✨ Permit2 ERC20 #1093
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✨ Permit2 ERC20 #1093
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Vectorized
commented
Sep 25, 2024
Comment on lines
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| let from_ := shl(96, from) | ||
| if iszero(eq(caller(), _PERMIT2)) { | ||
| // Compute the allowance slot and load its value. | ||
| mstore(0x20, caller()) | ||
| mstore(0x0c, or(from_, _ALLOWANCE_SLOT_SEED)) | ||
| let allowanceSlot := keccak256(0x0c, 0x34) | ||
| let allowance_ := sload(allowanceSlot) | ||
| // If the allowance is not the maximum uint256 value. | ||
| if not(allowance_) { | ||
| // Revert if the amount to be transferred exceeds the allowance. | ||
| if gt(amount, allowance_) { | ||
| mstore(0x00, 0x13be252b) // `InsufficientAllowance()`. | ||
| revert(0x1c, 0x04) | ||
| } | ||
| // Subtract and store the updated allowance. | ||
| sstore(allowanceSlot, sub(allowance_, amount)) | ||
| } | ||
| } | ||
| // Compute the balance slot and load its value. | ||
| mstore(0x0c, or(from_, _BALANCE_SLOT_SEED)) | ||
| let fromBalanceSlot := keccak256(0x0c, 0x20) | ||
| let fromBalance := sload(fromBalanceSlot) | ||
| // Revert if insufficient balance. | ||
| if gt(amount, fromBalance) { | ||
| mstore(0x00, 0xf4d678b8) // `InsufficientBalance()`. | ||
| revert(0x1c, 0x04) | ||
| } | ||
| // Subtract and store the updated allowance. | ||
| sstore(allowanceSlot, sub(allowance_, amount)) | ||
| // Subtract and store the updated balance. | ||
| sstore(fromBalanceSlot, sub(fromBalance, amount)) | ||
| // Compute the balance slot of `to`. | ||
| mstore(0x00, to) | ||
| let toBalanceSlot := keccak256(0x0c, 0x20) | ||
| // Add and store the updated balance of `to`. | ||
| // Will not overflow because the sum of all user balances | ||
| // cannot exceed the maximum uint256 value. | ||
| sstore(toBalanceSlot, add(sload(toBalanceSlot), amount)) | ||
| // Emit the {Transfer} event. | ||
| mstore(0x20, amount) | ||
| log3(0x20, 0x20, _TRANSFER_EVENT_SIGNATURE, shr(96, from_), shr(96, mload(0x0c))) |
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This chunk of code is the same for both branches, with the only exception being that for the _givePermit2InfiniteAllowance() branch, if msg.sender == _PERMIT2, the allowance logic will be skipped.
Vectorized
commented
Sep 25, 2024
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| // If `spender == _PERMIT2 && value != type(uint256).max`. | ||
| if iszero(or(xor(shr(96, shl(96, spender)), _PERMIT2), iszero(not(value)))) { | ||
| mstore(0x00, 0x3f68539a) // `Permit2AllowanceIsFixedAtInfinity()`. | ||
| revert(0x1c, 0x04) | ||
| } |
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This expression's equivalence has been verified with Halmos.
Vectorized
commented
Sep 25, 2024
| let allowance_ := sload(allowanceSlot) | ||
| // If the allowance is not the maximum uint256 value. | ||
| if add(allowance_, 1) { | ||
| if not(allowance_) { |
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Vectorized
commented
Sep 25, 2024
Comment on lines
+189
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| // If `spender == _PERMIT2 && amount != type(uint256).max`. | ||
| if iszero(or(xor(shr(96, shl(96, spender)), _PERMIT2), iszero(not(amount)))) { | ||
| mstore(0x00, 0x3f68539a) // `Permit2AllowanceIsFixedAtInfinity()`. | ||
| revert(0x1c, 0x04) | ||
| } |
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Description
✨
Confidence level is 99.999%.
transferFromlogic is duplicated in a super left-curved way.Checklist
Ensure you completed all of the steps below before submitting your pull request:
forge fmt?forge test?Pull requests with an incomplete checklist will be thrown out.