Add hashCommitment to public API (#51)

* export hashCommitment

* add basic test

* update tests

Author: acolytec3

src.ts/index.ts

@@ -32,12 +32,14 @@ export const loadVerkleCrypto = async (): Promise<VerkleCrypto> => {
 
   const zeroCommitment = zeroCommitmentBase()
 
+  const hashCommitment = (commitment: Uint8Array) => verkleFFI.hashCommitment(commitment)
   return {
     getTreeKey,
     getTreeKeyHash,
     updateCommitment,
     zeroCommitment,
-    verifyExecutionWitnessPreState
+    verifyExecutionWitnessPreState,
+    hashCommitment
   }
 }
 
@@ -52,6 +54,7 @@ export interface VerkleCrypto {
   ) => Commitment
   zeroCommitment: Uint8Array
   verifyExecutionWitnessPreState: (prestateRoot: string, execution_witness_json: string) => boolean
+  hashCommitment: (commitment: Uint8Array) => Uint8Array
 }
 
 // This is a 32 byte serialized field element

src.ts/tests/ffi.spec.ts

@@ -1,5 +1,5 @@
 import { bytesToHex, randomBytes } from '@ethereumjs/util'
-import { beforeAll, describe, expect, test } from 'vitest'
+import { beforeAll, describe, expect, test, assert } from 'vitest'
 
 import { VerkleCrypto, loadVerkleCrypto } from '../index.js'
 import { verifyExecutionWitnessPreState, Context as VerkleFFI } from '../wasm/rust_verkle_wasm.js'
@@ -181,6 +181,16 @@ describe('bindings', () => {
     const updatedCommitmentHex = bytesToHex(updatedCommitment)
 
     expect(updatedCommitmentHex).toBe(expectedHex)
+
+    // Create a brand new commitment (i.e. an empty array) and update it
+    const zeros = new Uint8Array(32)
+    const zc = verkleCrypto.zeroCommitment
+    const index = 0
+    const value = Uint8Array.from(zeros)
+    value[0] = 1
+    const newCommitment = verkleCrypto.updateCommitment(zc, index, zeros, value)
+    const expectedCommitment = ffi.scalarMulIndex(value, 0)
+    assert.deepEqual(newCommitment, expectedCommitment)
   })
 
   test('verifyExecutionProof: block with a few txs', () => {