I wrote in C a struct like that
struct IMAGE {
unsigned int x, y;
unsigned char **data;
};
Could anybody please tell me how to marshall this struct to use in C#?
my solution does not work.
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class IMAGE
{
public UInt32 x;
public UInt32 y;
public byte[][] data;
};
Managed arrays are different than pointers. A managed array requires the size of the array, and if you're trying to marshal a struct, it requires a fixed size to marshal directly.
You can use the SizeConst parameter of the MarshalAs attribute to set the size of data when it gets marshaled.
But I'm guessing that x and y are the dimensions of the image and that the size of data depends on those variables. The best solution here is to marshal it over as an IntPtr and access the data when you need it:
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class IMAGE
{
public UInt32 x;
public UInt32 y;
private IntPtr data;
public byte[][] Data
{
get
{
byte[][] newData = new byte[y][];
for(int i = 0; i < y; i++)
{
newData[i] = new byte[x];
Marshal.Copy(new IntPtr(data.ToInt64() + (i * x)), newData[i], 0, x);
}
return newData;
}
set
{
for (int i = 0; i < value.Length; i++)
{
Marshal.Copy(value[i], 0, new IntPtr(data.ToInt64() + (i * x)), value[i].Length);
}
}
}
}
If you are allowed to use unsafe code, you can change the IntPtr to a byte** and work with it directly.
With the setter, you'll probably want to verify the dimensions of the value before you blindly write to unmanaged memory.
My guess is that it is:
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class IMAGE
{
public UInt32 x;
public UInt32 y;
public ref IntPtr data;
};
A very handy reference is the p/invoke cheatsheet.
Related
Days ago I made this question: Passing a complex Struct (with inner array of struct) from C# to C++
Fortunately it as been answered and the code seems to work.
Now I need to do the oposite case, I mean, I need to get the struct from the C++ dll to my C# code.
I was researching in this site, trying the use of the IntPtr type, but didnt work. Then as my struct in C# was defined correctly I tried to use an out reference.
As a sumary, gonna repost the structs defined in both languages
typedef struct _ImParam
{
UINT Format;
UINT Resolution;
UINT ColorDepth;
} IM_PARAM;
typedef struct _sValues
{
UINT Xpos;
UINT Ypos;
UINT Width;
UINT Height;
BOOL Milli;
} S_VALUES;
typedef struct _sProperties
{
BOOL Enable;
S_VALUES Properties;
} S_PROPERTIES;
typedef struct _DevParam
{
BOOL Enable;
UINT Font;
char Symbol;
IM_PARAM Image1;
IM_PARAM Image2;
S_PROPERTIES Properties[10];
UINT FeedMode;
} DevParam;
// more code, comments, etc. etc.
// The function I want to use
BOOL GetParameters( DWORD ID, DevParam *dParam );
This is how I build the structs in C#
[StructLayout(LayoutKind.Sequential)]
public struct ImParam
{
public uint Format;
public uint Resolution;
public uint ColorDepth;
public ImParam(uint n)
{
Format = n;
Resolution = 300;
ColorDepth = 256;
}
};
[StructLayout(LayoutKind.Sequential)]
public struct sValues
{
public uint Xpos;
public uint Ypos;
public uint Width;
public uint Height;
public bool Milli;
public sValues(uint n)
{
Xpos = n;
Ypos = n;
Width = n;
Height = n;
Milli = false;
}
};
[StructLayout(LayoutKind.Sequential)]
public struct sProperties
{
public bool Enable;
public sValues Properties;
public sProperties(int n)
{
Enable = false;
Properties = new sValues(n);
}
};
[StructLayout(LayoutKind.Sequential)]
public struct DevParam
{
public bool Enable;
public uint Font;
public char Symbol;
public ImParam Image1;
public ImParam Image2;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 10)]
public sProperties[] Properties;
public uint FeedMode;
public DeviceParameters(int n)
{
Enable = true;
Font = 0;
Symbol = '?';
Image1 = new ImParam(3);
Image2 = new ImParam(3);
Properties = new sProperties[10];
for(int i = 0; i < 10; i++)
Properties[i] = new sProperties(n);
FeedMode = 1;
}
};
// This is the method imported from the C++ dll
[DllImport(path, EntryPoint = "?GetParameters##YGHKPAU_DevParam###Z")]
public static extern bool GetParameters(int ID, out DevParam dParam);
And here's the call
// Already got ID from somewhere else
DevParam DP;
bool res = Class1.GetParameters(ID, out DP);
Console.WriteLine("Result: " + res);
The code seems to work, since I'm getting a "true" as result. The problem is it's getting wrong values in the structs members, placing the default ones (always 0 the numbers, always false the booleans), even if I use the SetParam(..) method before (and I know that one works because when I change the image format scanner decreases scanning speed).
