Delphi ActiveX
REST Stream Multipart Body from File

Demonstrates how to send a multipart/form-data HTTP request, where one of the parts contains data streamed directly from a file. This is good for cases where the file to be uploaded is very large.
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Delphi ActiveX
uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Integer;
rest: TChilkatRest;
bTls: Integer;
port: Integer;
bAutoReconnect: Integer;
sbHtml: TChilkatStringBuilder;
fileStream: TChilkatStream;
responseBody: WideString;

begin
success := 0;

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

rest := TChilkatRest.Create(Self);

// Connect to the destination web server.
bTls := 1;
port := 443;
bAutoReconnect := 1;
success := rest.Connect('www.somewebserver.com',port,bTls,bAutoReconnect);

// This example will send the following multipart/form-data request.
// The Content-Length is automatically computed and added by Chilkat.

// 	POST /some_path HTTP/1.1
// 	Content-Type: multipart/form-data; boundary=---------------------------735323031399963166993862150
// 	Content-Length: 834
// 
// 	-----------------------------735323031399963166993862150
// 	Content-Disposition: form-data; name="text1"
// 
// 	text 123 abc
// 	-----------------------------735323031399963166993862150
// 	Content-Disposition: form-data; name="text2"
// 
// 	xyz
// 	-----------------------------735323031399963166993862150
// 	Content-Disposition: form-data; name="file1"; filename="a.txt"
// 	Content-Type: text/plain
// 
// 	Content of a.txt.
// 
// 	-----------------------------735323031399963166993862150
// 	Content-Disposition: form-data; name="file2"; filename="a.html"
// 	Content-Type: text/html
// 
// 	<!DOCTYPE html><title>Content of a.html.</title>
// 
// 	-----------------------------735323031399963166993862150
// 	Content-Disposition: form-data; name="file3"; filename="starfish.jpg"
// 	Content-Type: image/jpeg
// 
// 	binary data goes here
// 	-----------------------------735323031399963166993862150--

// Set the Content-Type for the topmost MIME part.
rest.AddHeader('Content-Type','multipart/form-data');

// Specify each part of the request.
rest.PartSelector := '1';
rest.AddHeader('Content-Disposition','form-data; name="text1"');
rest.SetMultipartBodyString('text 123 abc');

rest.PartSelector := '2';
rest.AddHeader('Content-Disposition','form-data; name="text2"');
rest.SetMultipartBodyString('xyz');

rest.PartSelector := '3';
rest.AddHeader('Content-Disposition','form-data; name="file1"; filename="a.txt"');
rest.AddHeader('Content-Type','text/plain');
rest.SetMultipartBodyString('Content of a.txt.');

rest.PartSelector := '4';
rest.AddHeader('Content-Disposition','form-data; name="file2"; filename="a.html"');
rest.AddHeader('Content-Type','text/html');
sbHtml := TChilkatStringBuilder.Create(Self);
sbHtml.LoadFile('qa_data/html/a.html','utf-8');
rest.SetMultipartBodySb(sbHtml.ControlInterface);

rest.PartSelector := '5';
rest.AddHeader('Content-Disposition','form-data; name="file3"; filename="starfish.jpg"');
rest.AddHeader('Content-Type','image/jpeg');

// When the request is sent, stream this part directly from the file.
// This avoids having to load the entire file into memory.
fileStream := TChilkatStream.Create(Self);
fileStream.SourceFile := 'qa_data/jpg/starfish.jpg';
rest.SetMultipartBodyStream(fileStream.ControlInterface);

responseBody := rest.FullRequestMultipart('POST','/some_path');
if (rest.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// ...
// ...

// Clear the REST object for any subsequent requests..
rest.ClearAllHeaders();
rest.ClearAllParts();
rest.PartSelector := '';
end;