listing-4.4.js

"use strict";

const fs = require('fs');
const moment = require('moment');

const records = JSON.parse(fs.readFileSync("./data/earthquakes.json", "utf8"));

const bufferSize = 4 + 8 * 5 * records.length;
const buffer = new Buffer(bufferSize);

buffer.writeInt32LE(records.length);

let bufferOffset = 4;

for (let recordIndex = 0; recordIndex < records.length; ++recordIndex) {

    const record = records[recordIndex];
    const time = moment(record.Time).toDate().getTime();
    buffer.writeDoubleLE(time, bufferOffset);
    bufferOffset += 8;

    buffer.writeDoubleLE(record.Latitude, bufferOffset);
    bufferOffset += 8;

    buffer.writeDoubleLE(record.Longitude, bufferOffset);
    bufferOffset += 8;

    buffer.writeDoubleLE(record.Depth_Km, bufferOffset);
    bufferOffset += 8;

    buffer.writeDoubleLE(record.Magnitude, bufferOffset);
    bufferOffset += 8;
}

fs.writeFileSync("./output/earthquakes.bin", buffer);