如何在Node.js中一次将一个可读流传输到两个可写流中?

问题描述

目标是:

1. 创建文件读取流.
2. 将其放入gzip(zlib.createGzip())

3. 然后将zlib输出的读取流通过管道传输到:

1. Create a file read stream.
2. Pipe it to gzip (zlib.createGzip())

3. Then pipe the read stream of zlib output to:

1)HTTP response对象

2)和可写文件流，以保存压缩后的输出.

2) and writable file stream to save the gzipped output.

现在我可以降低到3.1:

Now I can do down to 3.1:

var gzip = zlib.createGzip(),
    sourceFileStream = fs.createReadStream(sourceFilePath),
    targetFileStream = fs.createWriteStream(targetFilePath);

response.setHeader('Content-Encoding', 'gzip');

sourceFileStream.pipe(gzip).pipe(response);

...效果很好，但我还需要将压缩后的数据保存到文件中，这样我就不必每次都进行zip压缩并能够直接将压缩后的数据流式传输为回应.

... which works fine, but I need to also save the gzipped data to a file so that I don't need to regzip every time and be able to directly stream the gzipped data as a response.

那么，如何在Node中一次将一个可读流传送到两个可写流中?

sourceFileStream.pipe(gzip).pipe(response).pipe(targetFileStream);是否可以在Node 0.8.x中工作?

Would sourceFileStream.pipe(gzip).pipe(response).pipe(targetFileStream); work in Node 0.8.x?

推荐答案

我发现zlib返回了一个可读流，该流随后可以通过管道传递到其他多个流中.因此，我执行以下操作来解决上述问题:

I found that zlib returns a readable stream which can be later piped into multiple other streams. So I did the following to solve the above problem:

var sourceFileStream = fs.createReadStream(sourceFile);
// Even though we could chain like
// sourceFileStream.pipe(zlib.createGzip()).pipe(response);
// we need a stream with a gzipped data to pipe to two
// other streams.
var gzip = sourceFileStream.pipe(zlib.createGzip());

// This will pipe the gzipped data to response object
// and automatically close the response object.
gzip.pipe(response);

// Then I can pipe the gzipped data to a file.
gzip.pipe(fs.createWriteStream(targetFilePath));

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