What am I missing?
Note: I dont have source code of the .dll
Edited:
Been trying with these modifications:
// At the dll wrapper class
[DllImport(path, EntryPoint = "?GetParameters##YGHKPAU_DevParam###Z")]
public static extern bool GetParameters(int ID, ref IntPtr dParam);
// At main
int size = Marshal.SizeOf(typeof(DevParam));
IntPtr Ptr = Marshal.AllocHGlobal(size);
bool res = Class1.GetParameters(ID, ref Ptr);
Console.WriteLine("Result: " + res);
var test = Marshal.PtrToStructure(Ptr, typeof(DevParam));
// No idea what I'll do here
Marshal.FreeHGlobal(Ptr);
If I try to print "test", it should give an adress, since it's a pointer, but it's null. Neither know how can I extract the data from the struct.
Any ideas?
Solved!
// At the dll wrapper class
[DllImport(path, EntryPoint = "?GetParameters##YGHKPAU_DevParam###Z")]
public static extern bool GetParameters(int ID, IntPtr dParam);
// At main
int size = Marshal.SizeOf(typeof(DevParam));
IntPtr Ptr = Marshal.AllocHGlobal(size);
bool res = Class1.GetParameters(ID, Ptr);
DevParam test = (DevParam)Marshal.PtrToStructure(Ptr, typeof(DevParam));
// For testing purpoises, previously changed the default values with another method
Console.WriteLine(test.Enable);
Marshal.FreeHGlobal(Ptr);
Had to remove the ref keyword.
I have an unmanaged interface I'm trying to marshal and use in C#.
And there is a function I'm not sure how to marshal correctly:
IDataInfo :
public IUnknown {
...
STDMETHOD_(BOOL, GetDataPackInfo) (UINT packIndex, void* pPackExtendedInfo) = 0;
...
}
The void* can be one of two different structures:
struct DataExtendedInfoArchive {
WORD Size;
BOOL Archived;
UINT SignalLength;
BYTE Captured;
};
struct DataExtendedInfoStorage {
WORD Size;
FLOAT SignalFreq;
UINT SignalLength;
CHAR Code[4];
};
I implement those in C# like this:
[StructLayout(LayoutKind.Sequential)]
public struct TrackExtendedInfoAudio
{
int Size;
[MarshalAs(UnmanagedType.Bool)]
bool Archived;
uint SignalLength;
byte Captured;
}
[StructLayout(LayoutKind.Sequential)]
public struct TrackExtendedInfoVideo
{
public int Size;
public double SignalFreq;
public uint SignalLength;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public StringBuilder Code;
}
The problem is I don't exactly understand what I'm going to get in void* pPackExtendedInfo and how to handle it and therefore don't know how to write a correct marshaling signature for this function.
The managed function signature (minus attributes and decorations) should be:
// make sure that the return is marshalled as UnmanagedTypes.Boolean.
bool GetDataPackInfo(uint packIndex, IntPtr pPackExtendedInfo);
To unpack the struct, first you need to determine which one you're working with. Fortunately the first member of each is a size parameter, which will give a clue as to the size of the struct. To read that size, then unpack the structure:
IntPtr ptr; // this is the pointer passed to your callback.
int cbSize = Marshal.ReadInt32(ptr, 0);
if (cbSize = Marshal.SizeOf(TrackExtendedInfoAudio))
{
TrackExtendedInfoAudio s = Marshal.PtrToStructure(ptr, typeof(TrackExtendedInfoAudio))
as TrackExtendedInfoAudio;
// Processing...
}
else if (cbSize == Marshal.SizeOf(TrackExtendedInfoVideo))
{
TrackExtendedInfoVideo s = Marshal.PtrToStructure(ptr, typeof(TrackExtendedInfoVideo))
as TrackExtendedInfoVideo;
// Processing...
