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Samla data med plattformsanrop

För att anropa funktioner som exporteras från ett ohanterat bibliotek kräver ett .NET Framework-program en funktionsprototyp i hanterad kod som representerar den ohanterade funktionen. Om du vill skapa en prototyp som gör att plattformsanrop kan konvertera data korrekt måste du göra följande:

  • DllImportAttribute Använd attributet för den statiska funktionen eller metoden i hanterad kod.

  • Ersätt hanterade datatyper med ohanterade datatyper.

Du kan använda dokumentationen som medföljer en ohanterad funktion för att konstruera en motsvarande hanterad prototyp genom att använda attributet med dess valfria fält och ersätta hanterade datatyper med ohanterade typer. För instruktioner om hur du tillämpar DllImportAttribute, se Förbruka ohanterade DLL-funktioner.

Det här avsnittet innehåller exempel som visar hur du skapar prototyper för hanterade funktioner för att skicka argument till och ta emot returvärden från funktioner som exporteras av ohanterade bibliotek. Exemplen visar också när du ska använda MarshalAsAttribute attributet och Marshal klassen för att explicit konvertera data.

Plattform som anropar datatyper

I följande tabell visas datatyper som används i Windows-API:er och C-formatfunktioner. Många ohanterade bibliotek innehåller funktioner som skickar dessa datatyper som parametrar och returvärden. Den tredje kolumnen visar motsvarande inbyggda .NET Framework-värdetyp eller -klass som du använder i hanterad kod. I vissa fall kan du ersätta en typ av samma storlek med den typ som anges i tabellen.

Ohanterad typ i Windows-API:er Ohanterad C-språktyp Hanterad typ Beskrivning
VOID void System.Void Tillämpas på en funktion som inte returnerar ett värde.
HANDLE void * System.IntPtr eller System.UIntPtr 32 bitar på 32-bitars Windows-operativsystem, 64 bitar på 64-bitars Windows-operativsystem.
BYTE unsigned char System.Byte 8 bitar
SHORT short System.Int16 16 bit
WORD unsigned short System.UInt16 16 bit
INT int System.Int32 32 bit
UINT unsigned int System.UInt32 32 bit
LONG long System.Int32 32 bit
BOOL long System.Boolean eller System.Int32 32 bit
DWORD unsigned long System.UInt32 32 bit
ULONG unsigned long System.UInt32 32 bit
CHAR char System.Char Dekorera med ANSI.
WCHAR wchar_t System.Char Dekorera med Unicode.
LPSTR char * System.String eller System.Text.StringBuilder Dekorera med ANSI.
LPCSTR const char * System.String eller System.Text.StringBuilder Dekorera med ANSI.
LPWSTR wchar_t * System.String eller System.Text.StringBuilder Dekorera med Unicode.
LPCWSTR const wchar_t * System.String eller System.Text.StringBuilder Dekorera med Unicode.
FLOAT float System.Single 32 bit
DOUBLE double System.Double 64 bitar

Motsvarande typer i Visual Basic, C#och C++finns i Introduktion till klassbiblioteket för .NET Framework.

PinvokeLib.dll

Följande kod definierar biblioteksfunktionerna som tillhandahålls av PInvokeLib.dll. Många av de exempel som beskrivs i det här avsnittet använder detta bibliotek.

Exempel

// PInvokeLib.cpp : Defines the entry point for the DLL application.
//

#define PINVOKELIB_EXPORTS
#include "PInvokeLib.h"

#include <strsafe.h>
#include <objbase.h>
#include <stdio.h>

#pragma comment(lib,"ole32.lib")

BOOL APIENTRY DllMain( HANDLE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved )
{
    switch (ul_reason_for_call)
    {
        case DLL_PROCESS_ATTACH:
        case DLL_THREAD_ATTACH:
        case DLL_THREAD_DETACH:
        case DLL_PROCESS_DETACH:
            break;
    }

    return TRUE;
}

//******************************************************************
// This is the constructor of a class that has been exported.
CTestClass::CTestClass()
{
    m_member = 1;
}

int CTestClass::DoSomething( int i )
{
    return i*i + m_member;
}

PINVOKELIB_API CTestClass* CreateTestClass()
{
    return new CTestClass();
}

PINVOKELIB_API void DeleteTestClass( CTestClass* instance )
{
    delete instance;
}

