FileGet() only gets zeroes
in [VB.NET]
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From: Saga on 11 May 2010 15:56 Hello all, I have the code listed below. This *was* working. The binary file has this structure: 2 bytes marker bytes 2 bytes flags 4 bytes 32 bit time stamp 2 bytes x bytes null terminated text string x bytes The Data The text string is optional, so it may be 0 bytes. The fourth header byte tells me this. I tested it thoroughly, but now that I have revisted this process the fileget() is reading all zeroes for the marker bytes and flags. I opened the file in DEBUG and verified that the expected data was there. Any suggestions or ideas on alternate methods are welcomed. Thank you, Saga Dim TheBytes() As Byte Dim strName As String = "" Dim bytHeader(3) As Byte Dim bytByte As Byte Dim lngTimeStamp As Integer Dim bytExtra(1) As Byte Dim intFH As Integer intFH = FreeFile() FileOpen(intFH, strDataFile, OpenMode.Binary) FileGet(intFH, (bytHeader)) 'Check for valid marker bytes If bytHeader(0) = 225 And bytHeader(1) = 179 Then FileGet(intFH, lngTimeStamp) '2 more bytes. FileGet(intFH, (bytExtra)) If (bytHeader(3) And 16) = 16 Then 'Get the name. Do FileGet(intFH, bytByte) If bytByte > 0 Then strName = strName & Chr(bytByte) End If Loop Until bytByte = 0 End If ReDim TheBytes(CInt(LOF(intFH) - 1)) FileGet(intFH, (TheBytes))
From: Armin Zingler on 11 May 2010 19:32 Am 11.05.2010 21:56, schrieb Saga: > Hello all, I have the code listed below. This *was* working. ....until you did _what_? Enable Option Strict and put the array names in () braces? > The binary > file has this structure: > > 2 bytes marker bytes > 2 bytes flags > 4 bytes 32 bit time stamp > 2 bytes > x bytes null terminated text string > x bytes The Data > > The text string is optional, so it may be 0 bytes. The fourth header > byte tells me this. I tested it thoroughly, but now that I have revisted > this process the fileget() is reading all zeroes for the marker bytes and > flags. I opened the file in DEBUG and verified that the expected data > was there. Any suggestions or ideas on alternate methods are welcomed. > Thank you, Saga Did you upgrade a VB6 project? Or why do you use the old VB functions? Use the System.IO namespace instead. > Dim TheBytes() As Byte > Dim strName As String = "" > Dim bytHeader(3) As Byte > Dim bytByte As Byte > Dim lngTimeStamp As Integer > Dim bytExtra(1) As Byte > Dim intFH As Integer > > > intFH = FreeFile() > > FileOpen(intFH, strDataFile, OpenMode.Binary) > > FileGet(intFH, (bytHeader)) With the "()" arround the 2nd arg, it is an expression. The value of the expressions is stored in an internal, local variable in order to be able to pass the reference to the variable to the FileGet method. This is because the 2nd arg is passed ByRef. FileGet returns a new array, and the reference is stored in that invisible local variable. After that it's lost. So the solution while keeping Option Strict On is: Dim tmpArray As Array = bytHeader FileGet(intFH, tmpArray) bytHeader = DirectCast(tmpArray, Byte()) Still I wouldn't use the FileXY methods anymore. -- Armin
From: Saga on 12 May 2010 11:46 Your reply is much appreciated. To answer some of your questions: Yes - I ported this algorithm from a VB6 project. After experimenting with various options I found that using fileX() family of functions was the fastest way to convert the VB6 code. Yes - I turned on Option Strict. All successful testing was done before I did that. Suspecting that this might have caused the change in behavior I turned option strict OFF, but this did not solve the problem. Yes - after the code failed I am looking for an alternative to using the fileX() family of functions. I am aware that using the current method is notthe best way to do this. Lack of time and ease won out this time, but I am looking for a different way to do this. I have made the change that you suggested and the routine is now once again functional. Thank you for you help. Your suggestions have not fallen on deaf ear and I will look into a way to do this not using the fileX() family. I am currently looking into using System.IO. FileStream. Regards, Saga "Armin Zingler" <az.nospam(a)freenet.de> wrote in message news:%23sHu7JW8KHA.1560(a)TK2MSFTNGP02.phx.gbl... > Am 11.05.2010 21:56, schrieb Saga: >> Hello all, I have the code listed below. This *was* working. > > ...until you did _what_? Enable Option Strict and put the array names > in () braces? > >> The binary >> file has this structure: >> >> 2 bytes marker bytes >> 2 bytes flags >> 4 bytes 32 bit time stamp >> 2 bytes >> x bytes null terminated text string >> x bytes The Data >> >> The text string is optional, so it may be 0 bytes. The fourth header >> byte tells me this. I tested it thoroughly, but now that I have revisted >> this process the fileget() is reading all zeroes for the marker bytes and >> flags. I opened the file in DEBUG and verified that the expected data >> was there. Any suggestions or ideas on alternate methods are welcomed. >> Thank you, Saga > > Did you upgrade a VB6 project? Or why do you use the old VB functions? > Use the System.IO namespace instead. > > >> Dim TheBytes() As Byte >> Dim