another WWW.LoadFromCacheOrDownload for Unity

WWWCache.cs

using UnityEngine;
using System;
using System.Collections;
using System.IO;

/// <summary>
///	Defalult WWW.LoadFromCacheOrDownload() can use only AssetBundle
///	this eneble chaching any file.
/// </summary>
public class WWWCache {
	
	string strToBase64(string str) {
		byte[] byt = System.Text.Encoding.UTF8.GetBytes(str);
		return Convert.ToBase64String(byt);
	}
	
	string base64ToStr(string base64) {
		byte[] b = Convert.FromBase64String(base64);
		return System.Text.Encoding.UTF8.GetString(b);
	}
	
	string urlToCachePath(string url) {
		return Application.persistentDataPath +"/"+ strToBase64(url);
	}
	
	public bool HasCache(string url) {
		return File.Exists(urlToCachePath(url));
	}
	
	public void WriteCache(WWW www) {
		File.WriteAllBytes(urlToCachePath(www.url), www.bytes);
	}
	
	public string CacheUrl(string url) {
		string path = urlToCachePath(url);
		if(File.Exists(path)) {
			return "file://" + path;
		}
		Debug.LogWarning("dont have cache url:"+url);
		return "";
	}
}

WWW.LoadFromCacheOrDownload does not store files at Application.persistentDataPath. It stores it at separate local cache which is managed by the OS. The WebPlayer shared cache allows up to 50 MB of cached AssetBundles. PC/Mac Standalone applications and iOS/Android applications have a limit of 4 GB. When the cache is full, the OS will delete the oldest files to make room for new ones (like any proper cache system should do). What would happen when your cache hits the limit? Also, files saved to Application.persistentData path are automatically backed up to iCloud. Consider using Application.temporaryCachePath instead.