NewWriter(&bytes.Buffer{}, LinkTypeEthernet)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := w.WritePacket(time.Now(), make([]byte, DefaultSnapLen+1)); err == nil {
+		t.Error("expected error for oversized packet")
+	}
+}