def create_p2pkh_transaction(private_key,
unspents,
outputs,
custom_pushdata=False):
public_key = private_key.public_key
public_key_len = len(public_key).to_bytes(1, byteorder='little')
scriptCode = private_key.scriptcode
scriptCode_len = int_to_varint(len(scriptCode))
version = VERSION_1
lock_time = LOCK_TIME
# sequence = SEQUENCE
hash_type = HASH_TYPE
input_count = int_to_unknown_bytes(len(unspents), byteorder='little')
output_count = int_to_unknown_bytes(len(outputs), byteorder='little')
output_block = construct_output_block(outputs,
custom_pushdata=custom_pushdata)
# Optimize for speed, not memory, by pre-computing values.
inputs = []
for unspent in unspents:
script = hex_to_bytes(unspent.script)
script_len = int_to_unknown_bytes(len(script), byteorder='little')
txid = hex_to_bytes(unspent.txid)[::-1]
txindex = unspent.txindex.to_bytes(4, byteorder='little')
amount = unspent.amount.to_bytes(8, byteorder='little')
inputs.append(TxIn(script, script_len, txid, txindex, amount))
hashPrevouts = double_sha256(b''.join([i.txid + i.txindex
for i in inputs]))
hashSequence = double_sha256(b''.join([SEQUENCE for i in inputs]))
hashOutputs = double_sha256(output_block)
# scriptCode_len is part of the script.
for i, txin in enumerate(inputs):
to_be_hashed = (version + hashPrevouts + hashSequence + txin.txid +
txin.txindex + scriptCode_len + scriptCode +
txin.amount + SEQUENCE + hashOutputs + lock_time +
hash_type)
hashed = sha256(to_be_hashed) # BIP-143: Used for Bitcoin Cash
# signature = private_key.sign(hashed) + b'\x01'
signature = private_key.sign(hashed) + b'\x41'
script_sig = (len(signature).to_bytes(1, byteorder='little') +
signature + public_key_len + public_key)
inputs[i].script = script_sig
inputs[i].script_len = int_to_unknown_bytes(len(script_sig),
byteorder='little')
return bytes_to_hex(version + input_count + construct_input_block(inputs) +
output_count + output_block + lock_time)
def create_pushdata(lst_of_pushdata):
"""
Creates encoded OP_RETURN pushdata as bytes Returns binary encoded OP_RETURN pushdata (automatically adds
intervening OP_CODES specifying number of bytes in each pushdata element) 0x6a (i.e. OP_RETURN) is added in
other, auxiliary functions; only pushdata is returned here. Max 220 bytes of pushdata
Parameters
----------
lst_of_pushdata : a list of tuples (pushdata, encoding) where encoding is either "hex" or "utf-8"
Returns
-------
pushdata : bytes
Examples
--------
lst_of_pushdata = [('6d01', 'hex'),
('bitPUSHER', 'utf-8')]
as per memo.cash protocol @ https://memo.cash/protocol this results in a "Set name" action to "bitPUSHER"
raw OP_RETURN will be:
0e 6a 02 6d01 09 626974505553484552
0e - 14 bytes to follow (in hex)
6a - OP_RETURN
02 - 2 bytes of pushdata to follow
6d01 - "communication channel" for memo.cash - "set name" action
09 - 9 bytes to follow
626974505553484552 - "bitPUSHER" utf-8 encoded bytes --> hex representation
Currently (this module) only allows up to 220 bytes maximum - as multiple OP_RETURNS in one transaction is
considered non-standard."""
pushdata = b''
for i in range(len(lst_of_pushdata)):
encoding = lst_of_pushdata[i][1]
if encoding == 'utf-8':
pushdata += get_op_pushdata_code(
lst_of_pushdata[i][0]) + lst_of_pushdata[i][0].encode('utf-8')
elif encoding == 'hex' and len(lst_of_pushdata[i][0]) % 2 != 0:
raise ValueError(
"hex encoded pushdata must have length = a multiple of two")
elif encoding == 'hex' and len(lst_of_pushdata[i][0]) % 2 == 0:
hex_data_as_bytes = utils.hex_to_bytes(lst_of_pushdata[i][0])
pushdata += get_op_pushdata_code(
hex_data_as_bytes) + hex_data_as_bytes
# check for size
if len(pushdata) > 220:
raise ValueError(
"Total bytes in OP_RETURN cannot exceed 220 bytes at present - apologies"
)
return pushdata
def calc_txid(tx_hex):
return bytes_to_hex(double_sha256(hex_to_bytes(tx_hex))[::-1])
def test_construct_input_block():
assert construct_input_block(INPUTS) == hex_to_bytes(INPUT_BLOCK)
def test_pushdata_message(self):
BYTES = len(b'hello').to_bytes(1, byteorder='little') + b'hello'
assert construct_output_block(OUTPUTS + [(BYTES, 0)],
custom_pushdata=True) == hex_to_bytes(
OUTPUT_BLOCK_MESSAGE_PUSHDATA)
def test_message(self):
assert construct_output_block(OUTPUTS + MESSAGES) == hex_to_bytes(
OUTPUT_BLOCK_MESSAGES)
def test_no_message(self):
assert construct_output_block(OUTPUTS) == hex_to_bytes(OUTPUT_BLOCK)
def test_hex_to_bytes():
assert hex_to_bytes(HEX) == BYTES_BIG
assert hex_to_bytes(ODD_HEX) == ODD_HEX_BYTES
