计算流的sha1哈希，但仍使用该流？

Question

I have a function which will write/consume a stream like so.

consume(stream, function(e,d){});

But I would like to calculate the SHA1 hash of the stream right before calling this function. I know you can get the hash like so:

var crypto = require('crypto');
var hash = crypto.createHash('sha1');

stream.on('data', function (data) {
    hash.update(data, 'utf8')
})

stream.on('end', function () {
    hash.digest('hex');c
})

But every time I try to call the consume function the stream is empty. How can I do this?

Answer 1

You could pipe stream to both sha1Calc and consume :

stream.pipe(sha1Calc);
stream.pipe(consume);