How to declare an array of C strings? (needed for a WinAPI function)

Question

I want to use HttpOpenRequest to download a file from internet using GET. I don't know how to declare the AcceptType parameter. The MS documentations says that it is an array of strings. So I declare it like this:

CONST
   AcceptType: packed array[0..1] of LPWSTR = (PChar('*/*'), nil);

I have done something wrong? LPWSTR is a pointer to a string, however, the documentation says that I need a string. How do I declare a matrix of strings that are compatible with C++ ?

procedure THTTPGetThread.Execute;
CONST
   AcceptType: packed array[0..1] of LPWSTR = (PChar('*/*'), nil);              // Originally was:   AcceptType:= PWideChar('Accept: ' + FTAcceptTypes);
VAR
   hConnect: hInternet;
   FileName: String;
   Data: Array[0..1024] of Char;
   TempStr: PAnsiChar;
   RequestMethod: PChar;
   InternetFlag: DWord;
begin
     ...
     hRequest:= HttpOpenRequest(hConnect, RequestMethod, PChar(FileName), PChar('HTTP/1.0'), PChar(FTReferer), @AcceptType, InternetFlag, 0);
     ...
end;

I use Delphi XE. The MS documentation is here: http://msdn.microsoft.com/en-us/library/windows/desktop/aa384233(v=vs.85).aspx My function is multi-threaded so it won't block the program while it downloads. Single threaded functions won't work for me.

There is nothing wrong in a way you pass AcceptType

kludg
– kludg

2011-10-11 12:04:55 +00:00
Commented Oct 11, 2011 at 12:04 — kludg
– kludg, Commented Oct 11, 2011 at 12:04

David Heffernan · Accepted Answer · 2011-10-11 13:21:55Z

3

You are almost there. You just need to pass a pointer to the first element of the array:

@AcceptType[0]

In fact, as @Serg points out, this is equivalent to your existing code. So it seems that, as you have commented below, the issue you are facing is unrelated to the passing of this parameter.

As an aside, I think I would use PWideChar rather than LPWSTR, but that's not the issue here since they are equivalent.

edited Oct 11, 2011 at 13:21

answered Oct 11, 2011 at 11:26

David Heffernan

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3 Comments

Error - CPU Not Foud Over a year ago

I have tried that but my program still has problems. More exactly the program cannot be shutdown WHEN I use that function to download a file. So I will try to find my problem somewhere else. Thanks anyway! +1

Error - CPU Not Foud Over a year ago

Yes David. I never said that it is otherwise.

Warren P Over a year ago

this is a surprising element of delphi pointer/address syntax, for some C programmers. I remember when I found it surprising. I'm so used to it now, that I've forgotten to be surprised anymore.

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