Attempted to read or write protected memory

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Hello,
At this code i have "Attempted to read or write protected memory.This is often an indicating that other memory is corrupt"

Unsafe codec is in StreamLibrary.dll a referenced c# dll includes unmanaged codes.Which i have download from github and compiled it.https://github.com/AnguisCaptor/StreamLibrary[^]

And this is my code

VB

Dim unsafeCodec As IUnsafeCodec = New UnsafeStreamCodec(80)
       Dim stream As New MemoryStream(10000000)
       Try
           While streamDesktop And client.Connected
               Dim bmp As Bitmap = CaptureDesktop()
               Dim rect As New Rectangle(0, 0, bmp.Width, bmp.Height)
               Dim size As Size = New System.Drawing.Size(bmp.Width, bmp.Height)
               Dim bmpData As BitmapData = bmp.LockBits(New Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadWrite, bmp.PixelFormat)
               unsafeCodec.CodeImage(bmpData.Scan0, rect, size, bmp.PixelFormat, stream)'Error at this line
               If stream.Length > 0 Then
                   MsgBox(stream.ToArray.Length)
                   Send("Desktop|", , stream.ToArray)
               End If
               bmp.UnlockBits(bmpData)
               bmp.Dispose()
           End While
       Catch ex As Exception
           MsgBox(ex.Message)
       End Try

How can i fix it ? Thanks

Posted 30-Jun-14 7:29am

suleymankenar

Updated 17-Feb-17 13:22pm

v3

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Comments

Sergey Alexandrovich Kryukov 30-Jun-14 14:17pm

In what line?
—SA

suleymankenar 30-Jun-14 16:07pm

Sorry forget to write it it gives at this line
unsafeCodec.CodeImage(bmpData.Scan0, rect, size, bmp.PixelFormat, stream)

Sergey Alexandrovich Kryukov 30-Jun-14 16:24pm

Good, but, unfortunately, I can only guess what unsafeCodec does and how it works... probably, it does something too unsafe... :-)
—SA

Duncan Edwards Jones 7-Jul-14 12:07pm

Are you passing bmpData.Scan0 by value, not by reference? (i.e. the address held in Scan0, not the address of the variable Scan0)?

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Valery Possoz · Answer 1 · 2017-02-17T13:22:00

Hello,

That's because you don't use stream and bitmpa properly, after a few iterations you'll get this exception because you have a memory leak.

MemoryStream implements

C#

IDisposable

and it is good practice to dispose of it when you have finished using it. One easy way to do this is to use

C#

using

What I would do first is refactor a bit to eliminate the leaks:

Dim unsafeCodec As IUnsafeCodec = New UnsafeStreamCodec(80)
Try
    While streamDesktop And client.Connected
        Using bmp As Bitmap = CaptureDesktop()
            Dim rect As New Rectangle(0, 0, bmp.Width, bmp.Height)
            Dim size As Size = New System.Drawing.Size(bmp.Width, bmp.Height)
            Dim bmpData As BitmapData = bmp.LockBits(New Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadWrite, bmp.PixelFormat)
            Using stream As New MemoryStream()
                unsafeCodec.CodeImage(bmpData.Scan0, rect, size, bmp.PixelFormat, stream) 'no more error here.
                If stream.Length > 0 Then
                    MsgBox(stream.ToArray.Length)
                    Send("Desktop|", , stream.ToArray)
                End If
                bmp.UnlockBits(bmpData)
            End Using
        End Using
    End While
Catch ex As Exception
    MsgBox(ex.Message)
End Try

Valery