//******************************************************************
PINVOKELIB_API int TestArrayOfInts( int* pArray, int size )
{
    int result = 0;

    for ( int i = 0; i < size; i++ )
    {
        result += pArray[ i ];
        pArray[i] += 100;
    }
    return result;
}

//******************************************************************
PINVOKELIB_API int TestRefArrayOfInts( int** ppArray, int* pSize )
{
    int result = 0;

    // CoTaskMemAlloc must be used instead of the new operator
    // because code on the managed side will call Marshal.FreeCoTaskMem
    // to free this memory.

    int* newArray = (int*)CoTaskMemAlloc( sizeof(int) * 5 );

    for ( int i = 0; i < *pSize; i++ )
    {
        result += (*ppArray)[i];
    }

    for ( int j = 0; j < 5; j++ )
    {
        newArray[j] = (*ppArray)[j] + 100;
    }

    CoTaskMemFree( *ppArray );
    *ppArray = newArray;
    *pSize = 5;

    return result;
}

//******************************************************************
PINVOKELIB_API int TestMatrixOfInts( int pMatrix[][COL_DIM], int row )
{
    int result = 0;

    for ( int i = 0; i < row; i++ )
    {
        for ( int j = 0; j < COL_DIM; j++ )
        {
            result += pMatrix[i][j];
            pMatrix[i][j] += 100;
        }
    }
    return result;
}

//******************************************************************
PINVOKELIB_API int TestArrayOfStrings( char* ppStrArray[], int count )
{
    int result = 0;
    STRSAFE_LPSTR temp;
    size_t len;
    const size_t alloc_size = sizeof(char) * 10;

    for ( int i = 0; i < count; i++ )
    {
        len = 0;
        StringCchLengthA( ppStrArray[i], STRSAFE_MAX_CCH, &len );
        result += len;

        temp = (STRSAFE_LPSTR)CoTaskMemAlloc( alloc_size );
        StringCchCopyA( temp, alloc_size, (STRSAFE_LPCSTR)"123456789" );

       // CoTaskMemFree must be used instead of delete to free memory.

       CoTaskMemFree( ppStrArray[i] );
       ppStrArray[i] = (char *) temp;
   }

   return result;
}

//******************************************************************
PINVOKELIB_API int TestArrayOfStructs( MYPOINT* pPointArray, int size )
{
    int result = 0;
    MYPOINT* pCur = pPointArray;

    for ( int i = 0; i < size; i++ )
    {
        result += pCur->x + pCur->y;
        pCur->y = 0;
        pCur++;
    }

    return result;
}

//******************************************************************
PINVOKELIB_API int TestStructInStruct( MYPERSON2* pPerson2 )
{
    size_t len = 0;

    StringCchLengthA( pPerson2->person->last, STRSAFE_MAX_CCH, &len );
    len = sizeof(char) * ( len + 2 ) + 1;

    STRSAFE_LPSTR temp = (STRSAFE_LPSTR)CoTaskMemAlloc( len );
    StringCchCopyA( temp, len, (STRSAFE_LPSTR)"Mc" );
    StringCbCatA( temp, len, (STRSAFE_LPSTR)pPerson2->person->last );

    CoTaskMemFree( pPerson2->person->last );
    pPerson2->person->last = (char *)temp;

    return pPerson2->age;
}

//******************************************************************
PINVOKELIB_API int TestArrayOfStructs2( MYPERSON* pPersonArray, int size )
{
    int result = 0;
    MYPERSON* pCur = pPersonArray;
    STRSAFE_LPSTR temp;
    size_t len;

    for ( int i = 0; i < size; i++ )
    {
        len = 0;
        StringCchLengthA( pCur->first, STRSAFE_MAX_CCH, &len );
        len++;
        result += len;
        len = 0;
        StringCchLengthA( pCur->last, STRSAFE_MAX_CCH, &len );
        len++;
        result += len;

        len = sizeof(char) * ( len + 2 );
        temp = (STRSAFE_LPSTR)CoTaskMemAlloc( len );
        StringCchCopyA( temp, len, (STRSAFE_LPCSTR)"Mc" );
        StringCbCatA( temp, len, (STRSAFE_LPCSTR)pCur->last );
        result += 2;

