Option Explicit
Private Type CellStruct
sText As String
Width As Long
Height As Long
Font As StdFont
ForeColor As OLE_COLOR
'...other boolean type and Long type member
End Type
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (lpvDest As Any, _
lpvSource As Any, _
ByVal cbCopy As Long)
Private Type CellLine
Cols() As CellStruct
End Type
Private m_CellRows() As CellLine
Private Sub Form_Load()
Dim i As Long, j As Long, copysize As Long
Dim myfont(3) As New StdFont
ReDim m_CellRows(3)
For i = 0 To 3
myfont(i).Name = "Tahoma"
myfont(i).Size = 10 + i
ReDim m_CellRows(i).Cols(1)
For j = 0 To 1
m_CellRows(i).Cols(j).sText = "Test String"
m_CellRows(i).Cols(j).Height = j
Set m_CellRows(i).Cols(j).Font = myfont(i)
Next
Next
For i = 0 To 3
ReDim Preserve m_CellRows(i).Cols(1)
For j = 0 To 1
Debug.Print i & ":" & j, m_CellRows(i).Cols(j).sText, m_CellRows(i).Cols(j).Font.Size
Next
Next
For i = 3 To 2 Step -1
m_CellRows(i) = m_CellRows(i - 1) '2-->3 1-->2
Next
'copysize = LenB(m_CellRows(0))
'copysize = copysize * 2
'CopyMemory ByVal VarPtr(m_CellRows(2)), ByVal VarPtr(m_CellRows(1)), copysize
For i = 0 To 3
ReDim Preserve m_CellRows(i).Cols(1)
For j = 0 To 1
Debug.Print i & ":" & j, m_CellRows(i).Cols(j).sText, m_CellRows(i).Cols(j).Font.Size
Next
Next
End Sub
Typically we directly assign array with OBJECT and String elements by the below code to shift array,there's no problem and works fine:
For i = 3 To 2 Step -1
m_CellRows(i) = m_CellRows(i - 1) '2-->3 1-->2
Next
Considering a huge m_CellRows with 1000 elements and 100 Cols (m_CellRows(999).Cols(99)), what is the fast way to shift position when inserting at index 2?
As above, we can use:
For i = 999 To 2 Step -1
m_CellRows(i) = m_CellRows(i - 1) '998-->999 997-->998,996-->997... (999 goes away)
Next
I am trying to use CopyMemory to increase performance, But I am not sure what is reliability and memory leak, looks like failed at some time:
copysize = LenB(m_CellRows(0)) '= 4
copysize = copysize * (999-2) 'shifting ONE position for #2 till #999,old #999 goes away
CopyMemory ByVal VarPtr(m_CellRows(3)), ByVal VarPtr(m_CellRows(2)), copysize
I may confuse you too much, For my case,what is the proper way to use CopyMemory to shift one position for m_CellRows from position 2 till last elements? Please take note UDT array m_CellRows has Font Object and sText string elements.
Last edited by Jonney; Jan 21st, 2013 at 05:35 AM.
It looks to me like you are just copying the safearray pointers rather than the data.
If any of these are lost as a result of the copymemory call (eg. #999) I think you will get a leak. Manually deallocate any of these before the call to copymemory (Erase m_CellRows(999)).
The copymemory call from the example will also create a second reference to array #2. After the call I think the original needs to be deallocated using copymemory or similar to avoid the garbage collection running twice on the same object (something like CopyMemory ByVal VarPtr(m_CellRows(2)), 0, 4)
CopyMemory probably won't be able to do what you're asking. VB arrays are implemented using the SAFEARRAY structure. The pvData member of that structure is a pointer to the actual elements of the array, which are located elsewhere in memory. Thus, CopyMemory won't be able to actually "shift" the elements of the array. Also, the VarPtr function cannot be used to get the address of an array. See How To Get the Address of Variables in Visual Basic.
On Local Error Resume Next: If Not Empty Is Nothing Then Do While Null: ReDim i(True To False) As Currency: Loop: Else Debug.Assert CCur(CLng(CInt(CBool(False Imp True Xor False Eqv True)))): Stop: On Local Error GoTo 0
I'm not sure its necessary to shift the elements, just the safearray pointers (eg the 4 byte value of the Array variables)
As long as any double references are cleaned and any lost array elements are deallocated it should work (i think)
It looks to me like you are just copying the safearray pointers rather than the data.
