demo3.zip (33.3 KB)

程序代码：

'我们先理解一下数组的概念，数组是由一组连续的内存区域构成
'比如有一排连续的房间，每个房间都有一个编号，这个编号也是连续的。
'例如房间1、房间2、...房间n,这个n就是房间的编号，如果我对你说“请”到房间2
'拿一本书给我，那么你完成这个任务首先就是找到房间2,然后进入房间2拿到这本书。
'显而易见这个编号实际上就是地址
'那么，如果我们取得数组的首地址，那么我们就可以根据地址对数组进行各种操作。
'C语言提供了取得数组地址的语言特性，而VB则没有这样的语言特性，但我们依然可以
'通过API得到数组的地址。我们先来认识下这一个DLL--Msvbvm60.dll,这个是vb6.0
'的程序运行库,其就提供了一个可以获得数组地址的API,它的api声明如下:
Private Declare Function VarPtrArray Lib "msvbvm60.dll" Alias "VarPtr" _
        (ptr() As Any) As Long
       
'CopyMemory API请参照《VB指针教程1》，地址:https://bbs.bccn.net/thread-305122-1-1.html
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" _
       (Destination As Any, Source As Any, ByVal Length As Long)

Private Sub Form_Load()
    Dim arr(1 To 3) As Integer
    For i = 1 To 3
        arr(i) = i * 10
    Next
    Dim arraddr As Long
    '取得arr数组的首地址
    arraddr = VarPtrArray(arr)
    Dim arr1 As Integer, arr2 As Integer, arr3 As Integer
    CopyMemory arr1, ByVal arraddr, 2
    CopyMemory arr2, ByVal arraddr + 2, 2
    CopyMemory arr3, ByVal arraddr + 4, 2
    List1.AddItem "arr(1)=" & arr1
    List1.AddItem "arr(2)=" & arr2
    List1.AddItem "arr(3)=" & arr3
End Sub
'观察运行的结果，显然不是我们所预期的，为什么呢？这是因为VB数组的存储结构不同于我们先前所说的。
'VB数组的存储结构是使用一种叫做SafeArray的结构，而VarPtrArray(arr)取得的即是指向SafeArray结
'构的指针 ,我们现在得先去了解下SafeArray结构:
'Private Type SafeArray
'    cDims As Integer     '指向数组维数的指针
'    fFeatures As Integer '用来描述数组如何分配和如何被释放的标志
'    cbElements As Long   '指向数组元素所占的字节数的指针
'    cLocks As Long       '一个计数器，用来跟踪该数组被锁定的次数
'    pvData As Long       '指向数组内一个元素的指针,最重要的部分
'    cElements As Long    '数组元素的个数
'    lLbound As Long      '数组的下限
'End Type
''以下是fFeatures的常量标志
'Private Const FADF_AUTO         As Integer = &H1   '在堆栈中执行的分配
'Private Const FADF_STATIC       As Integer = &H2   '静态分配
'Private Const FADF_EMBEDDED     As Integer = &H4   '在结构中创建
'Private Const FADF_FIXEDSIZE   As Integer = &H10   '不能改变数组大小
'Private Const FADF_RECORD      As Integer = &H20   '记录容器
'Private Const FADF_HAVEIID     As Integer = &H40   '有IID 身份标记 数组
'Private Const FADF_HAVEVARTYPE As Integer = &H80   'VT 类型数组
'Private Const FADF_BSTR       As Integer = &H100   'BSTR数组
'Private Const FADF_UNKNOWN    As Integer = &H200   'IUnknown* 数组
'Private Const FADF_DISPATCH   As Integer = &H400   'IDispatch* 数组
'Private Const FADF_VARIANT    As Integer = &H800   'VARIANTs数组
'Private Const FADF_RESERVED  As Integer = &HF008   '余留，将来使用
  
Private Sub Command1_Click()
   List2.Clear
   List3.Clear
   Dim arr(1 To 3) As Integer
   For i = 1 To 3
       arr(i) = i * 10
   Next
   '指向SafeArrayld结构的指针
   Dim SafeArrayldPoint As Long
  
   '把arr数组的首地址复制到SafeArrayldPoint
   CopyMemory SafeArrayldPoint, ByVal VarPtrArray(arr), 4
  
   '数组的维数
   Dim dims As Integer
   CopyMemory dims, ByVal SafeArrayldPoint, 2
   List2.AddItem "数组的维数:" & dims
  
   Dim elements As Long
   CopyMemory elements, ByVal SafeArrayldPoint + 4, 4
   List2.AddItem "数组元素所占的字节数:" & elements
  
   Dim eCount As Long
   CopyMemory eCount, ByVal SafeArrayldPoint + 16, 4
   List2.AddItem "数组元素的个数:" & eCount

 
   Dim lBd As Long
   CopyMemory lBd, ByVal SafeArrayldPoint + 20, 4
   List2.AddItem "数组的下限:" & lBd
  
  '读取数组的值
   Dim arraddr As Long
   CopyMemory arraddr, ByVal SafeArrayldPoint + 12, 4
   Dim arr1 As Integer, arr2 As Integer, arr3 As Integer
   CopyMemory arr1, ByVal arraddr, 2
   CopyMemory arr2, ByVal arraddr + 2, 2
   CopyMemory arr3, ByVal arraddr + 4, 2
   List3.AddItem "arr(1)=" & arr1
   List3.AddItem "arr(2)=" & arr2
   List3.AddItem "arr(3)=" & arr3
   '修改数组的值
   CopyMemory ByVal arraddr, 13, 2
   CopyMemory ByVal arraddr + 2, 28, 2
   MsgBox "arr(1)=" & arr(1)
   MsgBox "arr(2)=" & arr(2)
   MsgBox "arr(3)=" & arr(3)
End Sub