FEATURE: Allow custom hash functions to Internal libraries of: IMT

[jimjimvalkema]

Description

I changed the internal library of IMT so the user can provide their own hash function with an address that implements their hash function with the interface that is the same as PoseidonT3(T6 for QuinaryIMT). And also their own default zeros for IMT.
I made the libraries that use the internal libraries use the poseidon so they behave like usual.

changes made

1. Remove PoseidonT3, _defaultZero, SNARK_SCALER_LIMT from InternalBinaryIMT.
2. Call PoseidonT3 through an interface instead like this IHasher(hasher).hash([left,right]) (this also saves gas).
3. Add hasher, _defaultZero, SNARK_SCALER_LIMT as added arguments to functions that need them.
4. Rename SNARK_SCALER_LIMT to hasherLimit since it not every hash function is snark based.
5. In BinaryIMT: add the hasher address as a constant, add _defaultZero, and set the hasherLimit

here is a snipet:

in InternalBinaryIMT

library InternalBinaryIMT {
...
  function _insert(
      BinaryIMTData storage self,
      uint256 leaf,
      address hasher,
      uint256 hasherLimit,
      function(uint256) pure returns (uint256) _defaultZero,
  ) internal returns (uint256) {
...
}

Then this is used as follows in BinaryIMT

import {SNARK_SCALAR_FIELD} from "./Constants.sol";
library BinaryIMT {
 // This is poseidonT3 from: https://github.com/chancehudson/poseidon-solidity
 address internal constant hasher = 0x3333333C0A88F9BE4fd23ed0536F9B6c427e3B93;
 
 uint256 internal constant Z_0 = 0;
 ...
 
function _defaultZero(uint256 index) internal pure returns (uint256) {
      if (index == 0) return Z_0;
      ...
      revert WrongDefaultZeroIndex();
  }

  function insert(BinaryIMTData storage self, uint256 leaf) public returns (uint256) {
      return InternalBinaryIMT._insert(self, leaf, hasher, SNARK_SCALAR_FIELD, _defaultZero);
  }
...
}

test changes

I changed the deploy-imt-test task to deploy poseidon with the deterministic proxy so it always deploys to the same address. See in the poseidon-solidity readme

Breaking changes

I changed error that mention SNARK_SCALAR_LIMIT to instead say hasherLimit, since the hash function is now generic. This might break error handling for users that expect the old error.

If an user used the Internal version of the libraries for some reason. Then they do have now pass these new parameters like hasher, hasherLimit and _defaultZeros.

Related Issue(s)

Closes #56

Other information

Calling poseidon with a interface saves from 10k - 100k gas for most functions. But making the libraries generic does add 0~100 gas on average.

Checklist

• I have read and understand the contributor guidelines and code of conduct.
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have run yarn style without getting any errors
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Important

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