move gotd fork into repo. (#111)

- update to latest telegram layer
- remove some references to fields in tg.Entities that don't exist in
the schema
- originally added here:
https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e
  - referenced here
-
https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3
-
https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e

pkg/gotd/bin/encoder_test.go

@@ -0,0 +1,125 @@
+package bin
+
+import (
+	"bytes"
+	"encoding/hex"
+	"math/big"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// error code:int32 message:string = Error;
+type Message struct {
+	Code    int32
+	Message string
+	Nonce   Int128
+	Key     Int256
+}
+
+// EncodeTo implements bin.Encoder.
+func (m Message) Encode(b *Buffer) error {
+	b.PutID(0x9bdd8f1a)
+	b.PutInt32(m.Code)
+	b.PutString(m.Message)
+	b.PutInt128(m.Nonce)
+	b.PutInt256(m.Key)
+	return nil
+}
+
+func (m *Message) Decode(b *Buffer) error {
+	if err := b.ConsumeID(0x9bdd8f1a); err != nil {
+		return err
+	}
+	{
+		v, err := b.Int32()
+		if err != nil {
+			return err
+		}
+		m.Code = v
+	}
+	{
+		v, err := b.String()
+		if err != nil {
+			return err
+		}
+		m.Message = v
+	}
+	{
+		v, err := b.Int128()
+		if err != nil {
+			return err
+		}
+		m.Nonce = v
+	}
+	{
+		v, err := b.Int256()
+		if err != nil {
+			return err
+		}
+		m.Key = v
+	}
+	return nil
+}
+
+func TestEncodeMessage(t *testing.T) {
+	m := Message{
+		Code:    204,
+		Message: "Wake up, Neo",
+		Nonce:   [16]byte{0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xA, 0xB, 0xC, 0xD, 0xE, 0xF},
+		Key: [32]byte{
+			0xFF, 0xAA, 0xFF, 0xBB, 0xEE, 0x11, 0x12, 0x13, 0x14, 0x10, 0x10, 0x02, 0x04, 0x06, 0x08, 0x0A,
+			0x00, 0x00, 0x00, 0x33, 0x55, 0xEE, 0x16, 0x11, 0x10, 0x14, 0x15, 0x02, 0x10, 0x10, 0x20, 0x20,
+		},
+	}
+	b := new(Buffer)
+	_ = m.Encode(b)
+	expected := []byte{
+		// Type ID.
+		0x1a, 0x8f, 0xdd, 0x9b,
+
+		// Code as int32.
+		204, 0x00, 0x00, 0x00,
+
+		// String length.
+		byte(len(m.Message)),
+
+		// "Wake up, Neo" in hex.
+		0x57, 0x61, 0x6b,
+		0x65, 0x20, 0x75, 0x70,
+		0x2c, 0x20, 0x4e, 0x65,
+		0x6f, 0x00, 0x00, 0x00,
+
+		// Nonce.
+		0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+		0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
+
+		// Key.
+		0xFF, 0xAA, 0xFF, 0xBB, 0xEE, 0x11, 0x12, 0x13,
+		0x14, 0x10, 0x10, 0x02, 0x04, 0x06, 0x08, 0x0A,
+		0x00, 0x00, 0x00, 0x33, 0x55, 0xEE, 0x16, 0x11,
+		0x10, 0x14, 0x15, 0x02, 0x10, 0x10, 0x20, 0x20,
+	}
+	if !bytes.Equal(expected, b.Buf) {
+		t.Log(hex.Dump(b.Buf))
+	}
+	var decoded Message
+	if err := decoded.Decode(b); err != nil {
+		t.Fatal(err)
+	}
+	require.Equal(t, m, decoded)
+
+	t.Run("BigInt", func(t *testing.T) {
+		// Byte order should not change (as defined in Telegram docs) and should be
+		// "same as openssl".
+		// This rule is correct for cryptographical big integers and parts of SHA1-s.
+		expectedKey, ok := big.NewInt(0).
+			SetString("FFAAFFBBEE111213141010020406080a0000003355EE16111014150210102020", 16)
+		require.True(t, ok)
+		require.Zero(t, expectedKey.Cmp(decoded.Key.BigInt()), "key big.Int unexpected")
+
+		expectedNonce, ok := big.NewInt(0).SetString("000102030405060708090A0B0C0D0E0F", 16)
+		require.True(t, ok)
+		require.Zero(t, expectedNonce.Cmp(decoded.Nonce.BigInt()), "nonce big.Int unexpected")
+	})
+}