Getting a set number of bytes from a file

toddw607 · August 15th, 2007, 12:45 PM

Hi everyone,
I have a seemingly simple problem which has been driving me crazy. I have a file consisting of a number of bytes and I want to take out eight bytes at a time, combine all eight bytes into a string, convert the new string to decimal and output the decimal to a text file. Here is my code that I've been working with:

Code:

                  Dim index As Integer = 8
                  For i = 0 To s1.Length() - 1 
                      bytes(i) = s1.ReadByte
                      If (i < index) Then
                          s2.WriteByte(bytes(i))
                      End If
                      index = index + 8
                  Next

Here s1 is my filestream reader and s2 is my filestream writer. So far this prints out to the writer file the same thing as the reader file. I am not familiar with working with bytes and this has been driving me crazy. Can someone please help me out. Thanks!

gbianchi · August 15th, 2007, 01:07 PM

hi there... homework????

anyway.. what are s1 and s2?? files??? opened like what???

you are writing one byte at a time, the same one you just readed ;)

look at this:

Code:

    Dim index As Integer = 8
    For i = 0 To s1.Length() - 1 
        'you read from somewhere a byte, and you store it inside a position of an array
        bytes(i) = s1.ReadByte
        If (i < index) Then
            'you get the same byte you read before, and put in into another file
            s2.WriteByte(bytes(i))
        End If
        index = index + 8
    Next

I think your logic is somehow wrong.. you have to read 8 bytes from the source, combine them (what's the diference between file 1 and 2??) and then you have to save it to destination...

HTH

Gonzalo

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toddw607 · August 15th, 2007, 01:17 PM

This isn't homework, here's an explanation of what I'm trying to do: I'm trying to get coordinates of text out of a CGM file, convert the hex values into decimal and place the decimal coordinates into a transparent layer to fit over the CGM in order for the CGM to be clickable in certain spots.
s1 (file 1) is defined as: s1 = New FileStream((FILE_NAME_IMAGE & fileName), FileMode.Open, FileAccess.Read). s2 (file 2) is defined as: s2 = New System.IO.FileStream(newName1, FileMode.Create, FileAccess.Write). All I am attempting to accomplish right now is reading in from s1, placing the hex values into a string (without any spaces between hex values) and place the string values into a text file. I know how to convert to a decimal after I get the string of 8 hex values into the file but all I am trying to do is get the string for every series of 8 hex values within the file. Sorry, I should have explained this before.

gbianchi · August 15th, 2007, 02:22 PM

I understand what are you trying to do, but I don't understand the way you are trying to achieve it..

Code:

    ' the next for is not necessary, search a better method to know when you reach eof
    For i = 0 To s1.Length() - 1 
        for j as int16 = 0 to 7
            'the next line could throw and error if reach the oef.
            bytes(j) = s1.ReadByte
        next j
        'better replace last for with something like:
        's1.read(bytes,0,8) that does the same and return the number of
        ' bytes readed...
        'convert your byte array to what you need, don't know how.
        s2.WriteByte(yournewbyte)
    'the next line surely will be replaced if you change the way you read the file
    Next

HTH

Gonzalo

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Read this if you want to know how to get a correct reply for your question:
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================================================== =========
My programs achieved a new certification (can you say the same?):
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http://www.codinghorror.com/blog/archives/000818.html
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http://worsethanfailure.com/Articles...-Hate-You.aspx
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