        // CoTaskMemFree must be used instead of delete to free memory.
        CoTaskMemFree( pCur->last );
        pCur->last = (char *)temp;
        pCur++;
   }

   return result;
}

//******************************************************************
PINVOKELIB_API void TestStructInStruct3( MYPERSON3 person3 )
{
    printf( "\n\nperson passed by value:\n" );
    printf( "first = %s last = %s age = %i\n\n",
            person3.person.first,
            person3.person.last,
            person3.age );
}

//*********************************************************************
PINVOKELIB_API void TestUnion( MYUNION u, int type )
{
    if ( ( type != 1 ) && ( type != 2 ) )
    {
        return;
    }
    if ( type == 1 )
    {
        printf( "\n\ninteger passed: %i", u.i );
    }
    else if ( type == 2 )
    {
        printf( "\n\ndouble passed: %f", u.d );
    }
}

//******************************************************************
PINVOKELIB_API void TestUnion2( MYUNION2 u, int type )
{
    if ( ( type != 1 ) && ( type != 2 ) )
    {
        return;
    }
    if ( type == 1 )
    {
        printf( "\n\ninteger passed: %i", u.i );
    }
    else if ( type == 2 )
    {
        printf( "\n\nstring passed: %s", u.str );
    }
}

//******************************************************************
PINVOKELIB_API void TestCallBack( FPTR pf, int value )
{
    printf( "\nReceived value: %i", value );
    printf( "\nPassing to callback..." );
    bool res = (*pf)(value);

    if ( res )
    {
        printf( "Callback returned true.\n" );
    }
    else
    {
        printf( "Callback returned false.\n" );
    }
}

//******************************************************************
PINVOKELIB_API void TestCallBack2( FPTR2 pf2, char* value )
{
    printf( "\nReceived value: %s", value );
    printf( "\nPassing to callback..." );
    bool res = (*pf2)(value);

    if ( res )
    {
        printf( "Callback2 returned true.\n" );
    }
    else
    {
        printf( "Callback2 returned false.\n" );
    }
}

//******************************************************************
PINVOKELIB_API void TestStringInStruct( MYSTRSTRUCT* pStruct )
{
    wprintf( L"\nUnicode buffer content: %s\n", pStruct->buffer );

    // Assuming that the buffer is big enough.
    StringCbCatW( pStruct->buffer, pStruct->size, (STRSAFE_LPWSTR)L"++" );
}

//******************************************************************
PINVOKELIB_API void TestStringInStructAnsi( MYSTRSTRUCT2* pStruct )
{
    printf( "\nAnsi buffer content: %s\n", pStruct->buffer );

    // Assuming that the buffer is big enough.
    StringCbCatA( (STRSAFE_LPSTR) pStruct->buffer, pStruct->size, (STRSAFE_LPSTR)"++" );
}

//******************************************************************
PINVOKELIB_API void TestOutArrayOfStructs( int* pSize, MYSTRSTRUCT2** ppStruct )
{
    const int cArraySize = 5;
    *pSize = 0;
    *ppStruct = (MYSTRSTRUCT2*)CoTaskMemAlloc( cArraySize * sizeof( MYSTRSTRUCT2 ));

    if ( ppStruct != NULL )
    {
        MYSTRSTRUCT2* pCurStruct = *ppStruct;
        LPSTR buffer;
        *pSize = cArraySize;

        STRSAFE_LPCSTR teststr = "***";
        size_t len = 0;
        StringCchLengthA(teststr, STRSAFE_MAX_CCH, &len);
        len++;

        for ( int i = 0; i < cArraySize; i++, pCurStruct++ )
        {
            pCurStruct->size = len;
            buffer = (LPSTR)CoTaskMemAlloc( len );
            StringCchCopyA( buffer, len, teststr );
            pCurStruct->buffer = (char *)buffer;
        }
    }
}

