[fpc-pascal] How To: Use lib curl example

[Rainer Stratmann]

Does that mean curl is always waiting until the whole operation (download) is 
complete?

Is it possible to do it in a nonblocked way? For example with a continuous 
nonblocked loop call and a flag when the operation is finished?


Am Dienstag, 28. September 2021, 02:01:00 CET schrieb Anthony Walter via fpc-
pascal:
> I was having some problems using vanilla sockets and OpenSSL to read a few
> specific web pages using HTTPS. Normally I don't have any problems
> using HTTPS, but with a few sites my code was not working. I ending up
> finding the RTL unit LibCurl in one of the FPC packages and got it working
> without too much trouble. LibCurl is a library allowing programmers to get
> the functionality of the curl program without launching an external process.
> 
> If anyone is interested, here is a small bit of code to GET a page over
> HTTP or HTTPS using LibCurl.
> 
> Interface:
> 
> function CurlGet(const Url: string; out Data: string; UserAgent: string =
> ''): Boolean;
> 
> Implementation:
> 
> uses
>   LibCurl;
> 
> function WriteData(Ptr: PChar; MemberSize, MemberCount: UIntPtr; var Data:
> string): UIntPtr; cdecl;
> var
>   S: string;
> begin
>   SetString(S, Ptr, MemberSize * MemberCount);
>   Data := Data + S;
>   Result := MemberSize * MemberCount;
> end;
> 
> function CurlGet(const Url: string; out Data: string; UserAgent: string =
> ''): Boolean;
> var
>   Curl: PCURL;
> begin
>   Data := '';
>   Result := False;
>   if Url = '' then
>     Exit;
>   Curl := curl_easy_init();
>   if Curl = nil then
>     Exit;
>   try
>     curl_easy_setopt(curl, CURLOPT_URL, [PChar(Url)]);
>     if UserAgent <> '' then
>       curl_easy_setopt(curl, CURLOPT_USERAGENT, [PChar(UserAgent)]);
>     curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, [@WriteData]);
>     curl_easy_setopt(curl, CURLOPT_WRITEDATA, [@Data]);
>     curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, [0]);
>     curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, [0]);
>     Result := curl_easy_perform(curl) = CURLE_OK;
>   finally
>     curl_easy_cleanup(Curl);
>   end;
> end;