OpenFile()

Syntax

Result = OpenFile(#File, Filename$, Callback [, Flags])
Description
Open an existing file for read and write operations.

Parameters

#File The number to identify the file. #PB_Any can be used to auto-generate this number.
Filename$ The name of the file to read. The filename can be an URL or a local file (if the flag #PB_LocalFile is set).
Callback The callback to be called when data has been read from the file. If the flag #PB_File_Streaming is not set, the callback will be called only when the whole file has been read. It has to use the following syntax:
  Procedure Callback(Status, Filename$, File, SizeRead)
    Select Status
      Case #PB_Status_Loaded
        ; File correctly loaded
        
      Case #PB_Status_Saved
        ; File correctly saved
        
      Case #PB_Status_Progress
        ; File loading in progress, use FileProgress() get the current progress

      Case #PB_Status_Error
        ; File loading has failed
    EndSelect
  EndProcedure
Flags (optional) It can be a combination (using the '| operand) of the following values:
  #PB_LocalFile: the filename is a local file. OpenFileRequester()() needs to be called before
                 to have access to local files. SelectedFileID()() is used to get the
                 local file identifier.
  #PB_GoogleDriveFile: the filename is a google drive file identifier. OpenFileRequester()() can be called with the #PB_Requester_GoogleDrive
                 flag, SelectedFileID()() can be used to get the google drive file identifier.
  #PB_File_Streaming: the file will be read chunk by chunk, using FetchData(). It is only 
                      supported with #PB_LocalFile. 
  #PB_LocalStorage: will save the file on client side using its filename when @closefile() is called. This file
                  could be opened again in anothe session in the same browser later, but it can be wiped if the
                  user clear its local cache. It's also domain related, so if the application domain name change,
                  the files won't be accessible anymore.

combined with one of the following values (the following flags affect the ReadString() and ReadCharacter() behaviour):
  #PB_Ascii  : all read string operation will use ascii if not specified otherwise.
  #PB_UTF8   : all read string operation will use UTF-8 if not specified otherwise (default).
  #PB_Unicode: all read string operation will use Unicode if not specified otherwise.

Return value

Returns nonzero if the file was opened successfully and zero if there was an error. If #PB_Any was used as the #File parameter then the new generated number is returned on success.

Remarks

To create a new and empty file, use the CreateFile() function.

Example


  Procedure ReadCallback(Status, Filename$, File, Size)
    If Status = #PB_Status_Loaded
      Debug "File: " + Filename$ + " - Size: " + Size + " bytes"
      
      ; Read the first 10 lines
      ;
      While Eof(0) = 0 And NbLine < 10 
        Debug ReadString(0)            
        NbLine+1
      Wend
      
      CloseFile(0)
      
    ElseIf Status = #PB_Status_Error
      Debug "Error when loading the file: " + Filename$
    EndIf
  EndProcedure
  
  Procedure OpenFileRequesterCallback()
    If NextSelectedFile()
      OpenFile(0, SelectedFileID(), @ReadCallback(), #PB_LocalFile)
    EndIf
  EndProcedure
  
  Procedure ChooseFileEvent()
    OpenFileRequester("*.txt", @OpenFileRequesterCallback())
  EndProcedure
  
  OpenWindow(0, 0, 0, 300, 50, "Read file example", #PB_Window_ScreenCentered)
    ButtonGadget(0, 10, 10, 280, 30, "Choose a file...")
    
  BindGadgetEvent(0, @ChooseFileEvent())

See Also

CreateFile(), ReadFile(), CloseFile(), FileProgress()()
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