'use strict'
const {
kState,
kError,
kResult,
kAborted,
kLastProgressEventFired
} = require('./symbols')
const { ProgressEvent } = require('./progressevent')
const { getEncoding } = require('./encoding')
const { DOMException } = require('../fetch/constants')
const { serializeAMimeType, parseMIMEType } = require('../fetch/dataURL')
const { types } = require('util')
const { StringDecoder } = require('string_decoder')
const { btoa } = require('buffer')
/** @type {PropertyDescriptor} */
const staticPropertyDescriptors = {
enumerable: true,
writable: false,
configurable: false
}
/**
* @see https://w3c.github.io/FileAPI/#readOperation
* @param {import('./filereader').FileReader} fr
* @param {import('buffer').Blob} blob
* @param {string} type
* @param {string?} encodingName
*/
function readOperation (fr, blob, type, encodingName) {
// 1. If fr’s state is "loading", throw an InvalidStateError
// DOMException.
if (fr[kState] === 'loading') {
throw new DOMException('Invalid state', 'InvalidStateError')
}
// 2. Set fr’s state to "loading".
fr[kState] = 'loading'
// 3. Set fr’s result to null.
fr[kResult] = null
// 4. Set fr’s error to null.
fr[kError] = null
// 5. Let stream be the result of calling get stream on blob.
/** @type {import('stream/web').ReadableStream} */
const stream = blob.stream()
// 6. Let reader be the result of getting a reader from stream.
const reader = stream.getReader()
// 7. Let bytes be an empty byte sequence.
/** @type {Uint8Array[]} */
const bytes = []
// 8. Let chunkPromise be the result of reading a chunk from
// stream with reader.
let chunkPromise = reader.read()
// 9. Let isFirstChunk be true.
let isFirstChunk = true
// 10. In parallel, while true:
// Note: "In parallel" just means non-blocking
// Note 2: readOperation itself cannot be async as double
// reading the body would then reject the promise, instead
// of throwing an error.
;(async () => {
while (!fr[kAborted]) {
// 1. Wait for chunkPromise to be fulfilled or rejected.
try {
const { done, value } = await chunkPromise
// 2. If chunkPromise is fulfilled, and isFirstChunk is
// true, queue a task to fire a progress event called
// loadstart at fr.
if (isFirstChunk && !fr[kAborted]) {
queueMicrotask(() => {
fireAProgressEvent('loadstart', fr)
})
}
// 3. Set isFirstChunk to false.
isFirstChunk = false
// 4. If chunkPromise is fulfilled with an object whose
// done property is false and whose value property is
// a Uint8Array object, run these steps:
if (!done && types.isUint8Array(value)) {
// 1. Let bs be the byte sequence represented by the
// Uint8Array object.
// 2. Append bs to bytes.
bytes.push(value)
// 3. If roughly 50ms have passed since these steps
// were last invoked, queue a task to fire a
// progress event called progress at fr.
if (
(
fr[kLastProgressEventFired] === undefined ||
Date.now() - fr[kLastProgressEventFired] >= 50
) &&
!fr[kAborted]
) {
fr[kLastProgressEventFired] = Date.now()
queueMicrotask(() => {
fireAProgressEvent('progress', fr)
})
}
// 4. Set chunkPromise to the result of reading a
// chunk from stream with reader.
chunkPromise = reader.read()
} else if (done) {
// 5. Otherwise, if chunkPromise is fulfilled with an
// object whose done property is true, queue a task
// to run the following steps and abort this algorithm:
queueMicrotask(() => {
// 1. Set fr’s state to "done".
fr[kState] = 'done'
// 2. Let result be the result of package data given
// bytes, type, blob’s type, and encodingName.
try {
const result = packageData(bytes, type, blob.type, encodingName)
// 4. Else:
if (fr[kAborted]) {
return
}
// 1. Set fr’s result to result.
fr[kResult] = result
// 2. Fire a progress event called load at the fr.
fireAProgressEvent('load', fr)
} catch (error) {
// 3. If package data threw an exception error:
// 1. Set fr’s error to error.
fr[kError] = error
// 2. Fire a progress event called error at fr.
fireAProgressEvent('error', fr)
}
// 5. If fr’s state is not "loading", fire a progress
// event called loadend at the fr.
if (fr[kState] !== 'loading') {
fireAProgressEvent('loadend', fr)
}
})
break
}
} catch (error) {
if (fr[kAborted]) {
return
}
// 6. Otherwise, if chunkPromise is rejected with an
// error error, queue a task to run the following
// steps and abort this algorithm:
queueMicrotask(() => {
// 1. Set fr’s state to "done".
fr[kState] = 'done'
// 2. Set fr’s error to error.
fr[kError] = error
// 3. Fire a progress event called error at fr.
fireAProgressEvent('error', fr)
// 4. If fr’s state is not "loading", fire a progress
// event called loadend at fr.
