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(Visual Basic 6.0) 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.
' 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 New ChilkatCrypt2 crypt.EncodingMode = "hex" crypt.HashAlgorithm = "sha-256" Dim fileToUploadPath As String fileToUploadPath = "qa_data/xml/hamlet.xml" Dim hashStr As String hashStr = crypt.HashFileENC(fileToUploadPath) Dim rest As New ChilkatRest ' Connect to the Amazon AWS REST server. Dim bTls As Long bTls = 1 Dim port As Long port = 443 Dim bAutoReconnect As Long bAutoReconnect = 1 Dim success As Long success = rest.Connect("s3.amazonaws.com",port,bTls,bAutoReconnect) ' Provide AWS credentials for the REST call. Dim authAws As New ChilkatAuthAws authAws.AccessKey = "AWS_ACCESS_KEY" authAws.SecretKey = "AWS_SECRET_KEY" authAws.ServiceName = "s3" ' Provide the pre-computed SHA-256 here: authAws.PrecomputedSha256 = hashStr success = rest.SetAuthAws(authAws) ' Set the bucket name via the HOST header. ' In this case, the bucket name is "chilkat100". rest.Host = "chilkat100.s3.amazonaws.com" Dim fileStream As New ChilkatStream fileStream.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. Dim responseStr As String responseStr = rest.FullRequestStream("PUT","/hamlet.xml",fileStream) If (rest.LastMethodSuccess <> 1) Then Text1.Text = Text1.Text & rest.LastErrorText & vbCrLf Exit Sub End If Text1.Text = Text1.Text & rest.LastErrorText & vbCrLf ' When successful, the S3 Storage service will respond with a 200 response code, ' with an XML body. If (rest.ResponseStatusCode = 200) Then Text1.Text = Text1.Text & responseStr & vbCrLf Text1.Text = Text1.Text & "File uploaded." & vbCrLf Else ' Examine the request/response to see what happened. Text1.Text = Text1.Text & "response status code = " & rest.ResponseStatusCode & vbCrLf Text1.Text = Text1.Text & "response status text = " & rest.ResponseStatusText & vbCrLf Text1.Text = Text1.Text & "response header: " & rest.ResponseHeader & vbCrLf Text1.Text = Text1.Text & "response body: " & responseStr & vbCrLf Text1.Text = Text1.Text & "---" & vbCrLf Text1.Text = Text1.Text & "LastRequestStartLine: " & rest.LastRequestStartLine & vbCrLf Text1.Text = Text1.Text & "LastRequestHeader: " & rest.LastRequestHeader & vbCrLf End If
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