Android Question Language Barrier - Fixed width strings.

[RickV]

Topic is ZModem. I have written a zmodem protocol back in VB6 days and need to convert to B4A and B4J. It was a very successful two way protocol that recovers from errors and continues without having to start a new download. ie: incomplete . I am aware that there is ftp available in b4x however zmodem over tcp connection is required.

I cannot work out how to have fixed width strings in b4x. Below is some code from vb6 to demonstrate what I require to achieve. As you will see this is set to a specific width or chunk size........

    Global c2048    As String * 2048
    Global c1024    As String * 1024
    Global c512     As String * 512
    Global c256     As String * 256
    Global c128     As String * 128
    Global c64      As String * 64
    Global c32      As String * 32
    Global c16      As String * 16
    Global c8       As String * 8
    Global c4       As String * 4
    Global c2       As String * 2
    Global c1       As String * 1

So after having our chunk size empty strings, we then pull a chunk from a file that we wish to transfer. The following VB function I wrote will retrieve the required next chunk and return the data as a string ready to poke down the tcp ip connection.

Function ZModem(TheFileName As String, Record As Long) As String

Dim RecNum      As Long
Dim TheFile     As Integer
Dim OutString   As String
Dim TotalBytes  As Long


TheFile = FreeFile
Open TheFileName For Binary Shared As #TheFile
Seek TheFile, 1
CPXLen = LOF(TheFile)
TotalBytes = CPXLen
mn = 0

If CPXLen > 0 Then
RecNum = 0
    Do 'While CPXLen > 0
        If CPXLen >= 2048 Then
            Get #1, , c2048
            OutString = c2048
            RecNum = RecNum + 1
            CPXLen = CPXLen - 2048
            mn = mn + 2048
        ElseIf CPXLen >= 1024 Then
            Get #1, , c1024
            OutString = c1024
            RecNum = RecNum + 1
            CPXLen = CPXLen - 1024
            mn = mn + 1024
        ElseIf CPXLen >= 512 Then
            Get #1, , c512
            OutString = c512
            RecNum = RecNum + 1
            CPXLen = CPXLen - 512
            mn = mn + 512
        ElseIf CPXLen >= 256 Then
            Get #1, , c256
            OutString = c256
            RecNum = RecNum + 1
            CPXLen = CPXLen - 256
            mn = mn + 256
        ElseIf CPXLen >= 128 Then
            Get #1, , c128
            OutString = c128
            RecNum = RecNum + 1
            CPXLen = CPXLen - 128
            mn = mn + 128
        ElseIf CPXLen >= 64 Then
            Get #1, , c64
            OutString = c64
            RecNum = RecNum + 1
            CPXLen = CPXLen - 64
            mn = mn + 64
        ElseIf CPXLen >= 32 Then
            Get #1, , c32
            OutString = c32
            RecNum = RecNum + 1
            CPXLen = CPXLen - 32
            mn = mn + 32
        ElseIf CPXLen >= 16 Then
            Get #1, , c16
            OutString = c16
            RecNum = RecNum + 1
            CPXLen = CPXLen - 16
            mn = mn + 16
        ElseIf CPXLen >= 8 Then
            Get #1, , c8
            OutString = c8
            RecNum = RecNum + 1
            CPXLen = CPXLen - 8
            mn = mn + 8
        ElseIf CPXLen >= 4 Then
            Get #1, , c4
            OutString = c4
            RecNum = RecNum + 1
            CPXLen = CPXLen - 4
            mn = mn + 4
        ElseIf CPXLen >= 2 Then
            Get #1, , c2
            OutString = c2
            RecNum = RecNum + 1
            CPXLen = CPXLen - 2
            mn = mn + 2
        ElseIf CPXLen >= 1 Then
            Get #1, , c1
            OutString = c1
            RecNum = RecNum + 1
            CPXLen = CPXLen - 1
            mn = mn + 1
        End If
        If CPXLen = 0 And (RecNum < Record) Then
            GoTo 100
            Exit Do
        End If
    Loop While RecNum < Record
    OutString = FillIt(Format(RecNum, "0"), 1, 8) + _
                FillIt(Format(TotalBytes, "0"), 1, 8) + _
                OutString
Else
'    OutString = FillIt(Format(RecNum, "0"), 1, 8) + OutString
100 OutString = ""
    OutString = FillIt(Format(0, "0"), 1, 8) + _
                FillIt(Format(TotalBytes, "0"), 1, 8) + _
                OutString
End If
Close #TheFile
   
ZModem = OutString + CRC(OutString)
    
End Function

the two questions I have, is
1. How to get a fixed width string and
2. Are we able to open a file for binary random access like in the function above ?

Any help would be greatly appreciated.

 

[RickV]

I have come up with this so far....

Dim aaa As String
    Dim RAF As RandomAccessFile
    Dim b() As Byte
    Dim x() As Byte
            
    TXRec = Rec
    RAF.Initialize(File.DirInternalCache, fName, True)
    RAF.CurrentPosition = Rec
    If RAF.Size - (RAF.CurrentPosition + 4096) > 4095 Then
            RAF.ReadBytes(b, 0, 4096, TXRec)
            TXRec = TXRec + 4096
            aaa = BytesToString(x, 0, x.Length, CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 2048) > 2047 Then
            RAF.ReadBytes(b, 0, 2048, TXRec)
            TXRec = TXRec + 2048
            aaa = BytesToString(x,0,x.Length,CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 1024) > 1023 Then
            RAF.ReadBytes(b, 0, 1024, TXRec)
            TXRec = TXRec + 1024
            aaa = BytesToString(x,0,x.Length,CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 512) > 511 Then
            RAF.ReadBytes(b, 0, 512, TXRec)
            TXRec = TXRec + 512
            aaa = BytesToString(x,0,x.Length,CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 256) > 255 Then
            RAF.ReadBytes(b, 0, 256, TXRec)
            TXRec = TXRec + 256
            aaa = BytesToString(x,0,x.Length,CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 128) > 127 Then
            RAF.ReadBytes(b, 0, 128, TXRec)
            TXRec = TXRec + 128
            aaa = BytesToString(x,0,x.Length,CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 64) > 63 Then
            RAF.ReadBytes(b, 0, 64, TXRec)
            TXRec = TXRec + 64
            aaa = BytesToString(x,0,x.Length,CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 32) > 31 Then
            RAF.ReadBytes(b, 0, 32, TXRec)
            TXRec = TXRec + 32
            aaa = BytesToString(x,0,x.Length,CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 16) > 15 Then
            RAF.ReadBytes(b, 0, 16, TXRec)
            TXRec = TXRec + 16
            aaa = BytesToString(x,0,x.Length,CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 8) > 7 Then
            RAF.ReadBytes(b, 0, 8, TXRec)
            TXRec = TXRec + 8
            aaa = BytesToString(x,0,x.Length,CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 4) > 3 Then
            RAF.ReadBytes(b, 0, 4, TXRec)
            TXRec = TXRec + 4
            aaa = BytesToString(x,0,x.Length,CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 2) > 1 Then
            RAF.ReadBytes(b, 0, 2, TXRec)
            TXRec = TXRec + 2
            aaa = BytesToString(x,0,x.Length,CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 1) > 0 Then
            RAF.ReadBytes(b, 0, 1, TXRec)
            TXRec = TXRec + 1
            aaa = BytesToString(x,0,x.Length,CharSet)
            SendIt(18550, Pad(fName,20,0) & aaa)
        End If
        If RAF.Size - (RAF.CurrentPosition + 1) > RAF.Size  Then
            SendIt(18551, Pad(fName,20,0))
        End If
    'End If
    RAF.Close