if (fr[kState] !== 'loading') {
fireAProgressEvent('loadend', fr)
}
})
break
}
}
})()
}
/**
* @see https://w3c.github.io/FileAPI/#fire-a-progress-event
* @see https://dom.spec.whatwg.org/#concept-event-fire
* @param {string} e The name of the event
* @param {import('./filereader').FileReader} reader
*/
function fireAProgressEvent (e, reader) {
// The progress event e does not bubble. e.bubbles must be false
// The progress event e is NOT cancelable. e.cancelable must be false
const event = new ProgressEvent(e, {
bubbles: false,
cancelable: false
})
reader.dispatchEvent(event)
}
/**
* @see https://w3c.github.io/FileAPI/#blob-package-data
* @param {Uint8Array[]} bytes
* @param {string} type
* @param {string?} mimeType
* @param {string?} encodingName
*/
function packageData (bytes, type, mimeType, encodingName) {
// 1. A Blob has an associated package data algorithm, given
// bytes, a type, a optional mimeType, and a optional
// encodingName, which switches on type and runs the
// associated steps:
switch (type) {
case 'DataURL': {
// 1. Return bytes as a DataURL [RFC2397] subject to
// the considerations below:
// * Use mimeType as part of the Data URL if it is
// available in keeping with the Data URL
// specification [RFC2397].
// * If mimeType is not available return a Data URL
// without a media-type. [RFC2397].
// https://datatracker.ietf.org/doc/html/rfc2397#section-3
// dataurl := "data:" [ mediatype ] [ ";base64" ] "," data
// mediatype := [ type "/" subtype ] *( ";" parameter )
// data := *urlchar
// parameter := attribute "=" value
let dataURL = 'data:'
const parsed = parseMIMEType(mimeType || 'application/octet-stream')
if (parsed !== 'failure') {
dataURL += serializeAMimeType(parsed)
}
dataURL += ';base64,'
const decoder = new StringDecoder('latin1')
for (const chunk of bytes) {
dataURL += btoa(decoder.write(chunk))
}
dataURL += btoa(decoder.end())
return dataURL
}
case 'Text': {
// 1. Let encoding be failure
let encoding = 'failure'
// 2. If the encodingName is present, set encoding to the
// result of getting an encoding from encodingName.
if (encodingName) {
encoding = getEncoding(encodingName)
}
// 3. If encoding is failure, and mimeType is present:
if (encoding === 'failure' && mimeType) {
// 1. Let type be the result of parse a MIME type
// given mimeType.
const type = parseMIMEType(mimeType)
// 2. If type is not failure, set encoding to the result
// of getting an encoding from type’s parameters["charset"].
if (type !== 'failure') {
encoding = getEncoding(type.parameters.get('charset'))
}
}
// 4. If encoding is failure, then set encoding to UTF-8.
if (encoding === 'failure') {
encoding = 'UTF-8'
}
// 5. Decode bytes using fallback encoding encoding, and
// return the result.
return decode(bytes, encoding)
}
case 'ArrayBuffer': {
// Return a new ArrayBuffer whose contents are bytes.
const sequence = combineByteSequences(bytes)
return sequence.buffer
}
case 'BinaryString': {
// Return bytes as a binary string, in which every byte
// is represented by a code unit of equal value [0..255].
let binaryString = ''
const decoder = new StringDecoder('latin1')
for (const chunk of bytes) {
binaryString += decoder.write(chunk)
}
binaryString += decoder.end()
return binaryString
}
}
}
/**
* @see https://encoding.spec.whatwg.org/#decode
* @param {Uint8Array[]} ioQueue
* @param {string} encoding
*/
function decode (ioQueue, encoding) {
const bytes = combineByteSequences(ioQueue)
// 1. Let BOMEncoding be the result of BOM sniffing ioQueue.
const BOMEncoding = BOMSniffing(bytes)
let slice = 0
// 2. If BOMEncoding is non-null:
if (BOMEncoding !== null) {
// 1. Set encoding to BOMEncoding.
encoding = BOMEncoding
// 2. Read three bytes from ioQueue, if BOMEncoding is
// UTF-8; otherwise read two bytes.
// (Do nothing with those bytes.)
slice = BOMEncoding === 'UTF-8' ? 3 : 2
}
// 3. Process a queue with an instance of encoding’s
// decoder, ioQueue, output, and "replacement".
// 4. Return output.
const sliced = bytes.slice(slice)
return new TextDecoder(encoding).decode(sliced)
}
/**
* @see https://encoding.spec.whatwg.org/#bom-sniff
* @param {Uint8Array} ioQueue
*/
function BOMSniffing (ioQueue) {
// 1. Let BOM be the result of peeking 3 bytes from ioQueue,
// converted to a byte sequence.
const [a, b, c] = ioQueue
// 2. For each of the rows in the table below, starting with
// the first one and going down, if BOM starts with the
// bytes given in the first column, then return the
// encoding given in the cell in the second column of that
// row. Otherwise, return null.
if (a === 0xEF && b === 0xBB && c === 0xBF) {
return 'UTF-8'
} else if (a === 0xFE && b === 0xFF) {
return 'UTF-16BE'
} else if (a === 0xFF && b === 0xFE) {
return 'UTF-16LE'
}
return null
}
/**
* @param {Uint8Array[]} sequences
*/
function combineByteSequences (sequences) {
const size = sequences.reduce((a, b) => {
return a + b.byteLength
}, 0)
let offset = 0
return sequences.reduce((a, b) => {
a.set(b, offset)
offset += b.byteLength
return a
}, new Uint8Array(size))
}
module.exports = {
staticPropertyDescriptors,
readOperation,
fireAProgressEvent
}
