如何编写 Node.js 模块来处理传入的管道流 [英] How do I write a Node.js module to handle an incoming piped stream

问题描述

我正在尝试编写一个节点模块，它接受传入的管道二进制(或 base-64 编码)流，但坦率地说，我什至不知道从哪里开始.我在 Node 文档中看不到任何关于处理传入流的示例；我只看到使用它们的示例?

比如说我希望能够做到这一点:

var asset = new ProjectAsset('myFile', __dirname + '/image.jpg')var stream = fs.createReadStream(__dirname + '/image.jpg', { encoding: 'base64' }).pipe(asset)stream.on('完成', function() {完毕()})

我已经让 ProjectAsset 看起来像这样，但我不知道下一步该去哪里:

'使用严格'var stream = require('stream'),util = require('util')var ProjectAsset = function() {var self = thisObject.defineProperty(self, 'binaryData', {可配置:真，可写:真})stream.Stream.call(self)self.on('pipe', function(src) {//它发生在这里吗?我如何设置 self.binaryData?})回归自我}util.inherits(ProjectAsset, stream.Stream)module.exports = ProjectAssetmodule.exports.DEFAULT_FILE_NAME = '文件'

解决方案

可以从 stream.Stream 继承并使其工作，但是基于 文档 我建议从 stream.Writable.管道到 stream.Writable 你需要有 _write(chunk, encoding, done) 定义为处理管道.下面是一个例子:

var asset = new ProjectAsset('myFile', __dirname + '/image.jpg')var stream = fs.createReadStream(__dirname + '/image.jpg', { encoding: 'base64' }).pipe(asset)stream.on('完成', function() {控制台日志(资产.二进制数据)；})

项目资产

'使用严格'var stream = require('stream'),util = require('util')var ProjectAsset = function() {var self = this自我数据self.binaryData = [];stream.Writable.call(self)self._write = 函数(块，编码，完成){//可以根据需要处理这些数据self.binaryData.push(chunk.toString())//处理完数据后调用完毕()}self.on('完成', function() {self.data = Buffer.concat(self.binaryData)})回归自我}util.inherits(ProjectAsset, stream.Writable)module.exports = ProjectAssetmodule.exports.DEFAULT_FILE_NAME = '文件'

如果您还希望从 stream 中读取数据，请查看从 stream.Duplex 并且还包括 _read(size) 方法.

还有 简化构造函数 api 如果您正在做一些更简单的事情.>

I'm trying to write a node module that accepts an incoming piped binary (or base-64-encoded) stream, but frankly I don't even know where to start. I can't see any examples in the Node docs about handling incoming streams; I only see examples on consuming them?

Say for example I want to be able to do this:

var asset = new ProjectAsset('myFile', __dirname + '/image.jpg')
var stream = fs.createReadStream(__dirname + '/image.jpg', { encoding: 'base64' }).pipe(asset)
stream.on('finish', function() {
    done()
})

I've gotten ProjectAsset looking like this, but I'm at a loss of where to go next:

'use strict'

var stream = require('stream'),
    util = require('util')

var ProjectAsset = function() {
    var self = this

    Object.defineProperty(self, 'binaryData', {
        configurable: true,
        writable: true
    })

    stream.Stream.call(self)

    self.on('pipe', function(src) {
        // does it happen here? how do I set self.binaryData?
    })

    return self
}

util.inherits(ProjectAsset, stream.Stream)

module.exports = ProjectAsset
module.exports.DEFAULT_FILE_NAME = 'file'

解决方案

It is possible to inherit from stream.Stream and make it work, however based on what's available in the documentation I would suggest inheriting from stream.Writable. Piping into a stream.Writable you'll need to have _write(chunk, encoding, done) defined to handle the piping. Here is an example:

var asset = new ProjectAsset('myFile', __dirname + '/image.jpg')
var stream = fs.createReadStream(__dirname + '/image.jpg', { encoding: 'base64' }).pipe(asset)
stream.on('finish', function() {
    console.log(asset.binaryData);
})

Project Asset

'use strict'

var stream = require('stream'),
    util = require('util')

var ProjectAsset = function() {
    var self = this

    self.data
    self.binaryData = [];

    stream.Writable.call(self)

    self._write = function(chunk, encoding, done) {
        // Can handle this data however you want
        self.binaryData.push(chunk.toString())
        // Call after processing data
        done()
    }
    self.on('finish', function() {
        self.data = Buffer.concat(self.binaryData)
    })

    return self
}

util.inherits(ProjectAsset, stream.Writable)

module.exports = ProjectAsset
module.exports.DEFAULT_FILE_NAME = 'file'

If you're looking to also read from the stream, take a look at inheriting from stream.Duplex and also including the _read(size) method.

There's also the simplified constructors api if you're doing something simpler.

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