//************************************************************************
PINVOKELIB_API char * TestStringAsResult()
{

    const size_t alloc_size = 64;
    STRSAFE_LPSTR result = (STRSAFE_LPSTR)CoTaskMemAlloc( alloc_size );
    STRSAFE_LPCSTR teststr = "This is return value";
    StringCchCopyA( result, alloc_size, teststr );

    return (char *) result;
}

//************************************************************************
PINVOKELIB_API void SetData( DataType typ, void* object )
{
    switch ( typ )
    {
        case DT_I2: printf( "Short %i\n", *((short*)object) ); break;
        case DT_I4: printf( "Long %i\n", *((long*)object) ); break;
        case DT_R4: printf( "Float %f\n", *((float*)object) ); break;
        case DT_R8: printf( "Double %f\n", *((double*)object) ); break;
        case DT_STR: printf( "String %s\n", (char*)object ); break;
        default: printf( "Unknown type" ); break;
    }
}

//************************************************************************
PINVOKELIB_API void TestArrayInStruct( MYARRAYSTRUCT* pStruct )
{
    pStruct->flag = true;
    pStruct->vals[0] += 100;
    pStruct->vals[1] += 100;
    pStruct->vals[2] += 100;
}

// PInvokeLib.h : The header file for the DLL application.
//

#pragma once

#define WIN32_LEAN_AND_MEAN
#include <windows.h>

// The following ifdef block is the standard way of creating macros which make exporting
// from a DLL simpler. All files within this DLL are compiled with the PINVOKELIB_EXPORTS
// symbol defined on the command line. this symbol should not be defined on any project
// that uses this DLL. This way any other project whose source files include this file see
// PINVOKELIB_API functions as being imported from a DLL, wheras this DLL sees symbols
// defined with this macro as being exported.
#ifdef PINVOKELIB_EXPORTS
#define PINVOKELIB_API __declspec(dllexport)
#else
#define PINVOKELIB_API __declspec(dllimport)
#endif

// Define the test structures

typedef struct _MYPOINT
{
    int x;
    int y;
} MYPOINT;

typedef struct _MYPERSON
{
    char* first;
    char* last;
} MYPERSON;

typedef struct _MYPERSON2
{
    MYPERSON* person;
    int age;
} MYPERSON2;

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

union MYUNION
{
    int i;
    double d;
};

union MYUNION2
{
    int i;
    char str[128];
};

typedef struct _MYSTRSTRUCT
{
    wchar_t* buffer;
    UINT size;
} MYSTRSTRUCT;

typedef struct _MYSTRSTRUCT2
{
    char* buffer;
    UINT size;
} MYSTRSTRUCT2;

typedef struct _MYARRAYSTRUCT
{
    bool flag;
    int vals[3];
} MYARRAYSTRUCT;

// constants and pointer definitions

const int COL_DIM = 5;

typedef bool (CALLBACK *FPTR)( int i );

typedef bool (CALLBACK *FPTR2)( char* str );

// Data type codes
enum DataType
{
    DT_I2 = 1,
    DT_I4,
    DT_R4,
    DT_R8,
    DT_STR
};

// This is an exported class.
class PINVOKELIB_API CTestClass
{
public:
    CTestClass( void );
    int DoSomething( int i );

private:
    int m_member;
};

// Exports for PInvokeLib.dll

#ifdef __cplusplus
extern "C"
{
#endif

PINVOKELIB_API CTestClass* CreateTestClass();

PINVOKELIB_API void DeleteTestClass( CTestClass* instance );

PINVOKELIB_API int TestArrayOfInts( int* pArray, int size );

PINVOKELIB_API int TestRefArrayOfInts( int** ppArray, int* pSize );

PINVOKELIB_API int TestMatrixOfInts( int pMatrix[][COL_DIM], int row );

PINVOKELIB_API int TestArrayOfStrings( char* ppStrArray[], int size );

PINVOKELIB_API int TestArrayOfStructs( MYPOINT* pPointArray, int size );

PINVOKELIB_API int TestArrayOfStructs2( MYPERSON* pPersonArray, int size );

