0926729c8f
* Add StandardBurnableToken implementation BurnableToken that extends from StandardToken and adds a burnFrom method that decrements allowance. Equivalent to a transferFrom plus burn in a single operation. * Return event object from expectEvent helper * Add comment on Approval event in burnFrom function * Improvements on burnable token tests - Inject initial balance as a parameter to the behaviour - Use expectEvent helper for assertions on events - Use chai bignumber for numbers - Change to bdd-style assertions
33 lines
871 B
Solidity
33 lines
871 B
Solidity
pragma solidity ^0.4.21;
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import "./BasicToken.sol";
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/**
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* @title Burnable Token
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* @dev Token that can be irreversibly burned (destroyed).
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*/
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contract BurnableToken is BasicToken {
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event Burn(address indexed burner, uint256 value);
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/**
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* @dev Burns a specific amount of tokens.
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* @param _value The amount of token to be burned.
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*/
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function burn(uint256 _value) public {
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_burn(msg.sender, _value);
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}
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function _burn(address _who, uint256 _value) internal {
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require(_value <= balances[_who]);
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// no need to require value <= totalSupply, since that would imply the
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// sender's balance is greater than the totalSupply, which *should* be an assertion failure
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balances[_who] = balances[_who].sub(_value);
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totalSupply_ = totalSupply_.sub(_value);
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emit Burn(_who, _value);
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emit Transfer(_who, address(0), _value);
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}
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}
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