Implement TX serialization

This will be used in other tests

electrumx/lib/tx.py

@@ -27,14 +27,14 @@
 
 '''Transaction-related classes and functions.'''
 
-
 from collections import namedtuple
-from struct import pack
 
 from electrumx.lib.hash import sha256, double_sha256, hash_to_hex_str
 from electrumx.lib.util import (
     cachedproperty, unpack_int32_from, unpack_int64_from,
-    unpack_uint16_from, unpack_uint32_from, unpack_uint64_from
+    unpack_uint16_from, unpack_uint32_from, unpack_uint64_from,
+    pack_le_int32, pack_varint, pack_le_uint32, pack_le_uint32, pack_le_int64,
+    pack_varbytes,
 )
 
 
@@ -45,7 +45,15 @@ class Tx(namedtuple("Tx", "version inputs outputs locktime")):
     def is_coinbase(self):
         return self.inputs[0].is_coinbase
 
-    # FIXME: add hash as a cached property?
+    def serialize(self):
+        return b''.join((
+            pack_le_int32(self.version),
+            pack_varint(len(self.inputs)),
+            b''.join(tx_in.serialize() for tx_in in self.inputs),
+            pack_varint(len(self.outputs)),
+            b''.join(tx_out.serialize() for tx_out in self.outputs),
+            pack_le_uint32(self.locktime)
+        ))
 
 
 class TxInput(namedtuple("TxInput", "prev_hash prev_idx script sequence")):
@@ -65,9 +73,22 @@ class TxInput(namedtuple("TxInput", "prev_hash prev_idx script sequence")):
         return ("Input({}, {:d}, script={}, sequence={:d})"
                 .format(prev_hash, self.prev_idx, script, self.sequence))
 
+    def serialize(self):
+        return b''.join((
+            self.prev_hash,
+            pack_le_uint32(self.prev_idx),
+            pack_varbytes(self.script),
+            pack_le_uint32(self.sequence),
+        ))
+
 
 class TxOutput(namedtuple("TxOutput", "value pk_script")):
-    pass
+
+    def serialize(self):
+        return b''.join((
+            pack_le_int64(self.value),
+            pack_varbytes(self.pk_script),
+        ))
 
 
 class Deserializer(object):
@@ -530,7 +551,7 @@ class DeserializerDecred(Deserializer):
 
         if produce_hash:
             # TxSerializeNoWitness << 16 == 0x10000
-            no_witness_header = pack('<I', 0x10000 | (version & 0xffff))
+            no_witness_header = pack_le_uint32(0x10000 | (version & 0xffff))
             prefix_tx = no_witness_header + self.binary[start+4:end_prefix]
             tx_hash = self.blake256(prefix_tx)
         else:

tests/lib/test_tx.py

@@ -0,0 +1,37 @@
+import electrumx.lib.tx as tx_lib
+
+tests = [
+    "020000000192809f0b234cb850d71d020e678e93f074648ed0df5affd0c46d3bcb177f"
+    "9ccf020000008b483045022100c5403bcf86c3ae7b8fd4ca0d1e4df6729cc1af05ff95"
+    "d9726b43a64b41dd5d9902207fab615f41871885aa3062fc7d8f8d9d3dcbc2e4867c5d"
+    "96dd7a176b99e927924141040baa4271a82c5f1a09a5ea63d763697ca0545b6049c4dd"
+    "8e8d099dd91f2da10eb11e829000a82047ac56969fb582433067a21c3171e569d1832c"
+    "34fdd793cfc8ffffffff030000000000000000226a20195ce612d20e5284eb78bb28c9"
+    "c50d6139b10b77b2d5b2f94711b13162700472bfc53000000000001976a9144a519c63"
+    "f985ba5ab8b71bb42f1ecb82a0a0d80788acf6984315000000001976a9148b80536aa3"
+    "c460258cda834b86a46787c9a2b0bf88ac00000000",
+    "0200000003ee933f16c93d433bfd45426e94ddb4c0406aecac66f1c23a9e55151430c2"
+    "b4c4a70000006b483045022100c940624ddbefcf86f3a3d820347de9c695204583a3ce"
+    "9977c45cb1d6f69d577202205e0d9e9c0bfc2993160edad71cd1474b6308d990a89a54"
+    "c80d7c62295edd2a394121039999e7c52a1447916b2af30478669c4e6e3ce52b895da7"
+    "78f0b46b73f8ea6f00feffffff30be91ac83fee19e06304732027a39f9ec9018c5aae1"
+    "159bf1c5de53dea61785fc0200006a473044022057cee17c3e123864336bdd6373e4bc"
+    "0bf030ca70dd078520705930a4168610d0022061fdeedfbeb0b89c3b20db220799978b"
+    "c94e11e4155b810b8b59df019b3f1859412103e2074e4387eeb3b1dec2fc8b953b0c13"
+    "c53d0d3b7b676e1b3ca75ee606ecf750feffffffdd462d60e51be69451f06c36ba4490"
+    "aaad8ebf40501dd27341e9c64a5f633324000000006a473044022043511ab874f0037c"
+    "5726b1efc69fcdb638fac74ab3f6766eb80947cff8c1175a02200606ccf8db60f56e77"
+    "03f6d5b81f5f5141f5b029a7b5a35700907f368b7e0f024121038daab4c77b9a428efb"
+    "23aa2ccadc5c5332f299f5e51d1f1600524c0313ab9ec2feffffff04fe66c200000000"
+    "001976a914a8c27c62fafec0a07d28b3b905912e9f385a7f1a88ac2a3b560800000000"
+    "1976a914c20992e92764ef7e33e2cf6ed538d34b18a1fff888ac00a3e1110000000019"
+    "76a9147137cd9dc7aad0d1cbc8e0ec12aae753d1acfaf488ac5d2b0f00000000001976"
+    "a914c10084f449e968b0d71ee23a308954c68d8c97e488ac28620700"
+]
+
+def test_tx_serialiazation():
+    for test in tests:
+        test = bytes.fromhex(test)
+        deser = tx_lib.Deserializer(test)
+        tx = deser.read_tx()
+        assert tx.serialize() == test