(Delphi DLL) REST Read Response with Stream API

Demonstrates how to make a REST call that returns a binary body, and to receive the body through a stream API.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, AuthAws, Rest, CkByteData, Task, Stream;

...

procedure TForm1.Button1Click(Sender: TObject);
var
rest: HCkRest;
bTls: Boolean;
port: Integer;
bAutoReconnect: Boolean;
success: Boolean;
authAws: HCkAuthAws;
responseStatusCode: Integer;
errResponse: PWideChar;
bodyStream: HCkStream;
readResponseBodyTask: HCkTask;
nextChunk: HCkByteData;

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

rest := CkRest_Create();

// Connect to the Amazon AWS REST server.
bTls := True;
port := 443;
bAutoReconnect := True;
success := CkRest_Connect(rest,'s3.amazonaws.com',port,bTls,bAutoReconnect);

// ----------------------------------------------------------------------------
// Important: For buckets created in regions outside us-east-1,
// there are three important changes that need to be made.
// See Working with S3 Buckets in Non-us-east-1 Regions for the details.
// ----------------------------------------------------------------------------

// Provide AWS credentials for the REST call.
authAws := CkAuthAws_Create();
CkAuthAws_putAccessKey(authAws,'AWS_ACCESS_KEY');
CkAuthAws_putSecretKey(authAws,'AWS_SECRET_KEY');
CkAuthAws_putServiceName(authAws,'s3');
success := CkRest_SetAuthAws(rest,authAws);

// Set the bucket name via the HOST header.
// In this case, the bucket name is "chilkat100".
CkRest_putHost(rest,'chilkat100.s3.amazonaws.com');

// Send the request to download the JPG.
success := CkRest_SendReqNoBody(rest,'GET','/starfish.jpg');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;

// Read the response header.
responseStatusCode := CkRest_ReadResponseHeader(rest);
if (responseStatusCode < 0) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;

Memo1.Lines.Add('Response status code = ' + IntToStr(responseStatusCode));

// We expect a 200 response status if the JPG data is coming.
// Otherwise, we'll get a string response body with an error message(or no response body).
if (responseStatusCode <> 200) then
  begin
    errResponse := CkRest__readRespBodyString(rest);
    if (CkRest_getLastMethodSuccess(rest) <> True) then
      begin
        Memo1.Lines.Add(CkRest__lastErrorText(rest));
      end
    else
      begin
        Memo1.Lines.Add(errResponse);
      end;
    Exit;
  end;

bodyStream := CkStream_Create();
// Set a 10 second read timeout for the stream. 
// (Give up if no data arrives within 10 seconds after calling a read method.)
CkStream_putReadTimeoutMs(bodyStream,10000);

// Create a background thread task to read the response body (which feeds
// it to the bodyStream object.)
readResponseBodyTask := CkRest_ReadRespBodyStreamAsync(rest,bodyStream,True);

// Start the task. 
success := CkTask_Run(readResponseBodyTask);

// The application can now read the bodyStream...
nextChunk := CkByteData_Create();
while (CkStream_getEndOfStream(bodyStream) <> True) do
  begin

    // Read the next chunk of bytes (whatever is immediately available,
    // or wait for more data (up to 10 seconds because we set the stream's ReadTimeoutMs property)
    success := CkStream_ReadBytes(bodyStream,nextChunk);
    if (success <> True) then
      begin
        Memo1.Lines.Add('Failed to receive more response data.');
        // Make sure the background task is aborted/cancelled.
        success := CkTask_Cancel(readResponseBodyTask);
        CkTask_Dispose(readResponseBodyTask);
        Exit;
      end;

    // OK.. the app has the next chunk of the body, and may do whatever it wishes with it...
    // See the CkByteData online reference documentation for 
    // information about accessing and manipulating the byte data.

  end;

CkTask_Dispose(readResponseBodyTask);

Memo1.Lines.Add('Successfully received the entire response body.');

CkRest_Dispose(rest);
CkAuthAws_Dispose(authAws);
CkStream_Dispose(bodyStream);
CkByteData_Dispose(nextChunk);

end;