32 lines
1.5 KiB
Solidity
32 lines
1.5 KiB
Solidity
// SPDX-License-Identifier: MIT
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pragma solidity ^0.8.0;
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import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
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/* The `increaseAllowance` function of OpenZeppelin's ERC20 implementation is
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being used, which is not part of the standard ERC20 interface. If the Codex
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token must be an ERC20 token (eg DAI), then that token will need to be wrapped in
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OpenZeppelin's ERC20Wrapped to ensure that `increaseAllowance` is available.
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The reason `increaseAllowance` is needed is because the sales state machine
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handles concurrent slot fills, which requires token approval. Because these
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approvals happen concurrently, simply calling `approve` is not sufficient as
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each `approve` amount will overwrite the previous. As an example, if a single
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node attempts to fill two slots simultaneously, it will send two `approve`
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transactions followed by two `fillSlot` transactions. The first two `approve`
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transactions will each approve the collateral amount for one `fillSlot`, the
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second overwriting the first, so the total approved will only ever be enough for
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one `fillSlot`. So after the first `fillSlot` is sent, the second one will fail
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as not enough tokens will have been approved. The solution is use
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`increaseAllowance` instead of `approve` which increases the allowance instead
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of overwriting it. */
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contract TestToken is ERC20 {
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// solhint-disable-next-line no-empty-blocks
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constructor() ERC20("TestToken", "TST") {}
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function mint(address holder, uint256 amount) public {
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_mint(holder, amount);
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}
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}
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