def write_ew_message(msg):
"""Write a message to the blockchain."""
print("write_ew_message({})" % msg)
# Create a bitcoin script object with our message
if len(msg) > 72:
raise Exception('Message is too long and may not be accepted.')
msg = "EW " + msg
message_script = Script('OP_RETURN 0x{}'.format(utils.bytes_to_str(msg.encode())))
# Define the fee we're willing to pay for the tx
tx_fee = 11000
# Get the first UTXO from our set that can cover the fee
utxo = None
for utxo_addr, utxos in wallet.get_utxos().items():
for u in utxos:
if u.value > tx_fee:
utxo = u
break
if utxo:
break
if not utxo:
raise Exception('No UTXOs available to pay for the transaction.')
# Build the transaction inputs (there is only one, but Transaction expects a list)
inputs = [TransactionInput(outpoint=utxo.transaction_hash,
outpoint_index=utxo.outpoint_index,
script=utxo.script,
sequence_num=0xffffffff)]
outputs = []
# Build one output with our custom message script
outputs.append(TransactionOutput(value=0, script=message_script))
# Build another output to pay the UTXO money back to one of our addresses
_, change_key_hash = utils.address_to_key_hash(wallet._accounts[0].get_next_address(True))
outputs.append(TransactionOutput(value=utxo.value - tx_fee,
script=Script.build_p2pkh(change_key_hash)))
# Build an unsigned transaction object
txn = Transaction(version=Transaction.DEFAULT_TRANSACTION_VERSION,
inputs=inputs,
outputs=outputs,
lock_time=0
)
# Sign the transaction with the correct private key
private_key = wallet.get_private_key(utxo_addr)
txn.sign_input(input_index=0,
hash_type=Transaction.SIG_HASH_ALL,
private_key=private_key,
sub_script=utxo.script
)
# Broadcast the transaction
tx = wallet.broadcast_transaction(txn.to_hex())
return tx
def create_deposit_tx(self, hash160):
"""Return a mocked deposit transaction."""
utxo_script_sig = Script.build_p2pkh(self._private_key.public_key.hash160())
inp = TransactionInput(
outpoint=Hash('0' * 64), outpoint_index=0, script=utxo_script_sig, sequence_num=0xffffffff)
out = TransactionOutput(value=120000, script=Script.build_p2sh(hash160))
txn = Transaction(version=Transaction.DEFAULT_TRANSACTION_VERSION, inputs=[inp], outputs=[out], lock_time=0)
txn.sign_input(
input_index=0, hash_type=Transaction.SIG_HASH_ALL, private_key=self._private_key,
sub_script=utxo_script_sig)
return txn
def create_deposit_tx(self, hash160):
"""Return a mocked deposit transaction."""
utxo_script_sig = Script.build_p2pkh(
self._private_key.public_key.hash160())
inp = TransactionInput(outpoint=Hash('0' * 64),
outpoint_index=0,
script=utxo_script_sig,
sequence_num=0xffffffff)
out = TransactionOutput(value=120000,
script=Script.build_p2sh(hash160))
txn = Transaction(version=Transaction.DEFAULT_TRANSACTION_VERSION,
inputs=[inp],
outputs=[out],
lock_time=0)
txn.sign_input(input_index=0,
hash_type=Transaction.SIG_HASH_ALL,
private_key=self._private_key,
sub_script=utxo_script_sig)
return txn