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stream.js
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/**
* @module FS.Stream
*/
import { Readable, Writable } from '../stream.js'
import { AbortError } from '../errors.js'
import { Buffer } from '../buffer.js'
export const DEFAULT_STREAM_HIGH_WATER_MARK = 64 * 1024
/**
* A `Readable` stream for a `FileHandle`.
*/
export class ReadStream extends Readable {
/**
* `ReadStream` class constructor
* @private
*/
constructor (options) {
super(options)
if (options?.signal?.aborted) {
throw new AbortError(options.signal)
}
if (typeof options?.highWaterMark !== 'number') {
this._readableState.highWaterMark = this.constructor.highWaterMark
}
this.end = typeof options?.end === 'number' ? options.end : Infinity
this.start = typeof options?.start === 'number' ? options.start : 0
this.handle = null
this.signal = options?.signal
this.timeout = options?.timeout || undefined
this.bytesRead = 0
this.shouldEmitClose = options?.emitClose !== false
if (this.start < 0) {
this.start = 0
}
if (this.end < 0) {
this.end = Infinity
}
if (options?.handle) {
this.setHandle(options.handle)
}
}
/**
* Sets file handle for the ReadStream.
* @param {FileHandle} handle
*/
setHandle (handle) {
setHandle(this, handle)
}
/**
* The max buffer size for the ReadStream.
*/
get highWaterMark () {
return this._readableState.highWaterMark
}
/**
* Relative or absolute path of the underlying `FileHandle`.
*/
get path () {
return this.handle?.path || null
}
/**
* `true` if the stream is in a pending state.
*/
get pending () {
return this.handle?.opened !== true
}
/**
* Handles `shouldEmitClose` setting from `options.emitClose` in constructor.
* @protected
*/
emit (event, ...args) {
if (event === 'close' && this.shouldEmitClose === false) {
return false
}
return super.emit(event, ...args)
}
async _open (callback) {
const { signal, handle, timeout } = this
if (!handle) {
return callback(new Error('Handle not set in ReadStream'))
}
if (signal?.aborted) {
return callback(new AbortError(signal))
}
if (handle?.opened) {
return callback(null)
}
this.once('ready', () => callback(null))
// open if not opening already
if (!handle.opening) {
try {
await handle.open({ signal, timeout })
} catch (err) {
return callback(err)
}
}
}
async _read (callback) {
const { signal, handle, timeout } = this
if (!handle || !handle.opened) {
return callback(new Error('File handle not opened'))
}
if (this.signal?.aborted) {
return callback(new AbortError(this.signal))
}
const position = Math.max(0, this.start) + this.bytesRead
const buffer = Buffer.alloc(this.highWaterMark)
const length = Math.max(0, this.end) < Infinity
? Math.min(this.end - position, buffer.length)
: buffer.length
let result = null
try {
result = await handle.read(buffer, 0, length, position, {
timeout,
signal
})
} catch (err) {
return callback(err)
}
if (typeof result.bytesRead === 'number' && result.bytesRead > 0) {
this.bytesRead += result.bytesRead
this.push(buffer.slice(0, result.bytesRead))
if (this.bytesRead >= this.end) {
this.push(null)
}
} else {
this.push(null)
}
callback(null)
}
}
/**
* A `Writable` stream for a `FileHandle`.
*/
export class WriteStream extends Writable {
/**
* `WriteStream` class constructor
* @private
*/
constructor (options) {
super(options)
if (typeof options?.highWaterMark !== 'number') {
this._writableState.highWaterMark = this.constructor.highWaterMark
}
this.start = typeof options?.start === 'number' ? options.start : 0
this.handle = null
this.signal = options?.signal
this.timeout = options?.timeout || undefined
this.bytesWritten = 0
this.shouldEmitClose = options?.emitClose !== false
if (this.start < 0) {
this.start = 0
}
if (options?.handle) {
this.setHandle(options.handle)
}
}
/**
* Sets file handle for the WriteStream.
* @param {FileHandle} handle
*/
setHandle (handle) {
setHandle(this, handle)
}
/**
* The max buffer size for the Writetream.
*/
get highWaterMark () {
return this._writableState.highWaterMark
}
/**
* Relative or absolute path of the underlying `FileHandle`.
*/
get path () {
return this.handle?.path || null
}
/**
* `true` if the stream is in a pending state.
*/
get pending () {
return this.handle?.opened !== true
}
async _open (callback) {
const { signal, handle, timeout } = this
if (!handle) {
return callback(new Error('Handle not set in WriteStream'))
}
if (signal?.aborted) {
return callback(new AbortError(signal))
}
if (handle?.opened) {
return callback(null)
}
this.once('ready', () => callback(null))
// open if not opening already
if (!handle.opening) {
try {
await handle.open({ signal, timeout })
} catch (err) {
return callback(err)
}
}
}
/**
* Handles `shouldEmitClose` setting from `options.emitClose` in constructor.
* @protected
*/
emit (event, ...args) {
if (event === 'close' && this.shouldEmitClose === false) {
return false
}
return super.emit(event, ...args)
}
async _write (buffer, callback) {
const { signal, handle, timeout } = this
if (!handle || !handle.opened) {
return callback(new Error('File handle not opened'))
}
const position = this.start + this.bytesWritten
let result = null
if (!buffer.length) {
return callback(null)
}
try {
result = await handle.write(buffer, 0, buffer.length, position, {
timeout,
signal
})
} catch (err) {
return callback(err)
}
if (typeof result.bytesWritten === 'number' && result.bytesWritten > 0) {
this.bytesWritten += result.bytesWritten
if (result.bytesWritten !== buffer.length) {
return await this._write(buffer.slice(result.bytesWritten), callback)
}
}
callback(null)
}
}
function setHandle (stream, handle) {
if (!handle) return
if (stream.handle) {
throw new Error('Stream handle already set.')
}
stream.handle = handle
if (handle.opened) {
queueMicrotask(() => stream.emit('ready'))
} else {
handle.once('open', (fd) => {
if (stream.handle === handle) {
stream.emit('open', fd)
stream.emit('ready')
}
})
}
stream.once('ready', () => {
handle.once('close', () => {
stream.emit('close')
})
})
}
ReadStream.highWaterMark = DEFAULT_STREAM_HIGH_WATER_MARK
WriteStream.highWaterMark = DEFAULT_STREAM_HIGH_WATER_MARK
export const FileReadStream = ReadStream
export const FileWriteStream = WriteStream