Structure Array To Byte Array And Vice Versa

2015-02-19

Question

_{Thursday, February 19, 2015 5:05 PM}

Is there any fast method to convert an array of structures to a byte array.

I have to convert millions of structures(e.g single,short etc).

It takes too much time to save every structure separately.

Allow time to reverse.

All replies (5)

_{Thursday, February 19, 2015 5:36 PM ✅Answered}

I tried.... But I do not think it is perfect solution:

    Public Shared Function GetBytes(Of Struct As Structure)(Obj() As Struct) As Byte()
        Dim Size = Runtime.InteropServices.Marshal.SizeOf(GetType(Struct))
        Dim Bytes(Size * Obj.Count - 1) As Byte
        Dim Ptr As IntPtr = Runtime.InteropServices.Marshal.AllocHGlobal(Size)
        For i = 0 To Obj.Count - 1
            Runtime.InteropServices.Marshal.StructureToPtr(Obj(i), Ptr, False)
            Runtime.InteropServices.Marshal.Copy(Ptr, Bytes, i * Size, Size)
        Next
        Runtime.InteropServices.Marshal.FreeHGlobal(Ptr)
        Return Bytes
    End Function
    Public Shared Function ToStructures(Of Struct As Structure)(Bytes() As Byte) As Struct()
        Dim Size = Runtime.InteropServices.Marshal.SizeOf(GetType(Struct))
        Dim Structs(Bytes.Count / Size - 1) As Struct
        Dim Ptr As IntPtr = Runtime.InteropServices.Marshal.AllocHGlobal(Size)
        For i = 0 To Structs.Count - 1
            Runtime.InteropServices.Marshal.Copy(Bytes, i * Size, Ptr, Size)
            Structs(i) = Runtime.InteropServices.Marshal.PtrToStructure(Ptr, GetType(Struct))
        Next
        Runtime.InteropServices.Marshal.FreeHGlobal(Ptr)
        Return Structs
    End Function

Allow time to reverse.

_{Thursday, February 19, 2015 7:07 PM ✅Answered | 2 votes}

If you mark your structure with <Serialisable> attribute, then you can serialise the whole array to a MemoryStream using BinaryFormatter, then obtain the bytes from MemoryStream (or serialise directly to file, database, etc.). Then you can deserialise the array.

It is also possible to write a portion of code in C# or C++/CLR, where you can obtain the bytes easier.

_{Thursday, February 19, 2015 7:22 PM ✅Answered | 1 vote}

Hi,

Viorel beat me to it but, i was thinking the same thing. Mark your structure as Serializable and use the BinaryFormatter class to Serialize the whole list to a MemoryStream and then you can Deserialize back to a List of your structure.

Here is a short basic example i just threw together to test it and it seems to work pretty good.

Imports System.Runtime.Serialization.Formatters.Binary

Public Class Form1
    Private Byts() As Byte

    <Serializable()> _
    Private Structure MyStruct
        Public str As String
        Public int As Integer
        Public dbl As Double
        Public sngl As Single
        Public shrt As Short
    End Structure

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim sList As New List(Of MyStruct)

        Dim s As New MyStruct
        s.str = "First"
        s.int = 50
        s.dbl = 33.523
        s.sngl = 12.33343
        s.shrt = 255
        sList.Add(s)

        s = New MyStruct
        s.str = "Second"
        s.int = 23
        s.dbl = 72.881
        s.sngl = 1.003
        s.shrt = 64
        sList.Add(s)

        Byts = GetBytesFromStructureList(sList)
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim sList As List(Of MyStruct) = GetStructureListFromBytes(Byts)

        For Each s As MyStruct In sList
            RichTextBox1.AppendText(s.str & vbNewLine)
            RichTextBox1.AppendText(s.int.ToString & vbNewLine)
            RichTextBox1.AppendText(s.dbl.ToString & vbNewLine)
            RichTextBox1.AppendText(s.sngl.ToString & vbNewLine)
            RichTextBox1.AppendText(s.shrt.ToString & vbNewLine)
            RichTextBox1.AppendText("" & vbNewLine)
        Next
    End Sub

    Private Function GetBytesFromStructureList(ByVal structList As List(Of MyStruct)) As Byte()
        Dim bts() As Byte
        Using ms As New IO.MemoryStream
            Dim formatter As New BinaryFormatter
            formatter.Serialize(ms, structList)
            bts = ms.GetBuffer
        End Using
        Return bts
    End Function

    Private Function GetStructureListFromBytes(ByVal bytesArray() As Byte) As List(Of MyStruct)
        Dim lst As New List(Of MyStruct)
        Using ms2 As New IO.MemoryStream(bytesArray)
            Dim formatter As New BinaryFormatter
            lst = CType(formatter.Deserialize(ms2), List(Of MyStruct))
        End Using
        Return lst
    End Function
End Class

If you say it can`t be done then i`ll try it

_{Thursday, February 19, 2015 8:16 PM ✅Answered | 1 vote}

Another one:

Imports System.Runtime.InteropServices

Public Class Main

   'Make sure the struct only contains value types and the StructLayout attribute is attached. No prob if just Single() or Integer().

   <StructLayout(LayoutKind.Sequential)> _
   Public Structure OpenDMLStandardIndexEntry
      Public Offset As UInteger
      Public Size As UInteger
   End Structure

   Public Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByVal Destination As IntPtr, ByVal Source As IntPtr, ByVal Length As IntPtr)

   Shared Sub Main()

      Dim Entries(3) As OpenDMLStandardIndexEntry
      Dim Bytes = GetBytes(Entries)

   End Sub

   Shared Function GetBytes(Of TStruct)(ByVal Values As TStruct()) As Byte()

      Dim StructSize = Marshal.SizeOf(GetType(TStruct))
      Dim Result As Byte()
      Dim gchSource, gchDest As GCHandle

      If Values Is Nothing Then Throw New ArgumentNullException("Values")

      ReDim Result((Values.Length * StructSize) - 1)

      If Values.Length > 0 Then
         gchSource = GCHandle.Alloc(Values, GCHandleType.Pinned)

         Try
            gchDest = GCHandle.Alloc(Result, GCHandleType.Pinned)

            Try
               CopyMemory(gchDest.AddrOfPinnedObject, gchSource.AddrOfPinnedObject, New IntPtr(Result.Length))
            Finally
               gchDest.Free()
            End Try
         Finally
            gchSource.Free()
         End Try
      End If

      Return Result

   End Function

End Class

Armin

_{Thursday, February 19, 2015 9:08 PM | 1 vote}

Another one:

Armin

Armin,

Hey (young man). I recognize your name from the before times. CIS, QB or somewhere after? I doubt you remember me I had other names. You helped me a lot as I recall.

Tom

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Structure Array To Byte Array And Vice Versa

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