65 lines
2.0 KiB
Solidity
65 lines
2.0 KiB
Solidity
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// SPDX-License-Identifier: MIT
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pragma solidity >=0.4.24 <0.7.0;
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/**
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* @title Initializable
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*
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* @dev Helper contract to support initializer functions. To use it, replace
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* the constructor with a function that has the `initializer` modifier.
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* WARNING: Unlike constructors, initializer functions must be manually
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* invoked. This applies both to deploying an Initializable contract, as well
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* as extending an Initializable contract via inheritance.
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* WARNING: When used with inheritance, manual care must be taken to not invoke
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* a parent initializer twice, or ensure that all initializers are idempotent,
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* because this is not dealt with automatically as with constructors.
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*/
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contract Initializable {
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/**
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* @dev Indicates that the contract has been initialized.
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*/
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bool private initialized;
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/**
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* @dev Indicates that the contract is in the process of being initialized.
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*/
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bool private initializing;
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/**
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* @dev Modifier to use in the initializer function of a contract.
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*/
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modifier initializer() {
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require(initializing || isConstructor() || !initialized, "Contract instance has already been initialized");
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bool isTopLevelCall = !initializing;
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if (isTopLevelCall) {
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initializing = true;
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initialized = true;
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}
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_;
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if (isTopLevelCall) {
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initializing = false;
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}
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}
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/// @dev Returns true if and only if the function is running in the constructor
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function isConstructor() private view returns (bool) {
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// extcodesize checks the size of the code stored in an address, and
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// address returns the current address. Since the code is still not
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// deployed when running a constructor, any checks on its code size will
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// yield zero, making it an effective way to detect if a contract is
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// under construction or not.
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address self = address(this);
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uint256 cs;
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assembly { cs := extcodesize(self) }
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return cs == 0;
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}
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// Reserved storage space to allow for layout changes in the future.
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uint256[50] private ______gap;
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}
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