B4R Question SOLVED One issue in sd file update.

Discussion in 'B4R Questions' started by tigrot, May 14, 2018.

  1. tigrot

    tigrot Well-Known Member Licensed User

    Hi everybody,
    I'm writing a sub to update a record in a 51 records file. They are 18 bytes each.
    The sub is:

    Sub writeprod(pezziin As ULong, allarmiin As ULong,prodottox As Int )
    Dim raf As RandomAccessFile
    Dim buffer(18As Byte
    Dim offset As Int = prodottox * 10 + 14
    Dim nomeprod() As Byte=leggiparam("macch",bc.StringToBytes(JoinStrings(Array As String"P"NumberFormat( offset + 10,1,0)))))
        Main.sd.Position = prodottox * buffer.Length
    Log("Scrive prodotto:",prodottox, " pos: ",prodottox*buffer.Length)
    'fill the buffer from the file
        Main.sd.Stream.ReadBytes(buffer, 0, buffer.Length)
    Dim r As Record
        raf.CurrentPosition = 
    'read the data from the buffer
        r.pezzi = raf.ReadULong32( raf.CurrentPosition)
        r.allarmi = raf.ReadDouble32(raf.CurrentPosition)
        Main.sd.Position = prodottox * buffer.Length
    End Sub
    The relevant log:
    Scrive prodotto:1 pos: 18
    The strange is that record instead of being updated is appended to the file. I have tried with fresh created files, but I always get the same result. The record is written to the 52th record instead of the 2nd record (offset 18). If I rerun the sub the record is written at record 53!

    Best regards
    Mauro Zanin
  2. tigrot

    tigrot Well-Known Member Licensed User

    The new libraries in Arduino distribution seem to have a bug updating records in SD file. They always append the updated records.
    I had the most recent one 1.2.2. Just to give a try, I dowloaded the 1.1.1 and it works. I have found anything about this subject on Google.
    Hope that 1.1.1 is not buggy too somewhere!
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