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// SPDX-License-Identifier: MIT
pragma solidity 0.8.15;
/// @title SafeCall
/// @notice Perform low level safe calls
library SafeCall {
/// @notice Performs a low level call without copying any returndata.
/// @dev Passes no calldata to the call context.
/// @param _target Address to call
/// @param _gas Amount of gas to pass to the call
/// @param _value Amount of value to pass to the call
function send(
address _target,
uint256 _gas,
uint256 _value
) internal returns (bool) {
bool _success;
assembly {
_success := call(
_gas, // gas
_target, // recipient
_value, // ether value
0, // inloc
0, // inlen
0, // outloc
0 // outlen
)
}
return _success;
}
/// @notice Perform a low level call without copying any returndata
/// @param _target Address to call
/// @param _gas Amount of gas to pass to the call
/// @param _value Amount of value to pass to the call
/// @param _calldata Calldata to pass to the call
function call(
address _target,
uint256 _gas,
uint256 _value,
bytes memory _calldata
) internal returns (bool) {
bool _success;
assembly {
_success := call(
_gas, // gas
_target, // recipient
_value, // ether value
add(_calldata, 32), // inloc
mload(_calldata), // inlen
0, // outloc
0 // outlen
)
}
return _success;
}
/// @notice Helper function to determine if there is sufficient gas remaining within the context
/// to guarantee that the minimum gas requirement for a call will be met as well as
/// optionally reserving a specified amount of gas for after the call has concluded.
/// @param _minGas The minimum amount of gas that may be passed to the target context.
/// @param _reservedGas Optional amount of gas to reserve for the caller after the execution
/// of the target context.
/// @return `true` if there is enough gas remaining to safely supply `_minGas` to the target
/// context as well as reserve `_reservedGas` for the caller after the execution of
/// the target context.
/// @dev !!!!! FOOTGUN ALERT !!!!!
/// 1.) The 40_000 base buffer is to account for the worst case of the dynamic cost of the
/// `CALL` opcode's `address_access_cost`, `positive_value_cost`, and
/// `value_to_empty_account_cost` factors with an added buffer of 5,700 gas. It is
/// still possible to self-rekt by initiating a withdrawal with a minimum gas limit
/// that does not account for the `memory_expansion_cost` & `code_execution_cost`
/// factors of the dynamic cost of the `CALL` opcode.
/// 2.) This function should *directly* precede the external call if possible. There is an
/// added buffer to account for gas consumed between this check and the call, but it
/// is only 5,700 gas.
/// 3.) Because EIP-150 ensures that a maximum of 63/64ths of the remaining gas in the call
/// frame may be passed to a subcontext, we need to ensure that the gas will not be
/// truncated.
/// 4.) Use wisely. This function is not a silver bullet.
function hasMinGas(uint256 _minGas, uint256 _reservedGas) internal view returns (bool) {
bool _hasMinGas;
assembly {
// Equation: gas × 63 ≥ minGas × 64 + 63(40_000 + reservedGas)
_hasMinGas := iszero(
lt(mul(gas(), 63), add(mul(_minGas, 64), mul(add(40000, _reservedGas), 63)))
)
}
return _hasMinGas;
}
/// @notice Perform a low level call without copying any returndata. This function
/// will revert if the call cannot be performed with the specified minimum
/// gas.
/// @param _target Address to call
/// @param _minGas The minimum amount of gas that may be passed to the call
/// @param _value Amount of value to pass to the call
/// @param _calldata Calldata to pass to the call
function callWithMinGas(
address _target,
uint256 _minGas,
uint256 _value,
bytes memory _calldata
) internal returns (bool) {
bool _success;
bool _hasMinGas = hasMinGas(_minGas, 0);
assembly {
// Assertion: gasleft() >= (_minGas * 64) / 63 + 40_000
if iszero(_hasMinGas) {
// Store the "Error(string)" selector in scratch space.
mstore(0, 0x08c379a0)
// Store the pointer to the string length in scratch space.
mstore(32, 32)
// Store the string.
//
// SAFETY:
// - We pad the beginning of the string with two zero bytes as well as the
// length (24) to ensure that we override the free memory pointer at offset
// 0x40. This is necessary because the free memory pointer is likely to
// be greater than 1 byte when this function is called, but it is incredibly
// unlikely that it will be greater than 3 bytes. As for the data within
// 0x60, it is ensured that it is 0 due to 0x60 being the zero offset.
// - It's fine to clobber the free memory pointer, we're reverting.
mstore(88, 0x0000185361666543616c6c3a204e6f7420656e6f75676820676173)
// Revert with 'Error("SafeCall: Not enough gas")'
revert(28, 100)
}
// The call will be supplied at least ((_minGas * 64) / 63) gas due to the
// above assertion. This ensures that, in all circumstances (except for when the
// `_minGas` does not account for the `memory_expansion_cost` and `code_execution_cost`
// factors of the dynamic cost of the `CALL` opcode), the call will receive at least
// the minimum amount of gas specified.
_success := call(
gas(), // gas
_target, // recipient
_value, // ether value
add(_calldata, 32), // inloc
mload(_calldata), // inlen
0x00, // outloc
0x00 // outlen
)
}
return _success;
}
}