streamsaver
Version:
StreamSaver writes stream to the filesystem directly - asynchronous
199 lines (180 loc) • 6.38 kB
JavaScript
class Crc32 {
constructor () {
this.crc = -1
}
append (data) {
var crc = this.crc | 0; var table = this.table
for (var offset = 0, len = data.length | 0; offset < len; offset++) {
crc = (crc >>> 8) ^ table[(crc ^ data[offset]) & 0xFF]
}
this.crc = crc
}
get () {
return ~this.crc
}
}
Crc32.prototype.table = (() => {
var i; var j; var t; var table = []
for (i = 0; i < 256; i++) {
t = i
for (j = 0; j < 8; j++) {
t = (t & 1)
? (t >>> 1) ^ 0xEDB88320
: t >>> 1
}
table[i] = t
}
return table
})()
const getDataHelper = byteLength => {
var uint8 = new Uint8Array(byteLength)
return {
array: uint8,
view: new DataView(uint8.buffer)
}
}
const pump = zipObj => zipObj.reader.read().then(chunk => {
if (chunk.done) return zipObj.writeFooter()
const outputData = chunk.value
zipObj.crc.append(outputData)
zipObj.uncompressedLength += outputData.length
zipObj.compressedLength += outputData.length
zipObj.ctrl.enqueue(outputData)
})
/**
* [createWriter description]
* @param {Object} underlyingSource [description]
* @return {Boolean} [description]
*/
function createWriter (underlyingSource) {
const files = Object.create(null)
const filenames = []
const encoder = new TextEncoder()
let offset = 0
let activeZipIndex = 0
let ctrl
let activeZipObject, closed
function next () {
activeZipIndex++
activeZipObject = files[filenames[activeZipIndex]]
if (activeZipObject) processNextChunk()
else if (closed) closeZip()
}
var zipWriter = {
enqueue (fileLike) {
if (closed) throw new TypeError('Cannot enqueue a chunk into a readable stream that is closed or has been requested to be closed')
let name = fileLike.name.trim()
const date = new Date(typeof fileLike.lastModified === 'undefined' ? Date.now() : fileLike.lastModified)
if (fileLike.directory && !name.endsWith('/')) name += '/'
if (files[name]) throw new Error('File already exists.')
const nameBuf = encoder.encode(name)
filenames.push(name)
const zipObject = files[name] = {
level: 0,
ctrl,
directory: !!fileLike.directory,
nameBuf,
comment: encoder.encode(fileLike.comment || ''),
compressedLength: 0,
uncompressedLength: 0,
writeHeader () {
var header = getDataHelper(26)
var data = getDataHelper(30 + nameBuf.length)
zipObject.offset = offset
zipObject.header = header
if (zipObject.level !== 0 && !zipObject.directory) {
header.view.setUint16(4, 0x0800)
}
header.view.setUint32(0, 0x14000808)
header.view.setUint16(6, (((date.getHours() << 6) | date.getMinutes()) << 5) | date.getSeconds() / 2, true)
header.view.setUint16(8, ((((date.getFullYear() - 1980) << 4) | (date.getMonth() + 1)) << 5) | date.getDate(), true)
header.view.setUint16(22, nameBuf.length, true)
data.view.setUint32(0, 0x504b0304)
data.array.set(header.array, 4)
data.array.set(nameBuf, 30)
offset += data.array.length
ctrl.enqueue(data.array)
},
writeFooter () {
var footer = getDataHelper(16)
footer.view.setUint32(0, 0x504b0708)
if (zipObject.crc) {
zipObject.header.view.setUint32(10, zipObject.crc.get(), true)
zipObject.header.view.setUint32(14, zipObject.compressedLength, true)
zipObject.header.view.setUint32(18, zipObject.uncompressedLength, true)
footer.view.setUint32(4, zipObject.crc.get(), true)
footer.view.setUint32(8, zipObject.compressedLength, true)
footer.view.setUint32(12, zipObject.uncompressedLength, true)
}
ctrl.enqueue(footer.array)
offset += zipObject.compressedLength + 16
next()
},
fileLike
}
if (!activeZipObject) {
activeZipObject = zipObject
processNextChunk()
}
},
close () {
if (closed) throw new TypeError('Cannot close a readable stream that has already been requested to be closed')
if (!activeZipObject) closeZip()
closed = true
}
}
function closeZip () {
var length = 0
var index = 0
var indexFilename, file
for (indexFilename = 0; indexFilename < filenames.length; indexFilename++) {
file = files[filenames[indexFilename]]
length += 46 + file.nameBuf.length + file.comment.length
}
const data = getDataHelper(length + 22)
for (indexFilename = 0; indexFilename < filenames.length; indexFilename++) {
file = files[filenames[indexFilename]]
data.view.setUint32(index, 0x504b0102)
data.view.setUint16(index + 4, 0x1400)
data.array.set(file.header.array, index + 6)
data.view.setUint16(index + 32, file.comment.length, true)
if (file.directory) {
data.view.setUint8(index + 38, 0x10)
}
data.view.setUint32(index + 42, file.offset, true)
data.array.set(file.nameBuf, index + 46)
data.array.set(file.comment, index + 46 + file.nameBuf.length)
index += 46 + file.nameBuf.length + file.comment.length
}
data.view.setUint32(index, 0x504b0506)
data.view.setUint16(index + 8, filenames.length, true)
data.view.setUint16(index + 10, filenames.length, true)
data.view.setUint32(index + 12, length, true)
data.view.setUint32(index + 16, offset, true)
ctrl.enqueue(data.array)
ctrl.close()
}
function processNextChunk () {
if (!activeZipObject) return
if (activeZipObject.directory) return activeZipObject.writeFooter(activeZipObject.writeHeader())
if (activeZipObject.reader) return pump(activeZipObject)
if (activeZipObject.fileLike.stream) {
activeZipObject.crc = new Crc32()
activeZipObject.reader = activeZipObject.fileLike.stream().getReader()
activeZipObject.writeHeader()
} else next()
}
return new ReadableStream({
start: c => {
ctrl = c
underlyingSource.start && Promise.resolve(underlyingSource.start(zipWriter))
},
pull () {
return processNextChunk() || (
underlyingSource.pull &&
Promise.resolve(underlyingSource.pull(zipWriter))
)
}
})
}
window.ZIP = createWriter