[Bitcoin] トランザクション

トランザクションとはエンティティから別のエンティティに移動する事

– トランザクションコンポーネント
バージョン(トランザクション追加機能)
インプット(どのビットコインを使うか)
アウトプット(どこにビットコインを移動するか)
ロックタイム(いつトランザクションが有効になるか)

### バージョン

class Tx:

	def __init__(self, version, tx_ins, tx_outs, locktime, testnet=False):
		self.version = version
		self.tx_ins = tx_ins
		self.tx_outs = tx_outs
		self.locktime = locktime
		self.testnet = testnet

	def __repr__(self):
		tx_ins = ''
		for tx_in in self.tx_ins:
			tx_ins += tx_in.__repr__() + '\n'
		tx_outs = ''
		for tx_out in self.tx_outs:
			tx_outs += tx_out.__repr__() + '\n'
		return 'tx: {}\nversion: {}\ntx_ins:\n{}tx_outs:\n{}locktime: {}'.format(
			self.id(),
			self.version,
			tx_ins,
			tx_outs,
			self.locktime,
		)

	def id(self):
		return self.hash().hex()

	def hash(self):
		return hash256(self.serialize())[::-1]

	@classmethod
	def parse(cls, s, testnet=False):
		version = little_endian_to_int(s.read(4))
		return cls(version, None, None, None, testnet=testnet)

### インプット
前のトランザクションのアウトプットを示す
L 前に受け取ったビットコインへの参照
L 支払う本人のビットコインである証明

variable integer = varintを使用する

def read_varint(s):
    i = s.read(1)[0]
    if i == 0xfd:
        return little_endian_to_int(s.read(2))
    elif i == 0xfe:
        return little_endian_to_int(s.read(4))
    elif i == 0xff:
        return little_endian_to_int(s.read(8))
    else:
        return i

def encode_varint(i):
    if i < 0xfd:
        return bytes([i])
    elif i < 0x10000:
        return b'\xfd' + int_to_little_endian(i, 2)
    elif i < 0x100000000:
        return b'\xfe' + int_to_little_endian(i, 4)
    elif i < 0x10000000000000000:
        return b'\xff' + int_to_little_endian(i, 8)
    else:
        raise ValueError('integer too large: {}'.format(i))

インプットフィールド
– 前のトランザクションID, トランザクションインデックス、ScriptSig, シーケンス

class TxIn:
	def __init__(self, prev_tx, prev_index, script_sig=None, sequence=0xffffffff):
		self.prev_tx = prev_tx
		self.prev_index = prev_index
		if script_sig is None:
			self.script_sig = Script()
		else:
			self.script_sig = script_sig
		self.sequence = sequence

	def __repr__(self):
		return '{}:{}'.format(
				self.prev_tx.hex(),
				self.prev_index,
			)

script_hex = ('6b483045022100ed81ff192e75a3fd2304004dcadb746fa5e24c5031ccf\
cf21320b0277457c98f02207a986d955c6e0cb35d446a89d3f56100f4d7f67801c31967743a9c8\
e10615bed01210349fc4e631e3624a545de3f89f5d8684c7b8138bd94bdd531d2e213bf016b278\
a')
stream = BytesIO(bytes.fromhex(script_hex))
script_sig = Script.parse(stream)
print(script_sig)

### アウトプット
ビットコインの送信先を定義
varint形式のアウトプット数で開始
フィールドには額とscriptpubkeyがある

TxOut

class tx:
	// 省略
	@classmethod
	def parse(cls, s, testnet=False):
		version = little_endian_to_int(s.read(4))
		num_inputs = read_varint(s)
		inputs = []
		for _ in range(num_inputs):
			inputs.append(TxIn.parse(s))
		num_outputs = read_variant(s)
		for _ in range(num_outputs):
			outputs.append(TxOut.parse(s))
		return cls(version, inputs, outpute, None, testnet=testnet)

class TxOut:

	def __init__(self, amount, script_pubkey):
		self.amount = amount
		self.script_pubkey = script_pubkey

	def __repr__(self):
		return '{}:{}'.format(self.amount, self.script_pubkey)

	@classmethod
	def parse(cls, s):
		amount = little_endian_to_int(s.read(8))
		script_pubkey = Script.parse(s)
		return cls(amount, script_pubkey)

