Snap.Util.GZip

Runs a Snap web handler with compression if available.

If the client has indicated support for gzip or deflate in its Accept-Encoding header, and the Content-Type in the response is one of the following types:

• application/x-javascript

• application/json

• text/css

• text/html

• text/javascript

• text/plain

• text/xml

• application/x-font-truetype

Then the given handler's output stream will be compressed, Content-Encoding will be set in the output headers, and the Content-Length will be cleared if it was set. (We can't process the stream in O(1) space if the length is known beforehand.)

The wrapped handler will be run to completion, and then the Response that's contained within the Snap monad state will be passed to finishWith to prevent further processing.

Example:

ghci> :set -XOverloadedStrings
ghci> import qualified Data.Map as M
ghci> import qualified Snap.Test as T
ghci> let r = T.get "/" M.empty >> T.addHeader "Accept-Encoding" "gzip,deflate"
ghci> let h = modifyResponse (Snap.Core.setContentType "text/plain") >> Snap.Core.writeBS "some text"
ghci> T.runHandler r h
HTTP/1.1 200 OK
content-type: text/plain
server: Snap/test
date: Fri, 08 Aug 2014 15:40:45 GMT

some text
ghci> T.runHandler r (withCompression h)
HTTP/1.1 200 OK
content-type: text/plain
vary: Accept-Encoding
content-encoding: gzip
server: Snap/test
date: Fri, 08 Aug 2014 15:40:10 GMT

The same as withCompression, with control over which MIME types to compress.

Turn off compression by setting "Content-Encoding: identity" in the response headers. withCompression is a no-op when a content-encoding is already set.

Thrown when the 'Accept-Encoding' request header has invalid format.