}
else
{
// unknown struct
}
You could marshal void* as IntPtr:
private static extern bool GetDataPackInfo(uint packIndex, [In,Out] IntPtr pPackExtendedInfo);
And copy structure using one of the Marshal.PtrToStructure (and Marshal.StructureToPtr) methods:
IntPtr p = IntPtr.Zero;
GetDataPackInfo(..., p);
TrackExtendedInfoAudio audioInfo = Marshal.PtrToStructure<TrackExtendedInfoAudio>(p);
or
TrackExtendedInfoVideo videoInfo = Marshal.PtrToStructure<TrackExtendedInfoVideo>(p);
PS. And I'm not sure the StringBuilder is an appropriate marshaling for the CHAR Code[4];.
Consider the following code as an example of copying memory between a struct [] and a byte []. The method of memory copy is irrelevant to the core question. It's there to demonstrate two pointers to managed arrays.
[DllImport("kernel32.dll", EntryPoint = "CopyMemory", SetLastError = false)]
public static extern void CopyMemory (IntPtr dest, IntPtr src, uint count);
public struct MyStruct { public float Value; public TimeSpan Value; }
var bufferSize = 1000000;
var size = Marshal.SizeOf(typeof(MyStruct));
var bufferSource = new MyStruct [bufferSize];
var bufferTarget = new byte [bufferSize * size];
for (int i = 0; i < bufferSource.Length; i++)
{
bufferSource [j] = new MyStruct() { Value = i; };
}
var handleSource = GCHandle.Alloc(bufferSource, GCHandleType.Pinned);
var handleTarget = GCHandle.Alloc(bufferTarget, GCHandleType.Pinned);
var pointerSource = handleSource.AddrOfPinnedObject();
var pointerTarget = handleTarget.AddrOfPinnedObject();
handleSource.Free();
handleTarget.Free();
CopyMemory(pointerTarget, pointerSource, (uint) (bufferSize * size));
The IntPtr pointerTarget did not originate as a MyStruct []. Is there a way to cast this allocated and initialized memory to a MyStruct []? I do not want to allocate a new array to be able to do this.
It's easier to redefine the p/invoke signature, in this case like this:
[DllImport("kernel32.dll", EntryPoint = "RtlMoveMemory")]
private static extern void CopyMemory([In, Out] byte[] pdst, Mystruct[] psrc, int cb);
define the struct layout for p/invoke:
[StructLayout(LayoutKind.Sequential)]
public struct MyStruct { public float Value; public TimeSpan Value;}
Then you can just use it like this:
CopyMemory(bufferTarget, bufferSource, bufferTarget.Length);
I am attempting to use an array of structures to pass data to/fro my C# ui and my C dll.
Further complicating matters is that the structure contains another array of structures.
I have figured out how to the simpler stuff using pinvoke, but how do I declare
the embedded structures, and how do I pass them?
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class csForm {
public int endDate;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 128)]
public char[] formId;
}
[DllImport("myDll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
public static extern void fillForm([In, Out] csForm data, 5);
// c code
typedef struct s_ptxRow {
int ptxNumber;
char primitive[128];
int primitiveParams[128];
} ptxRow;
typedef struct s_workSpace{
char formId[128];
int endDate;
ptxRow PtxRow[128];
} cForm;
extern "C" __declspec(dllexport) fillForm(cForm csForm[], interface csFormCount)
{
for (int i = 0, j = 0; i < csFormCount; ++i)
{
j = int / 2;
csForm[i].endDate = i;
strcpy(csForm[i].formId, "formId here");
csForm[i].PtxRow[j].ptxNumber = i;
csForm[i].PtxRow[j].primitiveParams[i] = i;
strcpy(csForm[i].PtxRow[j].primitive, "someText");
}
}
You were going in the right direction. You just needed to declare the ptxRow structure in C# and then add an array of it to csForm. You even don't need to allocate any arrays beforehand - apparently P/Invoke does it for you since it knows their sizes. The entire sample code is included because there were minute errors in some declarations.
Note: When I tried to use classes in C# I got strange results (e.g. incorrect member and pointer values in the C++ code) which led to various errors. Switching to structs made the problem go away. I think this has something to do with reference and value types, but would appreciate input from more knowledgeable people. I'm testing with .NET 3.5 if it matters.