If any of these are lost as a result of the copymemory call (eg. #999) I think you will get a leak. Manually deallocate any of these before the call to copymemory (Erase m_CellRows(999)).
The copymemory call from the example will also create a second reference to array #2. After the call I think the original needs to be deallocated using copymemory or similar to avoid the garbage collection running twice on the same object (something like CopyMemory ByVal VarPtr(m_CellRows(2)), 0, 4)
Thank you,Milk. It needs CopyMemory ByVal VarPtr(m_CellRows(2)), 0, 4 to do garbage clean. After I put this, the data looks OK. Without this, the data got mad even though no crash.
Thanks Bonnie West.
Last edited by Jonney; Jan 21st, 2013 at 07:04 PM.
Reason: Give thanks
Re: [RESOLVED] CopyMemory Shift Array one position
OK, so the mighty CopyMemory can do what you want.
Code:
Option Explicit
#If False Then
Private Type SAFEARRAY1D 'Offsets
cDims As Integer ' +0
fFeatures As Integer ' +2
cbElements As Long ' +4
cLocks As Long ' +8
pvData As Long ' +12 <-- points to first array element
cElements As Long ' +16
lLbound As Long ' +20
End Type
#End If
Private Type CellStruct 'LenB
sText As String ' 4
Width As Long ' 4
Height As Long ' 4
Font As StdFont ' 4
ForeColor As OLE_COLOR ' 4
'...other boolean type ' 2
' and Long type member ' 4
End Type
Private Type CellLine 'Elements of m_CellRows() are UDTs whose only member is a pointer to a SAFEARRAY1D UDT
Cols() As CellStruct '0 1 2 3 ... 98 99 <-- Indices
End Type '0 4 8 12 ... 392 396 <-- Offsets in Bytes
Private Declare Function VarPtrArray Lib "msvbvm60.dll" Alias "VarPtr" (ByRef ArrayVar() As Any) As Long
Private Declare Sub CopyMemory Lib "kernel32.dll" Alias "RtlMoveMemory" (ByVal Destination As Long, ByVal Source As Long, ByVal Length As Long)
Private Declare Sub GetMem4 Lib "msvbvm60.dll" (ByVal Addr As Long, ByRef RetVal As Long)
Private m_CellRows() As CellLine
Private Sub Form_Load()
Dim i As Long, j As Long, Ptr As Long
Dim MyFont As StdFont, sText As String
ReDim m_CellRows(0& To 99&) As CellLine
For i = 0& To 99&
Set MyFont = New StdFont 'Don't use As New
MyFont.Name = "Tahoma"
MyFont.Size = 10@ + i
ReDim m_CellRows(i).Cols(0& To 19&) As CellStruct
For j = 0& To 19&
m_CellRows(i).Cols(j).sText = "Test String"
m_CellRows(i).Cols(j).Height = j
Set m_CellRows(i).Cols(j).Font = MyFont
Next
Set MyFont = Nothing
Next
For i = 0& To 99&
'ReDim Preserve m_CellRows(i).Cols(1) As CellStruct <-- What for?
For j = 0& To 19&
sText = sText & i & ":" & j & vbTab & _
"""" & m_CellRows(i).Cols(j).sText & """" & vbTab _
& m_CellRows(i).Cols(j).Font.Size & vbNewLine
Next 'String concatenation isn't optimized
Next 'since this is for debugging purposes only
Clipboard.Clear: Clipboard.SetText sText
Stop 'Paste text to a text editor
'IMPORTANT!!! Free the memory occupied by the element to be overwritten
For i = 0& To 19&
m_CellRows(99&).Cols(i).sText = vbNullString 'must not be ""
Set m_CellRows(99&).Cols(i).Font = Nothing 'Long and Boolean
Next 'need not be freed
Erase m_CellRows(99&).Cols() 'Not sure if everything
ReDim m_CellRows(99&).Cols(0& To 19&) As CellStruct 'is fully deallocated here
Stop 'Step Into the code here (F8)
'Get the address of the first element of m_CellRows()
GetMem4 VarPtrArray(m_CellRows()), Ptr: Debug.Assert Ptr 'Pointer to SAFEARRAY1D
GetMem4 UAdd(Ptr, 12&), Ptr: Debug.Assert Ptr 'SAFEARRAY1D.pvData
'Shift elements up (2-98 >>> 3-99)
CopyMemory UAdd(Ptr, 12&), UAdd(Ptr, 8&), 4& * 97& '97 Long elements (pointers)
sText = vbNullString
For i = 0& To 99&
'ReDim Preserve m_CellRows(i).Cols(1) As CellStruct <-- What for?
