How To Get and Set the Memory Settings with eVB (306826)

MORE INFORMATION

On Microsoft Windows CE devices, you can adjust the memory settings to allocate memory between object store (storage) and program memory. This adjustment is typically made in the system's Control Panel. The sample code to follow illustrates how you can use the SetSystemMemoryDivision function to programmatically set this boundary line.

Step-by-Step Example

1. Start a new PocketPC project in eVB. Form1 is created by default.
2. Add six labels, two text boxes, two command buttons, one horizontal scroll bar, and one shape control to Form1. Do not be concerned with the placement of these controls.
3. Paste the following code into Form1:

   Option Explicit
   Const SYSMEM_CHANGED = 0
   Const SYSMEM_FAILED = 3
   
   Declare Function GetLastError Lib "coredll" () As Long
   
   Declare Function GetSystemMemoryDivision Lib "coredll" _
       (lpdwStorePages As Long, _
        lpdwRamPages As Long, _
        lpdwPageSize As Long) As Long
   
   Declare Function SetSystemMemoryDivision Lib "coredll" _
       (ByVal dwStorePages As Long) As Long
   
   Dim lStorePages As Long
   Dim lPageSize As Long
   Dim lRamPages As Long
       
   Private Sub GetMemoryInfo()
       Dim lRet As Long
       lRet = GetSystemMemoryDivision(lStorePages, lRamPages, lPageSize)
       If lRet > 0 Then
           SetUI
       Else
           MsgBox "Call failed"
       End If
   End Sub
   
   Private Sub Command1_Click()
       GetMemoryInfo
   End Sub
   
   Private Sub Command2_Click()
       Dim lRet As Long
       lRet = SetSystemMemoryDivision(lStorePages)
       
       If lRet = SYSMEM_FAILED Then
           MsgBox "Failure....GetLastError returned: " & GetLastError
       End If
       
       GetMemoryInfo
   End Sub
   
   Private Sub Form_OKClick()
       App.End
   End Sub
   
   Sub SetUI()
       HScroll1.Max = lStorePages + lRamPages
       HScroll1.Value = lStorePages
       Label4.Caption = "Total main memory: " & _
           FormatNumber(TurntoMB(lStorePages + lRamPages)) & " MB"
       Text1.Text = FormatNumber(TurntoMB(lStorePages), 2) & " MB"
       Text2.Text = FormatNumber(TurntoMB(lRamPages), 2) & " MB"
       Label5.Caption = Text1.Text
       Label6.Caption = Text2.Text
   End Sub
   
   Public Function TurntoMB(lsize As Long) As Long
       TurntoMB = (lsize * lPageSize) / 1024 ^ 2
   End Function
   
   Public Function TurnToMem(lsize As Long) As Long
       TurnToMem = (lsize / lPageSize) * 1024 ^ 2
   End Function
   
   Private Sub HScroll1_Change()
       Text1.Text = FormatNumber(TurntoMB(HScroll1.Value), 2) & " MB"
       Text2.Text = FormatNumber(TurntoMB(HScroll1.Max - _
           HScroll1.Value), 2) & " MB"
       lStorePages = HScroll1.Value
   End Sub
   
   Private Sub Form_Load()
       Label1.Caption = "Storage"
       Label2.Caption = "Program"
       Label3.Caption = "Allocated"
       Label4.Caption = ""
       Label5.Caption = ""
       Label6.Caption = ""
       Text1.Text = ""
       Text2.Text = ""
       Form1.Caption = "Memory Division"
       Command1.Caption = "Get Memory Info"
       Command2.Caption = "Set Memory Info"
       HScroll1.Min = 0
       HScroll1.Max = 8000
       HScroll1.LargeChange = 100
       HScroll1.SmallChange = 10
       Label1.Move 120, 480, 735, 255
       Label2.Move 2400, 480, 735, 255
       Label3.Move 1320, 1680, 855, 255
       Label4.Move 120, 120, 2895, 255
       Label5.Move 240, 1680, 975, 255
       Label6.Move 2280, 1680, 975, 255
       Text1.Move 120, 840, 975, 255
       Text2.Move 2400, 840, 975, 255
       Command1.Move 120, 2520, 2055, 375
       Command2.Move 120, 3000, 2055, 375
       HScroll1.Move 120, 1200, 3255, 255
       Shape1.Move 120, 1560, 3255, 495
   
       GetMemoryInfo
   End Sub
   					

4. Ensure that the remote device is being targeted, and run the application.
5. Scroll the horizontal scroll bar, and click Set Memory Info to change the memory settings.

IMPORTANT: A PocketPC runs a memory division check at least once every 5 seconds and whenever the Task Manager starts an application. As a part of this check, the memory division is set to equal parts if it is determined that free memory in one division is 5 times larger than the free memory in the other.