Opensubtitle hash algorithm for swift

README.markdown

var osha = OSHashAlgorithm()
var result = osha.hashForPath(fileName)
println(result.fileHash)
println(result.fileSize)

OSHashAlgorithm.swift

// Implemented from Objective-C version http://trac.opensubtitles.org/projects/opensubtitles/wiki/HashSourceCodes#Objective-C
import Foundation

class OSHashAlgorithm: NSObject {
    let chunkSize: Int = 65536;

    struct VideoHash {
        var fileHash: String
        var fileSize: UInt64
    }
    
    func hashForPath (path: String) -> VideoHash {
        var fileHash = VideoHash(fileHash: "", fileSize: 0)
        var fileHandler = NSFileHandle(forReadingAtPath: path)!

        var fileDataBegin: NSData = fileHandler.readDataOfLength(chunkSize)
        fileHandler.seekToEndOfFile()

        var fileSize: UInt64 = fileHandler.offsetInFile
        if (UInt64(chunkSize) > fileSize) {
            return fileHash
        }

        fileHandler.seekToFileOffset(max(0, fileSize - UInt64(chunkSize)))
        var fileDataEnd: NSData = fileHandler.readDataOfLength(chunkSize)

        var hash: UInt64 = fileSize
        
        var data_bytes = UnsafeBufferPointer<UInt64>(
            start: UnsafePointer(fileDataBegin.bytes),
            count: fileDataBegin.length/sizeof(UInt64)
        )
        hash = reduce(data_bytes, hash) { $0 &+ $1 }
        
        data_bytes = UnsafeBufferPointer<UInt64>(
            start: UnsafePointer(fileDataEnd.bytes),
            count: fileDataEnd.length/sizeof(UInt64)
        )
        hash = reduce(data_bytes, hash) { $0 &+ $1 }

        fileHash.fileHash = String(format:"%qx", arguments: [hash])
        fileHash.fileSize = fileSize

        fileHandler.closeFile()
        return fileHash
    }
}