C 和 C# 混编

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字符串传递

MSDN 上给出 C/C++ 字符串类型与 C#字符串类型的对应关系
Wtypes.h 中的非托管类型 非托管 C/C++ 语言类型 托管类名 说明
CHAR char System.Char 用 ANSI 修饰
LPSTR char* System.String 或 System.Text.StringBuilder 用 ANSI 修饰
LPCSTR Const char* System.String 或 System.Text.StringBuilder 用 ANSI 修饰
LPWSTR wchar_t* System.String 或 System.Text.StringBuilder 用 Unicode 修饰
LPCWSTR Const wchar_t* System.String 或 System.Text.StringBuilder 用 Unicode 修饰
MSDN 给出 MarshalAs 属性控制字符串封送行为:
枚举类型 非托管格式说明
UnmanagedType.AnsiBStr 长度前缀为双字节的 Unicode 字符的 COM 样式的 BSTR
UnmanagedType.LPStr 单字节、null 空终止的 ANSI 字符数组的指针。(默认值)
UnmanagedType.LPTStr null 空终止与平台相关的字符数组的指针。
UnmanagedType.LPWStr null 空终止与 Unicode 的字符数组的指针。
UnmanagedType.TBStr 一个有长度前缀的与平台相关的 COM 样式的 BSTR。
void __stdcall PrintString(char * hello)
 public static extern void PrintStringByBytes(byte[] hello);
 public static extern void PrintStringByMarshal([MarshalAs(UnmanagedType.LPStr)]string hello);
char * __stdcall GetStringReturn()
[DllImport("TestDll", EntryPoint = "GetStringReturn")]
public static extern IntPtr GetStringReturnByBytes();

[DllImport("TestDll", EntryPoint = "GetStringReturn")]
[return:MarshalAs(UnmanagedType.LPStr)]
public static extern string GetStringReturnByMarshal();

Console.WriteLine(Marshal.PtrToStringAnsi(GetStringReturnByBytes()));

封送字符串数组
C++
int TestArrayOfStrings(char* ppStrArray[], int size);

C#:
[ DllImport( "test.dll" )]
public static extern int TestArrayOfStrings( [In, Out]   String[] ppStrArray, int size );

使用:
String[] strArray = { "one", "two", "three", "four", "five" };
int lenSum = LibWrap.TestArrayOfStrings( strArray, strArray.Length );

结构体传送

按顺序字节方式即可:[StructLayout(LayoutKind.Sequential)]

C:
  struct Lable1  {
        BYTELabFilterChan0[4][256];
        BYTELabFilterChan1[4][256];
  }

C#:
   [StructLayout(LayoutKind.Sequential)]
    public structByteStru    {
       [MarshalAs(UnmanagedType.ByValArray, SizeConst = 256)]
        public byte[]a;
    };


   [StructLayout(LayoutKind.Sequential)]
    public structLabel1    {
       [MarshalAs(UnmanagedType.ByValArray, SizeConst = 4)]
        publicByteStru[] LabFilterChan0 ;

       [MarshalAs(UnmanagedType.ByValArray, SizeConst = 4)]
        public ByteStru[] LabFilterChan1 ;
    };
C:
typedef struct _MYPERSON{
char* first;              //字符指针
} MYPERSON, *LP_MYPERSON;

C#:
[ StructLayout( LayoutKind.Sequential, CharSet=CharSet.Ansi )]
public struct MyPerson {
public String first;
}
C:
typedef struct _MYPERSON1{
	char first[20];       //字符数组
} MYPERSON1, *LP_MYPERSON1;

C#:
[ StructLayout( LayoutKind.Sequential, CharSet=CharSet.Ansi )]
public struct MyPerson1 {
	[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 20)]
	public String first;
}
C:
typedef struct _MYARRAYSTRUCT{
	bool flag;
	int vals[ 3 ];           //值类型数组
} MYARRAYSTRUCT;
C#:
public struct MyArrayStruct {
	public bool flag;
	[ MarshalAs( UnmanagedType.ByValArray, SizeConst=3 )]
	public int[] vals;
}
  • 结构体声明必须保证:字段声明顺序、字段类型、字段在内存中的大小原来的一致!结构体名称,其成员名称可以不同。
  • 结构体中,char*与 char[]在 C#声明区别很大,前者直接对应 string,后者(字符数组)很容易被初学者误用 char[]来对应,它还是要用 string 来对应,但还需要用[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 20)]来指明该字段的封送行为。
  • 其他值类型的数组,直接用数组方式对应,但也需要用[ MarshalAs( UnmanagedType.ByValArray, SizeConst=3 )] 指明封送行为。
  • 有直接结构体对应的结构体指针,建议直接用 ref + 具体类型,而不采用 IntPtr,省去一些不必要的转换操作,

TestArrayInStruct、TestStructInStruct2、TestStructInStruct3 都是如此。

结构体作为函数返回值

C++
MYPERSON* TestReturnStruct();
void FreeStruct(MYPERSON* pStruct);

C#:
[ DllImport( "test.dll" ,CharSet = CharSet.Ansi)]
public static extern IntPtr TestReturnStruct();         //注意对应的是IntPtr指针

[ DllImport( "test.dll" ,CharSet = CharSet.Ansi)]
public static extern void FreeStruct(IntPtr pStruct);

使用:

IntPtr pStruct=TestReturnStruct();
MYPERSON person=(MYPERSON)Marshal.PtrToStructure(pStruct,typeof(MYPERSON));

//在非托管代码,大多用 new/malloc 分配内存,net 无法正确释放,
//需要对应的调用释放内存的方法释放非托管内存

FreeStruct(pStruct);

结构体数组作为输入输出参数

C++
int TestArrayOfStructs2 (MYPERSON* pPersonArray, int size);

