flashloan-rs 0.2.1

Minimal Multicall3 Flashloan Module
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71

/// @title Refunded
/// @notice SPDX-License-Identifier: MIT
/// @author asnared <https://github.com/abigger87>
/// @notice Efficient gas refunds distributed through a modifier
/// @notice Adapted from Zolidity (https://github.com/z0r0z/zolidity/blob/main/src/utils/Refunded.sol)

#include "./Errors.huff"
#include "./ReentrancyGuard.huff"

/// @notice The base cost of refunding
#define constant BASE_COST = 0x6359 // 25433

/// @notice The maximum amount of gas that can be refunded
#define constant GAS_PRICE_MAX = 0x9502F9000 // 4e10

// Refunded custom errors
#define constant MAX_GAS_ERROR = 0x4d41585f47415300000000000000000000000000000000000000000000000000
#define constant MAX_GAS_LENGTH = 0x07

/// @notice Refunds contract calls up to a maximum of 4e10 gas
/// @notice Modified functions over 21k gas benefit most from a refund
#define macro REFUNDED(dest) = takes (0) returns (0) {
    // Get the starting amount of gas
    gas                                 // [gasLeft]

    // Prevent Reentrancy
    LOCK()                              // [gasLeft]

    basefee [GAS_PRICE_MAX] add         // [currMaxGas, gasLeft]
    gasprice gt iszero                  // [!(gasPrice > currMaxGas), gasLeft]
    __Safe_Gas_Refund__j jumpi          // [gasLeft]
        MAX_GAS(0x00)

    __Safe_Gas_Refund__j:

    // The below attempts to mimic `_;` using a jump
    // NOTE: This must jump back to `__Refund_Return_Dest` to complete the refund
    <dest> jump
    __Refund_Return_Dest:

    // Calculate refund amount
    gas swap1 sub                       // [gasUsed]
    [BASE_COST] add                     // [gasUsed + BASE_COST]
    gasprice mul                        // [(gasUsed + BASE_COST) * gasPrice]

    // Refund the gas to origin
    0x00                                // [retOffset, value]
    0x00                                // [argSize, retOffset, value]
    0x00                                // [argOffset, argSize, retOffset, value]
    0x00                                // [retSize, argOffset, argSize, retOffset, value]
    swap4                               // [value, argOffset, argSize, retOffset, retSize]
    origin                              // [to, value, argOffset, argSize, retOffset, retSize]
    gas                                 // [gas, to, value, argOffset, argSize, retOffset, retSize]
    call
    iszero iszero __Refund_Successful__j jumpi
        0x00 dup1 revert

    // The refund was successful!
    __Refund_Successful__j:

    // Finally, unlock the guard
    UNLOCK()
}

/// @notice Reverts with an "MAX_GAS" message if the condition is false
#define macro MAX_GAS(condition) = takes (0) returns (0) {
    [MAX_GAS_ERROR]                 // ["MAX_GAS"]
    [MAX_GAS_LENGTH]                // [7 (length), "MAX_GAS"]
    <condition>                     // [condition, 7 (length), "MAX_GAS"]
    REQUIRE()                       // []
}