def transfer_from(spender, holder, to, amount):
# check if spender_address is tx sender
if not IsValid(spender) or not IsValid(holder) or not IsValid(to):
raise Exception("Address length error.")
if GetTxSender() != spender:
raise Exception("Please use the operator account.")
if amount < 0:
raise Exception("Please enter the correct amount.")
# check allowance
key = concat(concat(KEY_APPROVE, holder), spender)
approved = Get(key)
if approved < amount:
raise Exception("The authorized amount is less than the account balance.")
# check balance of holder
if balance_of(holder) < amount:
raise Exception("Insufficient balance.")
# send token and update allowance
TokenSend(holder, to, amount)
if approved == amount:
Delete(key)
if approved > amount:
Put(key, approved - amount)
return True
def transfer(from_address, to_address, amount):
# check if address freezing
timestamp = GetTime()
freeze_out_end = Get(concat(KEY_FREEZE_OUT, from_address))
freeze_in_end = Get(concat(KEY_FREEZE_IN, to_address))
if timestamp < freeze_out_end or timestamp < freeze_in_end:
raise Exception("There is currently a frozen address.")
#call StandardTokenContract transfer
param = state('string:transfer', '[string:', from_address, 'string:',
to_address, 'int:', amount, ']')
StandardTokenContract(param)
return True
def approve(holder, spender, amount):
# check if holder_address is tx sender
if not IsValid(holder) or not IsValid(spender):
raise Exception("Address length error.")
if GetTxSender() != holder:
raise Exception("Please use the operator account.")
if amount < 0:
raise Exception("Please enter the correct amount.")
key = concat(concat(KEY_APPROVE, holder), spender)
Put(key, amount)
return True
def decrease_approval(holder, spender, subtracted):
# check if holder_address is tx sender
if not IsValid(holder) or not IsValid(spender):
raise Exception("Address length error.")
if GetTxSender() != holder:
raise Exception("Please use the operator account.")
if subtracted < 0:
raise Exception("Please enter the correct amount.")
amount = allowance(holder, spender) - subtracted
if amount < 0:
raise Exception("The amount to be reduced is greater than the current amount.")
key = concat(concat(KEY_APPROVE, holder), spender)
Put(key, amount)
return True
def freeze_out(operator, address, end_time):
# check if freeze disabled
if not IsValid(operator) or not IsValid(address):
raise Exception("Address length error.")
if freeze_disabled():
raise Exception("Currently disabled.")
# check if operator is token owner
if GetTxSender() != operator:
raise Exception("Please use the operator account.")
if operator != Get(KEY_OWNER):
raise Exception("Please use the owner address.")
Put(concat(KEY_FREEZE_OUT, address), end_time)
return True
def allowance(holder, spender):
if not IsValid(holder) or not IsValid(spender):
raise Exception("Address length error.")
key = concat(concat(KEY_APPROVE, holder), spender)
return Get(key)