ERC20Upgradeable

Inherits: Initializable, ContextUpgradeable, IERC20, IERC20Metadata, IERC20Errors

Implementation of the {IERC20} interface. This implementation is agnostic to the way tokens are created. This means that a supply mechanism has to be added in a derived contract using {_mint}. TIP: For a detailed writeup see our guide https://forum.openzeppelin.com/t/how-to-implement-erc20-supply-mechanisms/226[How to implement supply mechanisms]. The default value of {decimals} is 18. To change this, you should override this function so it returns a different value. We have followed general OpenZeppelin Contracts guidelines: functions revert instead returning false on failure. This behavior is nonetheless conventional and does not conflict with the expectations of ERC-20 applications.

State Variables

ERC20StorageLocation

bytes32 private constant ERC20StorageLocation = 0x52c63247e1f47db19d5ce0460030c497f067ca4cebf71ba98eeadabe20bace00;

Functions

_getERC20Storage

function _getERC20Storage() private pure returns (ERC20Storage storage $);

__ERC20_init

Sets the values for name and {symbol}. Both values are immutable: they can only be set once during construction.

function __ERC20_init(string memory name_, string memory symbol_) internal onlyInitializing;

__ERC20_init_unchained

function __ERC20_init_unchained(string memory name_, string memory symbol_) internal onlyInitializing;

name

Returns the name of the token.

function name() public view virtual returns (string memory);

symbol

Returns the symbol of the token, usually a shorter version of the name.

function symbol() public view virtual returns (string memory);

decimals

Returns the number of decimals used to get its user representation. For example, if decimals equals 2, a balance of 505 tokens should be displayed to a user as 5.05 (505 / 10 ** 2). Tokens usually opt for a value of 18, imitating the relationship between Ether and Wei. This is the default value returned by this function, unless it's overridden. NOTE: This information is only used for display purposes: it in no way affects any of the arithmetic of the contract, including IERC20-balanceOf and {IERC20-transfer}.

function decimals() public view virtual returns (uint8);

totalSupply

function totalSupply() public view virtual returns (uint256);

balanceOf

function balanceOf(address account) public view virtual returns (uint256);

transfer

*See IERC20-transfer. Requirements:

to cannot be the zero address.
the caller must have a balance of at least value.*

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

allowance

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

approve

*See IERC20-approve. NOTE: If value is the maximum uint256, the allowance is not updated on transferFrom. This is semantically equivalent to an infinite approval. Requirements:

spender cannot be the zero address.*

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

transferFrom

*See IERC20-transferFrom. Skips emitting an {Approval} event indicating an allowance update. This is not required by the ERC. See {xref-ERC20-_approve-address-address-uint256-bool-}[_approve]. NOTE: Does not update the allowance if the current allowance is the maximum uint256. Requirements:

from and to cannot be the zero address.
from must have a balance of at least value.
the caller must have allowance for from's tokens of at least value.*

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

_transfer

Moves a value amount of tokens from from to to. This internal function is equivalent to transfer, and can be used to e.g. implement automatic token fees, slashing mechanisms, etc. Emits a {Transfer} event. NOTE: This function is not virtual, {_update} should be overridden instead.

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

_update

Transfers a value amount of tokens from from to to, or alternatively mints (or burns) if from (or to) is the zero address. All customizations to transfers, mints, and burns should be done by overriding this function. Emits a {Transfer} event.

function _update(address from, address to, uint256 value) internal virtual;

_mint

Creates a value amount of tokens and assigns them to account, by transferring it from address(0). Relies on the _update mechanism Emits a {Transfer} event with from set to the zero address. NOTE: This function is not virtual, {_update} should be overridden instead.

function _mint(address account, uint256 value) internal;

_burn

Destroys a value amount of tokens from account, lowering the total supply. Relies on the _update mechanism. Emits a {Transfer} event with to set to the zero address. NOTE: This function is not virtual, {_update} should be overridden instead

function _burn(address account, uint256 value) internal;

_approve

*Sets value as the allowance of spender over the owner's tokens. This internal function is equivalent to approve, and can be used to e.g. set automatic allowances for certain subsystems, etc. Emits an {Approval} event. Requirements:

owner cannot be the zero address.
spender cannot be the zero address. Overrides to this logic should be done to the variant with an additional bool emitEvent argument.*

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

_approve

*Variant of _approve with an optional flag to enable or disable the {Approval} event. By default (when calling {_approve}) the flag is set to true. On the other hand, approval changes made by _spendAllowance during the transferFrom operation set the flag to false. This saves gas by not emitting any Approval event during transferFrom operations. Anyone who wishes to continue emitting Approval events on thetransferFrom operation can force the flag to true using the following override:

function _approve(address owner, address spender, uint256 value, bool) internal virtual override {
super._approve(owner, spender, value, true);
}

Requirements are the same as {_approve}.*

function _approve(address owner, address spender, uint256 value, bool emitEvent) internal virtual;

_spendAllowance

Updates owner's allowance for spender based on spent value. Does not update the allowance value in case of infinite allowance. Revert if not enough allowance is available. Does not emit an {Approval} event.

function _spendAllowance(address owner, address spender, uint256 value) internal virtual;

Structs

ERC20Storage

Note: storage-location: erc7201:openzeppelin.storage.ERC20

struct ERC20Storage {
    mapping(address account => uint256) _balances;
    mapping(address account => mapping(address spender => uint256)) _allowances;
    uint256 _totalSupply;
    string _name;
    string _symbol;
}

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