For j = 0& To 19&
sText = sText & i & ":" & j & vbTab & _
"""" & m_CellRows(i).Cols(j).sText & """" & vbTab _
& m_CellRows(i).Cols(j).Font.Size & vbNewLine
Next
Next
Clipboard.Clear: Clipboard.SetText sText
End Sub 'Paste text to a text editor and compare with previous
That code has not been thoroughly tested for leaks, so watch out for any suspicious increase in memory usage.
EDIT
The pointer arithmetic in the above code has been modified to use the following function (inspired by Matt Curland's code):
Code:
'Increments the given pointer address by the specified positive value using unsigned arithmetic.
Private Function UAdd(ByVal Ptr As Long, ByVal Incr As Long) As Long
Const MSB = &H80000000
UAdd = (Ptr Xor MSB) + Incr Xor MSB
End Function
Last edited by Bonnie West; Mar 8th, 2013 at 07:08 AM.
On Local Error Resume Next: If Not Empty Is Nothing Then Do While Null: ReDim i(True To False) As Currency: Loop: Else Debug.Assert CCur(CLng(CInt(CBool(False Imp True Xor False Eqv True)))): Stop: On Local Error GoTo 0
Re: [RESOLVED] CopyMemory Shift Array one position
Code:
Option Explicit
#If False Then
Private Type SAFEARRAY1D 'Offsets
cDims As Integer ' +0
fFeatures As Integer ' +2
cbElements As Long ' +4
cLocks As Long ' +8
pvData As Long ' +12 <-- points to first array element
cElements As Long ' +16
lLbound As Long ' +20
End Type
#End If
Private Type CellStruct 'LenB
sText As String ' 4
Width As Long ' 4
Height As Long ' 4
Font As StdFont ' 4
ForeColor As OLE_COLOR ' 4
'...other boolean type ' 2
' and Long type member ' 4
End Type
Private Type CellLine 'Elements of m_CellRows() are UDTs whose only member is a pointer to a SAFEARRAY1D UDT
Cols() As CellStruct '0 1 2 3 ... 98 99 <-- Indices
End Type '0 4 8 12 ... 392 396 <-- Offsets in Bytes
Private Declare Function VarPtrArray Lib "msvbvm60.dll" Alias "VarPtr" (ByRef ArrayVar() As Any) As Long
Private Declare Sub CopyMemory Lib "kernel32.dll" Alias "RtlMoveMemory" (ByVal Destination As Long, ByVal Source As Long, ByVal Length As Long)
Private Declare Sub GetMem4 Lib "msvbvm60.dll" (ByVal Addr As Long, ByRef RetVal As Long)
Private m_CellRows() As CellLine
Private Sub Form_Load()
Dim i As Long, j As Long, Ptr As Long
Dim MyFont As StdFont, sText As String
Dim iDelRow As Long, num As Long, m_CntOfRows As Long
ReDim m_CellRows(0& To 5&) As CellLine
For i = 0& To 5&
Set MyFont = New StdFont 'Don't use As New
MyFont.Name = "Tahoma"
MyFont.Size = 10@ + i
ReDim m_CellRows(i).Cols(0& To 19&) As CellStruct
For j = 0& To 2&
m_CellRows(i).Cols(j).sText = "Test String" & CStr(j * Rnd)
m_CellRows(i).Cols(j).Height = j
Set m_CellRows(i).Cols(j).Font = MyFont
Next
Set MyFont = Nothing
Next
For i = 0& To 5&
'ReDim Preserve m_CellRows(i).Cols(1) As CellStruct <-- What for?
