Michael Snoyman wrote:
It's a good question. The advantage of a Builder is that we get cheap concatenation, so you can create a stream of smaller ByteStrings and then Warp will automatically concatenate them together into larger chunks. There are a few claims against this:
Q1. Shouldn't it be at the user's discretion to use Builders internally and then create a stream of ByteStrings? A1. That would be less efficient, as we wouldn't get cheap concatenation with the response headers.
Q2. Isn't it really inefficient to convert from ByteString to Builder, and then right back to ByteString? A2. No. If the ByteStrings are small, then they will be copied into a larger buffer, which should be a performance gain overall (less system calls). If they are already large, then blaze-builder uses an InsertByteString instruction to avoid copying.
Q3. Doesn't this prevent us from creating comet-style servers, since data will be cached? A3. You can force blaze-builder to output a ByteString before it is an optimal size by sending a flush command.
If these answers make sense, I'll add them to the WAI docs.
+1 Cheers, Erik -- ---------------------------------------------------------------------- Erik de Castro Lopo http://www.mega-nerd.com/