using System;
using System.IO;
using System.Text;
using System.Threading;
using System.Web;
namespace NewLife.Web
{
/// <summary>提供网页下载支持，在服务端把一个数据流作为附件传给浏览器，带有断点续传和限速的功能</summary>
public class WebDownload
{
#region 属性
private Stream _Stream;
/// <summary>数据流</summary>
public Stream Stream { get { return _Stream; } set { _Stream = value; } }
private String _FileName;
/// <summary>文件名</summary>
public String FileName { get { return _FileName; } set { _FileName = value; } }
private String _ContentType = "application/octet-stream";
/// <summary>内容类型</summary>
public String ContentType { get { return _ContentType; } set { _ContentType = value; } }
private DispositionMode _Mode = DispositionMode.None;
/// <summary>附件配置模式，是在浏览器直接打开，还是提示另存为</summary>
public DispositionMode Mode { get { return _Mode; } set { _Mode = value; } }
private Int64 _Speed;
/// <summary>速度，每秒传输字节数，根据包大小，每响应一个包后睡眠指定毫秒数，0表示不限制</summary>
public Int64 Speed { get { return _Speed; } set { _Speed = value; } }
/// <summary>是否启用浏览器缓存 默认禁用</summary>
public Boolean BrowserCache { get; set; }
private TimeSpan _browserCacheMaxAge = new TimeSpan(30, 0, 0, 0);
/// <summary>浏览器最大缓存时间 默认30天。通过Cache-Control头控制max-age，直接使用浏览器缓存，不会发出Http请求，对F5无效</summary>
public TimeSpan BrowserCacheMaxAge { get { return _browserCacheMaxAge; } set { _browserCacheMaxAge = value; } }
private DateTime _ModifyTime;
/// <summary>文件数据最后修改时间，浏览器缓存时用</summary>
public DateTime ModifyTime { get { return _ModifyTime; } set { _ModifyTime = value; } }
#endregion
#region 枚举
/// <summary>附件配置模式</summary>
public enum DispositionMode
{
/// <summary>不设置</summary>
None,
/// <summary>内联模式，在浏览器直接打开</summary>
Inline,
/// <summary>附件模式，提示另存为</summary>
Attachment
}
/// <summary>分析模式</summary>
/// <param name="mode"></param>
/// <returns></returns>
public static DispositionMode ParseMode(String mode)
{
return (DispositionMode)Enum.Parse(typeof(DispositionMode), mode);
}
#endregion
#region 构造
/// <summary>构造函数</summary>
public WebDownload() { }
/// <summary>构造函数</summary>
/// <param name="stream"></param>
public WebDownload(Stream stream) { Stream = stream; }
/// <summary>构造函数</summary>
/// <param name="html"></param>
/// <param name="encoding"></param>
public WebDownload(String html, Encoding encoding)
{
var ms = new MemoryStream();
var writer = new StreamWriter(ms, encoding);
writer.Write(html);
ms.Position = 0;
Stream = ms;
}
#endregion
/// <summary>检查浏览器缓存是否依然有效，如果有效则跳过Render</summary>
/// <returns></returns>
public virtual Boolean CheckCache(HttpContext context)
{
//增加 浏览器缓存 304缓存
//if (BrowserCache)
{
var Request = context.Request;
var Response = context.Response;
var since = Request.ServerVariables["HTTP_IF_MODIFIED_SINCE"];
if (!String.IsNullOrEmpty(since))
{
//if (DateTime.TryParse(since, out dt) && dt >= attachment.UploadTime)
//!!! 注意：本地修改时间精确到毫秒，而HTTP_IF_MODIFIED_SINCE只能到秒
if (DateTime.TryParse(since, out var dt) && (dt - ModifyTime).TotalSeconds > -1)
{
Response.StatusCode = 304;
return true;
}
}
// WebDev不支持HTTP_IF_MODIFIED_SINCE，但是可以用HTTP_IF_NONE_MATCH
var etag = Request.ServerVariables["HTTP_IF_NONE_MATCH"];
