Q147668: PRB: Len and LenB May Differ on Size of User-Defined Types

Article: Q147668
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:5.0
Operating System(s): 
Keyword(s): kbprogramming kbVBp400 kb32bitOnly
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Standard Edition, 32-bit, for Windows, version 5.0 
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 5.0 
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 5.0 
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SYMPTOMS
========

When used with a user-defined type, the LenB function may return a different
value than the Len function on 32-bit Windows platforms. This behavior occurs
because the LenB function returns the in-memory size of a type, while the Len
function returns the amount of size that a UDT would take if stored on disk.
This occurs because Visual Basic 4.0 32-bit represents strings internally in
Unicode, but externally (on disk) as ANSI. A string in the two-byte Unicode
standard will occupy twice as much space as its ANSI equivalent.

STATUS
======

This behavior is by design.

MORE INFORMATION
================

The reproduction sample below demonstrates this behavior. Note that the
fixed-length string is what causes different values for Len and LenB. The
non-fixed-length string will always return a value of 4, because that is the
space required to store a pointer to the location where the actual string is
stored. The array of bytes of size five needs 5 bytes of storage, regardless of
the contents of the array.

Steps to Reproduce
------------------

1. Start a new Visual Basic 4.0 32-bit project. Form1 is created by default.

2. Add a single module to the project by selecting Module from the Insert menu.

3. Add this code to the General Declarations section of Module1:

        Type MyUDT
           x As String * 5      'size of 10 or 5
           y As String       'size of 4
           z (1 to 5) As Byte   'size of 5
        End Type

4. Add this code to the Form_Click event of Form1:

        Private Sub Form_Click()
           Dim test As MyUDT

           test.x = "hello"
           test.y = "world"
           test.z(1) = 64
           test.z(2) = 65
           test.z(3) = 66
           test.z(4) = 67

           Print LenB(test)     'returns 21
           Print Len(test)      'returns 14
        End Sub

5. Press the F5 key or select Start from the Run menu to run the application and
  observe the behavior.

Additional query words:

======================================================================
Keywords          : kbprogramming kbVBp400 kb32bitOnly 
Technology        : kbVBSearch kbAudDeveloper kbVB400Search
Version           : WINDOWS:5.0
Issue type        : kbprb

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