如何编写DLL(动态链接库)

以下内容引用自《Windows程序设计（第5版）》，作者：（美）Charles Petzold

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首先我们建立一个头文件　　newDLL.h

#ifdef _cplusplus
#define EXPORT extern "C" _declspec (dllexport)
#else
#define EXPORT _declspec (dllexport)
#endif

EXPORT BOOL CALLBACK EdrCenterTextA(HDC, PRECT, PCSTR);
EXPORT BOOL CALLBACK EdrCenterTextW(HDC, PRECT, PCWSTR);

#ifdef UNICODE
#define EdrCenterText EdrCenterTextW
#else
#define EdrCenterText EdrCenterTextA
#endif

然后　　我们建立个 C/C++文件　　newDLL.cpp　　实现头文件中的函数接口

#include <Windows.h>
#include "newDLL.h"

int WINAPI DllMain(HINSTANCE hInstance, DWORD fdwReason, PVOID pvReserved)
{
    return TRUE;
}

EXPORT BOOL CALLBACK EdrCenterTextA(HDC hdc, PRECT prc, PCSTR pString)
{
    int iLength;
    SIZE size;

    iLength = lstrlenA(pString);
    GetTextExtentPoint32A(hdc, pString, iLength, &size);
    return TextOutA(hdc, (prc->right - prc->left - size.cx) / 2,
        (prc->bottom - prc->top - size.cy) / 2,
        pString, iLength);
}

EXPORT BOOL CALLBACK EdrCenterTextW(HDC hdc, PRECT prc, PCWSTR pString)
{
    int iLength;
    SIZE size;

    iLength = lstrlenW(pString);
    GetTextExtentPoint32W(hdc, pString, iLength, &size);
    return TextOutW(hdc, (prc->right - prc->left - size.cx) / 2,
        (prc->bottom - prc->top - size.cy) / 2,
        pString, iLength);
}