(Tcl) Streaming Download Large File to the Local Filesystem

Downloads a large file in a streaming fashion to the local filesystem.

Chilkat Tcl Extension Downloads Chilkat Tcl Extension Downloads

load ./chilkat.dll

# Azure File Service Example: Downloads a large file to the local filesystem using a Chilkat stream.
# See:  https://docs.microsoft.com/en-us/rest/api/storageservices/get-file

# 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 Azure Storage Blob Service
set bTls 1
set port 443
set bAutoReconnect 1
# In this example, the storage account name is "chilkat".
set success [CkRest_Connect $rest "chilkat.file.core.windows.net" $port $bTls $bAutoReconnect]
if {$success != 1} then {
    puts [CkRest_lastErrorText $rest]
    delete_CkRest $rest
    exit
}

# Provide Azure Cloud credentials for the REST calls.
set azAuth [new_CkAuthAzureStorage]

CkAuthAzureStorage_put_AccessKey $azAuth "AZURE_ACCESS_KEY"
# The account name used here should match the 1st part of the domain passed in the call to Connect (above).
CkAuthAzureStorage_put_Account $azAuth "chilkat"
CkAuthAzureStorage_put_Scheme $azAuth "SharedKey"
CkAuthAzureStorage_put_Service $azAuth "File"
# This causes the "x-ms-version: 2020-08-04" header to be automatically added.
CkAuthAzureStorage_put_XMsVersion $azAuth "2020-08-04"
set success [CkRest_SetAuthAzureStorage $rest $azAuth]

# Note: The application does not need to explicitly set the following
# headers: x-ms-date, Authorization.  These headers
# are automatically set by Chilkat.

# When streaming a download to the local filesystem or directed elsewhere,
# the complete HTTP GET operation must be broken into parts.
# For example, an HTTP GET consists of sending the request, followed by reading the response header,
# and then finally the response body.  We'll want to read the response header, and then based
# on the information received (such as success or failure), either read the response body
# as an error message, or as the file data.

# Send the HTTP GET request to download the file.
# The share is named "pip".
set success [CkRest_SendReqNoBody $rest "GET" "/pip/somethingBig.zip"]
if {$success != 1} then {
    puts [CkRest_lastErrorText $rest]
    delete_CkRest $rest
    delete_CkAuthAzureStorage $azAuth
    exit
}

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

puts "Response status code = $responseStatusCode"

# We expect a 200 response status if the file data is coming.
# Otherwise, we'll get a string response body with an error message(or no response body).
if {$responseStatusCode == 200} then {

    set bodyStream [new_CkStream]

    # The stream's sink will be a file.
    CkStream_put_SinkFile $bodyStream "qa_output/somethingBig.zip"

    # Read the response body to the stream.  Given that we've
    # set the stream's sink to a file, it will stream directly
    # to the file.
    set success [CkRest_ReadRespBodyStream $rest $bodyStream 1]
    if {$success != 1} then {
        puts [CkRest_lastErrorText $rest]
        delete_CkRest $rest
        delete_CkAuthAzureStorage $azAuth
        delete_CkStream $bodyStream
        exit
    }

    puts "Successfully received the large file."

} else {
    set errResponse [CkRest_readRespBodyString $rest]
    if {[CkRest_get_LastMethodSuccess $rest] != 1} then {
        puts [CkRest_lastErrorText $rest]
    }     else {
        puts "$errResponse"
    }

}


delete_CkRest $rest
delete_CkAuthAzureStorage $azAuth
delete_CkStream $bodyStream