if (!String.IsNullOrEmpty(etag))
{
if (Int64.TryParse(etag, out var ticks) && (new DateTime(ticks) - ModifyTime).TotalSeconds > -1)
{
Response.StatusCode = 304;
return true;
}
}
}
return false;
}
/// <summary>输出数据流</summary>
public virtual void Render(HttpContext context)
{
var Request = context.Request;
var Response = context.Response;
var stream = Stream;
// 速度
var speed = Speed;
// 包大小
var pack = 1024000;
// 计算睡眠时间
var sleep = speed > 0 ? (Int32)Math.Floor(1000 * (Double)pack / speed) + 1 : 0;
// 输出Accept-Ranges，表示支持断点
Response.AddHeader("Accept-Ranges", "bytes");
Response.Buffer = false;
var fileLength = stream.Length;
Int64 startBytes = 0;
// 如果请求里面指定范围，表示需要断点
if (Request.Headers["Range"] != null)
{
Response.StatusCode = 206;
var range = Request.Headers["Range"].Split(new Char[] { '=', '-' });
startBytes = Convert.ToInt64(range[1]);
}
// 计算真正的长度
Response.AddHeader("Content-Length", (fileLength - startBytes).ToString());
if (startBytes != 0)
{
// 指定数据范围
Response.AddHeader("Content-Range", String.Format(" bytes {0}-{1}/{2}", startBytes, fileLength - 1, fileLength));
}
Response.AddHeader("Connection", "Keep-Alive");
Response.ContentType = ContentType;
if (Mode != DispositionMode.None)
{
/*
* 按照RFC2231的定义， 多语言编码的Content-Disposition应该这么定义：
* Content-Disposition: attachment; filename*="utf8''%e6%94%b6%e6%ac%be%e7%ae%a1%e7%90%86.xls"
* filename后面的等号之前要加 *
* filename的值用单引号分成三段，分别是字符集(utf8)、语言(空)和urlencode过的文件名。
* 最好加上双引号，否则文件名中空格后面的部分在Firefox中显示不出来
*/
//var cd = String.Format("attachment;filename=\"{0}\"", filename);
//if (Request.UserAgent.Contains("MSIE"))
// cd = String.Format("attachment;filename=\"{0}\"", HttpUtility.UrlEncode(filename, encoding));
//else if (Request.UserAgent.Contains("Firefox"))
// cd = String.Format("attachment;filename*=\"{0}''{1}\"", encoding.WebName, HttpUtility.UrlEncode(filename, encoding));
Response.AddHeader("Content-Disposition", Mode + ";filename=" + HttpUtility.UrlEncode(FileName, Encoding.UTF8));
}
//增加 浏览器缓存 304缓存
if (BrowserCache)
{
//Response.ExpiresAbsolute = DateTime.Now.Add(BrowserCacheMaxAge);
//Response.Cache.SetMaxAge(BrowserCacheMaxAge);
//Response.Cache.SetRevalidation(HttpCacheRevalidation.AllCaches);
//Response.Cache.SetCacheability(HttpCacheability.Public);
//Response.Cache.SetLastModified(ModifyTime);
Response.Cache.SetETag(ModifyTime.Ticks.ToString());
Response.Cache.SetLastModified(ModifyTime);
Response.Cache.SetCacheability(HttpCacheability.Public);
Response.Cache.SetMaxAge(BrowserCacheMaxAge);
Response.Cache.SetSlidingExpiration(true);
}
//stream.Seek(startBytes, SeekOrigin.Begin);
var maxCount = (Int32)Math.Floor((fileLength - startBytes) / (Double)pack) + 1;
// 如果不足一个包，则缩小缓冲区，避免浪费内存
if (pack > stream.Length) pack = (Int32)stream.Length;
var buffer = new Byte[pack];
for (var i = 0; i < maxCount; i++)
{
if (!Response.IsClientConnected) break;
var count = stream.Read(buffer, 0, buffer.Length);
if (count == pack)
Response.BinaryWrite(buffer);
else
{
var data = new Byte[count];
Buffer.BlockCopy(buffer, 0, data, 0, count);
Response.BinaryWrite(data);
}
if (sleep > 0) Thread.Sleep(sleep);
}
}
}
}
|