B4X

Wasabi File Streaming Upload

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Demonstrates how to do a streaming upload from a file to the Wasabi 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.

B4X

Dim success As Boolean = False

'  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.
Dim crypt As ChilkatCrypt2
crypt.Initialize("crypt")
'  ----------------------------------------------------
'  Important: Wasabi requires a lowercase hex format.
'  ----------------------------------------------------
crypt.EncodingMode = "hex-lower"
crypt.HashAlgorithm = "sha-256"
Dim fileToUploadPath As String = "qa_data/xml/hamlet.xml"
Dim hashStr As String = crypt.HashFileENC(fileToUploadPath)

Dim rest As ChilkatRest
rest.Initialize("rest")

'  Connect to the Amazon AWS REST server.
Dim bTls As Boolean = True
Dim port As Int = 443
Dim bAutoReconnect As Boolean = True
'  This example will demonstrate uploading to a bucket in the eu-west-2 region
success = rest.Connect("s3.eu-west-2.wasabisys.com", port, bTls, bAutoReconnect)

'  Provide AWS credentials for the REST call.
Dim authAws As ChilkatAuthAws
authAws.Initialize
authAws.AccessKey = "access-key"
authAws.SecretKey = "secret-key"
authAws.ServiceName = "s3"
'  Provide the pre-computed SHA-256 here:
authAws.PrecomputedSha256 = hashStr

success = rest.SetAuthAws(authAws)

rest.AddHeader("Expect", "100-continue")
rest.AddHeader("Content-Type", "application/xml")

'  Set the bucket name via the HOST header.
'  In this case, the bucket name is "chilkat100".
rest.Host = "chilkat100.s3.eu-west-2.wasabisys.com"

Dim fileStream As ChilkatStream
fileStream.Initialize("fileStream")
fileStream.SourceFile = fileToUploadPath

'  Upload to the Wasabi 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.
Dim responseStr As String = rest.FullRequestStream("PUT", "/hamlet.xml", fileStream)
If rest.LastMethodSuccess <> True Then
    Log(rest.LastErrorText)
    Return
End If


'  When successful, the Wasabi Storage service will respond with a 200 response code,
'  with an XML body.  
If rest.ResponseStatusCode = 200 Then
    Log(responseStr)
    Log("File uploaded.")
Else
    '  Examine the request/response to see what happened.
    Log("response status code = " & rest.ResponseStatusCode)
    Log("response status text = " & rest.ResponseStatusText)
    Log("response header: " & rest.ResponseHeader)
    Log("response body: " & responseStr)
    Log("---")
    Log("LastRequestStartLine: " & rest.LastRequestStartLine)
    Log("LastRequestHeader: " & rest.LastRequestHeader)
End If