(PureBasic) Download File (Stream to Local Filesystem)

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

Chilkat PureBasic Module Download Chilkat PureBasic Module

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

Procedure ChilkatExample()

    success.i = 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