我想用TIdHttp (Indy10)实现一个简单的http下载器。我在网上找到了两种代码示例。不幸的是,没有一个能让我100%满意。这是代码,我需要一些建议。
变体1
var
Buffer: TFileStream;
HttpClient: TIdHttp;
begin
Buffer := TFileStream.Create('somefile.exe', fmCreate or fmShareDenyWrite);
try
HttpClient := TIdHttp.Create(nil);
try
HttpClient.Get('http://somewhere.com/somefile.exe', Buffer); // wait until it is done
finally
HttpClient.Free;
end;
finally
Buffer.Free;
end;
end;
代码很紧凑,很容易理解。问题是它会在下载开始时分配磁盘空间。另一个问题是,我们不能在图形用户界面中直接显示下载进度,除非代码在后台线程中执行(或者我们可以绑定HttpClient.OnWork事件)。
变体2:
const
RECV_BUFFER_SIZE = 32768;
var
HttpClient: TIdHttp;
FileSize: Int64;
Buffer: TMemoryStream;
begin
HttpClient := TIdHttp.Create(nil);
try
HttpClient.Head('http://somewhere.com/somefile.exe');
FileSize := HttpClient.Response.ContentLength;
Buffer := TMemoryStream.Create;
try
while Buffer.Size < FileSize do
begin
HttpClient.Request.ContentRangeStart := Buffer.Size;
if Buffer.Size + RECV_BUFFER_SIZE < FileSize then
HttpClient.Request.ContentRangeEnd := Buffer.Size + RECV_BUFFER_SIZE - 1
else
HttpClient.Request.ContentRangeEnd := FileSize;
HttpClient.Get(HttpClient.URL.URI, Buffer); // wait until it is done
Buffer.SaveToFile('somefile.exe');
end;
finally
Buffer.Free;
end;
finally
HttpClient.Free;
end;
end;
首先,我们从服务器查询文件大小,然后分块下载文件内容。检索到的文件内容将在完全接收后保存到磁盘。潜在的问题是我们必须向服务器发送多个GET请求。我不确定某些服务器(例如megaupload)是否会在特定时间段内限制请求的数量。
My expectations
任何提示都是值得感谢的。
https://stackoverflow.com/questions/13641055
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