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(PureBasic) 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.
IncludeFile "CkRest.pb" IncludeFile "CkStream.pb" IncludeFile "CkAuthAws.pb" IncludeFile "CkCrypt2.pb" Procedure ChilkatExample() ; 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. crypt.i = CkCrypt2::ckCreate() If crypt.i = 0 Debug "Failed to create object." ProcedureReturn EndIf CkCrypt2::setCkEncodingMode(crypt, "hex") CkCrypt2::setCkHashAlgorithm(crypt, "sha-256") fileToUploadPath.s = "qa_data/xml/hamlet.xml" hashStr.s = CkCrypt2::ckHashFileENC(crypt,fileToUploadPath) rest.i = CkRest::ckCreate() If rest.i = 0 Debug "Failed to create object." ProcedureReturn EndIf ; Connect to the Amazon AWS REST server. bTls.i = 1 port.i = 443 bAutoReconnect.i = 1 success.i = CkRest::ckConnect(rest,"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. authAws.i = CkAuthAws::ckCreate() If authAws.i = 0 Debug "Failed to create object." ProcedureReturn EndIf CkAuthAws::setCkAccessKey(authAws, "AWS_ACCESS_KEY") CkAuthAws::setCkSecretKey(authAws, "AWS_SECRET_KEY") CkAuthAws::setCkServiceName(authAws, "s3") ; Provide the pre-computed SHA-256 here: CkAuthAws::setCkPrecomputedSha256(authAws, hashStr) success = CkRest::ckSetAuthAws(rest,authAws) ; Set the bucket name via the HOST header. ; In this case, the bucket name is "chilkat100". CkRest::setCkHost(rest, "chilkat100.s3.amazonaws.com") fileStream.i = CkStream::ckCreate() If fileStream.i = 0 Debug "Failed to create object." ProcedureReturn EndIf CkStream::setCkSourceFile(fileStream, 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. responseStr.s = CkRest::ckFullRequestStream(rest,"PUT","/hamlet.xml",fileStream) If CkRest::ckLastMethodSuccess(rest) <> 1 Debug CkRest::ckLastErrorText(rest) CkCrypt2::ckDispose(crypt) CkRest::ckDispose(rest) CkAuthAws::ckDispose(authAws) CkStream::ckDispose(fileStream) ProcedureReturn EndIf ; When successful, the S3 Storage service will respond with a 200 response code, ; with an XML body. If CkRest::ckResponseStatusCode(rest) = 200 Debug responseStr Debug "File uploaded." Else ; Examine the request/response to see what happened. Debug "response status code = " + Str(CkRest::ckResponseStatusCode(rest)) Debug "response status text = " + CkRest::ckResponseStatusText(rest) Debug "response header: " + CkRest::ckResponseHeader(rest) Debug "response body: " + responseStr Debug "---" Debug "LastRequestStartLine: " + CkRest::ckLastRequestStartLine(rest) Debug "LastRequestHeader: " + CkRest::ckLastRequestHeader(rest) EndIf CkCrypt2::ckDispose(crypt) CkRest::ckDispose(rest) CkAuthAws::ckDispose(authAws) CkStream::ckDispose(fileStream) ProcedureReturn EndProcedure
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