(Unicode C++) AWS S3 File Streaming Upload

Demonstrates how to do a streaming upload from a file to the AWS S3 storage service. The AWS authorization presents some difficulties when the REST request body is to be streamed from a file (or from some other source). The issue is that the SHA-256 hash of the file data must be calculated. There are only two possible ways to do this: (1) stream the file into memory in its entirety and calculate the SHA-256 hash prior to uploading, or (2) pre-calculate the SHA-256 in a streaming fashion, and then provide it to the AWS authentication object.

If the application does NOT pre-compute the SHA-256, then Chilkat (internally) is forced to stream into memory, calculate the SHA-256, and then upload from the in-memory copy of the file.

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#include <CkCrypt2W.h>
#include <CkRestW.h>
#include <CkAuthAwsW.h>
#include <CkStreamW.h>

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

    // This first part is optional.  AWS authentication requires
    // the SHA-256 hash of the request body (i.e. the contents of the file
    // to be uploaded).  We can choose to pre-calculate the SHA-256 in a streaming fashion
    // and then provide it to the authenticator object.  This way, if the file is
    // extremely large, it never needs to completely reside in memory.
    CkCrypt2W crypt;
    crypt.put_EncodingMode(L"hex");
    crypt.put_HashAlgorithm(L"sha-256");
    const wchar_t *fileToUploadPath = L"qa_data/xml/hamlet.xml";
    const wchar_t *hashStr = crypt.hashFileENC(fileToUploadPath);

    CkRestW rest;

    // Connect to the Amazon AWS REST server.
    bool bTls = true;
    int port = 443;
    bool bAutoReconnect = true;
    bool success = rest.Connect(L"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.
    CkAuthAwsW authAws;
    authAws.put_AccessKey(L"AWS_ACCESS_KEY");
    authAws.put_SecretKey(L"AWS_SECRET_KEY");
    authAws.put_ServiceName(L"s3");
    // Provide the pre-computed SHA-256 here:
    authAws.put_PrecomputedSha256(hashStr);

    success = rest.SetAuthAws(authAws);

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

    CkStreamW fileStream;
    fileStream.put_SourceFile(fileToUploadPath);

    // Upload to the S3 Storage service.
    // If the application provided the SHA-256 hash of the file contents (as shown above)
    // then file is streamed and never has to completely reside in memory.
    // If the application did NOT provide the SHA-256, then Chilkat will (internally) 
    // load the entire file into memory, calculate the SHA-256, and then upload.
    const wchar_t *responseStr = rest.fullRequestStream(L"PUT",L"/hamlet.xml",fileStream);
    if (rest.get_LastMethodSuccess() != true) {
        wprintf(L"%s\n",rest.lastErrorText());
        return;
    }

    // When successful, the S3 Storage service will respond with a 200 response code,
    // with an XML body.  
    if (rest.get_ResponseStatusCode() == 200) {
        wprintf(L"%s\n",responseStr);
        wprintf(L"File uploaded.\n");
    }
    else {
        // Examine the request/response to see what happened.
        wprintf(L"response status code = %d\n",rest.get_ResponseStatusCode());
        wprintf(L"response status text = %s\n",rest.responseStatusText());
        wprintf(L"response header: %s\n",rest.responseHeader());
        wprintf(L"response body: %s\n",responseStr);
        wprintf(L"---\n");
        wprintf(L"LastRequestStartLine: %s\n",rest.lastRequestStartLine());
        wprintf(L"LastRequestHeader: %s\n",rest.lastRequestHeader());
    }
    }