downzip/src/zip/ZipUtils.js

Library to enable client-side code to stream potentially large files into a zipped download

import WorkerUtils from '../WorkerUtils'

const Utils = new WorkerUtils('ZipUtils')
const LITTLE_ENDIAN = true

class ZipUtils {
    // Data is an array in the format: [{data: 0x0000, size: 2} or {data: Buffer()}, ...]
    createByteArray = (data) => {
        const size = data.reduce((acc, value) => {
            return acc + (value.size ? value.size : value.data.length)
        }, 0)
        const array = new Uint8Array(size)
        const dataView = new DataView(array.buffer)

        let i = 0
        data.forEach((entry) => {
            if(entry.data.length !== undefined){
                // Entry data is some kind of buffer / array
                array.set(entry.data, i)
                i += entry.data.length
            } else {
                // Entry data is some kind of integer
                switch (entry.size) {
                    case 1:
                        dataView.setInt8(i, parseInt(entry.data))
                        break
                    case 2:
                        dataView.setInt16(i, parseInt(entry.data), LITTLE_ENDIAN)
                        break
                    case 4:
                        dataView.setInt32(i, parseInt(entry.data), LITTLE_ENDIAN)
                        break
                    case 8:
                        dataView.setBigInt64(i, BigInt(entry.data), LITTLE_ENDIAN)
                        break
                    default:
                        const error = `createByteArray: No handler defined for data size ${entry.size} of entry data ${JSON.stringify(entry.data)}`
                        Utils.error(error)
                        throw error
                }
                i += entry.size
            }
        })
        return array
    }

    calculateSize = (files) => {
        const localHeaderSizeBig = (file) => BigInt(30 + file.name.length)
        const dataDescriptorSizeBig = BigInt(12)
        const centralDirectoryHeaderSizeBig = (file) => BigInt(46 + file.name.length)
        const endOfCentralDirectorySizeBig = BigInt(22)
        const zip64ExtraFieldSizeBig = BigInt(32)
        const zip64DataDescriptorSizeBig = BigInt(20)
        const zip64EndOfCentralDirectoryRecordSizeBig = BigInt(56)
        const zip64EndOfCentralDirectoryLocatorSizeBig = BigInt(20)


        let totalSizeBig = files.reduce((acc, val) => {
            return (acc
                + localHeaderSizeBig(val)
                + BigInt(val.size)
                + dataDescriptorSizeBig
                + centralDirectoryHeaderSizeBig(val)
            )
        }, BigInt(0))
        totalSizeBig += endOfCentralDirectorySizeBig

        if(totalSizeBig >= BigInt("0xFFFFFFFF")){
            // We have a ZIP64! Add all the data we missed before
            totalSizeBig = files.reduce((acc, val) => {
                return (acc
                    + zip64ExtraFieldSizeBig
                    + (zip64DataDescriptorSizeBig - dataDescriptorSizeBig)
                    + zip64ExtraFieldSizeBig
                )
            }, totalSizeBig)
            totalSizeBig += zip64EndOfCentralDirectoryRecordSizeBig
            totalSizeBig += zip64EndOfCentralDirectoryLocatorSizeBig
        }

        return totalSizeBig
    }

    getTimeStruct = (date) => {
        return ((((date.getHours() << 6) | date.getMinutes()) << 5) | date.getSeconds() / 2)
    }

    getDateStruct = (date) => {
        return (((((date.getFullYear() - 1980) << 4) | (date.getMonth() + 1)) << 5) | date.getDate())
    }
}

const staticZipUtils = new ZipUtils()
export default staticZipUtils