/// <summary> 获取下载流
/// </summary>
/// <param name="fileName"></param>
/// <returns></returns>
public Stream GetDownloadStream(HttpContext httpContext, string fileName)
{
string filePath = this.GetServerFilePath(fileName);
if (!File.Exists(filePath))
{
return(null);
}
PartialFileInfo partialFileInfo = this.GetPartialFileInfo(httpContext.Request, filePath);
this.SetResponseHeaders(httpContext.Response, partialFileInfo);
return(this.GetPartialFileStream(partialFileInfo));
}
/// <summary> 异步获取下载流
/// </summary>
/// <param name="fileName"></param>
/// <returns></returns>
public Task <Stream> GetDownloadStreamAsync(HttpContext httpContext, string fileName)
{
return(Task.Run <Stream>(() =>
{
string filePath = this.GetServerFilePath(fileName);
if (!File.Exists(filePath))
{
return null;
}
PartialFileInfo partialFileInfo = this.GetPartialFileInfo(httpContext.Request, filePath);
this.SetResponseHeaders(httpContext.Response, partialFileInfo);
return this.GetPartialFileStream(partialFileInfo);
}));
}
/// <summary>
/// 设置响应头信息
/// </summary>
/// <param name="response"></param>
/// <param name="partialFileInfo"></param>
/// <param name="fileLength"></param>
/// <param name="fileName"></param>
private void SetResponseHeaders(HttpResponse response, PartialFileInfo partialFileInfo)
{
response.Headers[HeaderNames.AcceptRanges] = "bytes";
response.StatusCode = partialFileInfo.IsPartial ? StatusCodes.Status206PartialContent : StatusCodes.Status200OK;
var contentDisposition = new ContentDispositionHeaderValue("attachment");
contentDisposition.SetHttpFileName(partialFileInfo.Name);
response.Headers[HeaderNames.ContentDisposition] = contentDisposition.ToString();
response.Headers[HeaderNames.ContentType] = "application/octet-stream";
//response.Headers[HeaderNames.ContentMD5] = partialFileInfo.MD5;
response.Headers[HeaderNames.ContentLength] = partialFileInfo.Length.ToString();
if (partialFileInfo.IsPartial)
{
response.Headers[HeaderNames.ContentRange] = new ContentRangeHeaderValue(partialFileInfo.From, partialFileInfo.To, partialFileInfo.FileLength).ToString();
}
}
/// <summary> 获取文件分块信息
/// </summary>
/// <param name="request"></param>
/// <param name="filePath"></param>
/// <returns></returns>
private PartialFileInfo GetPartialFileInfo(HttpRequest request, string filePath)
{
PartialFileInfo partialFileInfo = new PartialFileInfo(filePath);
if (RangeHeaderValue.TryParse(request.Headers[HeaderNames.Range].ToString(), out RangeHeaderValue rangeHeaderValue))
{
var range = rangeHeaderValue.Ranges.FirstOrDefault();
if (range.From.HasValue && range.From < 0 || range.To.HasValue && range.To > partialFileInfo.FileLength - 1)
{
return(null);
}
var from = range.From;
var to = range.To;
if (from.HasValue)
{
if (from.Value >= partialFileInfo.FileLength)
{
return(null);
}
if (!to.HasValue || to.Value >= partialFileInfo.FileLength)
{
to = partialFileInfo.FileLength - 1;
}
}
else
{
if (to.Value == 0)
{
return(null);
}
var bytes = Math.Min(to.Value, partialFileInfo.FileLength);
from = partialFileInfo.FileLength - bytes;
to = from + bytes - 1;
}
partialFileInfo.IsPartial = true;
partialFileInfo.Length = to.Value - from.Value + 1;
}
return(partialFileInfo);
}
/// <summary> 获取分块文件流
/// </summary>
/// <param name="partialFileInfo"></param>
/// <returns></returns>
private Stream GetPartialFileStream(PartialFileInfo partialFileInfo)
{
return(new PartialFileStream(partialFileInfo.FilePath, partialFileInfo.From, partialFileInfo.To));
}
