Delphi：使用Pointer函数

问题描述

我是delphi的新手，我的delphi开发的程序与C ++开发的dll一起使用，我需要使用抛出Access Violation地址异常的指针函数，并且经过多次测试，我不知道如何解决它。 / p>

这是在delphi中定义的指针函数，该函数自标头c ++以来就进行转换

  type 
 TMICRCallback =函数：对象的整数； stdcall; 
 TStatusCallback = function（dwParam：Cardinal）：对象的整数； stdcall; 
 
类型
 TBiMICRSetReadBackFunction = 
函数（const nHande：Integer; 
 pMicrCB：TMICRCallback; 
 var pReadBuffSize：Byte; 
 var readCharBuff：字节; 
 var pStatus：字节; 
 var pDetail：字节
）：整数; stdcall; 
 var 
 BiMICRSetReadBackFunction：TBiMICRSetReadBackFunction; 
 
类型
 TBiMICRSetReadBackFunction = 
函数（const nHande：Integer; 
 pMicrCB：TMICRCallback; 
 var pReadBuffSize：Byte; 
 var readCharBuff：字节; 
 var pStatus：字节; 
 var pDetail：字节
）：整数; stdcall; 
 var 
 BiMICRSetReadBackFunction：TBiMICRSetReadBackFunction; 
  

---

这是调用指针函数的代码

  type 
函数CBMICRRead：整数; stdcall; 
函数CBMICRStatus（dwStatus：LongWord）：整数; stdcall; 
 
 
 Respuesta：TMICRCallback; 
 Estado：TStatusCallback; 
 
 BiSetStatusBackFunction（m_hApi，Estado）; 
 
 BiMICRSetReadBackFunction（m_hApi，
 Respuesta，
 m_MICRReadBuffSize，
 m_MICRReadBuff [0]，
 m_MICRReadStatus，
 m_MICRReadStDetail）; 
  

---

这是接口的C ++一侧：

  typedef int（CALLBACK * MICRCallback）（void）; 
 typedef int（CALLBACK * StatusCallback）（DWORD）; 
 
 
 int WINAPI BiSetStatusBackFunction（int nHandle，
 int（CALLBACK * pStatusCB）（DWORD dwStatus））; 
 
 int WINAPI BiMICRSetReadBackFunction（int nHandle，
 int（CALLBACK * pMicrCB）（void），
 LPBYTE pReadBuffSize，
 LPBYTE readCharBuff，
 LPBYTE pStatus， 
 LPBYTE pDetail）; 
  

解决方案

您必须避免 Object 作为DLL函数调用结果的传递参数。

  TMICRCallback = function：Integer; stdcall; 
 TStatusCallback = function（dwParam：Cardinal）：整数; stdcall; 
  

I'm new in delphi, my program developed in delphi working with a dll developed in C++, I need working with pointer functions that throw exceptions of Access Violation address and after many test I don't know how resolve It.

this is defintion of the pointer function in delphi that translate since header c++

type
  TMICRCallback   = function: Integer of Object;  stdcall;
  TStatusCallback = function(dwParam: Cardinal): Integer of Object; stdcall;

  type
   TBiMICRSetReadBackFunction =
      function(const nHande:        Integer;
               pMicrCB:             TMICRCallback;
               var pReadBuffSize:    Byte;
               var readCharBuff:     Byte;
               var pStatus:          Byte;
               var pDetail:          Byte
      ): Integer; stdcall;
var
   BiMICRSetReadBackFunction: TBiMICRSetReadBackFunction;

type
   TBiMICRSetReadBackFunction =
      function(const nHande:        Integer;
               pMicrCB:             TMICRCallback;
               var pReadBuffSize:    Byte;
               var readCharBuff:     Byte;
               var pStatus:          Byte;
               var pDetail:          Byte
      ): Integer; stdcall;
var
   BiMICRSetReadBackFunction: TBiMICRSetReadBackFunction;

---

this is a code that call the pointer functions

type
  function CBMICRRead : Integer; stdcall;
  function CBMICRStatus(dwStatus: LongWord) : Integer;  stdcall;


  Respuesta      : TMICRCallback;
  Estado         : TStatusCallback;

  BiSetStatusBackFunction(m_hApi, Estado);

 BiMICRSetReadBackFunction (m_hApi,
                                    Respuesta,
                                    m_MICRReadBuffSize,
                                    m_MICRReadBuff[0],
                                    m_MICRReadStatus,
                                    m_MICRReadStDetail);

---

This is the C++ side of the interface:

typedef int (CALLBACK* MICRCallback)(void);
typedef int (CALLBACK* StatusCallback)(DWORD);


int WINAPI BiSetStatusBackFunction(int  nHandle,
                               int (CALLBACK *pStatusCB)(DWORD dwStatus));

int WINAPI BiMICRSetReadBackFunction(int    nHandle,
                                     int    (CALLBACK *pMicrCB)(void),
                                     LPBYTE pReadBuffSize,
                                     LPBYTE readCharBuff,
                                     LPBYTE pStatus,
                                     LPBYTE pDetail);

解决方案

You must avoid Object as passing parameters from/to DLL function call result.

TMICRCallback   = function: Integer;  stdcall;
TStatusCallback = function(dwParam: Cardinal): Integer; stdcall;

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