DownloadHandlerScript

Description

An abstract base class for custom, scriptable DownloadHandler implementations.

Derive from DownloadHandlerScript and override some or all of its callbacks to implement custom data handling for key events in the download process.

For example, override DownloadHandler.ReceiveData to implement custom handling when data arrives from the remote server and override DownloadHandler.ReceiveContentLengthHeader to implement custom handling when a Content-Length header is received.

The UnityWebRequest system permits the pre-allocation of a managed-code byte array, which is used to deliver downloaded data to the DownloadHandler.ReceiveData callback. Using this function eliminates managed-code memory allocation when using classes derived from DownloadHandlerScript-to capture downloaded data.

To make a DownloadHandlerScript operate with a pre-allocated managed buffer, supply a byte array to the ctor. The size of the byte array limits the amount of data that can be received in each ReceiveData call. If data arrives slowly, over many frames, the supplied byte array might be too small.

Note: The actual downloads occur on a worker thread, but all DownloadHandlerScript callbacks operate on the main thread. Avoid performing computationally heavy operations from these callbacks.

Additional resources: DownloadHandler.ReceiveData, DownloadHandler.ReceiveContentLengthHeader, DownloadHandler.CompleteContent.

using UnityEngine;
using UnityEngine.Networking;

public class LoggingDownloadHandler : DownloadHandlerScript {

    // Standard scripted download handler - allocates memory on each ReceiveData callback

    public LoggingDownloadHandler(): base() {
    }

    // Pre-allocated scripted download handler
    // reuses the supplied byte array to deliver data.
    // Eliminates memory allocation.

    public LoggingDownloadHandler(byte[] buffer): base(buffer) {
    }

    // Required by DownloadHandler base class. Called when you address the 'bytes' property.

    protected override byte[] GetData() { return null; }

    // Called once per frame when data has been received from the network.

    protected override bool ReceiveData(byte[] data, int dataLength) {
        if(data == null) {
            Debug.Log("LoggingDownloadHandler :: ReceiveData - received a null/empty buffer");
            return false;
        }

        Debug.Log(string.Format("LoggingDownloadHandler :: ReceiveData - received {0} bytes", dataLength));
        return true;
    }

    // Called when all data has been received from the server and delivered via ReceiveData.

    protected override void CompleteContent() {
        Debug.Log("LoggingDownloadHandler :: CompleteContent - DOWNLOAD COMPLETE!");
    }

    // Called when a Content-Length header is received from the server.

    protected override void ReceiveContentLengthHeader(ulong contentLength) {
        Debug.Log(string.Format("LoggingDownloadHandler :: ReceiveContentLength - length {0}", contentLength));
    }
}

Constructors

Inherited Members