Standard ERC20 token

• (ERC20.sol)

View Source: openzeppelin-solidity/contracts/token/ERC20/ERC20.sol

↗ Extends: IERC20 ↘ Derived Contracts: SecurityToken

ERC20

Implementation of the basic standard token. https://eips.ethereum.org/EIPS/eip-20 Originally based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol

• This implementation emits additional Approval events, allowing applications to reconstruct the allowance status for

  all accounts just by listening to said events. Note that this isn't required by the specification, and other

  compliant implementations may not do it.

Contract Members

Constants & Variables

mapping(address => uint256) private _balances;
mapping(address => mapping(address => uint256)) private _allowed;
uint256 private _totalSupply;

Functions

• totalSupply()

• balanceOf(address owner)

• allowance(address owner, address spender)

• transfer(address to, uint256 value)

• approve(address spender, uint256 value)

• transferFrom(address from, address to, uint256 value)

• increaseAllowance(address spender, uint256 addedValue)

• decreaseAllowance(address spender, uint256 subtractedValue)

• _transfer(address from, address to, uint256 value)

• _mint(address account, uint256 value)

• _burn(address account, uint256 value)

• _approve(address owner, address spender, uint256 value)

• _burnFrom(address account, uint256 value)

totalSupply

⤾ overrides IERC20.totalSupply

Total number of tokens in existence

function totalSupply() public view
returns(uint256)

Arguments

Name	Type	Description

balanceOf

⤾ overrides IERC20.balanceOf

Gets the balance of the specified address.

function balanceOf(address owner) public view
returns(uint256)

Returns

A uint256 representing the amount owned by the passed address.

Arguments

Name	Type	Description
owner	address	The address to query the balance of.

allowance

⤾ overrides IERC20.allowance

Function to check the amount of tokens that an owner allowed to a spender.

function allowance(address owner, address spender) public view
returns(uint256)

Returns

A uint256 specifying the amount of tokens still available for the spender.

Arguments

Name	Type	Description
owner	address	address The address which owns the funds.
spender	address	address The address which will spend the funds.

transfer

⤾ overrides IERC20.transfer

⤿ Overridden Implementation(s): SecurityToken.transfer

Transfer token to a specified address

function transfer(address to, uint256 value) public nonpayable
returns(bool)

Arguments

Name	Type	Description
to	address	The address to transfer to.
value	uint256	The amount to be transferred.

approve

⤾ overrides IERC20.approve

Approve the passed address to spend the specified amount of tokens on behalf of msg.sender. Beware that changing an allowance with this method brings the risk that someone may use both the old and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards: https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729

function approve(address spender, uint256 value) public nonpayable
returns(bool)

Arguments

Name	Type	Description
spender	address	The address which will spend the funds.
value	uint256	The amount of tokens to be spent.

transferFrom

⤾ overrides IERC20.transferFrom

⤿ Overridden Implementation(s): SecurityToken.transferFrom

Transfer tokens from one address to another. Note that while this function emits an Approval event, this is not required as per the specification, and other compliant implementations may not emit the event.

function transferFrom(address from, address to, uint256 value) public nonpayable
returns(bool)

Arguments

Name	Type	Description
from	address	address The address which you want to send tokens from
to	address	address The address which you want to transfer to
value	uint256	uint256 the amount of tokens to be transferred

increaseAllowance

Increase the amount of tokens that an owner allowed to a spender. approve should be called when _allowed[msg.sender][spender] == 0. To increment allowed value is better to use this function to avoid 2 calls (and wait until the first transaction is mined) From MonolithDAO Token.sol Emits an Approval event.

function increaseAllowance(address spender, uint256 addedValue) public nonpayable
returns(bool)

Arguments

Name	Type	Description
spender	address	The address which will spend the funds.
addedValue	uint256	The amount of tokens to increase the allowance by.

decreaseAllowance

Decrease the amount of tokens that an owner allowed to a spender. approve should be called when _allowed[msg.sender][spender] == 0. To decrement allowed value is better to use this function to avoid 2 calls (and wait until the first transaction is mined) From MonolithDAO Token.sol Emits an Approval event.

function decreaseAllowance(address spender, uint256 subtractedValue) public nonpayable
returns(bool)

Arguments

Name	Type	Description
spender	address	The address which will spend the funds.
subtractedValue	uint256	The amount of tokens to decrease the allowance by.

_transfer

Transfer token for a specified addresses

function _transfer(address from, address to, uint256 value) internal nonpayable

Arguments

Name	Type	Description
from	address	The address to transfer from.
to	address	The address to transfer to.
value	uint256	The amount to be transferred.

_mint

Internal function that mints an amount of the token and assigns it to an account. This encapsulates the modification of balances such that the proper events are emitted.

function _mint(address account, uint256 value) internal nonpayable

Arguments

Name	Type	Description
account	address	The account that will receive the created tokens.
value	uint256	The amount that will be created.

_burn

Internal function that burns an amount of the token of a given account.

function _burn(address account, uint256 value) internal nonpayable

Arguments

Name	Type	Description
account	address	The account whose tokens will be burnt.
value	uint256	The amount that will be burnt.

_approve

Approve an address to spend another addresses' tokens.

function _approve(address owner, address spender, uint256 value) internal nonpayable

Arguments

Name	Type	Description
owner	address	The address that owns the tokens.
spender	address	The address that will spend the tokens.
value	uint256	The number of tokens that can be spent.

_burnFrom

Internal function that burns an amount of the token of a given account, deducting from the sender's allowance for said account. Uses the internal burn function. Emits an Approval event (reflecting the reduced allowance).

function _burnFrom(address account, uint256 value) internal nonpayable

Arguments

Name	Type	Description
account	address	The account whose tokens will be burnt.
value	uint256	The amount that will be burnt.