如何在 node.js 流中等待一些固定数量的字节? [英] How to wait for some fixed amount of bytes in a node.js stream?

问题描述

我有一个 node.js 可读流，我想读取前 20 个字节并对其进行一些处理，为处理后的数据设置回调或接收承诺.

I have a node.js Readable stream and I want to read the first 20 bytes and do some processing with them, setting a callback for the processed data or receiving a promise.

节点或 NPM 中的其他地方是否有任何内置函数可以做到这一点?

Is there any function built in node or elsewhere in NPM to do that?

例如，它可能看起来像这样:

For example, it could look something like this:

var stream = getStreamSomehow();
readPromise(stream, 20)
  .then(function(data) {
    console.log("I have read 20 bytes! %s", data.toString());
  });

推荐答案

使用 node core 执行此操作的典型方法是调用 stream.read(20)，检查返回值是否为 null 如果是这样，请在再次尝试 stream.read(20) 之前侦听 readable 事件.否则，如果返回值不为 null，则它是一个 20 字节的缓冲区，其中包含来自流的数据.

The typical way to do this with node core is by calling stream.read(20), checking if the return value is null and if so, listen for the readable event before trying to stream.read(20) again. Otherwise if the return is not null, it's a 20-byte Buffer containing data from the stream.

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