Save a stream to file in vibe.d

Question

I would like to save a vibe.d stream such as HTTPClientResponse.bodyReader (of type InterfaceProxy!InputStream), but also other potential vibe.d streams to a file, how do I best do that in a memory efficient way without copying all data to RAM?

Answer 1

In general for downloading files using a HTTP client you can use the vibe.inet.urltransfer package which offers a download convenience function which performs a HTTP request, handles redirects and stores the final output to a file.

download(url, file);

However if you want to take a raw input stream (for example when not handling redirects) you can use vibe.core.file : openFile to open/create a file as file stream and then write to that.

To then write to the file stream you've got two options:

1. Either you directly call file.write(otherStream)
2. Otherwise you can use vibe.core.stream : pipe

Directly calling write on the FileStream object is what is being used inside the vibe.d urltransfer module and is also recommended for files as it will read directly from the stream into the write buffer instead of using an additional temporary buffer which pipe would use.

Sample:

// createTrunc creates a file if it doesn't exist and clears it if it does exist
// You might want to use readWrite or append instead.
auto fil = openFile(filename, FileMode.createTrunc);
scope(exit) fil.close();
fil.write(inputStream);