获取流的内容长度 [英] get a stream's content-length

问题描述

在我的node.js应用程序，我使用的是克（一实：graphicsmagick包装）和的aws2js（亚马逊CLI包装）。问题是，亚马逊需要知道内容长度，这样我可以把S3流。

我上传图片到我的应用程序，读取该文件通过创建一个流：

  VAR FILESTREAM = fs.createReadStream（file.path）
 

我通过这个文件来克，调整其大小，然后告诉它流的文件。然后，我希望把他们流AWS：

  GM（FILESTREAM，some.png）。
    识别（{bufferStream：真}，功能（ERR，资讯）{
        this.stream（PNG功能（ERR，标准输出，标准错误）{
            如果（ERR）{执行console.log（ERR）; CB（ERR）;回报;}

            aws.S3.putStream（路径，标准输出，大众阅读，{内容长度：?????，内涵式：图像/ PNG'}，功能（错了，结果）{
            .....
            }
        }）;
    }）;
}）;
 

的问题是，亚马逊需要知道该内容 - 长度（其不是库）放流。 AWS不支持分块的数据流。

有谁知道我怎么能确定一个流的内容长度？或者将唯一的解决办法是tmp下写入到磁盘上，读取该文件作为流，然后把它放到亚马逊的临时文件的内容长度？

解决方案

 克（FILESTREAM）.filesize（{bufferStream：真}，功能（错误，文件大小）{
  this.stream（功能（错误，标准输出，标准错误）{
    aws.S3.putStream（路径，标准输出，大众阅读，{内容长度：文件大小，内涵式：图像/ PNG'}，功能（错误结果）{
      // .....
    }）;
  }）;
}）;
 

In my node.js app, I'm using gm (a graphicsmagick wrapper) and aws2js (amazon cli wrapper). The problem is that Amazon needs to know the content-length so that I can put the stream on S3.

I'm uploading an image to my app, read that file by creating a stream:

var fileStream=fs.createReadStream(file.path)

I pass that file to gm, resize it and then tell it to stream that file. I then want to put that stream to aws:

gm( fileStream, "some.png" ).                               
    identify({bufferStream: true}, function(err, info) {
        this.stream("png", function (err, stdout, stderr) {
            if (err){console.log(err);cb(err);return;}

            aws.S3.putStream(path, stdout, 'public-read', {'content-length': ?????, 'content-type': 'image/png'}, function (err, result) {
            .....       
            }
        });
    });
});

The problem is that Amazon needs to know the content-length (its not the library) to put the stream. AWS doesn't support chunked streams.

Does anyone know how I could determine the content-length of a stream? Or would the only solution be to tmp write it to the disk, read the file as a stream and then put it to amazon with the content-length of the temp file?

解决方案

gm( fileStream ).filesize({bufferStream: true}, function (error, filesize) {
  this.stream(function (error, stdout, stderr) {
    aws.S3.putStream(path, stdout, 'public-read', {'content-length': filesize, 'content-type': 'image/png'}, function (error, result) {
      // .....       
    });
  });
});

这篇关于获取流的内容长度的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！