(Tcl) 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.

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load ./chilkat.dll

# 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.
set crypt [new_CkCrypt2]

CkCrypt2_put_EncodingMode $crypt "hex"
CkCrypt2_put_HashAlgorithm $crypt "sha-256"
set fileToUploadPath "qa_data/xml/hamlet.xml"
set hashStr [CkCrypt2_hashFileENC $crypt $fileToUploadPath]

set rest [new_CkRest]

# Connect to the Amazon AWS REST server.
set bTls 1
set port 443
set bAutoReconnect 1
set success [CkRest_Connect $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.
set authAws [new_CkAuthAws]

CkAuthAws_put_AccessKey $authAws "AWS_ACCESS_KEY"
CkAuthAws_put_SecretKey $authAws "AWS_SECRET_KEY"
CkAuthAws_put_ServiceName $authAws "s3"
# Provide the pre-computed SHA-256 here:
CkAuthAws_put_PrecomputedSha256 $authAws $hashStr

set success [CkRest_SetAuthAws $rest $authAws]

# Set the bucket name via the HOST header.
# In this case, the bucket name is "chilkat100".
CkRest_put_Host $rest "chilkat100.s3.amazonaws.com"

set fileStream [new_CkStream]

CkStream_put_SourceFile $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.
set responseStr [CkRest_fullRequestStream $rest "PUT" "/hamlet.xml" $fileStream]
if {[CkRest_get_LastMethodSuccess $rest] != 1} then {
    puts [CkRest_lastErrorText $rest]
    delete_CkCrypt2 $crypt
    delete_CkRest $rest
    delete_CkAuthAws $authAws
    delete_CkStream $fileStream
    exit
}

# When successful, the S3 Storage service will respond with a 200 response code,
# with an XML body.  
if {[CkRest_get_ResponseStatusCode $rest] == 200} then {
    puts "$responseStr"
    puts "File uploaded."
} else {
    # Examine the request/response to see what happened.
    puts "response status code = [CkRest_get_ResponseStatusCode $rest]"
    puts "response status text = [CkRest_responseStatusText $rest]"
    puts "response header: [CkRest_responseHeader $rest]"
    puts "response body: $responseStr"
    puts "---"
    puts "LastRequestStartLine: [CkRest_lastRequestStartLine $rest]"
    puts "LastRequestHeader: [CkRest_lastRequestHeader $rest]"
}


delete_CkCrypt2 $crypt
delete_CkRest $rest
delete_CkAuthAws $authAws
delete_CkStream $fileStream