stream.pipeline()方法是一种模块方法,通过链接传递错误的流并精确清理并在完成管道后提供回调函数,将其用于管道。
用法:
stream.pipeline(...streams, callback)
参数:该方法接受上面提到和下面描述的两个参数。
- …streams:这是两个或多个要通过管道传输的流。
- callback:管道完全完成后会调用此函数,如果管道未完成,则会显示“错误”。
返回值:它返回清除函数。
以下示例说明了Node.js中stream.pipeline()方法的用法:
范例1:
// Node.js program to demonstrate the
// stream.pipeline() method
// Includng fs and zlib module
var fs = require('fs');
const zlib = require('zlib');
// Constructing finished from stream
const { pipeline } = require('stream');
// Constructing promisify from
// util
const { promisify } = require('util');
// Defining pipelineAsync method
const pipelineAsync = promisify(pipeline);
// Constructing readable stream
const readable = fs.createReadStream("input.text");
// Contructing writable stream
var writable = fs.createWriteStream("output.text");
// Creating transform stream
const transform = zlib.createGzip();
// Async function
(async function run() {
try{
// pipelining three streams
await pipelineAsync(
readable,
transform,
writable
);
console.log("pipeline accomplished.");
}
// Shows error
catch(err) {
console.error('pipeline failed with error:', err);
}
})();
输出:
Promise { } pipeline accomplished.
范例2:
// Node.js program to demonstrate the
// stream.pipeline() method
// Includng fs and zlib module
var fs = require('fs');
const zlib = require('zlib');
// Constructing finished from stream
const { pipeline } = require('stream');
// Constructing promisify from
// util
const { promisify } = require('util');
// Defining pipelineAsync method
const pipelineAsync = promisify(pipeline);
// Constructing readable stream
const readable = fs.createReadStream("input.text");
// Contructing writable stream
var writable = fs.createWriteStream("output.text");
// Creating transform stream
const transform = zlib.createGzip();
// Async function
(async function run() {
try{
// pipelining three streams
await pipelineAsync(
readable,
writable,
transform
);
console.log("pipeline accomplished.");
}
// Shows error
catch(err) {
console.error('pipeline failed with error:', err);
}
})();
输出:在此,配管时流的顺序不正确,因此会发生错误。
Promise { } pipeline failed with error:Error [ERR_STREAM_CANNOT_PIPE]:Cannot pipe, not readable at WriteStream.Writable.pipe (_stream_writable.js:243:24) at pipe (internal/streams/pipeline.js:57:15) at Array.reduce () at pipeline (internal/streams/pipeline.js:88:18) at Promise (internal/util.js:274:30) at new Promise () at pipeline (internal/util.js:273:12) at run (/home/runner/ThirstyTimelyKey/index.js:33:11) at /home/runner/ThirstyTimelyKey/index.js:45:5 at Script.runInContext (vm.js:133:20)
参考: https://nodejs.org/api/stream.html#stream_stream_pipeline_streams_callback。
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注:本文由纯净天空筛选整理自nidhi1352singh大神的英文原创作品 Node.js | Stream.pipeline() Method。非经特殊声明,原始代码版权归原作者所有,本译文未经允许或授权,请勿转载或复制。