Question

我在C程序中使用了以下结构

typedef enum
{
  ndberror_st_success = 0,
  ndberror_st_temporary = 1,
  ndberror_st_permanent = 2,
  ndberror_st_unknown = 3
} ndberror_status_enum;

typedef enum
{
 ndberror_cl_none = 0,  
 ndberror_cl_application = 1,  
 ndberror_cl_no_data_found = 2,
 ndberror_cl_constraint_violation = 3,
 ndberror_cl_schema_error = 4,
 ndberror_cl_user_defined = 5,
 ndberror_cl_insufficient_space = 6,
 ndberror_cl_temporary_resource = 7,
 ndberror_cl_node_recovery = 8,
 ndberror_cl_overload = 9,
 ndberror_cl_timeout_expired = 10,
 ndberror_cl_unknown_result = 11,
 ndberror_cl_internal_error = 12,
 ndberror_cl_function_not_implemented = 13,
 ndberror_cl_unknown_error_code = 14,
 ndberror_cl_node_shutdown = 15,
 ndberror_cl_configuration = 16,
 ndberror_cl_schema_object_already_exists = 17,
 ndberror_cl_internal_temporary = 18
} ndberror_classification_enum;


typedef struct {
  ndberror_status_enum status;
  ndberror_classification_enum classification;
  int code;
  int mysql_code;
  const char * message;
  char * details;
} ndberror_struct;

我需要在c＃程序中编组它，C＃端声明是：

    public enum ndberror_status
    {
        ndberror_st_success = 0,
        ndberror_st_temporary = 1,
        ndberror_st_permanent = 2,
        ndberror_st_unknown = 3,
    }

    public enum ndberror_classification
    {
        ndberror_cl_none = 0,
        ndberror_cl_application = 1,
        ndberror_cl_no_data_found = 2,
        ndberror_cl_constraint_violation = 3,
        ndberror_cl_schema_error = 4,
        ndberror_cl_user_defined = 5,
        ndberror_cl_insufficient_space = 6,
        ndberror_cl_temporary_resource = 7,
        ndberror_cl_node_recovery = 8,
        ndberror_cl_overload = 9,
        ndberror_cl_timeout_expired = 10,
        ndberror_cl_unknown_result = 11,
        ndberror_cl_internal_error = 12,
        ndberror_cl_function_not_implemented = 13,
        ndberror_cl_unknown_error_code = 14,
        ndberror_cl_node_shutdown = 15,
        ndberror_cl_configuration = 16,
        ndberror_cl_schema_object_already_exists = 17,
        ndberror_cl_internal_temporary = 18,
    }
[System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
    public struct ndberror_struct
    {      
        public ndberror_status status;
        public ndberror_classification classification;
        public int code;
        public int mysql_code;
       [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.LPStr)]
        public string message;
        [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.LPStr)]
        public string details;
    }

要调用的方法的C-Side签名是：

const ndberror_struct __stdcall Ndb_getNdbError(void* obj);

C＃-Side代替：

        [System.Runtime.InteropServices.DllImportAttribute("Ndb_CWrapper.dll", EntryPoint = "Ndb_getNdbError", CallingConvention = System.Runtime.InteropServices.CallingConvention.StdCall,CharSet = CharSet.Ansi)]
        private static extern ndberror_struct Ndb_getNdbError(System.IntPtr obj);

当我尝试从托管代码调用方法时，MarshalDirectiveException会引发。我认为问题是在字符串编组中的某个地方，但我无法解决问题。本机库是为x64系统多字节字符集代码编译的（使用visual studio c ++ 2012）

替代方案可能是本机代码中的一些奇怪操作，我将NdbError（在另一个标头中定义）转换为ndberror_struct，这里是代码：

Ndb* tmp=(Ndb*)obj;
ndberror_struct tmpRes=(ndberror_struct)tmp->getNdbError();

由NdbStruct返回的tmp->getNdbError()重载了转换操作符（我想），这是声明：

operator ndberror_struct() const {
    ndberror_struct ndberror;
    ndberror.status = (ndberror_status_enum) status;
    ndberror.classification = (ndberror_classification_enum) classification;
    ndberror.code = code;
    ndberror.mysql_code = mysql_code;
    ndberror.message = message;
    ndberror.details = details;
    return ndberror;
}

任何帮助将不胜感激。

编辑：我试图以这种方式改变方法的签名： C-侧：

void* __stdcall Ndb_getNdbError(void* obj)

C＃侧的：

IntPtr Ndb_getNdbError(IntPtr obj)

本机方法返回&tmpRes并且在托管代码中我手动编组了结构调用

var tmp=Ndb_getNdbError(raw);
var f = (ndberror_struct)Marshal.PtrToStructure(tmp, typeof(ndberror_struct));

Answer 1

marshaller不会将本地代码中的char*个字段封送到托管代码。你必须自己做这件事。

一种方法是更改C＃结构声明，如下所示：

public struct ndberror_struct
{      
    public ndberror_status status;
    public ndberror_classification classification;
    public int code;
    public int mysql_code;
    public IntPtr message;
    public IntPtr details;
}

保留你的p / invoke声明：

[DllImport("Ndb_CWrapper.dll")]
private static extern ndberror_struct Ndb_getNdbError(IntPtr obj);

您现在可以调用此功能。要将两个IntPtr字段转换为字符串，请调用Marshal.PtrToStringAnsi。

使用char *将结构编组到C＃

1 个答案: