evm/src/opcodes/iszero.ts

An ethereum virtual machine (EVM) bytecode decompiler

import EVM from '../classes/evm.class';
import Opcode from '../interfaces/opcode.interface';
import * as BigNumber from '../../node_modules/big-integer';
import { LT } from './lt';
import { GT } from './gt';
import stringify from '../utils/stringify';

export class ISZERO {
    readonly name: string;
    readonly type?: string;
    readonly wrapped: boolean;
    readonly item: any;

    constructor(item: any) {
        this.name = 'ISZERO';
        this.wrapped = true;
        this.item = item;
    }

    toString() {
        return stringify(this.item) + ' == 0';
    }
}

export default (opcode: Opcode, state: EVM): void => {
    const item = state.stack.pop();
    if (BigNumber.isInstance(item)) {
        state.stack.push(BigNumber(item.isZero() === true ? 1 : 0));
    } else if (item.name === 'LT') {
        if (item.equal) {
            state.stack.push(new GT(item.left, item.right));
        } else {
            state.stack.push(new GT(item.left, item.right, true));
        }
    } else if (item.name === 'GT') {
        if (item.equal) {
            state.stack.push(new LT(item.left, item.right));
        } else {
            state.stack.push(new LT(item.left, item.right, true));
        }
    } else if (item instanceof ISZERO) {
        state.stack.push(item.item);
    } else {
        state.stack.push(new ISZERO(item));
    }
    /* == -> != */
    /* != -> == */
};