For j = 0& To 2&
sText = sText & i & ":" & j & vbTab & _
"""" & m_CellRows(i).Cols(j).sText & """" & vbTab _
& m_CellRows(i).Cols(j).Font.Size & vbNewLine
Next 'String concatenation isn't optimized
Next 'since this is for debugging purposes only
Clipboard.Clear: Clipboard.SetText sText
Stop 'Paste text to a text editor
Stop 'Step Into the code here (F8)
'Get the address of the first element of m_CellRows()
GetMem4 VarPtrArray(m_CellRows()), Ptr: Debug.Assert Ptr 'Pointer to SAFEARRAY1D
GetMem4 Ptr + 12&, Ptr: Debug.Assert Ptr 'SAFEARRAY1D.pvData
'delete item #3 and #4
iDelRow = 3: num = 2: m_CntOfRows = UBound(m_CellRows) + 1
CopyMemory Ptr + 4& * iDelRow, Ptr + 4& * (iDelRow + num), 4& * (m_CntOfRows - (iDelRow + num)) '(m_CntOfRows - (iDelRow + num)) Long elements (pointers)
m_CntOfRows = m_CntOfRows - num
ReDim Preserve m_CellRows(m_CntOfRows - 1)
sText = vbNullString
For i = 0& To UBound(m_CellRows)
For j = 0& To 2&
sText = sText & i & ":" & j & vbTab & _
"""" & m_CellRows(i).Cols(j).sText & """" & vbTab _
& m_CellRows(i).Cols(j).Font.Size & vbNewLine
Next
Next
Clipboard.Clear: Clipboard.SetText sText
End Sub 'Paste text to a text editor and compare with previous
For real case, I want to delete item #3 and item#4 (total item count is 6 -#0 to #5), I got errors. Look like the data of Cols was collapsed.
Re: [RESOLVED] CopyMemory Shift Array one position
I think you will need to understand how VB arrays (and UDTs) are arranged in memory. See the earlier link on SAFEARRAY in post #3. Once you get a better understanding, it should be simple enough to modify the necessary pointer values. Research on Pointer Arithmetic as well.
BTW, I see you've taken out the part about memory deallocation. I hope you know the consequences of doing that.
Last edited by Bonnie West; Jan 31st, 2013 at 05:42 AM.
On Local Error Resume Next: If Not Empty Is Nothing Then Do While Null: ReDim i(True To False) As Currency: Loop: Else Debug.Assert CCur(CLng(CInt(CBool(False Imp True Xor False Eqv True)))): Stop: On Local Error GoTo 0
Re: [RESOLVED] CopyMemory Shift Array one position
Originally Posted by Bonnie West
I think you will need to understand how VB arrays (and UDTs) are arranged in memory. See the earlier link on SAFEARRAY in post #3. Once you get a better understanding, it should be simple enough to modify the necessary pointer values. Research on Pointer Arithmetic as well.
BTW, I see you've taken out the part about memory deallocation. I hope you know the consequences of doing that.
Oh, it is advance stuff beyond my capability at this moment. The code looks logic but failed after I call ReDim Preserve m_CellRows(m_CntOfRows - 1). I met the same problem with pure CopyMemory:
Re: [RESOLVED] CopyMemory Shift Array one position
Could you please post the complete code that you would like to optimize? Also, please state clearly what it is that you want to accomplish. Thank you.
On Local Error Resume Next: If Not Empty Is Nothing Then Do While Null: ReDim i(True To False) As Currency: Loop: Else Debug.Assert CCur(CLng(CInt(CBool(False Imp True Xor False Eqv True)))): Stop: On Local Error GoTo 0
Re: [RESOLVED] CopyMemory Shift Array one position
Originally Posted by Bonnie West
Could you please post the complete code that you would like to optimize? Also, please state clearly what it is that you want to accomplish. Thank you.
It's a Excel-like Grid control but much simple. I am in charge of Data structure.
For MS Excel like cells, we can insert a Row or a Col, Delete/Add few Rows and Cols at a time.
Those operations are no problem with VB native Array function (MAGIC ). But I want to use CopyMemory to speed up the shifting. Refer to my attached file. I believe you understand the code.
Last edited by Jonney; Jan 31st, 2013 at 02:54 PM.
Re: [RESOLVED] CopyMemory Shift Array one position
Would you be willing to learn how to do it with CopyMemory? I'm currently making a diagram that illustrates the in-memory relationship of your data structure. It's quite complicated and I can tell you, manually shifting your array is no easy task, especially since you would have to deallocated the overwritten array element(s) yourself. So, unless you fully understand what you're doing, I would suggest don't do it.
On Local Error Resume Next: If Not Empty Is Nothing Then Do While Null: ReDim i(True To False) As Currency: Loop: Else Debug.Assert CCur(CLng(CInt(CBool(False Imp True Xor False Eqv True)))): Stop: On Local Error GoTo 0
Re: [RESOLVED] CopyMemory Shift Array one position
Originally Posted by Bonnie West
Would you be willing to learn how to do it with CopyMemory? I'm currently making a diagram that illustrates the in-memory relationship of your data structure. It's quite complicated and I can tell you, manually shifting your array is no easy task, especially since you would have to deallocated the overwritten array element(s) yourself. So, unless you fully understand what you're doing, I would suggest don't do it.
