前面在做文件下载的时候，有时会遇到url指定的文件并不存在，所以在下载过程中会出现一些错误，尽管这些错误可以except掉，但还是需事先检测一下，如果url不正确则不用再调用download过程了。下面的函数可以进行检测并函数返回boolean型值：
1
function TFrameChannel.CheckUrl(url:
string
; TimeOut: Integer
=
5000
): boolean;
2 var
3 hSession, hfile : hInternet;
4 dwindex, dwcodelen: dword;
5 dwcode: array[ 1 .. 20 ] of char ;
6 res: pchar;
7 re: integer;
8 Err1: integer;
9 j: integer;
10 begin
11 if pos( ' http:// ' , lowercase(url)) = 0 then
12 url : = ' http:// ' + url;
13 Result : = false ;
14 hSession : = nil;
15 hFile : = nil;
16
17 // 设置超时
18 InternetSetOption(hSession, Internet_OPTION_CONNECT_TIMEOUT, @TimeOut, 4 );
19 hSession : = InternetOpen( ' Mozilla/4.0 ' , INTERNET_OPEN_TYPE_PRECONFIG, nil, nil, 0 );
20 if assigned(hsession) then begin
21 j : = 1 ;
22 while true do begin
23 hfile : = InternetOpenUrl(hsession, pchar(url), nil, 0 , INTERNET_FLAG_RELOAD, 0 );
24 if hfile = nil then begin
25 j : = j + 1 ;
26 Err1 : = GetLastError;
27 if j > 5 then break ;
28 if (Err1 <> 12002 ) or (Err1 <> 12152 ) then break ;
29 sleep( 2 );
30 end else begin
31 break ;
32 end;
33 end;
34 dwIndex : = 0 ;
35 dwCodeLen : = 10 ;
36 HttpQueryInfo(hfile, HTTP_QUERY_STATUS_CODE, @dwcode, dwcodeLen, dwIndex);
37 res : = pchar(@dwcode);
38 re : = strtointdef(res, 404 );
39 case re of
40 400 .. 450 : result : = false ;
41 else result : = true ;
42 end;
43 if assigned(hfile) then
44 InternetCloseHandle(hfile);
45 InternetCloseHandle(hsession);
46 end;
47 end;
48
2 var
3 hSession, hfile : hInternet;
4 dwindex, dwcodelen: dword;
5 dwcode: array[ 1 .. 20 ] of char ;
6 res: pchar;
7 re: integer;
8 Err1: integer;
9 j: integer;
10 begin
11 if pos( ' http:// ' , lowercase(url)) = 0 then
12 url : = ' http:// ' + url;
13 Result : = false ;
14 hSession : = nil;
15 hFile : = nil;
16
17 // 设置超时
18 InternetSetOption(hSession, Internet_OPTION_CONNECT_TIMEOUT, @TimeOut, 4 );
19 hSession : = InternetOpen( ' Mozilla/4.0 ' , INTERNET_OPEN_TYPE_PRECONFIG, nil, nil, 0 );
20 if assigned(hsession) then begin
21 j : = 1 ;
22 while true do begin
23 hfile : = InternetOpenUrl(hsession, pchar(url), nil, 0 , INTERNET_FLAG_RELOAD, 0 );
24 if hfile = nil then begin
25 j : = j + 1 ;
26 Err1 : = GetLastError;
27 if j > 5 then break ;
28 if (Err1 <> 12002 ) or (Err1 <> 12152 ) then break ;
29 sleep( 2 );
30 end else begin
31 break ;
32 end;
33 end;
34 dwIndex : = 0 ;
35 dwCodeLen : = 10 ;
36 HttpQueryInfo(hfile, HTTP_QUERY_STATUS_CODE, @dwcode, dwcodeLen, dwIndex);
37 res : = pchar(@dwcode);
38 re : = strtointdef(res, 404 );
39 case re of
40 400 .. 450 : result : = false ;
41 else result : = true ;
42 end;
43 if assigned(hfile) then
44 InternetCloseHandle(hfile);
45 InternetCloseHandle(hsession);
46 end;
47 end;
48
本文转自 OldHawk 博客园博客，原文链接：http://www.cnblogs.com/taobataoma/archive/2007/04/26/728269.html，如需转载请自行联系原作者