C#:
[ DllImport( "test.dll" )]
public static extern int TestArrayOfStructs2( [In, Out] MyPerson[] personArray, int size );

使用:
MyPerson[] persons = { new MyPerson( "Kim", "Akers" ), new MyPerson( "Adam", "Barr" )};
int namesSum = TestArrayOfStructs2( persons, persons.Length );
总结:
  • 一般我们数组作为输入输出参数,需要显式加上[In,Out]属性,标识为输入输入参数。如果不写,默认为 In 方向,CLR 将不会回传修改后的内存值

结构体嵌套结构体

C++
typedef struct _MYPERSON2{
	MYPERSON* person;
	int age;
} MYPERSON2, *LP_MYPERSON2;

typedef struct _MYPERSON3{
	MYPERSON person;
	int age;
} MYPERSON3;

int TestStructInStruct(MYPERSON2* pPerson2);
void TestStructInStruct3(MYPERSON3 person3);

C#:
[ StructLayout( LayoutKind.Sequential )]
public struct MyPerson2 {
	public IntPtr person;
	public int age;
}

[ StructLayout( LayoutKind.Sequential )]
public struct MyPerson3 {
	public MyPerson person;
	public int age;
}

[ DllImport( "test.dll" )]
public static extern int TestStructInStruct( ref MyPerson2 person2 );

[ DllImport( "test.dll" )]
public static extern int TestStructInStruct3( MyPerson3 person3 );

使用:

MyPerson personName;
personName.first = "Mark";
personName.last = "Lee";

MyPerson2 personAll;
personAll.age = 30;
IntPtr buffer = Marshal.AllocCoTaskMem( Marshal.SizeOf( personName ));

Marshal.StructureToPtr( personName, buffer, false );
personAll.person = buffer;

int res = TestStructInStruct( ref personAll );
MyPerson personRes = (MyPerson)Marshal.PtrToStructure( personAll.person, typeof( MyPerson ));

Marshal.FreeCoTaskMem( buffer );

MyPerson3 person3 = new MyPerson3();
person3.person.first = "John";
person3.person.last = "Evens";
person3.age = 27;

TestStructInStruct3( person3 );
总结:
  • 结构体嵌套,如果是实体成员,直接用结构体类型对应,如上面的 MyPerson3;
  • 如果是指针变量,则用 IntPtr 对应,如上面的 MYPERSON2;
  • 如果嵌套的是结构体数组,那么,出来办法以值类型数组方式对应,如 MYARRAYSTRUCT,只不过,类型为具体的结构体类型。这里不另外在举例。(还是给个例子)
C++
typedef struct Student  {
	char name[20];
	int age;
	double scores[32];
}Student;
typedef struct Class  {
	int number;
	Student students[126];
}Class;

C#:
	[StructLayout(LayoutKind.Sequential)]
	public struct Student
	{
           [MarshalAs(UnmanagedType.ByValTStr,SizeConst=20)]
           public string name;
           public int age;
           [MarshalAs(UnmanagedType.ByValArray,SizeConst=32)]
           public double[] scores;
	}

	[StructLayout(LayoutKind.Sequential)]
	struct Class
	{
          public int number;
          [MarshalAs(UnmanagedType.ByValArray,SizeConst=126)]
          public Student[] students;
	}

函数调用

C:
int TestStructInStruct1(MYPERSON pPerson);
int TestStructInStruct2(MYPERSON* pPerson);
int TestStructInStruct3(MYPERSON1* pPerson);
void TestArrayInStruct( MYARRAYSTRUCT* pStruct );

C#:
[ DllImport( "test.dll" ,CharSet = CharSet.Ansi)]
public static extern int TestStructInStruct( MyPerson person);

[ DllImport( "test.dll" ,CharSet = CharSet.Ansi)]
public static extern int TestStructInStruct1(ref  MyPerson person);

[ DllImport( "test.dll" ,CharSet = CharSet.Ansi)]
public static extern int TestStructInStruct2(ref  MyPerson1 person);

[ DllImport( "test.dll" ,CharSet = CharSet.Ansi)]
public static extern int TestArrayInStruct(ref MYARRAYSTRUCT person);

函数调用标准

    // Summary:
    //     Specifies the calling convention required to call methods implemented in
    //     unmanaged code.
    [Serializable]
    [ComVisible(true)]
    public enum CallingConvention
    {
        // Summary:
        //     This member is not actually a calling convention, but instead uses the default
        //     platform calling convention. For example, on Windows the default is System.Runtime.InteropServices.CallingConvention.StdCall
        //     and on Windows CE.NET it is System.Runtime.InteropServices.CallingConvention.Cdecl.
        Winapi = 1,
        //
        // Summary:
        //     The caller cleans the stack. This enables calling functions with varargs,
        //     which makes it appropriate to use for methods that accept a variable number
        //     of parameters, such as Printf.
        Cdecl = 2,
        //
        // Summary:
        //     The callee cleans the stack. This is the default convention for calling unmanaged
        //     functions with platform invoke.
        StdCall = 3,
        //
        // Summary:
        //     The first parameter is the this pointer and is stored in register ECX. Other
        //     parameters are pushed on the stack. This calling convention is used to call
        //     methods on classes exported from an unmanaged DLL.
        ThisCall = 4,
        //
        // Summary:
        //     This calling convention is not supported.
        FastCall = 5,
    }
  • C#
    29 引用 • 34 回帖 • 5 关注
  • C

    C 语言是一门通用计算机编程语言,应用广泛。C 语言的设计目标是提供一种能以简易的方式编译、处理低级存储器、产生少量的机器码以及不需要任何运行环境支持便能运行的编程语言。

    85 引用 • 165 回帖

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