flashloan-rs 0.2.0

Minimal Multicall3 Flashloan Module
Documentation 
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/// @title Reentrancy Guard
/// @notice SPDX-License-Identifier: MIT
/// @author rayquaza7 <https://github.com/rayquaza7>
/// @notice Gas optimized reentrancy guard for smart contracts.
/// @notice Adapted from Solmate (https://github.com/transmissions11/solmate/blob/main/src/utils/ReentrancyGuard.sol)

#include "./CommonErrors.huff"

// Interface
#define function lock() nonpayable returns ()
#define function unlock() nonpayable returns ()

// Constants
#define constant LOCKED_SLOT = FREE_STORAGE_POINTER()
#define constant _UNLOCKED = 0x01
#define constant _LOCKED = 0x02

/// @title Lock
/// @notice Locks the contract to prevent reentrancy
#define fn LOCK() = takes (0) returns (0) {
    [_LOCKED]                // [0x02]
    dup1                     // [0x02, 0x02]
    [LOCKED_SLOT]            // [locked_slot, 0x02, 0x02]
    sload                    // [locked_slot_value, 0x02, 0x02]
    lt                       // [locked_slot_value < 0x02, 0x02]
    lock jumpi

    // Otherwise revert with re-entrancy
    REENTRANCY(0x00)

    lock:
        [LOCKED_SLOT] sstore
}

/// @title Unlock
/// @notice Unlocks the contract
#define fn UNLOCK() = takes (0) returns (0) {
    [_UNLOCKED] [LOCKED_SLOT] sstore
}

#define macro REENTRANCY_GUARD_MAIN() = takes (0) returns (0) {
    pc calldataload 0xE0 shr

    dup1 __FUNC_SIG(lock) eq lock_jump jumpi
    dup1 __FUNC_SIG(unlock) eq unlock_jump jumpi

    reentrancy_sig_no_match_found jump

    lock_jump:
        LOCK()
    unlock_jump:
        UNLOCK()

    reentrancy_sig_no_match_found:
}

/// @notice Test Unlocking
#define test TEST_LOCK() = takes (0) returns (0) {
    // Make sure our slot is set to the UNLOCKED state
    UNLOCK()

    // Lock
    LOCK()
    [LOCKED_SLOT] sload

    // We expect the locked slot to be set to 2 - the LOCKED state
    0x02 eq succeed jumpi
    0x00 dup1 revert

    succeed:
}

/// @notice Test Unlocking
#define test TEST_UNLOCK() = takes (0) returns (0) {
    // Make sure our slot is set to the LOCKED state
    LOCK()

    // Unlock
    UNLOCK()
    [LOCKED_SLOT] sload

    // We expect the locked slot to be set to 1 - the UNLOCKED state
    0x01 eq succeed jumpi
    0x00 dup1 revert

    succeed:
}