(Tcl) REST Read Response with Stream API

Demonstrates how to make a REST call that returns a binary body, and to receive the body through a stream API.

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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.

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"
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"

# Send the request to download the JPG.
set success [CkRest_SendReqNoBody $rest "GET" "/starfish.jpg"]
if {$success != 1} then {
    puts [CkRest_lastErrorText $rest]
    delete_CkRest $rest
    delete_CkAuthAws $authAws
    exit
}

# Read the response header.
set responseStatusCode [CkRest_ReadResponseHeader $rest]
if {$responseStatusCode < 0} then {
    puts [CkRest_lastErrorText $rest]
    delete_CkRest $rest
    delete_CkAuthAws $authAws
    exit
}

puts "Response status code = $responseStatusCode"

# We expect a 200 response status if the JPG data is coming.
# Otherwise, we'll get a string response body with an error message(or no response body).
if {$responseStatusCode != 200} then {
    set errResponse [CkRest_readRespBodyString $rest]
    if {[CkRest_get_LastMethodSuccess $rest] != 1} then {
        puts [CkRest_lastErrorText $rest]
    }     else {
        puts "$errResponse"
    }

    delete_CkRest $rest
    delete_CkAuthAws $authAws
    exit
}

set bodyStream [new_CkStream]

# Set a 10 second read timeout for the stream. 
# (Give up if no data arrives within 10 seconds after calling a read method.)
CkStream_put_ReadTimeoutMs $bodyStream 10000

# Create a background thread task to read the response body (which feeds
# it to the bodyStream object.)
# readResponseBodyTask is a CkTask
set readResponseBodyTask [CkRest_ReadRespBodyStreamAsync $rest $bodyStream 1]

# Start the task. 
set success [CkTask_Run $readResponseBodyTask]

# The application can now read the bodyStream...
set nextChunk [new_CkByteData]

while {[CkStream_get_EndOfStream $bodyStream] != 1} {

    # Read the next chunk of bytes (whatever is immediately available,
    # or wait for more data (up to 10 seconds because we set the stream's ReadTimeoutMs property)
    set success [CkStream_ReadBytes $bodyStream $nextChunk]
    if {$success != 1} then {
        puts "Failed to receive more response data."
        # Make sure the background task is aborted/cancelled.
        set success [CkTask_Cancel $readResponseBodyTask]
        delete_CkTask $readResponseBodyTask

        delete_CkRest $rest
        delete_CkAuthAws $authAws
        delete_CkStream $bodyStream
        delete_CkByteData $nextChunk
        exit
    }

    # OK.. the app has the next chunk of the body, and may do whatever it wishes with it...
    # See the CkByteData online reference documentation for 
    # information about accessing and manipulating the byte data.

}

delete_CkTask $readResponseBodyTask

puts "Successfully received the entire response body."

delete_CkRest $rest
delete_CkAuthAws $authAws
delete_CkStream $bodyStream
delete_CkByteData $nextChunk