Xbase++

AWS S3 File Streaming Upload

See more Amazon S3 (new) Examples

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.

Xbase++

LOCAL nSuccess
LOCAL oCrypt
LOCAL cFileToUploadPath
LOCAL cHashStr
LOCAL oRest
LOCAL nBTls
LOCAL nPort
LOCAL nBAutoReconnect
LOCAL oAuthAws
LOCAL oFileStream
LOCAL cResponseStr

nSuccess := 0

//  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.
oCrypt := CreateObject("Chilkat.Crypt2")
oCrypt:EncodingMode := "hex"
oCrypt:HashAlgorithm := "sha-256"
cFileToUploadPath := "qa_data/xml/hamlet.xml"
cHashStr := oCrypt:HashFileENC(cFileToUploadPath)

oRest := CreateObject("Chilkat.Rest")

//  Connect to the Amazon AWS REST server.
nBTls := 1
nPort := 443
nBAutoReconnect := 1
nSuccess := oRest:Connect("s3.amazonaws.com", nPort, nBTls, nBAutoReconnect)

//  ----------------------------------------------------------------------------
//  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.
oAuthAws := CreateObject("Chilkat.AuthAws")
oAuthAws:AccessKey := "AWS_ACCESS_KEY"
oAuthAws:SecretKey := "AWS_SECRET_KEY"
oAuthAws:ServiceName := "s3"
//  Provide the pre-computed SHA-256 here:
oAuthAws:PrecomputedSha256 := cHashStr

nSuccess := oRest:SetAuthAws(oAuthAws)

//  Set the bucket name via the HOST header.
//  In this case, the bucket name is "chilkat100".
oRest:Host := "chilkat100.s3.amazonaws.com"

oFileStream := CreateObject("Chilkat.Stream")
oFileStream:SourceFile := cFileToUploadPath

//  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.
cResponseStr := oRest:FullRequestStream("PUT", "/hamlet.xml", oFileStream)
IF (oRest:LastMethodSuccess != 1)
    ? oRest:LastErrorText
    oCrypt:destroy()
    oRest:destroy()
    oAuthAws:destroy()
    oFileStream:destroy()
    RETURN
ENDIF

//  When successful, the S3 Storage service will respond with a 200 response code,
//  with an XML body.  
IF (oRest:ResponseStatusCode == 200)
    ? cResponseStr
    ? "File uploaded."
ELSE
    //  Examine the request/response to see what happened.
    ? "response status code = " + Str(oRest:ResponseStatusCode)
    ? "response status text = " + oRest:ResponseStatusText
    ? "response header: " + oRest:ResponseHeader
    ? "response body: " + cResponseStr
    ? "---"
    ? "LastRequestStartLine: " + oRest:LastRequestStartLine
    ? "LastRequestHeader: " + oRest:LastRequestHeader
ENDIF

oCrypt:destroy()
oRest:destroy()
oAuthAws:destroy()
oFileStream:destroy()