snarkjs/src/bigarray.js

zkSNARKs implementation in JavaScript

/*
    Copyright 2018 0KIMS association.

    This file is part of snarkJS.

    snarkJS is a free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    snarkJS is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
    License for more details.

    You should have received a copy of the GNU General Public License
    along with snarkJS. If not, see <https://www.gnu.org/licenses/>.
*/

const SUBARRAY_SIZE = 0x40000;

const BigArrayHandler = {
    get: function(obj, prop) {
        if (!isNaN(prop)) {
            return obj.getElement(prop);
        } else return obj[prop];
    },
    set: function(obj, prop, value) {
        if (!isNaN(prop)) {
            return obj.setElement(prop, value);
        } else {
            obj[prop] = value;
            return true;
        }
    }
};

class _BigArray {
    constructor (initSize) {
        this.length = initSize || 0;
        this.arr = new Array(SUBARRAY_SIZE);

        for (let i=0; i<initSize; i+=SUBARRAY_SIZE) {
            this.arr[i/SUBARRAY_SIZE] = new Array(Math.min(SUBARRAY_SIZE, initSize - i));
        }
        return this;
    }
    push () {
        for (let i=0; i<arguments.length; i++) {
            this.setElement (this.length, arguments[i]);
        }
    }

    slice (f, t) {
        const arr = new Array(t-f);
        for (let i=f; i< t; i++) arr[i-f] = this.getElement(i);
        return arr;
    }
    getElement(idx) {
        idx = parseInt(idx);
        const idx1 = Math.floor(idx / SUBARRAY_SIZE);
        const idx2 = idx % SUBARRAY_SIZE;
        return this.arr[idx1] ? this.arr[idx1][idx2] : undefined;
    }
    setElement(idx, value) {
        idx = parseInt(idx);
        const idx1 = Math.floor(idx / SUBARRAY_SIZE);
        if (!this.arr[idx1]) {
            this.arr[idx1] = new Array(SUBARRAY_SIZE);
        }
        const idx2 = idx % SUBARRAY_SIZE;
        this.arr[idx1][idx2] = value;
        if (idx >= this.length) this.length = idx+1;
        return true;
    }
    getKeys() {
        const newA = new BigArray();
        for (let i=0; i<this.arr.length; i++) {
            if (this.arr[i]) {
                for (let j=0; j<this.arr[i].length; j++) {
                    if (typeof this.arr[i][j] !== "undefined") {
                        newA.push(i*SUBARRAY_SIZE+j);
                    }
                }
            }
        }
        return newA;
    }
}

class BigArray {
    constructor( initSize ) {
        const obj = new _BigArray(initSize);
        const extObj = new Proxy(obj, BigArrayHandler);
        return extObj;
    }
}

export default BigArray;