Custom DownloadHandler for UnityWebRequest to stream contents into a file. Useful for preloading AssetBundles without them automatically being uncompressed and loaded into memory.

DownloadHandlerFile.cs

/**
 * DownloadHandlerFile.cs
 * Author: Luke Holland (http://lukeholland.me/)
 */

using UnityEngine;
using UnityEngine.Networking;
using System.IO;

public class DownloadHandlerFile : DownloadHandlerScript 
{

	public int contentLength { get { return _received>_contentLength ? _received : _contentLength; } }

	private int _contentLength;
	private int _received;
	private FileStream _stream;

	public DownloadHandlerFile(string localFilePath, int bufferSize = 4096, FileShare fileShare = FileShare.ReadWrite) : base(new byte[bufferSize])
	{
		string directory = Path.GetDirectoryName(localFilePath);
		if(!Directory.Exists(directory)) Directory.CreateDirectory(directory);

		_contentLength = -1;
		_received = 0;
		_stream = new FileStream(localFilePath,FileMode.OpenOrCreate, FileAccess.Write, fileShare, bufferSize);
	}

	protected override float GetProgress ()
	{
		return contentLength<=0 ? 0 : Mathf.Clamp01((float)_received/(float)contentLength);
	}

	protected override void ReceiveContentLength (int contentLength)
	{
		_contentLength = contentLength;
	}
		 
	protected override bool ReceiveData (byte[] data, int dataLength)
	{
		if(data==null || data.Length==0) return false;

		_received += dataLength;
		_stream.Write(data,0,dataLength);

		return true;
	}

	protected override void CompleteContent ()
	{
		CloseStream();
	}

	public new void Dispose()
	{
		CloseStream();
		base.Dispose();
	}

	private void CloseStream()
	{
		if(_stream!=null){
			_stream.Dispose();
			_stream = null;
		}
	}

}