What I saw others have done so, but all of example is just RomoveItem / AddItem by one position at one time.
In VBIDE, my code is ok if I Delete a Row or Col at one time, VBIDE won't crash and the data remain OK. But If I delete more that (>=) 5 Rows at one time, VBIDE got crash and data may lost.
I Really don't understand.
My Code is logic but doesn't work . If you come out of a diagram and a solution, I am appreciated.
Re: [RESOLVED] CopyMemory Shift Array one position
OK, I'm not done yet so I'll post it later...
On Local Error Resume Next: If Not Empty Is Nothing Then Do While Null: ReDim i(True To False) As Currency: Loop: Else Debug.Assert CCur(CLng(CInt(CBool(False Imp True Xor False Eqv True)))): Stop: On Local Error GoTo 0
Re: [RESOLVED] CopyMemory Shift Array one position
Originally Posted by Bonnie West
OK, I'm not done yet so I'll post it later...
Thanks.
VB allows direct assign between two arrays and ReDim Preserve / ReDim to resize the array. I am wondering what VB did at back. Does VB also use CopyMemory / GetMem4 /VarPtrArray / Varptr / Strptr / SAFEARRAY to accomplish those functions?
For I = iDelRow + num To m_CntOfRows - 1
m_CellRows(I - num) = m_CellRows(I)
Next
m_CntOfRows = m_CntOfRows - num
ReDim Preserve m_CellRows(m_CntOfRows - 1)
Re: [RESOLVED] CopyMemory Shift Array one position
The diagram below shows how your data structure is internally represented:
The m_CellRows() dynamic array variable is actually just a pointer variable. As mentioned before, VB implements arrays using the SAFEARRAY structure. That means, m_CellRows() points to the memory address of a SAFEARRAY structure, beginning with its first member which is cDims. In other words, m_CellRows() points to the cDims Integer variable.
There is a trick in VB used for obtaining the address of the SAFEARRAY structure which is contained in the pointer variable.
Code:
SA1D = Not Not ArrayName
That trick is much more efficient than the GetMem4 VarPtrArray(m_CellRows()), Ptr line in post #6, provided that the array is already initialized.
The pvData member of a SAFEARRAY is also a pointer and it points to the real array elements. In the case of your data structure, pvData points to the CellLine UDT.
Your CellLine UDT contains a single member (Cols()) which is again a dynamic array variable. Therefore, it also points to its own SAFEARRAY structure. Like the first array, you can retrieve the address to the SAFEARRAY efficiently by using the Not Not ArrayName trick.
The pvData member of the SAFEARRAY structure for the Cols() array points to the first member of the CellStruct UDT which is the Text string variable.
Like array variables, String variables are also just pointers to the actual data. Even the Font member of the CellStruct UDT, which is a StdFont Object, is also just a pointer. Pointers in 32 Bit systems are 4 Bytes long, same as the Long data type.
BTW, use the following code when performing arithmetic on memory addresses (e.g., Ptr + 12& should be SumUnsignedLong(Ptr, 12&)):
Code:
'Sum Unsigned Long from Arithmetic operations on memory address pointers
'
'Enables valid addition and subtraction of unsigned long integers.
'Treats lPtr as an unsigned long and returns an unsigned long.
'Allows safe arithmetic operations on memory address pointers.
'Assumes valid pointer and pointer offset.