#include <string.h>
typedef struct s_ptxRow {
int ptxNumber;
char primitive[128];
int primitiveParams[128];
} ptxRow;
typedef struct s_workSpace {
char formId[128];
int endDate;
ptxRow PtxRow[128];
} cForm;
extern "C" __declspec(dllexport) void fillForm(cForm csForm[], int csFormCount)
{
for (int i = 0, j = 0; i < csFormCount; ++i)
{
j = i / 2;
csForm[i].endDate = i;
strcpy(csForm[i].formId, "formId here");
csForm[i].PtxRow[j].ptxNumber = i;
csForm[i].PtxRow[j].primitiveParams[i] = i;
strcpy(csForm[i].PtxRow[j].primitive, "someText");
}
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
namespace PInvokeStructsCS
{
class Program
{
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct PtxRow
{
public int ptxNumber;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 128)]
public char[] primitive;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 128)]
public int[] primitiveParams;
}
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct csForm
{
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 128)]
public char[] formId;
public int endDate;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 128)]
public PtxRow[] ptxRow;
}
[DllImport("PInvokeStructsC.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
public static extern void fillForm([In, Out]csForm[] data, int count);
static void Main(string[] args)
{
csForm[] forms = new csForm[2];
try
{
fillForm(forms, 2);
}
catch (Exception e)
{
Console.Out.WriteLine(e.Message);
return;
}
}
}
}
I'm trying to pass a struct array into a C++ DLL and running into issues. I've been trying to figure it out for several days with no avail. I can get the data fine from from C++, I just run into problems when I try to get the struct array using .NET.
The C++ prototype is:
static __declspec(dllexport) int SocketAPI::api_get_data(int iSize, buffer_node *data);
In my C# code, I defined the function as:
[DllImport("SocketAPI.dll")]
static extern int api_get_data(int iSize, buffer_node[] data);
My Struct is buffer_node which is defined as:
[StructLayout(LayoutKind.Sequential, Size = 23), Serializable]
public struct header
{
// HEADER
public UInt16 h_type;
public UInt32 frame_num;
public UInt16 count_1pps;
public byte data_options;
public byte project_type;
public byte tile_num;
public byte tile_set;
public byte total_rows;
public byte total_cols;
public byte num_rows;
public byte num_cols;
public byte first_row;
public byte first_col;
public UInt16 num_sensors;
public UInt16 num_data_bytes;
public byte h_checksum;
}
[StructLayout(LayoutKind.Sequential, Size = 25), Serializable]
public struct footer
{
// FOOTER
public UInt16 f_type;
public byte ts_len;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
public byte[] ts_array;
public byte frame_status;
public byte f_checksum;
}
[StructLayout(LayoutKind.Sequential, Size = 51), Serializable]
public struct buffer_node
{
// HEADER
public header data_header;
// DATA
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)]
public byte[] data;
// FOOTER
public footer data_footer;
}
If tried the following Imports:
// See buffer, but everything is 0 - ie. not being populated
unsafe static extern int api_get_data(int iSize, buffer_node[] data);
// fails somewhere in the API
static extern int api_get_data(int iSize, out buffer_node[] data);
static extern int api_get_data(int iSize, ref buffer_node[] data);
My C# GetData program currently looks like this:
// Get current data size
int iSize = api_is_data_available();
// Create buffer to hold the data
buffer_node[] buf_data = new buffer_node[iSize];
for (int i = 0; i < iSize; i++)
{
buf_data[i].data = new byte[3];
buf_data[i].data_footer.ts_array = new byte[20];
}
// Get the data
//int iStructSize = Marshal.SizeOf(buf_data[0]);
//IntPtr bufNodePtr = IntPtr.Zero;
//IntPtr buffer = Marshal.AllocHGlobal(iStructSize * iSize);
//api_get_data(iSize, buffer);
//for (int i = 0; i < iSize; i++)
//{
// IntPtr ptr = new IntPtr(buffer.ToInt64() + iStructSize * i);
// buf_data[i] = (buffer_node)Marshal.PtrToStructure(ptr, typeof(buffer_node));
//}
//api_get_data(iSize, buf_data); // See buffer, but everything is 0 - ie. not being populated
// api_get_data(iSize, out buf_data); // fails no error
api_get_data(iSize, ref buf_data); // fails no error
// api_get_data(iSize, ref buf_data);
// Print the data
for (int i = 0; i < iSize; i++)
{
StringBuilder sb = new StringBuilder();
sb.Append("Tile Number: " + Convert.ToString(buf_data[i].data_header.tile_num));
AppendTextBox(sb.ToString());
}
Thank you again. Any help would be greatly appreciated, as what I though would be a simple task is really throwing me for a loop!
