React Native

REST Download Bandwidth Throttle

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Demonstrates how to use download bandwidth throttling with the REST API. This example will download a file from Drobox using a file stream, with a limit on the bandwidth that can be used for the transfer. React Native

import { CkDateTime, DtObj, JsonObject, Rest, Socket, Stream } from '@chilkat/react-native'

async function chilkatExample() {
  // This example requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  // A Dropbox access token should have been previously obtained.
  // Dropbox access tokens do not expire.
  // See Dropbox Access Token.

  // To use bandwidth throttling, the connection should be made using the socket API.
  // This provides numerous properties to customize the connection, such as
  // BandwidthThrottleDown, BandwidthThrottleUp, ClientIpAddress, ClintPort, Http Proxy,
  // KeepAlive, PreferIpv6, RequireSslCertVerify, SoRcvBuf, SoSndBuf, SoReuseAddr,
  // SOCKS proxy, TcpNoSDelay, TlsPinSet, TlsCipherSuite, SslAllowedCiphers, etc.

  const socket = new Socket();
  const maxWaitMs = 5000;
  try {
    await socket.connectAsync('content.dropboxapi.com', 443, true, maxWaitMs);
  } catch {
    console.log(socket.lastErrorText);
    console.log(`Connect Fail Reason: ${socket.connectFailReason}`);
    return;
  }

  // Set the download bandwidth throttle rate to 50000 bytes per second.
  socket.bandwidthThrottleDown = 50000;

  const rest = new Rest();

  // Tell the REST object to use the connected socket.
  rest.useConnection(socket, true);

  // The remainder of this example is identical to the example at:
  // Dropbox Download File.

  // Add request headers.
  rest.addHeader('Authorization', 'Bearer DROPBOX_ACCESS_TOKEN');

  // The download "parameters" are contained in JSON passed in an HTTP request header.
  // This is the JSON indicating the file to be downloaded:
  // { 
  //    "path": "/Homework/lit/hamlet.xml",
  // }

  const json = new JsonObject();
  json.appendString('path', '/Homework/lit/hamlet.xml');
  rest.addHeader('Dropbox-API-Arg', json.emit());

  // Setup a file stream for the download
  const fileStream = new Stream();
  fileStream.sinkFile = 'qa_output/hamletFromDropbox.xml';

  // Indicate that the call to FullRequestNoBody should send the response body
  // to fileStream if the response status code is 200.
  // If a non-success response status code is received, then nothing
  // is streamed to the output file and the error response is returned by FullRequestNoBody.
  const expectedStatus = 200;
  rest.setResponseBodyStream(expectedStatus, true, fileStream);

  let responseStr: string;
  try {
    responseStr = await rest.fullRequestNoBodyAsync('POST', '/2/files/download');
  } catch {
    console.log(rest.lastErrorText);
    return;
  }

  // When successful, Dropbox responds with a 200 response code.
  if (rest.responseStatusCode !== 200) {
    // Examine the request/response to see what happened.
    console.log(`response status code = ${rest.responseStatusCode}`);
    console.log(`response status text = ${rest.responseStatusText}`);
    console.log(`response header: ${rest.responseHeader}`);
    console.log(`response body (if any): ${responseStr}`);
    console.log('---');
    console.log(`LastRequestStartLine: ${rest.lastRequestStartLine}`);
    console.log(`LastRequestHeader: ${rest.lastRequestHeader}`);
    return;
  }

  // Information about the downloaded file is also available as JSON in a response header.
  // The "dropbox-api-result" response header contains the information.  For example:
  const apiResult = rest.responseHdrByName('dropbox-api-result');
  console.log(apiResult);

  // In this case, the pretty-formatted dropbox-api-result JSON looks like this:
  // { 
  //   "name": "hamlet.xml",
  //   "path_lower": "/homework/lit/hamlet.xml",
  //   "path_display": "/Homework/lit/hamlet.xml",
  //   "id": "id:74FkdeNuyKAAAAAAAAAAAQ",
  //   "client_modified": "2016-06-02T23:19:00Z",
  //   "server_modified": "2016-06-02T23:19:00Z",
  //   "rev": "9482db15f",
  //   "size": 279658
  // }

  // Load the JSON, pretty-print it, and demonstrate how to get some values...
  const jsonResult = new JsonObject();
  jsonResult.emitCompact = false;
  jsonResult.load(apiResult);
  // Show the JSON pretty-printed...
  console.log(jsonResult.emit());

  // Sample code to get data from the JSON response:
  const size = jsonResult.intOf('size');
  console.log(`size = ${size}`);

  const rev = jsonResult.stringOf('rev');
  console.log(`rev = ${rev}`);

  const clientModified = jsonResult.stringOf('client_modified');
  const ckdt = new CkDateTime();
  ckdt.setFromTimestamp(clientModified);
  const bLocalTime = true;
  const dt = new DtObj();
  ckdt.toDtObj(bLocalTime, dt);

  console.log(`${dt.day}/${dt.month}/${dt.year} ${dt.hour}:${dt.minute}`);
}