Shifting Byte arrays?

This could be very easy if you happen to be using VB6

In VB6 you are allowed to assign the value of a byte array to a string and vice versa.

Simply move your byte array to a string, concatenate the 10 characters and move it back.

I think the questioner meant something else. He want to move memory.

Here is a sample:
Private Declare Sub CopyMem Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)


 Call CopyMem(udtVerBuffer, ByVal lplpBuffer, Len(udtVerBuffer))

What I want to do is "insert" bytes to the beginning of an existing byte array, not append...

Hello Mirkwood,

As I read the question, Johnn's byte array might contain something line "ABC" (looking at byte array as if it were a string)

Now what Johnn wants to do is insert 10 "blanks" before:
"          ABC" so that he has room to put in some "header" information.

In VB6 this can be achieved like I said.

Johnn, if you haven't got VB6 I think Mirkwood's suggestion might be the best alternative.

"concatenate the 10 characters"

or of course:

concatenate it to 10 characters (to insert it before)

caraf_g:
It could be that the byte array is a string but you never know.
Btw: VB5 support also the assigning byte array to string and vice versa as far as I rememeber. The problem with this that this is different under NT and win95 because of unicode.

The solution you posted(VB5 works as well) works for all strings, however I'm mixing string and numeric data.  No that I've played with the idea I might want something like this...
dim myByte() as byte
redim myByte(0 to 3)'four byte long header info, aka length of string
mybyte(0)=0
mybyte(1)=0
mybyte(2)=5
mybyte(3)=1
'now I want to "append" to this byte array a string, how do we do it without a loop? OR we could build the string byte array first and then insert this in front...

How does that unicode affect things?  Which os uses which?  From my tests(win95), assigning a string to a byte array doubles it which is not something I want(I know it recreates it properly, but we could be talking alot of loop cycles here)

It depends on your string and OS.
In general win95 uses 1 byte characters
and winnt uses 2 byte characters

are you sure you didn't get the two os' mixed up?  I'm using win95 and my bytearrays were double the size of the string.

Hello Johnn,

Can you reject my answer please - it looks like Mirkwood is getting close to having a solution for you.

as requested, although neither is close yet...

>>How does that unicode affect things?

Unicode uses a word (16 bits = TWO bytes) for each character.

VB5 Internally uses unicode or at least 2-byte strings: See following code.
This code prefixes 4 bytes to an existing byte array. But to make sure I set sensible data I set the first two bytes to 65 and 0 (making up a capital A in unicode) and the second two bytes to 66 and 0 (making up a capital B)


Dim barTEST() As Byte
Dim barTEST2(1 To 4) As Byte

Dim strTEST1 As String
Dim strTEST2 As String

strTEST2 = "Hello"
barTEST = strTEST2

MsgBox barTEST

barTEST2(1) = 65
barTEST2(2) = 0
barTEST2(3) = 66
barTEST2(4) = 0
strTEST1 = barTEST2

strTEST2 = strTEST1 & strTEST2
barTEST = strTEST2

MsgBox barTEST

PS - I'm running Windows NT 4.0 + SP3

If you want it fast, and you don't need any Wide character, use this mapping:
1 character (2 bytes) <-> 1 byte
Using CopyMemory is >2x faster than copying array members.

Paste this to your form:

Option Explicit
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (dest As Any, source As Any, ByVal bytes As Long)
Private Declare Sub ZeroMemory Lib "kernel32" Alias "RtlZeroMemory" (dest As Any, ByVal bytes As Long)
Dim myByte() As Byte

Private Sub Form_Click()
    ReDim myByte(0 To 5) 'four byte long header info, aka length of string
    myByte(0) = 1
    myByte(1) = 1
    myByte(2) = 5
    myByte(3) = 5
    myByte(4) = 7
    myByte(5) = 7
    'we could build the string byte array first and then insert this in front...
    Dim mystring As String, mylen As Long, ub As Long
    ub = UBound(myByte)
    mystring = "A A"
    mylen = Len(mystring)
    ReDim Preserve myByte(0 To ub + mylen)
    report
    CopyMemory ByVal VarPtr(myByte(mylen)), ByVal VarPtr(myByte(0)), ub + 1
    ZeroMemory ByVal VarPtr(myByte(0)), mylen
    report
' insert string
    CopyMemory myByte(0), ByVal mystring, mylen
    report
End Sub

Private Sub report()
    Dim i As Long, msg As String
    For i = 0 To UBound(myByte)
        msg = msg & myByte(i) & ","
    Next
    Debug.Print msg
End Sub

I see your invading my other thread! :) I'm looking into your solution...thanks

Johnn,

I'm a bit confused now. You've just accepted my answer but from your comments it looks like you're responding to ameba's comments.

I don't mind getting a few points but maybe in this case they should have gone to ameba? Or did you genuinely intend to accept my answer?