pass fixes size array arg in solidity poseidon implementation

src/poseidon_gencontract.js

@@ -4,6 +4,7 @@
 
 const Contract = require("./evmasm");
 const { unstringifyBigInts } = require("snarkjs");
+const Web3Utils = require("web3-utils");
 
 const { C:K, M } = unstringifyBigInts(require("./poseidon_constants.json"));
 
@@ -99,7 +100,7 @@ function createCode(nInputs) {
     C.push(0);
     C.calldataload();
     C.div();
-    C.push("0xc4420fb4"); // poseidon(uint256[])
+    C.push(Web3Utils.keccak256(`poseidon(uint256[${nInputs}])`).slice(0, 10)); // poseidon(uint256[])
     C.eq();
     C.jmpi("start");
     C.invalid();
@@ -112,11 +113,10 @@ function createCode(nInputs) {
 
     // Load t values from the call data.
     // The function has a single array param param
-    // [Selector (4)] [Pointer (32)][Length (32)] [data1 (32)] ....
-    // We ignore the pointer and the length and just load t values to the state
-    // (Stack positions 0-{t-1}) If the array is shorter, we just set zeros.
+    // [Selector (4)] [item1 (32)] [item2 (32)] ....
+    // Stack positions 0-nInputs.
     for (let i=0; i<t; i++) {
-        C.push(0x44+(0x20*(t-1-i)));
+        C.push(0x04+(0x20*(nInputs-i)));
         C.calldataload();
     }
 
@@ -155,18 +155,21 @@ function createCode(nInputs) {
     return C.createTxData();
 }
 
-module.exports.abi = [
+function generateABI(nInputs) {
+  return [
     {
         "constant": true,
         "inputs": [
             {
+                "internalType": `uint256[${nInputs}]`,
                 "name": "input",
-                "type": "uint256[]"
+                "type": `uint256[${nInputs}]`
             }
         ],
         "name": "poseidon",
         "outputs": [
             {
+                "internalType": "uint256",
                 "name": "",
                 "type": "uint256"
             }
@@ -175,8 +178,10 @@ module.exports.abi = [
         "stateMutability": "pure",
         "type": "function"
     }
-];
+  ]
+};
 
+module.exports.generateABI = generateABI;
 module.exports.createCode = createCode;
 
 

test/poseidoncontract.js

@@ -14,6 +14,8 @@ describe("Poseidon Smart contract test", function () {
     let poseidon4;
     let accounts;
     this.timeout(100000);
+    let C2
+    let C4
 
     before(async () => {
         web3 = new Web3(ganache.provider(), null, { transactionConfirmationBlocks: 1 });
@@ -21,15 +23,17 @@ describe("Poseidon Smart contract test", function () {
     });
 
     it("Should deploy the contract", async () => {
-        const C = new web3.eth.Contract(poseidonGenContract.abi);
         
-        poseidon2 = await C.deploy({
+        C2 = new web3.eth.Contract(poseidonGenContract.generateABI(2));
+        poseidon2 = await C2.deploy({
             data: poseidonGenContract.createCode(2)
         }).send({
             gas: 5000000,
             from: accounts[0]
         });
-        poseidon4 = await C.deploy({
+        
+        C4 = new web3.eth.Contract(poseidonGenContract.generateABI(4));
+        poseidon4 = await C4.deploy({
             data: poseidonGenContract.createCode(4)
         }).send({
             gas: 5000000,
@@ -37,8 +41,7 @@ describe("Poseidon Smart contract test", function () {
         });
     });
 
-    it("Shold calculate the poseidon correctly for 2 inputs", async () => {
-
+    it("Should calculate the poseidon correctly for 2 inputs", async () => {
         const res = await poseidon2.methods.poseidon([1, 2]).call();
 
         // console.log("Cir: " + bigInt(res.toString(16)).toString(16));
@@ -48,7 +51,7 @@ describe("Poseidon Smart contract test", function () {
 
         assert.equal(res.toString(), res2.toString());
     });
-    it("Shold calculate the poseidon correctly for 4 inputs", async () => {
+    it("Should calculate the poseidon correctly for 4 inputs", async () => {
 
         const res = await poseidon4.methods.poseidon([1, 2, 3, 4]).call();