Private Function SumUnsignedLong(ByVal lPtr As Long, ByVal lOffset As Long) As Long
Const DW_MSB = &H80000000 'DWord Most Significant Bit
If lOffset > 0& Then
If lPtr And DW_MSB Then 'if ptr < 0
SumUnsignedLong = lPtr + lOffset 'ignores > unsigned max (see assumption)
ElseIf (lPtr Or DW_MSB) < -lOffset Then
SumUnsignedLong = lPtr + lOffset 'result is below signed int max
Else 'result wraps to min signed int
SumUnsignedLong = (lPtr + DW_MSB) + (lOffset + DW_MSB)
End If
ElseIf lOffset < 0& Then
If (lPtr And DW_MSB) = 0& Then 'if ptr > 0
SumUnsignedLong = lPtr + lOffset 'ignores unsigned < zero (see assumption)
ElseIf (lPtr - DW_MSB) >= -lOffset Then
SumUnsignedLong = lPtr + lOffset 'result is above signed int min
Else 'result wraps to max signed int
SumUnsignedLong = (lOffset - DW_MSB) + (lPtr - DW_MSB)
End If
Else 'lOffset = 0&
SumUnsignedLong = lPtr
End If
End Function
Here's a simplified example of how your data structure looks like in memory:
Code:
'Memory
'Addresses
&H00000001 m_CellRows() As CellLine 'points to &H00000010
Private Type SAFEARRAY1D 'Offsets
&H00000010 cDims As Integer ' +0
&H00000011
&H00000012 fFeatures As Integer ' +2
&H00000013
&H00000014 cbElements As Long ' +4
&H00000015
&H00000016
&H00000017
&H00000018 cLocks As Long ' +8
&H00000019
&H0000001A
&H0000001B
&H0000001C pvData As Long ' +12 <-- points to &H00000100
&H0000001D
&H0000001E
&H0000001F
&H00000020 cElements As Long ' +16
&H00000021
&H00000022
&H00000023
&H00000024 lLbound As Long ' +20
&H00000025
&H00000026
&H00000027
End Type
'>>>>> ARRAY ELEMENTS THAT WILL BE SHIFTED >>>>>
Private Type CellLine 'm_CellRows(0)
&H00000100 Cols() As CellStruct 'points to &H00000200
&H00000101
&H00000102
&H00000103
End Type
Private Type CellLine 'm_CellRows(1)
&H00000104 Cols() As CellStruct
&H00000105
&H00000106
&H00000107
End Type
Private Type CellLine 'm_CellRows(2)
&H00000108 Cols() As CellStruct
&H00000109
&H0000010A
&H0000010B
End Type
'<<<<< ARRAY ELEMENTS THAT WILL BE SHIFTED <<<<<
Private Type SAFEARRAY1D 'Offsets
&H00000200 cDims As Integer ' +0
&H00000201
&H00000202 fFeatures As Integer ' +2
&H00000203
&H00000204 cbElements As Long ' +4
&H00000205
&H00000206
&H00000207
&H00000208 cLocks As Long ' +8
&H00000209
&H0000020A
&H0000020B
&H0000020C pvData As Long ' +12 <-- points to &H00001000
&H0000020D
&H0000020E
&H0000020F
&H00000210 cElements As Long ' +16
&H00000211
&H00000212
&H00000213
&H00000214 lLbound As Long ' +20
&H00000215
&H00000216
&H00000217
End Type
Private Type CellStruct 'Cols(0)
&H00001000 Text As String
&H00001001
&H00001002
&H00001003
&H00001004 Width As Long
&H00001005
&H00001006
&H00001007
&H00001008 Height As Long
&H00001009
&H0000100A
&H0000100B
&H0000100C Font As StdFont
&H0000100D
&H0000100E
&H0000100F
&H00001010 ForeColor As OLE_COLOR
&H00001011
&H00001012
&H00001013
End Type
Private Type CellStruct 'Cols(1)
&H00001014 Text As String
&H00001015
&H00001016
&H00001017
&H00001018 Width As Long
&H00001019
&H0000101A
&H0000101B
&H0000101C Height As Long
&H0000101D
&H0000101E
&H0000101F
&H00001020 Font As StdFont
&H00001021
&H00001022
&H00001023
&H00001024 ForeColor As OLE_COLOR
&H00001025
&H00001026
&H00001027
End Type
Before shifting the array elements, make sure the overwritten elements are deallocated first. Not doing this results in a memory leak. I'm not sure if the code in post #6 completely frees all the associated memory.
Originally Posted by Jonney
VB allows direct assign between two arrays and ReDim Preserve / ReDim to resize the array. I am wondering what VB did at back. Does VB also use CopyMemory / GetMem4 /VarPtrArray / Varptr / Strptr / SAFEARRAY to accomplish those functions?
VB uses the SAFEARRAY structure to implement and manipulate arrays. I don't know what VB does when directly assigning an array to another.
On Local Error Resume Next: If Not Empty Is Nothing Then Do While Null: ReDim i(True To False) As Currency: Loop: Else Debug.Assert CCur(CLng(CInt(CBool(False Imp True Xor False Eqv True)))): Stop: On Local Error GoTo 0
[RESOLVED] CopyMemory Shift Array one position
Reply With Quote
Originally Posted by Milk
. If you come out of a diagram and a solution, I am appreciated.