(C++) Download File from Dropbox (Streaming)

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Downloads a file from Dropbox, streaming it directly to a file in the filesystem.

Chilkat C/C++ Library Downloads
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#include <CkRest.h>
#include <CkJsonObject.h>
#include <CkStream.h>
#include <CkDateTime.h>
#include <CkDtObj.h>

void ChilkatSample(void)
    {
    // 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.

    CkRest rest;

    // Connect to Dropbox
    bool success = rest.Connect("content.dropboxapi.com",443,true,true);
    if (success != true) {
        std::cout << rest.lastErrorText() << "\r\n";
        return;
    }

    // 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",
    // }

    CkJsonObject json;
    json.AppendString("path","/Homework/lit/hamlet.xml");
    rest.AddHeader("Dropbox-API-Arg",json.emit());

    // Setup a file stream for the download
    CkStream fileStream;
    fileStream.put_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.
    int expectedStatus = 200;
    rest.SetResponseBodyStream(expectedStatus,true,fileStream);

    const char *responseStr = rest.fullRequestNoBody("POST","/2/files/download");
    if (rest.get_LastMethodSuccess() != true) {
        std::cout << rest.lastErrorText() << "\r\n";
        return;
    }

    // When successful, Dropbox responds with a 200 response code.
    if (rest.get_ResponseStatusCode() != 200) {
        // Examine the request/response to see what happened.
        std::cout << "response status code = " << rest.get_ResponseStatusCode() << "\r\n";
        std::cout << "response status text = " << rest.responseStatusText() << "\r\n";
        std::cout << "response header: " << rest.responseHeader() << "\r\n";
        std::cout << "response body (if any): " << responseStr << "\r\n";
        std::cout << "---" << "\r\n";
        std::cout << "LastRequestStartLine: " << rest.lastRequestStartLine() << "\r\n";
        std::cout << "LastRequestHeader: " << rest.lastRequestHeader() << "\r\n";
        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 char *apiResult = rest.responseHdrByName("dropbox-api-result");
    std::cout << apiResult << "\r\n";

    // 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...
    CkJsonObject jsonResult;
    jsonResult.put_EmitCompact(false);
    jsonResult.Load(apiResult);
    // Show the JSON pretty-printed...
    std::cout << jsonResult.emit() << "\r\n";

    // Sample code to get data from the JSON response:
    int size = jsonResult.IntOf("size");
    std::cout << "size = " << size << "\r\n";

    const char *rev = jsonResult.stringOf("rev");
    std::cout << "rev = " << rev << "\r\n";

    const char *clientModified = jsonResult.stringOf("client_modified");
    CkDateTime ckdt;
    ckdt.SetFromTimestamp(clientModified);
    bool bLocalTime = true;
    CkDtObj *dt = ckdt.GetDtObj(bLocalTime);
    std::cout << dt->get_Day() << "/" << dt->get_Month() << "/" << dt->get_Year() << " " << dt->get_Hour()
         << ":" << dt->get_Minute() << "\r\n";
    delete dt;
    }