How to convert IO to Slice(UInt8)?

Help & Support
1

I’m trying to use Kemal’s send_file to send a public file from S3. I’m loading the S3 file and it comes back as IO, though send_file requires a Slice(UInt8).

get "/my.pdf" do |env|
  HTTP::Client.get("https://xxxxxxxxx.s3.amazonaws.com/downloads/my.pdf") do |response|
    send_file env, response.body_io, "application/pdf"
  end
end

410 | send_file env, response.body_io, “application/pdf”
^--------
Error: no overload matches ‘send_file’ with types HTTP::Server::Context, IO+, String

Overloads are:

  • send_file(env : HTTP::Server::Context, path : String, mime_type : String | ::Nil = nil, *, filename : String | ::Nil = nil, disposition : String | ::Nil = nil)
  • send_file(env : HTTP::Server::Context, data : Slice(UInt8), mime_type : String | ::Nil = nil, *, filename : String | ::Nil = nil, disposition : String | ::Nil = nil)

Is there a way to convert the IO to a Slice(UInt8)? Or, is there a better way to do this? My goal is to stream the PDF to the browser client and not force an automatic download.

Incidentally, I had this working locally by just sending the file from src/public/downloads/my.pdf. However, that doesn’t work when deployed to Heroku, so I had to switch to hosting the file on S3.

2

I.e. you want the response body to consist of the contents of the pdf correct? If so you could prob just do like:

get "/my.pdf" do |env|
  HTTP::Client.get("https://xxxxxxxxx.s3.amazonaws.com/downloads/my.pdf") do |response|
    IO.copy response.body_io, env.response
  end
end

send_file is for file downloads, e.g. via Content-Disposition - HTTP | MDN.

1 Like
3

That works! I had to manually set the content-type too, since the default was text/html.

get "/my.pdf" do |env|
  env.response.headers["Content-Type"] = "application/pdf"
  HTTP::Client.get("https://xxxxxxxxx.s3.amazonaws.com/downloads/my.pdf") do |response|
    IO.copy response.body_io, env.response
  end
end

Thanks!

1 Like