Xbase++

Streaming Download Large File to the Local Filesystem

See more Azure Cloud Storage Examples

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

LOCAL nSuccess
LOCAL oRest
LOCAL nBTls
LOCAL nPort
LOCAL nBAutoReconnect
LOCAL oAzAuth
LOCAL nResponseStatusCode
LOCAL oBodyStream
LOCAL cErrResponse

nSuccess := 0

//  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.

oRest := CreateObject("Chilkat.Rest")

//  Connect to the Azure Storage Blob Service
nBTls := 1
nPort := 443
nBAutoReconnect := 1
//  In this example, the storage account name is "chilkat".
nSuccess := oRest:Connect("chilkat.file.core.windows.net", nPort, nBTls, nBAutoReconnect)
IF (nSuccess != 1)
    ? oRest:LastErrorText
    oRest:destroy()
    RETURN
ENDIF

//  Provide Azure Cloud credentials for the REST calls.
oAzAuth := CreateObject("Chilkat.AuthAzureStorage")
oAzAuth:AccessKey := "AZURE_ACCESS_KEY"
//  The account name used here should match the 1st part of the domain passed in the call to Connect (above).
oAzAuth:Account := "chilkat"
oAzAuth:Scheme := "SharedKey"
oAzAuth:Service := "File"
//  This causes the "x-ms-version: 2021-08-06" header to be automatically added.
oAzAuth:XMsVersion := "2021-08-06"
nSuccess := oRest:SetAuthAzureStorage(oAzAuth)

//  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".
nSuccess := oRest:SendReqNoBody("GET", "/pip/somethingBig.zip")
IF (nSuccess != 1)
    ? oRest:LastErrorText
    oRest:destroy()
    oAzAuth:destroy()
    RETURN
ENDIF

//  Read the response header.
nResponseStatusCode := oRest:ReadResponseHeader()
IF (nResponseStatusCode < 0)
    ? oRest:LastErrorText
    oRest:destroy()
    oAzAuth:destroy()
    RETURN
ENDIF

? "Response status code = " + Str(nResponseStatusCode)

//  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 (nResponseStatusCode == 200)

    oBodyStream := CreateObject("Chilkat.Stream")

    //  The stream's sink will be a file.
    oBodyStream:SinkFile := "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.
    nSuccess := oRest:ReadRespBodyStream(oBodyStream, 1)
    IF (nSuccess != 1)
        ? oRest:LastErrorText
        oRest:destroy()
        oAzAuth:destroy()
        oBodyStream:destroy()
        RETURN
    ENDIF

    ? "Successfully received the large file."

ELSE
    cErrResponse := oRest:ReadRespBodyString()
    IF (oRest:LastMethodSuccess != 1)
        ? oRest:LastErrorText
    ELSE
        ? cErrResponse
    ENDIF

ENDIF

oRest:destroy()
oAzAuth:destroy()
oBodyStream:destroy()