snarkjs/src/misc.js

const Blake2b = require("blake2b-wasm");

const _revTable = [];
for (let i=0; i<256; i++) {
    _revTable[i] = _revSlow(i, 8);
}

function _revSlow(idx, bits) {
    let res =0;
    let a = idx;
    for (let i=0; i<bits; i++) {
        res <<= 1;
        res = res | (a &1);
        a >>=1;
    }
    return res;
}

function bitReverse(idx, bits) {
    return (
        _revTable[idx >>> 24] |
        (_revTable[(idx >>> 16) & 0xFF] << 8) |
        (_revTable[(idx >>> 8) & 0xFF] << 16) |
        (_revTable[idx & 0xFF] << 24)
    ) >>> (32-bits);
}


function log2( V )
{
    return( ( ( V & 0xFFFF0000 ) !== 0 ? ( V &= 0xFFFF0000, 16 ) : 0 ) | ( ( V & 0xFF00FF00 ) !== 0 ? ( V &= 0xFF00FF00, 8 ) : 0 ) | ( ( V & 0xF0F0F0F0 ) !== 0 ? ( V &= 0xF0F0F0F0, 4 ) : 0 ) | ( ( V & 0xCCCCCCCC ) !== 0 ? ( V &= 0xCCCCCCCC, 2 ) : 0 ) | ( ( V & 0xAAAAAAAA ) !== 0 ) );
}


function formatHash(b) {
    const a = new DataView(b.buffer);
    let S = "";
    for (let i=0; i<4; i++) {
        if (i>0) S += "\n";
        S += "\t\t";
        for (let j=0; j<4; j++) {
            if (j>0) S += " ";
            S += a.getUint32(i*16+j*4).toString(16).padStart(8, "0");
        }
    }
    return S;
}

function hashIsEqual(h1, h2) {
    if (h1.byteLength != h2.byteLength) return false;
    var dv1 = new Int8Array(h1);
    var dv2 = new Int8Array(h2);
    for (var i = 0 ; i != h1.byteLength ; i++)
    {
        if (dv1[i] != dv2[i]) return false;
    }
    return true;
}

function cloneHasher(h) {
    const ph = h.getPartialHash();
    const res = Blake2b(64);
    res.setPartialHash(ph);
    return res;
}

async function sameRatio(curve, g1s, g1sx, g2s, g2sx) {
    if (curve.G1.isZero(g1s)) return false;
    if (curve.G1.isZero(g1sx)) return false;
    if (curve.G2.isZero(g2s)) return false;
    if (curve.G2.isZero(g2sx)) return false;
    // return curve.F12.eq(curve.pairing(g1s, g2sx), curve.pairing(g1sx, g2s));
    const res = await curve.pairingEq(g1s, g2sx, curve.G1.neg(g1sx), g2s);
    return res;
}

module.exports.bitReverse = bitReverse;
module.exports.log2 = log2;
module.exports.formatHash = formatHash;
module.exports.hashIsEqual = hashIsEqual;
module.exports.cloneHasher = cloneHasher;
module.exports.sameRatio = sameRatio;