我需要下载一些超过25 MB的文件,但我的网络只允许请求25 MB的文件。
我正在使用以下代码
const long DefaultSize = 26214400;
long Chunk = 26214400;
long offset = 0;
byte[] bytesInStream;
public void Download(string url, string filename)
{
long size = Size(url);
int blocksize = Convert.ToInt32(size / DefaultSize);
int remainder = Convert.ToInt32(size % DefaultSize);
if (remainder > 0) { blocksize++; }
FileStream fileStream = File.Create(@"D:\Download TEST\" + filename);
for (int i = 0; i < blocksize; i++)
{
if (i == blocksize - 1)
{
Chunk = remainder;
}
HttpWebRequest req = (HttpWebRequest)System.Net.WebRequest.Create(url);
req.Method = "GET";
req.AddRange(Convert.ToInt32(offset), Convert.ToInt32(Chunk+offset));
HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
// StreamReader sr = new StreamReader(resp.GetResponseStream());
using (Stream responseStream = resp.GetResponseStream())
{
bytesInStream = new byte[Chunk];
responseStream.Read(bytesInStream, 0, (int)bytesInStream.Length);
// Use FileStream object to write to the specified file
fileStream.Seek((int)offset, SeekOrigin.Begin);
fileStream.Write(bytesInStream,0, bytesInStream.Length);
}
offset += Chunk;
}
fileStream.Close();
}
public long Size(string url)
{
System.Net.WebRequest req = System.Net.HttpWebRequest.Create(url);
req.Method = "HEAD";
System.Net.WebResponse resp = req.GetResponse();
resp.Close();
return resp.ContentLength;
}
正确地在磁盘上写内容但内容无法正常工作
答案 0 :(得分:4)
你应该检查写入之前读了多少,这样(你不需要记住寻找的偏移量,你写的时候自动寻找):
int read;
do
{
read = responseStream.Read(bytesInStream, 0, (int)bytesInStream.Length);
if (read > 0)
fileStream.Write(bytesInStream, 0, read);
}
while(read > 0);
答案 1 :(得分:1)
有类似的SO问题可能会对您有所帮助 Segmented C# file downloader
和
How to open multiple connections to download single file?
此代码项目文章也是如此 http://www.codeproject.com/Tips/307548/Resume-Suppoert-Downloading
答案 2 :(得分:0)
范围基于零,您应该从上限减去1.
request.Headers.Range = new System.Net.Http.Headers.RangeHeaderValue(offset, chunkSize + offset - 1);
我在以下链接发布了正确的代码片段: https://stackoverflow.com/a/48019611/1099716
答案 3 :(得分:0)
Akka流可以使用多线程帮助从System.IO.Stream少量下载文件。 https://getakka.net/articles/intro/what-is-akka.html
Download方法会将字节添加到以long fileStart开头的文件中。如果文件不存在,则fileStart值必须为0。
using Akka.Actor;
using Akka.IO;
using Akka.Streams;
using Akka.Streams.Dsl;
using Akka.Streams.IO;
private static Sink<ByteString, Task<IOResult>> FileSink(string filename)
{
return Flow.Create<ByteString>()
.ToMaterialized(FileIO.ToFile(new FileInfo(filename), FileMode.Append), Keep.Right);
}
private async Task Download(string path, Uri uri, long fileStart)
{
using (var system = ActorSystem.Create("system"))
using (var materializer = system.Materializer())
{
HttpWebRequest request = WebRequest.Create(uri) as HttpWebRequest;
request.AddRange(fileStart);
using (WebResponse response = request.GetResponse())
{
Stream stream = response.GetResponseStream();
await StreamConverters.FromInputStream(() => stream, chunkSize: 1024)
.RunWith(FileSink(path), materializer);
}
}
}