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Lianja Examples

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(Lianja) Download Binary File to In-Memory Bytes

This example demonstrates how to download the binary content of a file from Google Drive directly into local memory.

Chilkat Lianja Extension Download

Chilkat Lianja Extension

llSuccess = .T.

//  It requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  This example uses a previously obtained access token having permission for the
//  Google Drive scope.

loGAuth = createobject("CkAuthGoogle")
loGAuth.AccessToken = "GOOGLE-DRIVE-ACCESS-TOKEN"

loRest = createobject("CkRest")

//  Connect using TLS.
//  A single REST object, once connected, can be used for many Google Drive REST API calls.
//  The auto-reconnect indicates that if the already-established HTTPS connection is closed,
//  then it will be automatically re-established as needed.
llBAutoReconnect = .T.
llSuccess = loRest.Connect("www.googleapis.com",443,.T.,llBAutoReconnect)

//  Provide the authentication credentials (i.e. the access token)
loRest.SetAuthGoogle(loGAuth)

//  ------------------------------------------------------------------------------
//  To download a file, we must know the file ID.
//  In a previous example (see Build Local Metadata Cache
//  we built a local cache to make it easy to lookup file IDs given a file path.
//  Let's say we want to download "testFolder/abc/123/penguins.jpg".
//  First we lookup the fileId in the cache.  With the fileId, we can download the file.
loGdCache = createobject("CkCache")
loGdCache.Level = 0
loGdCache.AddRoot("C:/ckCache/googleDrive")

lcFileId = loGdCache.FetchText("testFolder/abc/123/penguins.jpg")
if (loGdCache.LastMethodSuccess <> .T.) then
    ? "Filepath not found in cache."
    release loGAuth
    release loRest
    release loGdCache
    return
endif

//  We need to send a GET request like this:
//  GET https://www.googleapis.com/drive/v3/files/fileId?alt=media
//  The fileId is part of the path.
loSbPath = createobject("CkStringBuilder")
loSbPath.Append("/drive/v3/files/")
loSbPath.Append(lcFileId)
loRest.AddQueryParam("alt","media")

//  To download to memory, we'll send the request in one call, then receive
//  the response header, and then the response body.
//  If the response header indicates failure or an unexpected response, then the
//  body is not the data we desire.

//  First send the HTTP request.
llSuccess = loRest.SendReqNoBody("GET",loSbPath.GetAsString())
if (llSuccess <> .T.) then
    ? loRest.LastErrorText
    release loGAuth
    release loRest
    release loGdCache
    release loSbPath
    return
endif

//  Get the response header.
lnStatusCode = loRest.ReadResponseHeader()
if (lnStatusCode <> 200) then
    ? "response status code = " + str(loRest.ResponseStatusCode)
    ? "response status text = " + loRest.ResponseStatusText
    ? "response header: " + loRest.ResponseHeader

    //  Read the response body (which should be error text or HTML)
    lcErrResponseBody = loRest.ReadRespBodyString()
    if (loRest.LastMethodSuccess = .T.) then
        ? "response body: " + lcErrResponseBody
    endif

    release loGAuth
    release loRest
    release loGdCache
    release loSbPath
    return
endif

//  Read the response body, which should contain the file data.

loJpgBytes = loRest.ReadRespBodyBinary()
if (loRest.LastMethodSuccess <> .T.) then
    ? loRest.LastErrorText
    release loGAuth
    release loRest
    release loGdCache
    release loSbPath
    return
endif

//  Save jpgBytes to a file so we can examine the file to verify that it worked.
loFac = createobject("CkFileAccess")
loFac.WriteEntireFile("qa_output/penguins_out.jpg",loJpgBytes)

? "File downloaded."


release loGAuth
release loRest
release loGdCache
release loSbPath
release loFac

 

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