node.js - EOF 后出现错误 : stream. Push()

Question

使用 Node 流

此代码从index.js 读取并写入indexCopy.js - 一种文件副本。目标文件已创建，但在执行过程中抛出异常:

node index.js
events.js:183
      throw er; // Unhandled 'error' event
      ^

Error: stream.push() after EOF
    at readableAddChunk (_stream_readable.js:240:30)
    at MyStream.Readable.push (_stream_readable.js:208:10)
    at ReadStream.f.on (C:\Node\index.js:16:28)
    at emitOne (events.js:116:13)
    at ReadStream.emit (events.js:211:7)
    at addChunk (_stream_readable.js:263:12)
    at readableAddChunk (_stream_readable.js:250:11)
    at ReadStream.Readable.push (_stream_readable.js:208:10)
    at fs.read (fs.js:2042:12)
    at FSReqWrap.wrapper [as oncomplete] (fs.js:658:17)

C:\Node>

这是代码:

var util = require('util');
var stream = require('stream');
var fs = require('fs');


var MyStream = function(){
    stream.Readable.call(this)
}

util.inherits(MyStream,stream.Readable);


MyStream.prototype._read = function(d){

    f = fs.createReadStream("index.js");
    f.on('data',(d)=>{this.push(d)});
    f.on('end',()=>{this.push(null)}); //when file finished need to close stream

}


var f = fs.createWriteStream("indexCopy.js")

var myStream = new MyStream()
myStream.pipe(f);

我尝试在“data”事件中调用 this.push(null)，在这种情况下，甚至不会创建目标文件，并且代码会失败并出现异常。

我意识到使用 Pipe() 函数应该更容易复制文件 - 我只是在试验/学习。我的方法有什么问题吗？

Answer 1

您不希望 _read 方法中包含 f = fs.createReadStream("index.js") 行 -- _read被重复调用，因此您正在创建多个读取流。将其放入您的构造函数中。

function MyStream () {
    stream.Readable.call(this);
    this.source = fs.createReadStream("index.js");
    this.haveBound = false;
}
MyStream.prototype._read = function () {
    if (this.haveBound) return; // Don't bind to events repeatedly
    this.haveBound = true;
    this.source.on("data", d => this.push(d));
    this.source.on("end", () => this.push(null));
};

不过这很尴尬。流意味着管道'ed。