3. Content Download

Content download via the Kollus SDK always proceeds through two steps. First, content metadata is loaded from the URL to obtain the media content key (mediaContentKey, mck) for device verification, and then the actual file download begins based on that key.

All example code in this document is based on the official sample app kollus_player_ios.

---

Download flow

extension StorageManager {

    // Step 1: Load content metadata (synchronous)
    public func loadContentURL(URL urlString: String,
                               completion: @escaping (Error?, String) -> Void) {
        do {
            let mck = try storage.loadContentURL(urlString)
            completion(nil, mck)
        } catch {
            completion(error, error.localizedDescription)
        }
    }

    // Step 2: Start actual download based on media content key
    func startDownloadContent(mediaContentKey: String) {
        do {
            try storage.downloadContent(mediaContentKey)
        } catch {
            print(error.localizedDescription)
        }
    }
}

The loadContentURL method registers content metadata in the SDK's persistent storage and returns the mediaContentKey. Even if the same URL is called multiple times, the returned mediaContentKey remains the same.

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Duplicate download check

Use the checkContentURL method to check whether the same URL is already registered in the download list before initiating a new download.

func checkIsDownloadContent(url: String,
                            completion: @escaping (Bool, KollusContent?) -> Void) {
    DispatchQueue.global().async { [unowned self] in
        do {
            let mck = try storage.checkContentURL(url)
            let list = storage.contents() as! [KollusContent]
            if let match = list.first(where: { $0.mediaContentKey == mck }) {
                DispatchQueue.main.async { completion(true, match) }
            } else {
                DispatchQueue.main.async { completion(false, nil) }
            }
        } catch {
            DispatchQueue.main.async { completion(false, nil) }
        }
    }
}

Difference between loadContentURL and checkContentURL

• loadContentURL: Entry point for a new download (registers new content information)
• checkContentURL: Matches against existing download history (returns an error if an unregistered URL is passed)

---

Download cancellation/pause/resume control policy

func cancelDownloadContent(mediaContentKey: String) {
    do {
        try storage.downloadCancelContent(mediaContentKey)
    } catch {
        print(error.localizedDescription)
    }
}

Action	API	Description
Start download	try storage.downloadContent(mck)	Starts the download.
Cancel download	try storage.downloadCancelContent(mck)	Stops the download session.
Pause download	No dedicated API	No explicit pause API is provided, so cancel with downloadCancelContent and restart. The SDK may internally preserve some data, but in general you should assume the download restarts from the beginning.
Resume download	Call try storage.downloadContent(mck) again	-

Sample application control model

The official sample app does not implement separate pause and resume UI components, and instead adopts a cancel and restart approach.

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Track download progress

Real-time download progress is tracked by referencing the properties of the KollusContent instance injected into the delegate callback kollusStorage(_:downloadContent:error:). For more details, refer to the 8. Download Events/Callbacks document.

Property	Type	Description
fileSize	long long	Content file size
downloadSize	long long	Downloaded size
downloadProgress	NSUInteger	Download progress (0–100)
downloadStopSize	long long	Size preserved at the point of download pause
downloaded	BOOL	Whether the download is complete
downloadStatus	NSInteger	Download progress status code