witness_calculator.js

module.exports = async function builder(code, options) {

    options = options || {};

    let wasmModule;
    try {
	wasmModule = await WebAssembly.compile(code);
    }  catch (err) {
	console.log(err);
	console.log("\nTry to run circom --c in order to generate c++ code instead\n");
	throw new Error(err);
    }

    let wc;

    let errStr = "";
    let msgStr = "";
    
    const instance = await WebAssembly.instantiate(wasmModule, {
        runtime: {
            exceptionHandler : function(code) {
		let err;
                if (code == 1) {
                    err = "Signal not found.\n";
                } else if (code == 2) {
                    err = "Too many signals set.\n";
                } else if (code == 3) {
                    err = "Signal already set.\n";
		} else if (code == 4) {
                    err = "Assert Failed.\n";
		} else if (code == 5) {
                    err = "Not enough memory.\n";
		} else if (code == 6) {
                    err = "Input signal array access exceeds the size.\n";
		} else {
		    err = "Unknown error.\n";
                }
                throw new Error(err + errStr);
            },
	    printErrorMessage : function() {
		errStr += getMessage() + "\n";
                // console.error(getMessage());
	    },
	    writeBufferMessage : function() {
			const msg = getMessage();
			// Any calls to `log()` will always end with a `\n`, so that's when we print and reset
			if (msg === "\n") {
				console.log(msgStr);
				msgStr = "";
			} else {
				// If we've buffered other content, put a space in between the items
				if (msgStr !== "") {
					msgStr += " "
				}
				// Then append the message to the message we are creating
				msgStr += msg;
			}
	    },
	    showSharedRWMemory : function() {
		printSharedRWMemory ();
            }

        }
    });

    const sanityCheck =
        options
//        options &&
//        (
//            options.sanityCheck ||
//            options.logGetSignal ||
//            options.logSetSignal ||
//            options.logStartComponent ||
//            options.logFinishComponent
//        );

    
    wc = new WitnessCalculator(instance, sanityCheck);
    return wc;

    function getMessage() {
        var message = "";
	var c = instance.exports.getMessageChar();
        while ( c != 0 ) {
	    message += String.fromCharCode(c);
	    c = instance.exports.getMessageChar();
	}
        return message;
    }
	
    function printSharedRWMemory () {
	const shared_rw_memory_size = instance.exports.getFieldNumLen32();
	const arr = new Uint32Array(shared_rw_memory_size);
	for (let j=0; j<shared_rw_memory_size; j++) {
	    arr[shared_rw_memory_size-1-j] = instance.exports.readSharedRWMemory(j);
	}

	// If we've buffered other content, put a space in between the items
	if (msgStr !== "") {
		msgStr += " "
	}
	// Then append the value to the message we are creating
	msgStr += (fromArray32(arr).toString());
	}

};

class WitnessCalculator {
    constructor(instance, sanityCheck) {
        this.instance = instance;

	this.version = this.instance.exports.getVersion();
        this.n32 = this.instance.exports.getFieldNumLen32();

        this.instance.exports.getRawPrime();
        const arr = new Uint32Array(this.n32);
        for (let i=0; i<this.n32; i++) {
            arr[this.n32-1-i] = this.instance.exports.readSharedRWMemory(i);
        }
        this.prime = fromArray32(arr);

        this.witnessSize = this.instance.exports.getWitnessSize();

        this.sanityCheck = sanityCheck;
    }
    
    circom_version() {
	return this.instance.exports.getVersion();
    }

    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()}`);
	}
    }

    async calculateWitness(input, sanityCheck) {

        const w = [];

        await this._doCalculateWitness(input, sanityCheck);

        for (let i=0; i<this.witnessSize; i++) {
            this.instance.exports.getWitness(i);
	    const arr = new Uint32Array(this.n32);
            for (let j=0; j<this.n32; j++) {
            arr[this.n32-1-j] = this.instance.exports.readSharedRWMemory(j);
            }
            w.push(fromArray32(arr));
        }

        return w;
    }
    

    async calculateBinWitness(input, sanityCheck) {

        const buff32 = new Uint32Array(this.witnessSize*this.n32);
	const buff = new  Uint8Array( buff32.buffer);
        await this._doCalculateWitness(input, sanityCheck);

        for (let i=0; i<this.witnessSize; i++) {
            this.instance.exports.getWitness(i);
	    const pos = i*this.n32;
            for (let j=0; j<this.n32; j++) {
		buff32[pos+j] = this.instance.exports.readSharedRWMemory(j);
            }
        }

	return buff;
    }
    

    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;
    }

}


function toArray32(rem,size) {
    const res = []; //new Uint32Array(size); //has no unshift
    const radix = BigInt(0x100000000);
    while (rem) {
        res.unshift( Number(rem % radix));
        rem = rem / radix;
    }
    if (size) {
	var i = size - res.length;
	while (i>0) {
	    res.unshift(0);
	    i--;
	}
    }
    return res;
}

function fromArray32(arr) { //returns a BigInt
    var res = BigInt(0);
    const radix = BigInt(0x100000000);
    for (let i = 0; i<arr.length; i++) {
        res = res*radix + BigInt(arr[i]);
    }
    return res;
}

function flatArray(a) {
    var res = [];
    fillArray(res, a);
    return res;

    function fillArray(res, a) {
        if (Array.isArray(a)) {
            for (let i=0; i<a.length; i++) {
                fillArray(res, a[i]);
            }
        } else {
            res.push(a);
        }
    }
}

function normalize(n, prime) {
    let res = BigInt(n) % prime
    if (res < 0) res += prime
    return res
}

function fnvHash(str) {
    const uint64_max = BigInt(2) ** BigInt(64);
    let hash = BigInt("0xCBF29CE484222325");
    for (var i = 0; i < str.length; i++) {
	hash ^= BigInt(str[i].charCodeAt());
	hash *= BigInt(0x100000001B3);
	hash %= uint64_max;
    }
    let shash = hash.toString(16);
    let n = 16 - shash.length;
    shash = '0'.repeat(n).concat(shash);
    return shash;
}