Folderitem.MoveTo Problem

Targets macOS
#1

Hello to everyone,

I’m usng folderitem.MoveTo(folderitem2) to move files from my internal harddisk to my Synology NAS. Everything works fine with files below 4 GB, but with files over 4 GB I get a hard crash.

I thought that the NAS who is connected either over SMB or AFP may not accept files over 4 GB like it’a the case for FAT 32 formated drives, but that does not seem to be the case as I can move a 6 GB file to it in the Finder.

I do also not understand why it crashes hard instead of aborting the move and generating an error message.

#2

As always please post your exact code and the relevant part of the crashlog.

Do you test if the NAS supports files that are larger than 4 GB? Something like VolumeSupportsHugeFilesMBS?

#3

Could that be another case of a “32bit problem in a 64bit environment” like with Xojo’s Math?

1 Like
#4

OK, I was a way too fast. After verifying my code, I remembered that I calculate an MD5 checksum before moving files and as this process is very fast I didn’t realise that the crash already occurs here.

Here is the code I use

Public Function GetMD5Hash(f As FolderItem) as String
  // test parameters
  If f=Nil Then Return ""
  If Not f.Exists or f.IsFolder Then Return ""
  
  var InputData As TextInputStream
  InputData=TextInputStream.Open(f)
  
  var FileData As String
  If InputData=Nil Then
    Return ""
  Else
    FileData=InputData.ReadAll
    InputData.Close
  End If
  
  Return EncodeHex(MD5(FileData))
  
End Function

It is the “FileData=InputData.ReadAll” (TextInputStream.ReadAll) who crashes hard if the file size exceeds 4GB

B.T.W The title of this post is no more accurate, but I don’t find a way to change it.

1 Like
#5

OK, finally I think that String has a limit of 4 GB.

#6

Eh, why are you reading 4 GB at once? Can you make an MD5 for like the first 100MB or does the MBS plugin have a checksum that’s working for huge files?

#7

A checksum should be most probably a different one for different files and by reading just 100 MB this will not be the case. I initially have done this because Xojo does not offer a way to generate a checksum for a file but only for strings or memory blocks.

Nevertheless, I’ve found a workaround with a terminal wrapper for Mac OS, but it is certainly possible for windows and I will develop it later. The wrapper is also able to calculate an SHA-512, SHA-256 or SHA-1 checksum. If someone is interested in it, the code is here and it costs nothing:

Public Function getChecksum(Extends f As FolderItem, type As String) as String
  var st As String
  var term As new Shell
  
  #If TargetMachO or TargetARM then
    select case type
    case "SHA512"
      term.Execute"shasum -a 512 "+f.ShellPath
    case "SHA256"
      term.Execute"shasum -a 256 "+f.ShellPath
    case "SHA1"
      term.Execute"shasum -a 1 "+f.ShellPath
    case "MD5"
      term.Execute"MD5 "+f.ShellPath
    end select
    
    st=term.Result
    if type="MD5" then
      if st.CountFields("=")<>2 then Return ""
      Return st.NthField("=",2).Trim.Uppercase
    else
      if st.CountFields("  ")<>2 then Return ""
      Return st.NthField("  ",1).Trim.Uppercase
    end if
    
  #elseif TargetWindows then
    
    // HAS TO BE CODED (real time test)
    // "certutil -hashfile "+f.ShellPath+" MD5"

    Return ""
  #endif
  
End Function