iOSアプリでWeb上の音楽ファイルをHTTPストリーミング再生しながらキャッシュにも入れるライブラリ、Choristerとその実装 ref: http://qiita.com/katryo/items/c152ea9de11edbdbc0e4

AudioLoader.swift

    private func respondWithDataForRequest(dataRequest: AVAssetResourceLoadingDataRequest) -> Bool {
        var startOffset = dataRequest.requestedOffset
        if dataRequest.currentOffset != 0 {
            startOffset = dataRequest.currentOffset
        }
        let songDataLength = Int64(self.songData.length)
        if songDataLength < startOffset {
            return false
        }
        let unreadBytes = songDataLength - startOffset
        let numberOfBytesToRespondWith: Int64
        if Int64(dataRequest.requestedLength) > unreadBytes {
            numberOfBytesToRespondWith = unreadBytes
        } else {
            numberOfBytesToRespondWith = Int64(dataRequest.requestedLength)
        }
        dataRequest.respondWithData(self.songData.subdataWithRange(NSMakeRange(Int(startOffset), Int(numberOfBytesToRespondWith))))
        let endOffset = startOffset + dataRequest.requestedLength
        let didRespondFully = songDataLength >= endOffset
        return didRespondFully
    }

audioLoader.swift

    func connectionDidFinishLoading(connection: NSURLConnection) {
        self.processPendingRequests()
        let url = getActualURL(connection.currentRequest.URL!)
        let urlString = url.absoluteString
        if (audioCache.objectForKey(urlString) != nil) {
            return
        }
        audioCache[urlString] = songData
    }

example.swift

    private func loadAsset(url: NSURL) -> NSURLAsset {

(省略)

            let scheme = url.scheme
            asset = AVURLAsset(URL: urlWithCustomScheme(url, scheme: scheme + "streaming"), options: nil)
        }
        asset.resourceLoader.setDelegate(audioLoader, queue: dispatch_get_main_queue())
        return asset
    }

    private func urlWithCustomScheme(url: NSURL, scheme: String) -> NSURL {
        let components = NSURLComponents(URL: url, resolvingAgainstBaseURL: false)!
        components.scheme = scheme
        return components.URL!
    }

file0.txt

pod "Chorister"