(Chilkat2-Python) 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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import sys
import chilkat2

# 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 = chilkat2.Crypt2()
crypt.EncodingMode = "hex"
crypt.HashAlgorithm = "sha-256"
fileToUploadPath = "qa_data/xml/hamlet.xml"
hashStr = crypt.HashFileENC(fileToUploadPath)

rest = chilkat2.Rest()

# Connect to the Amazon AWS REST server.
bTls = True
port = 443
bAutoReconnect = True
success = rest.Connect("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 = chilkat2.AuthAws()
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"

fileStream = chilkat2.Stream()
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.
responseStr = rest.FullRequestStream("PUT","/hamlet.xml",fileStream)
if (rest.LastMethodSuccess != True):
    print(rest.LastErrorText)
    sys.exit()

# When successful, the S3 Storage service will respond with a 200 response code,
# with an XML body.  
if (rest.ResponseStatusCode == 200):
    print(responseStr)
    print("File uploaded.")
else:
    # Examine the request/response to see what happened.
    print("response status code = " + str(rest.ResponseStatusCode))
    print("response status text = " + rest.ResponseStatusText)
    print("response header: " + rest.ResponseHeader)
    print("response body: " + responseStr)
    print("---")
    print("LastRequestStartLine: " + rest.LastRequestStartLine)
    print("LastRequestHeader: " + rest.LastRequestHeader)