Two ways to download files from the network

The COM functions used by both methods are derived from the Urlmon, remember to refer to them first.

First, Urldownloadtofile

To download files directly to disk, Urldownloadtofile declares as follows:

function Urldownloadtofile (
Caller:iunknown;
Url:pwidechar; {Path to download}
Filename:pwidechar; {The path saved to}
Reserved:dword;
Statuscb:ibindstatuscallback
): HResult; stdcall;

Urldownloadtofilea (Caller:iunknown; Url:pansichar; Filename:pansichar; Reserved:dword; Statuscb:ibindstatuscallback): HResult; stdcall; function Urldownloadtofilew (Caller:iunknown; Url:pwidechar; Filename:pwidechar; Reserved:dword; Statuscb:ibindstatuscallback): HResult; stdcall;

Invocation Example:
If Urldownloadtofile (nil, ' http://www.xxxx.com/xxx.xx ', ' c:/1.xx ', 0, nil) = 0 Then
MessageBox (handle, ' download successful ', ' ', 0)

Else

MessageBox (handle, ' download failed ', ' ', 0);

Urldownloadtofile before downloading the file in the local cache to find the file, if the cache will not go to the internet to catch the latest files, you want to always get a new file when you can add a random number after the URL, or with deleteurlcacheentry (URL) Clean up the cache before downloading

Second, Urlopenstream

Download to IStream Stream, declared as:

function Urlopenstream (
P1:iunknown;

P2:pwidechar; {Path to download}

P3:dword;

P4:ibindstatuscallback {interface, which obtains data through it after download}

): HResult; stdcall;

function Urlopenstreama (P1:iunknown; p2:pansichar; p3:dword; p4:ibindstatuscallback): HResult; stdcall;

function URLOPENSTREAMW (P1:iunknown; p2:pwidechar; p3:dword; p4:ibindstatuscallback): HResult; stdcall;

Implementation of the IBindStatusCallback interface

Tbindstatuscallback =class(Tinterfacelist, IBindStatusCallback) Public    functionOnstartbinding (Dwreserved:dword; pib:ibinding): HResult;stdcall;functionGetPriority ( outnpriority): HResult;stdcall;functionOnlowresource (Reserved:dword): HResult;stdcall;functionOnProgress (ulprogress, ulProgressMax, Ulstatuscode:ulong; SZSTATUSTEXT:LPCWSTR): HResult;stdcall;functionOnstopbinding (Hresult:hresult; szerror:lpcwstr): HRESULT;stdcall;functionGetbindinfo ( outGrfbindf:dword;varBindinfo:tbindinfo): HResult;stdcall;functionOnDataAvailable (Grfbscf:dword; dwsize:dword; formatetc:pformatetc; Stgmed:pstgmedium): HResult;stdcall;functionOnobjectavailable (ConstIid:tguid; Punk:iunknown): HResult;stdcall;

End;

{Tbindstatuscallback}functionTbindstatuscallback.getbindinfo ( outGrfbindf:dword;varBindinfo:tbindinfo): HResult;beginResult: = S_OK;End;functionTbindstatuscallback.getpriority ( outnpriority): HResult;beginResult: = S_OK;End;functionTbindstatuscallback.ondataavailable (GRFBSCF, Dwsize:dword; FORMATETC:PFORMATETC; Stgmed:pstgmedium): HResult;varStream:istream; Ms:tmemorystream;begin  ifdwsize > 0 Then  beginStream: = IStream (stgmed.stm); MS: = tmemorystream.create;
Ms. SetSize (dwsize);
Stream.read (MS. Memory, dwsize,Nil);
Fetching data from MS ...
Ms. Free;
Result: = S_OK;End ElseResult: = E_abort;End;functionTbindstatuscallback.onlowresource (Reserved:dword): HResult;beginResult: = S_OK;End;functionTbindstatuscallback.onobjectavailable (ConstIid:tguid; Punk:iinterface): HResult;beginResult: = S_OK;End;functionTbindstatuscallback.onprogress (ulprogress, ulProgressMax, Ulstatuscode:ulong; szstatustext:lpcwstr): HResult;beginCan realize the detection progress, the implementation code writes Result: = S_OK;End;functionTbindstatuscallback.onstartbinding (Dwreserved:dword; pib:ibinding): HResult;beginResult: = S_OK;End;functionTbindstatuscallback.onstopbinding (Hresult:hresult; SZERROR:LPCWSTR): HResult;beginResult: = S_OK;End;

Calling code:
var
  string;
  Mybindstatuscallback:ibindstatuscallback;

begin  Mybindstatuscallback: = tbindstatuscallback.create;  if Succeeded (Urlopenstream (nil Then
    Download successful!  Else    Download failed!; End;

http://blog.csdn.net/nhconch/article/details/5470777

Two ways to download files from the network