### ロックタイム

	@classmethod
	def parse(cls, s, testnet=False):
		version = little_endian_to_int(s.read(4))
		num_inputs = read_varint(s)
		inputs = []
		for _ in range(num_inputs):
			inputs.append(TxIn.parse(s))
		num_outputs = read_variant(s)
		outputs = []
		for _ in range(num_outputs):
			outputs.append(TxOut.parse(s))
		locktime = little_endian_to_int(s.read(4))
		return cls(version, inputs, outpute, locktime, testnet=testnet)

hex_transaction = '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'
stream = BytesIO(bytes.fromhex(hex_transaction))
tx_obj = Tx.parse(stream)
print(tx_obj.tx_ins[1].script_sig)
print(tx_obj.tx_outs[0].script_pubkey)
print(tx_obj.tx_outs[1].amount)

$ python3 app.py
304402207899531a52d59a6de200179928ca900254a36b8dff8bb75f5f5d71b1cdc26125022008b422690b8461cb52c3cc30330b23d574351872b7c361e9aae3649071c1a71601 035d5c93d9ac96881f19ba1f686f15f009ded7c62efe85a872e6a19b43c15a2937
OP_DUP OP_HASH160 ab0c0b2e98b1ab6dbf67d4750b0a56244948a879 OP_EQUALVERIFY OP_CHECKSIG
40000000

### シリアライズ

class tx
	def serialize(self):
		result = int_to_little_endian(self.version, 4)
		result += encode_varint(len(self.tx_ins))
		for tx_in in self.tx_ins:
			result += tx_in.serialize()
		result += encode_varint(len(self.tx_outs))
		for tx_out in self.tx_outs:
			result += tx_out.serialize()
		result += int_to_little_endian(self.locktime, 4)
		return result

class TxIn
	def serialize(self):
		result = self.prev_tx[::-1]
		result += int_to_little_endian(self.prev_index, 4)
		result += self.script_sig.serialize()
		result += int_to_little_endian(self.sequence, 4)
		return result

class TxOut
	def serialize(self):
		result = int_to_little_endian(self.amount, 8)
		result += self.script_pubkey.serialize()
		return result

### トランザクション手数料
マイナーがトランザクションに取り込む手数料がトランザクション手数料となる

class TxIn:
	def fetch_tx(self, testnet=False):
		return TxFetcher.fetch(self.prev_tx.hex(), testnet=testnet)

	def value(self, testnet=False)
		tx = self.fetch_tx(testnet=testnet)
		return tx.tx_outs[self.prev_index].amount

	def script_pubkey(self, testnet=False):
		tx = self.fetch_tx(testnet=testnet)
		return tx.tx_outs[self.prev_index].script_pubkey

class TxFetcher:
	cache = {}

	@classmethod
	def get_url(cls, testnet=False)
		if testnet:
			return 'http://testnet.programmingbitcoin.com'
		else:
			return 'http://mainnet.programmingbitcoin.com'

	@classmethod
	def fetch(cls, tx_id, testnet=False, fresh=False):
		if fresh or (tx_id not in cls.cache):
			url = '{}/tx/{}.hex'.format(cls.get_url(testnet), tx_id)
			response = requests.get(url)
			try:
				raw = bytes.fromhex(response.text.strip())
			ecept ValueError:
				raise ValueError('unexpected response: {}'.format(response.text))
			if raw[4] == 0:
				raw = raw[:4] + raw[6:]
				tx = Tx.parse(BytesIO(raw), testnet=testnet)
				tx.locktime = little_endian_to_int(raw[-4:])
			else:
				tx = Tx.parse(BytesIO(raw), testnet=testnet)
			if tx.id() != tx_id:
				raise ValueError('not the same id: {} vs {}'.foramt(tx.id(), tx_id))
				clc.cache[tx_id] = tx
			cls.cache[tx_id].testnet = testnet
			return cls.cache[tx_id]

class Tx:

	def fee(self, testnet=False):
		input_sum, output_sum = 0, 0
		for tx_in in self.tx_ins:
			input_sum += tx_in.value(testnet=testnet)
		for tx_out in self.tx_outs:
			output_suum += tx_out.amount
		return input_sum - output_sum