dllimport：C代码影响通过引用传递的结构（C＃）

Question

I've got ac dll that contains an exposed function, that takes three parameters :

int ParseInput(char* opt_path, char* input, SENNA_RESULT_ARRAY* result);

I want to call this from C#, which actually works. The problem is that the result struct is not affected. Here is the structure defined in c code :

    typedef struct RESULT_
{
    char* word;
    int pos_start;
    int pos_end;
    char* pos;
    char* chk;
    char* ner;
    char* psg;

} RESULT;

typedef struct RESULT_ARRAY_
{
    int size;
    RESULT* Results;    
} RESULT_ARRAY;

and my c# code :

[StructLayout(LayoutKind.Sequential)]
    public struct SENNA_RESULT
    {
        [MarshalAs(UnmanagedType.LPStr)]
        public string word;
        [MarshalAs(UnmanagedType.I4)]
        public int pos_start;
        [MarshalAs(UnmanagedType.I4)]
        public int pos_end;
        [MarshalAs(UnmanagedType.LPStr)]
        public string pos;
        [MarshalAs(UnmanagedType.LPStr)]
        public string chk;
        [MarshalAs(UnmanagedType.LPStr)]
        public string ner;
        [MarshalAs(UnmanagedType.LPStr)]
        public string psg;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct SENNA_RESULT_ARRAY
    {
        public SENNA_RESULT[] Results;     
        public int size;
    }

    [DllImport("Senna-32.dll", CharSet = CharSet.Ansi)]
    static extern int Parse(string msg, string stream, ref SENNA_RESULT_ARRAY results);

Parse(@"path", "sentence", ref result_array)

I've tried many things, like : 1-use classes instead of struct without ref keyword 2-use a pointer instead of passing a struct

Each time i got a different error like array is not of the specified type low level error( corrupted heap)

even if i don't specify the array in the first struct, the size member has not the correct value (the C code prints the value in the console)

Any advice ?

Thanks

Answer 1

Consider using code below.

[StructLayout(LayoutKind.Sequential)]
public struct SENNA_RESULT
{
    public IntPtr word;
    public int pos_start;
    public int pos_end;
    public IntPtr pos;
    public IntPtr chk;
    public IntPtr ner;
    public IntPtr psg;
}

[StructLayout(LayoutKind.Sequential)]
public struct SENNA_RESULT_ARRAY
{
    public IntPtr Results;     
    public int size;
}

[DllImport("Senna-32.dll")]
static extern int Parse(string msg, string stream, out SENNA_RESULT_ARRAY results);

Here is usage example

        SENNA_RESULT_ARRAY array = new SENNA_RESULT_ARRAY();
        int result = Parse("path", "sentence", out array);
        if (result == SUCCESS && array.Results != IntPtr.Zero)
        {
            for (int index = 0; index < array.size; index++)
            {
                IntPtr offset = (IntPtr)((int)array.Results + index * Marshal.SizeOf(typeof(SENNA_RESULT)));
                SENNA_RESULT senna = (SENNA_RESULT)Marshal.PtrToStructure(offset, typeof(SENNA_RESULT));
            }
        }

I hope that you understand that it is just idea. Make sure that code is working properly and then improve it to make it more comfotable to use. I talking about replacing IntPtr with string .