You will have to use the CallingConvention property in the [DllImport] attribute. The default is StdCall, you need Cdecl here since the C++ declaration didn't used __stdcall.
Use [In, Out] attributes for buffer_node[] data parameter:
[DllImport("SocketAPI.dll")]
static extern int api_get_data(int iSize, [In, Out] buffer_node[] data);
If int iSize is the size of the array in elements (e.g. data.Length), try using MarshallAs.SizeParamIndex. That will tell the marshaller how many elements should be in data.
[DllImport("SocketAPI.dll")]
static extern int api_get_data(int iSize, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex=0)] buffer_node[] data);
More info on how arrays are mashalled at MSDN.
The ones with ref and out don't work, because they pass a pointer to the reference, not a pointer to the first element.
Edit 1: I just noticed, you can't pass arrays around like you're doing right now -- managed arrays inside structs don't usually get marshaled the way you want them. I'll write a solution when I think of one, but I think you're going to have to marshal things by hand.
Edit 2: If you're able to use unsafe code, then this should fix the problem: Change everything from a ByValArray to a fixed byte[], then use this code:
[StructLayout(LayoutKind.Sequential, Size = 23), Serializable]
public struct header
{
// HEADER
public UInt16 h_type;
public UInt32 frame_num;
public UInt16 count_1pps;
public byte data_options;
public byte project_type;
public byte tile_num;
public byte tile_set;
public byte total_rows;
public byte total_cols;
public byte num_rows;
public byte num_cols;
public byte first_row;
public byte first_col;
public UInt16 num_sensors;
public UInt16 num_data_bytes;
public byte h_checksum;
}
[StructLayout(LayoutKind.Sequential, Size = 25), Serializable]
public struct footer
{
// FOOTER
public UInt16 f_type;
public byte ts_len;
public unsafe fixed byte ts_array[20];
public byte frame_status;
public byte f_checksum;
}
[StructLayout(LayoutKind.Sequential, Size = 51), Serializable]
public struct buffer_node
{
// HEADER
public header data_header;
// DATA
public unsafe fixed byte data[3];
// FOOTER
public footer data_footer;
}
unsafe static extern int api_get_data(int iSize, buffer_node* pData);
//...
// Get current data size
int iSize = api_is_data_available();
// Create buffer to hold the data
buffer_node[] buf_data = new buffer_node[iSize];
unsafe
{
fixed (buffer_node* pBufData = buf_data)
{
api_get_data(iSize, pBufData); // fails no error
}
}
(You'll have to change the declaration to be a pointer to an element.)
Edit 3: I just noticed... have you tried saying [Out] like this?
[DllImport("SocketAPI.dll")]
static extern int api_get_data(int iSize, [Out] buffer_node[] data);
That might just work, without the pain of doing what I did above.
Side note: Saying Size = 23 won't do anything unless you also change the alignment, because the structure will be padded to reach the default alignment.
I had the same problem with having to pass an empty array from C# to a C function in a dll. The function would then return the pointer pointing to the first element of the array filled with structs.
This is how I declare the external function:
[DllImport(LIB_NAME, CallingConvention = CallingConvention.StdCall, EntryPoint = "getData")]
unsafe extern void getData(IntPtr data, ref UInt32 dataLen);
The struct in question:
[StructLayout(LayoutKind.Sequential)]
internal struct DataC
{
internal UInt16 xRes, yRes;
internal fixed float rot[9];
}
This is how I call the function and how I cast the IntPtr to my struct:
unsafe
{
UInt32 dataLen = 10;
IntPtr dataPtr = Marshal.AllocHGlobal((int)dataLen * Marshal.SizeOf(typeof(DataC)));
getData(dataPtr, ref dataLen);
// check here for null, obviously
DataC* dataArr = (DataC*)dataPtr;
for (int i = 0; i < dataLen; i++)
{
DataC data = dataArr[i];
// I fill a managed class/struct with the unmanaged data and add it to a List or whatever
result.Add(new Data(data->xRes, data->yRes, data->rot[0], ...));
}
// As we have the data in managed memory now, we free the allocated space
Marshal.FreeHGlobal(dataPtr);
}