private Task handleResource(IOwinContext context, Stream stream, DateTime?lastModified, string path, double expires, IDictionary <string, string> addonHttpHeaders)
{
var req = context.Request;
var rep = context.Response;
//验证缓存有效
if (lastModified.HasValue)
{
//===================
//先验证最后修改时间
//===================
var resourceLastModified = lastModified.Value;
//最后修改时间判断部分
var clientLastModified = req.Headers.Get("If-Modified-Since");
if (clientLastModified != null)
{
if (clientLastModified == resourceLastModified.ToString("R"))
{
rep.StatusCode = 304;
return(Task.Run(() => stream.Dispose()));
}
}
//===================
//然后验证ETag
//===================
//ETag设置判断部分
String serverETag = null;
if (UseMd5ETag)
{
serverETag = HashUtils.ComputeETagByMd5(stream);
if (stream.CanSeek)
{
stream.Position = 0;
}
}
else
{
serverETag = lastModified.Value.Ticks.ToString();
}
var clientETag = req.Headers.Get("If-None-Match");
//如果客户端的ETag值与服务端相同，则返回304，表示资源未修改
if (serverETag == clientETag)
{
rep.StatusCode = 304;
return(Task.Run(() => stream.Dispose()));
}
rep.ETag = serverETag;
}
rep.Expires = new DateTimeOffset(DateTime.Now.AddSeconds(expires));
rep.Headers["Cache-Control"] = $"max-age={expires}";
if (lastModified.HasValue)
{
rep.Headers["Last-Modified"] = lastModified.Value.ToUniversalTime().ToString("R");
}
return(context.Output(stream, true, EnableCompress, path, addonHttpHeaders));
}
