Dart

Streaming Download Large File to the Local Filesystem

See more Azure Cloud Storage Examples

Downloads a large file in a streaming fashion to the local filesystem. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // Azure File Service Example: Downloads a large file to the local filesystem using a Chilkat stream.
  // See:  https://docs.microsoft.com/en-us/rest/api/storageservices/get-file

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

  final rest = CkRest();

  // Connect to the Azure Storage Blob Service
  final bTls = true;
  final port = 443;
  final bAutoReconnect = true;
  // In this example, the storage account name is "chilkat".
  try {
    rest.connect('chilkat.file.core.windows.net', port, bTls, bAutoReconnect);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Provide Azure Cloud credentials for the REST calls.
  final azAuth = CkAuthAzureStorage();
  azAuth.accessKey = 'AZURE_ACCESS_KEY';
  // The account name used here should match the 1st part of the domain passed in the call to Connect (above).
  azAuth.account = 'chilkat';
  azAuth.scheme = 'SharedKey';
  azAuth.service = 'File';
  // This causes the "x-ms-version: 2021-08-06" header to be automatically added.
  azAuth.xMsVersion = '2021-08-06';
  rest.setAuthAzureStorage(azAuth);

  // Note: The application does not need to explicitly set the following
  // headers: x-ms-date, Authorization.  These headers
  // are automatically set by Chilkat.

  // When streaming a download to the local filesystem or directed elsewhere,
  // the complete HTTP GET operation must be broken into parts.
  // For example, an HTTP GET consists of sending the request, followed by reading the response header,
  // and then finally the response body.  We'll want to read the response header, and then based
  // on the information received (such as success or failure), either read the response body
  // as an error message, or as the file data.

  // Send the HTTP GET request to download the file.
  // The share is named "pip".
  try {
    rest.sendReqNoBody('GET', '/pip/somethingBig.zip');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Read the response header.
  final responseStatusCode = rest.readResponseHeader();
  if (responseStatusCode < 0) {
    print(rest.lastErrorText);
    return;
  }

  print('Response status code = $responseStatusCode');

  // We expect a 200 response status if the file data is coming.
  // Otherwise, we'll get a string response body with an error message(or no response body).
  if (responseStatusCode == 200) {

    final bodyStream = CkStream();

    // The stream's sink will be a file.
    bodyStream.sinkFile = 'qa_output/somethingBig.zip';

    // Read the response body to the stream.  Given that we've
    // set the stream's sink to a file, it will stream directly
    // to the file.
    try {
      rest.readRespBodyStream(bodyStream, true);
    } on ChilkatException catch (e) {
      print(e.lastErrorText);
      return;
    }

    print('Successfully received the large file.');
  } else {
    try {
      final errResponse = rest.readRespBodyString();
      print(errResponse);
    } on ChilkatException catch (e) {
      print(e.lastErrorText);
    }
  }
}