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channel.js
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channel.js
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const SimpleMessageChannel = require('simple-message-channels')
const { EventEmitter } = require('events')
const assert = require('nanoassert')
// quick util
const bind = (o, f) => (...args) => f.call(o, ...args)
/**
* The `Channel` class represents a channel for a running process that
* leverages IPC channels falling back to `stdin` and `stdout` streams to
* send and receive messages on.
* @class
* @extends EventEmitter
*/
class Channel extends EventEmitter {
/**
* `Channel` class constructor.
* @param {Process} child
* @param {?(Object)} opts
*/
constructor(child, opts) {
super()
this.setMaxListeners(0)
if (!opts || 'object' !== typeof opts) {
opts = {}
}
assert(child.opened || global.process === child,
'Expecting process to be a `nanoprocess` or `global.process`.')
this.ondata = bind(this, this.ondata)
this.onerror = bind(this, this.onerror)
this.onmessage = bind(this, this.onmessage)
this.onmissing = bind(this, this.onmissing)
this.process = child
this.destroyed = false
this.channels = new SimpleMessageChannel({
context: this,
types: opts.types,
onmessage: this.onmessage,
onmissing: this.onmissing,
})
if (this.process.channel) {
const onmessage = (message) => this.ondata(Buffer.from(message))
this.process.on('message', onmessage)
this.once('close', () => {
this.process.removeListener('message', onmessage)
})
} else if (this.process === global.process && this.process.stdin) {
this.process.stdin.on('data', this.ondata)
} else if (this.process.stdout) {
this.process.stdout.on('data', this.ondata)
}
this.once('close', () => {
// istanbul ignore next
if (this.process) {
if (this.process.stdout) {
this.process.stdout.removeListener('data', this.ondata)
}
if (this.process.stdin) {
this.process.stdin.removeListener('data', this.ondata)
}
this.process.removeListener('error', this.onerror)
}
})
if (this.process !== global.process) {
this.process.on('error', this.onerror)
}
}
/**
* Instance level error handler to emit `err` when called.
* @protected
* @param {?(Error)} err
* @emits error
*/
onerror(err) {
this.emit('error', err)
}
/**
* Instance level data handler to receive sent messages into
* the message channel.
* @protected
* @param {Buffer} data
* @emits data
*/
ondata(data) {
if (this.channels.recv(data)) {
this.emit('data', data)
}
}
/**
* Instance level handler for missing/unhandled bytes in message channel.
* @protected
* @param {Number} bytes
* @emits missing
*/
onmissing(bytes) {
this.emit('missing', bytes)
}
/**
* Instance level handler for incoming message channel messages.
* @protected
* @param {Number} channel
* @param {Number} type
* @param {Buffer} message
* @emits message
*/
onmessage(channel, type, message) {
this.emit('message', message, channel, type)
}
/**
* Sends a `buffer` to the process through the message channel.
* @param {Buffer} buffer
* @param {?(Object)} opts
* @param {?(Object)} opts.id
* @param {?(Object)} opts.type
* @return {Boolean}
*/
send(buffer, opts) {
// istanbul ignore next
if (!opts || 'object' !== typeof opts) {
opts = {}
}
buffer = Buffer.from(buffer) // ensure buffer
const message = this.channels.send(opts.id || 0, opts.type || 0, buffer)
if (this.process.channel && 'function' === typeof this.process.send) {
return this.process.send(message)
} else if (this.process === global.process) {
return this.process.stdout.write(message)
} else if (this.process.stdin) {
return this.process.stdin.write(message)
} else {
return false
}
}
/**
* Closes channel calling `callback(err)` upon success or error.
* @param {?(Function)} callback
* @emits close
*/
close(callback) {
if (this.destroyed) {
// istanbul ignore next
if ('function' === typeof callback) {
process.nextTick(callback, new Error('Channel closed.'))
}
return
}
if ('function' === typeof callback) {
this.once('close', () => callback(null))
}
this.destroy()
}
/**
* Close process message channel and cleans up all resources.
* @param {?(Error)} err
* @emits close
*/
destroy(err) {
this.channels.destroy(err)
this.destroyed = true
process.nextTick(() => this.emit('close'))
if (err) {
this.onerror(err)
}
}
}
/**
* Module exports.
*/
module.exports = {
Channel
}