PureBasic

Download File (Stream to Local Filesystem)

See more Google Drive Examples

This example demonstrates how to download the content of a file from Google Drive. The file is streamed to the local filesystem. PureBasic

IncludeFile "CkStringBuilder.pb"
IncludeFile "CkAuthGoogle.pb"
IncludeFile "CkRest.pb"
IncludeFile "CkStream.pb"
IncludeFile "CkCache.pb"

Procedure ChilkatExample()

    success.i = 0

    success = 1

    ; 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.

    gAuth.i = CkAuthGoogle::ckCreate()
    If gAuth.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkAuthGoogle::setCkAccessToken(gAuth, "GOOGLE_DRIVE_ACCESS_TOKEN")

    rest.i = CkRest::ckCreate()
    If rest.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; 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.
    bAutoReconnect.i = 1
    success = CkRest::ckConnect(rest,"www.googleapis.com",443,1,bAutoReconnect)

    ; Provide the authentication credentials (i.e. the access token)
    CkRest::ckSetAuthGoogle(rest,gAuth)

    ; ------------------------------------------------------------------------------
    ; 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.
    gdCache.i = CkCache::ckCreate()
    If gdCache.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkCache::setCkLevel(gdCache, 0)
    CkCache::ckAddRoot(gdCache,"C:/ckCache/googleDrive")

    fileId.s = CkCache::ckFetchText(gdCache,"testFolder/abc/123/penguins.jpg")
    If CkCache::ckLastMethodSuccess(gdCache) <> 1
        Debug "Filepath not found in cache."
        CkAuthGoogle::ckDispose(gAuth)
        CkRest::ckDispose(rest)
        CkCache::ckDispose(gdCache)
        ProcedureReturn
    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.
    sbPath.i = CkStringBuilder::ckCreate()
    If sbPath.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkStringBuilder::ckAppend(sbPath,"/drive/v3/files/")
    CkStringBuilder::ckAppend(sbPath,fileId)
    CkRest::ckAddQueryParam(rest,"alt","media")

    ; Create a stream object with a SinkFile set to the path where the downloaded file will go.
    fileStream.i = CkStream::ckCreate()
    If fileStream.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkStream::setCkSinkFile(fileStream, "qa_output/penguins.jpg")
    ; Indicate that the response body should stream directly to fileStream,
    ; but only if the response status is 200.  
    CkRest::ckSetResponseBodyStream(rest,200,1,fileStream)

    ; Download the file, streaming the content to the SinkFile.
    jsonResponse.s = CkRest::ckFullRequestNoBody(rest,"GET",CkStringBuilder::ckGetAsString(sbPath))
    If CkRest::ckLastMethodSuccess(rest) <> 1
        Debug CkRest::ckLastErrorText(rest)
        CkAuthGoogle::ckDispose(gAuth)
        CkRest::ckDispose(rest)
        CkCache::ckDispose(gdCache)
        CkStringBuilder::ckDispose(sbPath)
        CkStream::ckDispose(fileStream)
        ProcedureReturn
    EndIf

    ; A successful response will have a status code equal to 200.
    If CkRest::ckResponseStatusCode(rest) <> 200
        Debug "response status code = " + Str(CkRest::ckResponseStatusCode(rest))
        Debug "response status text = " + CkRest::ckResponseStatusText(rest)
        Debug "response header: " + CkRest::ckResponseHeader(rest)
        CkAuthGoogle::ckDispose(gAuth)
        CkRest::ckDispose(rest)
        CkCache::ckDispose(gdCache)
        CkStringBuilder::ckDispose(sbPath)
        CkStream::ckDispose(fileStream)
        ProcedureReturn
    EndIf

    Debug "File downloaded."


    CkAuthGoogle::ckDispose(gAuth)
    CkRest::ckDispose(rest)
    CkCache::ckDispose(gdCache)
    CkStringBuilder::ckDispose(sbPath)
    CkStream::ckDispose(fileStream)


    ProcedureReturn
EndProcedure