MultipartUpload with Presigned URLs to upload parts

[WolfgangVogl]

Hello,
I am creating a multipart upload using the function "createMultipartUploadRequest".
Now I want to create a predefined url so that someone can upload one (or more) parts.

The problem is that I have no idea how to generate the predefined URLs. The GeneratePresignedUrl method of the S3Client has the signature

Aws::String GeneratePresignedUrl(
const Aws::String& bucket,
const Aws::String& key,
Aws::Http::HttpMethod method,
const Http::HeaderValueCollection& customizedHeaders,
long long expirationInSeconds = MAX_EXPIRATION_SECONDS);

• "bucket" seems clear to me
• for "key" I would use the same key I used to create my multipart upload - or do I have to use the UploadId from the CreateMultipartUploadResult?
• as method I would use PUT
  => But how do you set the part number?

I can't find any example or documentation on this problem related to the C++ SDK - just a tutorial (https://www.altostra.com/blog/multipart-uploads-with-s3-presigned-url), but with a different programming language and I can't apply it to my project.

Hopefully someone can give me a hint!

[WolfgangVogl]

OK, I've found a (hidden) GeneratePresignedUrl Method in AWSClient I could use:
Aws::String GeneratePresignedUrl(const Aws::AmazonWebServiceRequest& request, Aws::Http::URI& uri, Aws::Http::HttpMethod method, const Aws::Http::QueryStringParameterCollection& extraParams = Aws::Http::QueryStringParameterCollection(), long long expirationInSeconds = 0) const;

But I don't know which value I have to use for 'url' - my environment is dynamically. Is it possible to get the url from my S3Client instance?

[WolfgangVogl]

Ok - I solved my problem by generating the resulting URL myself. I found the "computeEndpointString" method in the S3Client implementation - but it's private, so I re-implemented it myself.
With the computed endpoint string, it was easy to generate the predefined URL using the GeneratePresignedUrl method from AwsClient (NOT S3Client - the methods from S3Client hide the methods from AWSClient).
Maybe this snippet will help someone else:
`
Aws::S3::Model::UploadPartRequest uploadRequest;
uploadRequest.SetBucket(myBucket);
uploadRequest.SetKey(uploadName);
uploadRequest.SetUploadId(myUploadID);
uploadRequest.SetPartNumber(currentPartNumber);

// generate URI to object (http(s)://bucket.region/uploadName or http(s)://endpointOverwrite.../uploadName
auto accessUrl = getAccessAddress(myConfig, myBucket, uploadName);
constexpr auto expirationInSeconds{60 * 5};

auto presignedUrl = s3Client->Aws::Client::AWSClient::GeneratePresignedUrl(
uploadRequest,
accessUrl,
Aws::Http::HttpMethod::HTTP_PUT,
Aws::Http::QueryStringParameterCollection(),
expirationInSeconds
);
`

[github-actions[bot]]

Hello! Reopening this discussion to make it searchable.