PINVOKELIB_API int TestStructInStruct( MYPERSON2* pPerson2 );

PINVOKELIB_API void TestStructInStruct3( MYPERSON3 person3 );

PINVOKELIB_API void TestUnion( MYUNION u, int type );

PINVOKELIB_API void TestUnion2( MYUNION2 u, int type );

PINVOKELIB_API void TestCallBack( FPTR pf, int value );

PINVOKELIB_API void TestCallBack2( FPTR2 pf2, char* value );

// buffer is an in/out param
PINVOKELIB_API void TestStringInStruct( MYSTRSTRUCT* pStruct );

// buffer is in/out param
PINVOKELIB_API void TestStringInStructAnsi( MYSTRSTRUCT2* pStruct );

PINVOKELIB_API void TestOutArrayOfStructs( int* pSize, MYSTRSTRUCT2** ppStruct );

PINVOKELIB_API char* TestStringAsResult();

PINVOKELIB_API void SetData( DataType typ, void* object );

PINVOKELIB_API void TestArrayInStruct( MYARRAYSTRUCT* pStruct );

#ifdef __cplusplus
}
#endif

Om du vill anropa biblioteksfunktionerna från hanterad kod implementerar du hanterade prototyper för varje funktion som du vill anropa. Om den ohanterade koden använder anpassade typer måste du även deklarera dessa typer i din hanterade kod. Dekorera varje prototyp med DllImportAttribute attributet och använd StructLayoutAttribute för att styra layouten för hanterade strukturer så att de matchar de ohanterade motsvarigheterna.

Deklarationer av hanterad typ

Följande kod visar de hanterade motsvarigheterna till de ohanterade typer som definierats i PInvokeLib.h. Varje struktur använder StructLayout för att säkerställa att fältlayouten matchar den ohanterade layouten.

// Managed type declarations that correspond to the unmanaged types in PinvokeLib.dll.

[StructLayout(LayoutKind.Sequential)]
internal struct MyPoint
{
    public int x;
    public int y;
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
internal struct MyPerson
{
    public string first;
    public string last;
}

[StructLayout(LayoutKind.Sequential)]
internal struct MyPerson2
{
    public IntPtr person; // Pointer to a MyPerson structure
    public int age;
}

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

[StructLayout(LayoutKind.Explicit)]
internal struct MyUnion
{
    [FieldOffset(0)] public int i;
    [FieldOffset(0)] public double d;
}

[StructLayout(LayoutKind.Sequential)]
internal struct MyArrayStruct
{
    public bool flag;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)]
    public int[] vals;
}

' Managed type declarations that correspond to the unmanaged types in PinvokeLib.dll.

<StructLayout(LayoutKind.Sequential)>
Friend Structure MyPoint
    Public x As Integer
    Public y As Integer
End Structure

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Ansi)>
Friend Structure MyPerson
    Public first As String
    Public last As String
End Structure

<StructLayout(LayoutKind.Sequential)>
Friend Structure MyPerson2
    Public person As IntPtr ' Pointer to a MyPerson structure
    Public age As Integer
End Structure

<StructLayout(LayoutKind.Sequential)>
Friend Structure MyPerson3
    Public person As MyPerson ' Embedded MyPerson structure
    Public age As Integer
End Structure

<StructLayout(LayoutKind.Explicit)>
Friend Structure MyUnion
    <FieldOffset(0)> Public i As Integer
    <FieldOffset(0)> Public d As Double
End Structure

<StructLayout(LayoutKind.Sequential)>
Friend Structure MyArrayStruct
    Public flag As Boolean

    <MarshalAs(UnmanagedType.ByValArray, SizeConst:=3)>
    Public vals As Integer()
End Structure

Prototyper för hanterade funktioner

Följande kod visar de DllImport deklarationer som exponerar ohanterade funktioner från PinvokeLib.dll till hanterad kod:

internal static class NativeMethods
{
    [DllImport("PinvokeLib.dll", CallingConvention = CallingConvention.Cdecl)]
    internal static extern int TestArrayOfInts(
        [In, Out] int[] array, int size);

