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 fetch_tx(self, testnet=False):
return TxFetcher.fetch(self.prev_tx.hex(), testnet=testnet)
def serialize(self):
# Returns the byte serialization of the transaction input
# serialize prev_tx, little endian
result = self.prev_tx[::-1]
# serialize prev_index, 4 bytes, little endian
result += int_to_little_endian(self.prev_index, 4)
# serialize the script_sig
result += self.script_sig.serialize()
# serialize sequence, 4 bytes, little endian
result += int_to_little_endian(self.sequence, 4)
return result
def script_pubkey(self, testnet=False):
# Get the ScriptPubKey by looking up the tx hash Returns a Script object
# use self.fetch_tx to get the transaction
tx = self.fetch_tx(testnet=testnet)
# get the output at self.prev_index
# return the script_pubkey property
return tx.tx_outs[self.prev_index].script_pubkey
@classmethod
def parse(cls, s):
# Takes a byte stream and parses the tx_input at the start. return a TxIn object
# prev_tx is 32 bytes, little endian
prev_tx = s.read(32)[::-1]
# prev_index is an integer in 4 bytes, little endian
prev_index = little_endian_to_int(s.read(4))
# use Script.parse to get the ScriptSig
script_sig = Script.parse(s)
# sequence is an integer in 4 bytes, little-endian
sequence = little_endian_to_int(s.read(4))
# return an instance of the class (see __init__ for args)
return cls(prev_tx, prev_index, script_sig, sequence)
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: # <1>
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,
)
# end::source2[]
@classmethod
def parse(cls, s):
'''Takes a byte stream and parses the tx_input at the start
return a TxIn object
'''
# prev_tx is 32 bytes, little endian
# prev_index is an integer in 4 bytes, little endian
# use Script.parse to get the ScriptSig
# sequence is an integer in 4 bytes, little-endian
# return an instance of the class (see __init__ for args)
# raise NotImplementedError
prev_tx = s.read(32)[::-1]
prev_index = little_endian_to_int(s.read(4))
script_sig = Script.parse(s)
sequence = little_endian_to_int(s.read(4))
return cls(prev_tx, prev_index, script_sig, sequence)
# tag::source5[]
def serialize(self):
'''Returns the byte serialization of the transaction input'''
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
# end::source5[]
# tag::source8[]
def fetch_tx(self, testnet=False):
return TxFetcher.fetch(self.prev_tx.hex(), testnet=testnet)
def value(self, testnet=False):
'''Get the output value by looking up the tx hash.
Returns the amount in satoshi.
'''
tx = self.fetch_tx(testnet=testnet)
return tx.tx_outs[self.prev_index].amount
def script_pubkey(self, testnet=False):
'''Get the ScriptPubKey by looking up the tx hash.
Returns a Script object.
'''
tx = self.fetch_tx(testnet=testnet)
return tx.tx_outs[self.prev_index].script_pubkey
