Create a router middleware for compression of data sent to requestor about kitura

[billabt]

I was planning on building a small framework for compression based on zlib. Basically pass in an NSData and get a compressed NSData and vice versa.

[dfirsht]

Just providing this link as reference to the team: https://en.wikipedia.org/wiki/HTTP_compression

[rfdickerson]

I agree we should probably use the "de facto" standard of zlib for this task. However, it would add another system-level library to our dependencies. (I realize that most systems use zlib, but we will need to install zlib1g-dev" for the development headers. The other option is for me to implement a pure Swift version of LZ77 and deflate.

[billabt]

Actually just found this. Nice favorable license, just needs a little code cleanup for Swift 3.0. https://github.com/1024jp/NSData-GZIP/blob/master/README.md

[rfdickerson]

I created a zLib modulemap Package.

I was able to import zLib and compile the following code, however it seems to always returns -5 and prints "Buffer error" after the compress2 command. Any ideas, @billabt ?

typealias Byte = UInt8

let size: Int = 100000

var simpleData = [Byte](repeating: 3, count: size)

var dataCompressed = [Byte](repeating: 6, count: size)

simpleData[3] = 2
simpleData[4] = 1

var sizeDataCompressed: uLongf = 0

let result = compress2( &dataCompressed, &sizeDataCompressed,
                        &simpleData, uLong(size), Z_BEST_SPEED )

switch result {
    case Z_OK:
        print("Everything's OK")
    case Z_BUF_ERROR:
        print("Buffer error")
    default:
        print("Some other error")
}

BTW, I tried another approach of doing a import Compression and using Apple's compression API. However, the build fails because Compression requires Mac OS X 10.11 (which I have), but the Open Source toolchain seems to report 10.9.

[rfdickerson]

We could use that existing library, but I'm somewhat reluctant to bring in yet another dependency for something that's pretty easy to do on our own. Plus, we would have to change it quite a bit to get it to work on Swift 3 (and Linux).

[shmuelk]

Reviewed looks great.