AmadiMichael
commented
1 year ago This looks nice and well executed ! Idk if this is that useful though and that it should be part of
huffmate, curious to see other's opinions.
currently there's no safe library for working with lower integer types in huff, constants can help...
Example: an extra macro in the safeMath library called SAFE_ADD_TYPE(), the same as SAFE_ADD() but would take a third stack input which is the max value of the intended type to cast the result into
/// a rewrite of safe add with max type
/// @notice Adds two numbers and reverts on overflow
#define macro SAFE_ADD_TYPE() = takes (3) returns (1) {
// input stack // [num1, num2, typeMax]
dup2 // [num2, num1, num2, typeMax]
add // [result, num2, typeMax]
dup1 // [result, result, num2, typeMax]
swap2 // [num2, result, result, typeMax]
gt // [is_overflow, result, typeMax]
iszero // [is_not_overflow, result, typeMax]
is_not_overflow jumpi // [result, typeMax]
[ARITHMETIC_OVERFLOW] PANIC()
is_not_overflow: // [result, typeMax]
swap1 // [typeMax, result]
dup2 // [result, typeMax, result]
gt // [is_type_overflow, result]
iszero // [is_not_type_overflow, result]
is_not_type_overflow jumpi // [result]
[ARITHMETIC_OVERFLOW] PANIC()
is_not_type_overflow:
}This can help in safe calculation of values of lower types like uint128 etc. After the initial overflow check (which accounts for only 256 bits) there's a check to ensure it doesn't overflow from the type you intend to keep it within.
someone can call this with
#include "utils/Constants.huff"
...
#define macro ADD_UINT128() = takes(0) returns(1) {
[__UINT128_MAX] // [Uint128Max]
0x01 // [0x01, uint128Max]
0x02 // [0x02, 0x01, uint128Max]
SAFE_ADD_TYPE() // [result]
}Returns a result in uint128
This will revert if trying to add numbers where either of them is higher than the max of result's type.
By importing utils/constants.huff. Cleaner code and helpers around other dynamic constants common in solidity and other higher level evm language.
The constant wrapper is an example of how it can be used and also has full test coverage.