如何从函数内部将数据推送到可读流？

Question

我正在努力实现以下目标：

• 函数getPaths读取目录路径并将找到的目录路径推送到readable流中
• readable流在接收路径时，将进入的路径保持管道（流化）到write流中。

代码

const fs = require('fs')
const zlib = require('zlib')
const zip = zlib.createGzip()
const Stream = require('stream')


let wstream = fs.createWriteStream('C:/test/file.txt.gz') 
let readable = new Stream.Readable({
  objectMode: true,
  read(item) {
    this.push(item)
  }
})

readable.pipe(zip).pipe(wstream)
.on('finish', (err) => {
  console.log('done');
})

let walkdir = require('walkdir')
function getPaths(dir) {
  let walker = walkdir.sync(dir, {"max_depth": 0, "track_inodes": true}, (path, stat) => {
    readable.push(path)
    console.log('pushing a path to readable')
  }) 
}
getPaths("C:/")
console.log('getPaths() ran')
readable.push(null)  // indicates the end of the stream

问题

当getPaths函数找到路径并将其推送到流中时，路径没有被压缩并写入文件，只有找到所有路径后，路径才会发生。我知道这可能是由于流程是同步的，但无法弄清楚如何使其工作。

我从日志中看到以下输出：

> // .gz file gets created with size of 0
> // Nothing happens for about 1 minute
> x(184206803) "pushing a path to readable"
> "getPaths() ran"
> // I see the data started being written into the file
> "Done"

更新：

如果我这样异步执行此操作（或使用下面答案中的代码）：

let walker = walkdir(dir, {"max_depth": 0, "track_inodes": true})
  walker.on('path', (path, stat) => {
    readable.push(path)
  }) 
  walker.on('end', (path, stat) => {
    readable.push(null)
  }) 

  ...

  // readable.push(null) 

我得到一个错误（我认为，在将数据推送到其中之后，如果它没有收到预期的数据块，它将引发该特定错误。如果从代码中删除最后一行：readable.push(null) ，然后尝试再次运行代码，它将引发相同的错误）：

TypeError [ERR_INVALID_ARG_TYPE]: The "chunk" argument must be one of type
 string or Buffer. Received type number

Answer 1

您的代码非常好，效果很好。您只需要删除this.push(item)并将read功能设置为空即可。

这是一个有效的代码段

const fs = require('fs')
const zlib = require('zlib')
const zip = zlib.createGzip()
const Stream = require('stream')


let wstream = fs.createWriteStream('C:/test/file.txt.gz') 
let readable = new Stream.Readable({
  objectMode: true,
  read() { }
})

readable.pipe(zip).pipe(wstream)
.on('finish', (err) => {
  console.log('done');
})

let walkdir = require('walkdir')
function getPaths(dir) {
  let walker = walkdir(dir, {"max_depth": 0, "track_inodes": true})
  walker.on('path', (path, stat) => {
    readable.push(path)
  }) 
  walker.on('end', (path, stat) => {
    readable.push(null)
  }) 
}
getPaths("C:/")
console.log('getPaths() ran')

顺便说一句，正确的参数名称是read(size)。它代表bytes to read

的数量

编辑 不需要可读流。您可以直接写zip。

const fs = require('fs');
const zlib = require('zlib');
const zip = zlib.createGzip();
const wstream = fs.createWriteStream('C:/test/file.txt.gz');

zip.pipe(wstream)
.on('finish', (err) => {
  console.log('done');
})

let walkdir = require('walkdir')
function getPaths(dir) {
  let walker = walkdir(dir, {"max_depth": 0, "track_inodes": true})
  walker.on('path', (path, stat) => {
    zip.write(path);
  })
  walker.on('end', (path, stat) => {
    zip.end();
  })
}
getPaths("C:/")
console.log('getPaths() ran')