Hello

i have used the following code to write a linked list.
but the code crashes at CopyMemoryRead in ReadDataToStructure.
may i know the reason for the failure of my code!?!?




Public Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" _
    (Destination As Any, Source As Any, ByVal Length As Long)
Public Declare Function GetProcessHeap Lib "kernel32" () As Long
Public Declare Function HeapAlloc Lib "kernel32" _
    (ByVal hHeap As Long, ByVal dwFlags As Long, _
    ByVal dwBytes As Long) As Long
Public Declare Function HeapFree Lib "kernel32" _
    (ByVal hHeap As Long, ByVal dwFlags As Long, _
    lpMem As Any) As Long
Public Declare Sub CopyMemoryPut Lib "kernel32" Alias _
    "RtlMoveMemory" (ByVal Destination As Long, _
    Source As Any, ByVal Length As Long)
Public Declare Sub CopyMemoryRead Lib "kernel32" Alias _
    "RtlMoveMemory" (Destination As Any, _
    ByVal Source As Long, ByVal Length As Long)

Public pHead As Long

Public Type struc_ewordptr

    sUserName As String
    sDir As String
    sFileName As String
    pNext As Long

End Type

Public Sub PutDataIntoStructure(ByVal ptr As Long, _
        szdata As String, ByVal ptrNext As Long)
Dim stLL As struc_ewordptr
    stLL.sUserName = szdata
    stLL.pNext = ptrNext
    CopyMemoryPut ptr, stLL, 504
End Sub

Public Sub ReadDataToStructure(ByVal ptr As Long, _
        struct As struc_ewordptr)
Dim stLL As struc_ewordptr
    CopyMemoryRead stLL, ptr, 504
    struct.sUserName = stLL.sUserName
    struct.pNext = stLL.pNext
End Sub

Public Sub ReadLinkedListDataAndFreeMemory()

Dim pLocal As Long
Dim hHeap As Long
Dim stLL As struc_ewordptr
Dim strData As String
    pLocal = pHead
    hHeap = GetProcessHeap()
    Do While pLocal <> 0
        ReadDataToStructure pLocal, stLL
        strData = strData & vbCrLf & stLL.sUserName
        HeapFree hHeap, 0, pLocal
        pLocal = stLL.pNext
    Loop
    MsgBox strData
End Sub
Public Sub CreateLinkedList()
'add three items to list
' get the heap first
    Dim pFirst As Long, pSecond As Long 'local pointers
    Dim hHeap As Long
    Dim str As String

    hHeap = GetProcessHeap()
    'allocate memory for the first and second element
    pFirst = HeapAlloc(hHeap, 0, 504)
    pSecond = HeapAlloc(hHeap, 0, 504)
    If pFirst <> 0 And pSecond <> 0 Then
    'memory is allocated
        str = InputBox("enter the user name")

        PutDataIntoStructure pFirst, str, pSecond
        PutDataIntoStructure pSecond, "Pointers", 0
        pHead = pFirst
    End If
    'put he second element in the list
End Sub


thanks in advance
Sruti