Can calculateWTNSBin() / _doCalculateWitness() ensure promise safety?

[yushihang]

circom/code_producers/src/wasm_elements/common/witness_calculator.js

Lines 131 to 169 in c133004

	async _doCalculateWitness(input, sanityCheck) {
	//input is assumed to be a map from signals to arrays of bigints
	this.instance.exports.init((this.sanityCheck || sanityCheck) ? 1 : 0);
	const keys = Object.keys(input);
	var input_counter = 0;
	keys.forEach( (k) => {
	const h = fnvHash(k);
	const hMSB = parseInt(h.slice(0,8), 16);
	const hLSB = parseInt(h.slice(8,16), 16);
	const fArr = flatArray(input[k]);
	let signalSize = this.instance.exports.getInputSignalSize(hMSB, hLSB);
	if (signalSize < 0){
	throw new Error(`Signal ${k} not found\n`);
	}
	if (fArr.length < signalSize) {
	throw new Error(`Not enough values for input signal ${k}\n`);
	}
	if (fArr.length > signalSize) {
	throw new Error(`Too many values for input signal ${k}\n`);
	}
	for (let i=0; i<fArr.length; i++) {
	const arrFr = toArray32(normalize(fArr[i],this.prime),this.n32)
	for (let j=0; j<this.n32; j++) {
	this.instance.exports.writeSharedRWMemory(j,arrFr[this.n32-1-j]);
	}
	try {
	this.instance.exports.setInputSignal(hMSB, hLSB,i);
	input_counter++;
	} catch (err) {
	// console.log(`After adding signal ${i} of ${k}`)
	throw new Error(err);
	}
	}
	});
	if (input_counter < this.instance.exports.getInputSize()) {
	throw new Error(`Not all inputs have been set. Only ${input_counter} out of ${this.instance.exports.getInputSize()}`);
	}
	}

circom/code_producers/src/wasm_elements/common/witness_calculator.js

Lines 208 to 273 in c133004

	async calculateWTNSBin(input, sanityCheck) {
	const buff32 = new Uint32Array(this.witnessSize*this.n32+this.n32+11);
	const buff = new Uint8Array( buff32.buffer);
	await this._doCalculateWitness(input, sanityCheck);
	//"wtns"
	buff[0] = "w".charCodeAt(0)
	buff[1] = "t".charCodeAt(0)
	buff[2] = "n".charCodeAt(0)
	buff[3] = "s".charCodeAt(0)
	//version 2
	buff32[1] = 2;
	//number of sections: 2
	buff32[2] = 2;
	//id section 1
	buff32[3] = 1;
	const n8 = this.n32*4;
	//id section 1 length in 64bytes
	const idSection1length = 8 + n8;
	const idSection1lengthHex = idSection1length.toString(16);
	buff32[4] = parseInt(idSection1lengthHex.slice(0,8), 16);
	buff32[5] = parseInt(idSection1lengthHex.slice(8,16), 16);
	//this.n32
	buff32[6] = n8;
	//prime number
	this.instance.exports.getRawPrime();
	var pos = 7;
	for (let j=0; j<this.n32; j++) {
	buff32[pos+j] = this.instance.exports.readSharedRWMemory(j);
	}
	pos += this.n32;
	// witness size
	buff32[pos] = this.witnessSize;
	pos++;
	//id section 2
	buff32[pos] = 2;
	pos++;
	// section 2 length
	const idSection2length = n8*this.witnessSize;
	const idSection2lengthHex = idSection2length.toString(16);
	buff32[pos] = parseInt(idSection2lengthHex.slice(0,8), 16);
	buff32[pos+1] = parseInt(idSection2lengthHex.slice(8,16), 16);
	pos += 2;
	for (let i=0; i<this.witnessSize; i++) {
	this.instance.exports.getWitness(i);
	for (let j=0; j<this.n32; j++) {
	buff32[pos+j] = this.instance.exports.readSharedRWMemory(j);
	}
	pos += this.n32;
	}
	return buff;
	}

I’m not quite sure if the term ‘promise safety’ is appropriate here, but when we make multiple witness generation requests simultaneously using promises, we might end up with duplicate witness results that don’t match our input values. Is there a way to optimize this issue?

Thank you very much for your time and help.

#299