求助

Question

阅读《DELPHI下深入WINDOWS核心编程》第2章钩子原理的第一个例子中这样一段定义函数的代码：我没有看懂得彩色的那段代码，其中的function不知道什么意思，请大家帮我解释一下，多谢
implementationvar
function NewCreateFileA(lpFileName: PChar;dwDesiredAccess, dwShareMode: DWORD;
   lpSecurityAttributes: PSecurityAttributes;dwCreationDisposition,dwFlagsAndAttributes: DWORD;
   hTemplateFile: THandle): THandle;stdcall;
type
  TCreateFileA=function(lpFileName: PChar;dwDesiredAccess, dwShareMode: DWORD;
   lpSecurityAttributes: PSecurityAttributes;dwCreationDisposition,dwFlagsAndAttributes: DWORD;
   hTemplateFile: THandle): THandle;stdcall;
begin
   ////////////////////
   end;

Answer 1

type
  TCreateFile = function(lpFileName: PChar; dwDesiredAccess, dwShareMode: DWORD;
                 lpSecurityAttributes: PSecurityAttributes; dwCreationDisposition, dwFlagsAndAttributes: DWORD;
                 hTemplateFile: THandle): THandle; stdcall;
  TCreateFileA = function(lpFileName: PAnsiChar; dwDesiredAccess, dwShareMode: DWORD;
                          lpSecurityAttributes: PSecurityAttributes; dwCreationDisposition, dwFlagsAndAttributes: DWORD;
                          hTemplateFile: THandle): THandle; stdcall;
  TCreateFileW = function(lpFileName: PWideChar; dwDesiredAccess, dwShareMode: DWORD;
                          lpSecurityAttributes: PSecurityAttributes; dwCreationDisposition, dwFlagsAndAttributes: DWORD;
                          hTemplateFile: THandle): THandle; stdcall;var
     OldCreateFile: TCreateFile;
   OldCreateFileA: TCreateFileA;
   OldCreateFileW: TCreateFileW;看了这个就大概懂了吧。你可以这样理解，TCreateFileA是个函数类型，可以用来定义这种类型的“函数变量”。

Answer 2

惭愧，感谢二楼，请问这种“函数变量”的概念是DELPHI哪部分知识里的，是动态链接库还是面向对象，我怎么没有查到？

Answer 3

这个是动态调用动态库的函数的定义，当你动态调用动态链接库的函数时，可以这样定义。和VC的typedef类似，给你个VC调用动态链接库函数的例子，你看了就懂了。
        HINSTANCE   hInst   =   LoadLibrary("seekcrypt.dll");    
        if(hInst)    
        {                          
            typedef   int   (*_seekcrypt)(int,unsigned   char*   ,int,unsigned   char*,unsigned   char*   ,int*   );                      
            _seekcrypt   seekcrypt   =   NULL;            
            seekcrypt   =   (_seekcrypt)GetProcAddress(hInst,   "seekcrpyt");  
            if(seekcrypt)            
    {                            
                int   i=seekcrypt(1,'12',2,'1212','2323',4);  
                CString   aa;  
                aa.Format("%d%s",i,aa);  
                AfxMessageBox(aa);  
    }  
            FreeLibrary(hInst);  
        }else{  
                      AfxMessageBox("找不到seekcrypt.dll文件。");  
        }