Contract module which provides a basic access control mechanism, where there is an account (an owner) that can be granted exclusive access to specific functions. By default, the owner account will be the one that deploys the contract. This can later be changed with {transferOwnership}. This module is used through inheritance. It will make available the modifier `onlyOwner`, which can be applied to your functions to restrict their use to the owner.

Implementation of the {IERC165} interface. Contracts may inherit from this and call {_registerInterface} to declare their support of an interface.

Interface of the ERC165 standard, as defined in the https://eips.ethereum.org/EIPS/eip-165[EIP]. Implementers can declare support of contract interfaces, which can then be queried by others ({ERC165Checker}). For an implementation, see {ERC165}.

Wrappers over Solidity's arithmetic operations with added overflow checks. Arithmetic operations in Solidity wrap on overflow. This can easily result in bugs, because programmers usually assume that an overflow raises an error, which is the standard behavior in high level programming languages. `SafeMath` restores this intuition by reverting the transaction when an operation overflows. Using this library instead of the unchecked operations eliminates an entire class of bugs, so it's recommended to use it always.

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}. For a generic mechanism see {ERC20PresetMinterPauser}. TIP: For a detailed writeup see our guide https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How to implement supply mechanisms]. We have followed general OpenZeppelin guidelines: functions revert instead of returning `false` on failure. This behavior is nonetheless conventional and does not conflict with the expectations of ERC20 applications. Additionally, an {Approval} event is emitted on calls to {transferFrom}. This allows applications to reconstruct the allowance for all accounts just by listening to said events. Other implementations of the EIP may not emit these events, as it isn't required by the specification. Finally, the non-standard {decreaseAllowance} and {increaseAllowance} functions have been added to mitigate the well-known issues around setting allowances. See {IERC20-approve}.

see https://eips.ethereum.org/EIPS/eip-721

Required interface of an ERC721 compliant contract.

See https://eips.ethereum.org/EIPS/eip-721

See https://eips.ethereum.org/EIPS/eip-721

Interface for any contract that wants to support safeTransfers from ERC721 asset contracts.

Interface of the ERC20 standard as defined in the EIP.

Wrappers around ERC20 operations that throw on failure (when the token contract returns false). Tokens that return no value (and instead revert or throw on failure) are also supported, non-reverting calls are assumed to be successful. To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract, which allows you to call the safe operations as `token.safeTransfer(...)`, etc.

Collection of functions related to the address type

Library for managing an enumerable variant of Solidity's https://solidity.readthedocs.io/en/latest/types.html#mapping-types[`mapping`] type. Maps have the following properties: - Entries are added, removed, and checked for existence in constant time (O(1)). - Entries are enumerated in O(n). No guarantees are made on the ordering. ``` contract Example { // Add the library methods using EnumerableMap for EnumerableMap.UintToAddressMap; // Declare a set state variable EnumerableMap.UintToAddressMap private myMap; } ``` As of v3.0.0, only maps of type `uint256 -> address` (`UintToAddressMap`) are supported.

Library for managing https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive types. Sets have the following properties: - Elements are added, removed, and checked for existence in constant time (O(1)). - Elements are enumerated in O(n). No guarantees are made on the ordering. ``` contract Example { // Add the library methods using EnumerableSet for EnumerableSet.AddressSet; // Declare a set state variable EnumerableSet.AddressSet private mySet; } ``` As of v3.0.0, only sets of type `address` (`AddressSet`) and `uint256` (`UintSet`) are supported.

Contract module that helps prevent reentrant calls to a function. Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier available, which can be applied to functions to make sure there are no nested (reentrant) calls to them. Note that because there is a single `nonReentrant` guard, functions marked as `nonReentrant` may not call one another. This can be worked around by making those functions `private`, and then adding `external` `nonReentrant` entry points to them. TIP: If you would like to learn more about reentrancy and alternative ways to protect against it, check out our blog post https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].

String operations.

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}. For a generic mechanism see {ERC20PresetMinterPauser}. TIP: For a detailed writeup see our guide https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How to implement supply mechanisms]. We have followed general OpenZeppelin guidelines: functions revert instead of returning `false` on failure. This behavior is nonetheless conventional and does not conflict with the expectations of ERC20 applications. Additionally, an {Approval} event is emitted on calls to {transferFrom}. This allows applications to reconstruct the allowance for all accounts just by listening to said events. Other implementations of the EIP may not emit these events, as it isn't required by the specification. Finally, the non-standard {decreaseAllowance} and {increaseAllowance} functions have been added to mitigate the well-known issues around setting allowances. See {IERC20-approve}.

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}. For a generic mechanism see {ERC20PresetMinterPauser}. TIP: For a detailed writeup see our guide https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How to implement supply mechanisms]. We have followed general OpenZeppelin guidelines: functions revert instead of returning `false` on failure. This behavior is nonetheless conventional and does not conflict with the expectations of ERC20 applications. Additionally, an {Approval} event is emitted on calls to {transferFrom}. This allows applications to reconstruct the allowance for all accounts just by listening to said events. Other implementations of the EIP may not emit these events, as it isn't required by the specification. Finally, the non-standard {decreaseAllowance} and {increaseAllowance} functions have been added to mitigate the well-known issues around setting allowances. See {IERC20-approve}.

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}. For a generic mechanism see {ERC20PresetMinterPauser}. TIP: For a detailed writeup see our guide https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How to implement supply mechanisms]. We have followed general OpenZeppelin guidelines: functions revert instead of returning `false` on failure. This behavior is nonetheless conventional and does not conflict with the expectations of ERC20 applications. Additionally, an {Approval} event is emitted on calls to {transferFrom}. This allows applications to reconstruct the allowance for all accounts just by listening to said events. Other implementations of the EIP may not emit these events, as it isn't required by the specification. Finally, the non-standard {decreaseAllowance} and {increaseAllowance} functions have been added to mitigate the well-known issues around setting allowances. See {IERC20-approve}.