CString Null characters ?

  1. last week
    Edited last week

    Hello .
    I have following code that works perfect for my project.
    The string s2 contains hexadecimal values that need to be splitted up in bytes (Uint8) into an array lVal()
    X is the CString containing the created array.

    Dim i As Integer
    Dim k As Integer
    Dim s2 As String
    Dim s3 As String
    Dim n As Uint8
    Dim lVal(5) As Uint8
    Dim X As CString
    s2 = "F0 43 73 26 00 F7"
         ' Remove all spaces in string
    s3 = RepalceAll(s2, " ", "")
    s2 = s3
         ' convert string to Uint8 (bytes)
    for k = 1 to len(s2) step 2
    s3 = midB(s2, k, 2)
    n = val("&h" + s3)
    lVal(i) = n
    if n = 247 Then Exit    ' 247 = &HF7
    i = i + 1
    X = ChrB(lVall(0)) + ChrB(lVal(1)) + ChrB(lVal(2)) + ChrB(lVal(3)) + ChrB(lVal(4)) + ChrB(lVal(5))
         ' send X to a dll that accepts CString 
    rtn = HpInsertSysex(Hpid, lTime, X)

    As mentioned this works perfect, even with the 00 included into the string s2.

    In my project the length of s2 can be up to 383 characters (127 bytes + spaces).
    So it would be a long X = ChrB(lVal(0)) + ChrB(lVal(1)) + .......... + ChrB(lVal127)).

    So I tried the following in my code
    Replace X = ChrB(lVall(0)) + ChrB(lVal(1)) + ChrB(lVal(2)) + ChrB(lVal(3)) + ChrB(lVal(4)) + ChrB(lVal(5)) by

    for i = 0 to 5
    X = X + ChrB(lVal(i))

    This does work if there are no '00' in the string s2.
    If a '00' exists in the string the CString does not includes this '00'.

    I know a CString is Null terminated and this seems normal because ChrB(&H00) = a Null,
    but why does it works even with 00 if i define X as ChrB() + Chrb() + .... and not if I create it with a for next code ?

    Can anyone explain why and is there a solution ?



  2. Greg O

    Aug 9 Xojo Inc Somewhere near Raleigh, NC

    What does your lVal method do?

  3. lVal() is an Array
    He is declared in the 5th line of my code

    Dim lVal() As Uint8

  4. Tim H

    Aug 9 Pre-Release Testers Portland, OR USA

    Don't define X as CString. Dim X as String. Then it will work. The reason your first set of code works is because Xojo builds the right hand side in a temporary String variable and then assigns it to X. Your second set of code uses X as a CString, so it discards the 00 value, as it should.

    CString is not suitable for use in Xojo code directly. It exists for use in declares.

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