strName As String = "" >> Dim bytHeader(3) As Byte >> Dim bytByte As Byte >> Dim lngTimeStamp As Integer >> Dim bytExtra(1) As Byte >> Dim intFH As Integer >> >> >> intFH = FreeFile() >> >> FileOpen(intFH, strDataFile, OpenMode.Binary) >> >> FileGet(intFH, (bytHeader)) > > With the "()" arround the 2nd arg, it is an expression. > The value of the expressions is stored in an internal, local variable > in order to be able to pass the reference to the variable to the > FileGet method. This is because the 2nd arg is passed ByRef. > > FileGet returns a new array, and the reference is stored in that > invisible local variable. After that it's lost. > > So the solution while keeping Option Strict On is: > > Dim tmpArray As Array = bytHeader > FileGet(intFH, tmpArray) > bytHeader = DirectCast(tmpArray, Byte()) > > > Still I wouldn't use the FileXY methods anymore. > > -- > Armin
From: Chris Dunaway on 12 May 2010 12:51 On May 12, 10:46 am, "Saga" <antiS...(a)nowhere.com> wrote: > Your reply is much appreciated. To answer some of your questions: > > Yes - I ported this algorithm from a VB6 project. After experimenting > with various options I found that using fileX() family of functions was > the fastest way to convert the VB6 code. > > Yes - I turned on Option Strict. All successful testing was done > before I did that. Suspecting that this might have caused the change in > behavior I turned option strict OFF, but this did not solve the problem. > > Yes - after the code failed I am looking for an alternative to using the > fileX() family of functions. I am aware that using the current method > is notthe best way to do this. Lack of time and ease won out this time, > but I am looking for a different way to do this. > > I have made the change that you suggested and the routine is now > once again functional. Thank you for you help. Your suggestions > have not fallen on deaf ear and I will look into a way to do this not > using the fileX() family. I am currently looking into using System.IO. > FileStream. Regards, Saga > > "Armin Zingler" <az.nos...(a)freenet.de> wrote in message > > news:%23sHu7JW8KHA.1560(a)TK2MSFTNGP02.phx.gbl... > > > Am 11.05.2010 21:56, schrieb Saga: > >> Hello all, I have the code listed below. This *was* working. > > > ...until you did _what_? Enable Option Strict and put the array names > > in () braces? > > >> The binary > >> file has this structure: > > >> 2 bytes marker bytes > >> 2 bytes flags > >> 4 bytes 32 bit time stamp > >> 2 bytes > >> x bytes null terminated text string > >> x bytes The Data > > >> The text string is optional, so it may be 0 bytes. The fourth header > >> byte tells me this. I tested it thoroughly, but now that I have revisted > >> this process the fileget() is reading all zeroes for the marker bytes and > >> flags. I opened the file in DEBUG and verified that the expected data > >> was there. Any suggestions or ideas on alternate methods are welcomed. > >> Thank you, Saga > > > Did you upgrade a VB6 project? Or why do you use the old VB functions? > > Use the System.IO namespace instead. > > >> Dim TheBytes() As Byte > >> Dim strName As String = "" > >> Dim bytHeader(3) As Byte > >> Dim bytByte As Byte > >> Dim lngTimeStamp As Integer > >> Dim bytExtra(1) As Byte > >> Dim intFH As Integer > > >> intFH = FreeFile() > > >> FileOpen(intFH, strDataFile, OpenMode.Binary) > > >> FileGet(intFH, (bytHeader)) > > > With the "()" arround the 2nd arg, it is an expression. > > The value of the expressions is stored in an internal, local variable > > in order to be able to pass the reference to the variable to the > > FileGet method. This is because the 2nd arg is passed ByRef. > > > FileGet returns a new array, and the reference is stored in that > > invisible local variable. After that it's lost. > > > So the solution while keeping Option Strict On is: > > > Dim tmpArray As Array = bytHeader > > FileGet(intFH, tmpArray) > > bytHeader = DirectCast(tmpArray, Byte()) > > > Still I wouldn't use the FileXY methods anymore. > > > -- > > Armin Look at the BinaryReader class. It has methods such as ReadByte, ReadInt32, ReadString, etc. that should work for your purposes and it's not any more difficult than FileGet. http://msdn.microsoft.com/en-us/library/system.io.binaryreader_methods%28v=VS.100%29.aspx Chris
From: Armin Zingler on 12 May 2010 14:27
As Chris says. And here's the code: Untested of course! ;) In the line "TheBytes = " I'm assuming that you want to read only the rest of the file. In your code the array was as long as the whole file. imports system.io '... Using fs As New FileStream("a:\devicemissing", FileMode.Open, FileAccess.Read, FileShare.Read) Dim br As New BinaryReader(fs) Dim header As Byte() Dim name As String Dim TheBytes As Byte() header = br.ReadBytes(4) If header(0) = 225 AndAlso header(1) = 179 Then Dim Timestamp = br.ReadInt32 br.ReadInt16() If (header(3) And 16) = 16 Then 'Get the name. Dim Codes As New List(Of Byte) Do Dim code = br.ReadByte If code = 0 Then Exit Do Codes.Add(code) Loop name = System.Text.Encoding.Default.GetString(Codes.ToArray) End If TheBytes = br.ReadBytes(CInt(fs.Length - fs.Position)) End If br.Close() End Using -- Armin |