    [DllImport("PinvokeLib.dll", CallingConvention = CallingConvention.Cdecl)]
    internal static extern int TestRefArrayOfInts(
        ref IntPtr array, ref int size);

    [DllImport("PinvokeLib.dll", CallingConvention = CallingConvention.Cdecl)]
    internal static extern int TestMatrixOfInts(
        [In, Out] int[,] matrix, int row);

    [DllImport("PinvokeLib.dll", CallingConvention = CallingConvention.Cdecl)]
    internal static extern int TestArrayOfStrings(
        [In, Out] string[] array, int size);

    [DllImport("PinvokeLib.dll", CallingConvention = CallingConvention.Cdecl)]
    internal static extern int TestArrayOfStructs(
        [In, Out] MyPoint[] pointArray, int size);

    [DllImport("PinvokeLib.dll", CallingConvention = CallingConvention.Cdecl)]
    internal static extern int TestArrayOfStructs2(
        [In, Out] MyPerson[] personArray, int size);

    [DllImport("PinvokeLib.dll", CallingConvention = CallingConvention.Cdecl)]
    internal static extern int TestStructInStruct(ref MyPerson2 person2);

    [DllImport("PinvokeLib.dll", CallingConvention = CallingConvention.Cdecl)]
    internal static extern void TestStructInStruct3(MyPerson3 person3);

    [DllImport("PinvokeLib.dll", CallingConvention = CallingConvention.Cdecl)]
    internal static extern void TestUnion(MyUnion u, int type);

    [DllImport("PinvokeLib.dll", CallingConvention = CallingConvention.Cdecl)]
    internal static extern void TestArrayInStruct(ref MyArrayStruct myStruct);
}

Friend Class NativeMethods
    <DllImport("PinvokeLib.dll", CallingConvention:=CallingConvention.Cdecl)>
    Friend Shared Function TestArrayOfInts(
        <[In], Out> ByVal array() As Integer, ByVal size As Integer) As Integer
    End Function

    <DllImport("PinvokeLib.dll", CallingConvention:=CallingConvention.Cdecl)>
    Friend Shared Function TestRefArrayOfInts(
        ByRef array As IntPtr, ByRef size As Integer) As Integer
    End Function

    <DllImport("PinvokeLib.dll", CallingConvention:=CallingConvention.Cdecl)>
    Friend Shared Function TestMatrixOfInts(
        <[In], Out> ByVal matrix(,) As Integer, ByVal row As Integer) As Integer
    End Function

    <DllImport("PinvokeLib.dll", CallingConvention:=CallingConvention.Cdecl)>
    Friend Shared Function TestArrayOfStrings(
        <[In], Out> ByVal array() As String, ByVal size As Integer) As Integer
    End Function

    <DllImport("PinvokeLib.dll", CallingConvention:=CallingConvention.Cdecl)>
    Friend Shared Function TestArrayOfStructs(
        <[In], Out> ByVal pointArray() As MyPoint, ByVal size As Integer) As Integer
    End Function

    <DllImport("PinvokeLib.dll", CallingConvention:=CallingConvention.Cdecl)>
    Friend Shared Function TestArrayOfStructs2(
        <[In], Out> ByVal personArray() As MyPerson, ByVal size As Integer) As Integer
    End Function

    <DllImport("PinvokeLib.dll", CallingConvention:=CallingConvention.Cdecl)>
    Friend Shared Function TestStructInStruct(
        ByRef person2 As MyPerson2) As Integer
    End Function

    <DllImport("PinvokeLib.dll", CallingConvention:=CallingConvention.Cdecl)>
    Friend Shared Sub TestStructInStruct3(ByVal person3 As MyPerson3)
    End Sub

    <DllImport("PinvokeLib.dll", CallingConvention:=CallingConvention.Cdecl)>
    Friend Shared Sub TestUnion(ByVal u As MyUnion, ByVal type As Integer)
    End Sub

    <DllImport("PinvokeLib.dll", CallingConvention:=CallingConvention.Cdecl)>
    Friend Shared Sub TestArrayInStruct(ByRef myStruct As MyArrayStruct)
    End Sub
End Class

Mer information och exempel finns i följande artiklar:

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