CODEWITHSUNDEEP
c#.net
Ashish
Ashish

Reputation: 407

memcpy in C# with different dataType

I am porting a c++ code into c#.There are 2 structures, as explained below. // Must be a total of 180 bytes

typedef struct MAINTENANCE_PARAM`
{
    BYTE bCommand;
    BYTE bSubCommand;
    USHORT usDataLength;
    union  // Must be no larger than 176 bytes
    {
        MyStruct1 myStruct1;
                MyStruct2 myStruct2;
        BYTE bDummy[176];
    } data;
} MAINTENANCE_PARAM;

typedef struct _OCI_PARAM {
    SHORT  sType;          // Size: 2
    LONG   lValue;         //  4
    SHORT  sScale;         //  2
    LONG   lValueTabIdx;   //  4
} OCI_PARAM[OCI_MAXPARAM];    //Size: OCI_MAXPARAM = 15  // 15 * 12 = 180

My code uses the memcpy in the following fashion.

MAINTENANCE_PARAM maintainanceParam;
    OCI_PARAM ociParam       

    // Copy recieved structure to correct format
    memcpy((void*)& maintainanceParam, (void*) ociParam, sizeof(OCI_PARAM));

As I know there is no code for memcpy in the C#. So how can I port the above code into the C#. I am new to C#. I don't know much regarding the C#. So can anybody tell me how exactly I can implement the above line of code in C#. I need to copy 180 bytes from one structure to another structure object with different datatype Thanks in Advance for any help. Regards, Ashish

Upvotes: 0

Views: 2493

Answers (2)

MaLio
MaLio

Reputation: 2540

Use the StructLayoutAttribute and FieldOffsetAttribute for your structs so that you can layout your fields explicitly, then import RtlMoveMemory (P/Invoke). You can modify the signature to take any pointer type (in unsafe context) or use the standard signature on PInvoke.net.

unsafe class Program {

    [System.Runtime.InteropServices.DllImport("Kernel32.dll", EntryPoint = "RtlMoveMemory", SetLastError = false)]
    private static extern void MoveMemory(void* dest, void* src, int size);

    static  void Main(string[] args) {

        Maintenance_Param p1 = new Maintenance_Param();
        p1.bCommand = 2;
        p1.bSubCommand = 3;
        p1.usDataLength = 3;
        p1.myStruct1 = new MyStruct1();

        Maintenance_Param p2 = new Maintenance_Param();
        MoveMemory(&p2, &p1, sizeof(Maintenance_Param));
    }
}

[System.Runtime.InteropServices.StructLayout(System.Runtime.InteropServices.LayoutKind.Explicit)]
public struct Maintenance_Param {

    // fields should be private and be accessed over properties ...
    [System.Runtime.InteropServices.FieldOffset(0)]
    public byte bCommand;
    [System.Runtime.InteropServices.FieldOffset(1)]
    public byte bSubCommand;
    [System.Runtime.InteropServices.FieldOffset(2)]
    public ushort usDataLength;
    [System.Runtime.InteropServices.FieldOffset(4)]
    public MyStruct1 myStruct1;
    [System.Runtime.InteropServices.FieldOffset(4)]
    public MyStruct2 myStruct2;
}

public struct MyStruct1 {
    int value;
}

public struct MyStruct2 {
    int value;
}

Upvotes: 3

6opuc
6opuc

Reputation: 1196

MemCpy DOES exist in .NET! Try googling for OpCodes.Cpblk. Here is an example: http://www.abstractpath.com/weblog/2009/04/memcpy-in-c.html

Upvotes: 1

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