// ShareDll.cpp : 定義 DLL 應用程序的入口點。
//
// Chen Danwei  2005-10-1
//
// for the demo of PV opreation in OS classe
//
//pls contact with chendanwei@hotmail.com if  any question about it

#include "stdafx.h"
#include "stdio.h"
#include "stdlib.h"
#include "windows.h"
#include "winnt.h"



//here we wana to export lib
#define __SHAREDLLLIB   extern "C" __declspec(dllexport)
#include "ShareDllLib.h"

#define   MAXBUFFNUM     8


#pragma data_seg("DvShareData")

//for count the instance
LONG glInstanceCounter    = 0;


//pointer of writer and reader
int pWriter               = 0;
int pReader				  = 0;


#pragma data_seg()

//to allocate the glob buffer in the DvShareData section
__declspec(allocate("DvShareData")) LONG glBuffer[MAXBUFFNUM];


//to share the section DvShareData
#pragma comment(linker, "/SECTION:DvShareData,RWS")


//a mutex between the producer and the customer
HANDLE hMutex             = NULL;

//semphore for producer
HANDLE hSemP              = NULL; 

//semphore for customer
HANDLE hSemC              = NULL;




//some local function
static void  IniatGlobParameter();





BOOL APIENTRY DllMain( HANDLE hModule, 
                       DWORD  ul_reason_for_call, 
                       LPVOID lpReserved
					 )
{
	switch(ul_reason_for_call)
	{
	case DLL_PROCESS_ATTACH:

	
		++glInstanceCounter;

		printf(" %d process attatch ........\n", glInstanceCounter);

		IniatGlobParameter();
		if( 1 == glInstanceCounter)   //attatch to the first process, so iniate the glob parameter
		{
			int i = 0;
			while( i < MAXBUFFNUM )
			{
				glBuffer[i] = 0;

				++i;
			}
		}		
         
		 break;
	case DLL_THREAD_ATTACH:
		printf("thread  attach module \n");
		break;
	case DLL_THREAD_DETACH:
		printf("thread  detach module \n");
		break;
	case DLL_PROCESS_DETACH:
		printf("process detah module \n");

		--glInstanceCounter;
		CloseHandle(hMutex);
		CloseHandle(hSemP);
		CloseHandle(hSemC);
		
		break;
	}

    return TRUE;
}



void  IniatGlobParameter()
{

	__try
	{
		hMutex = CreateMutex(NULL, false, "ChenDanweiOsClassMutex");
		hSemP = CreateSemaphore(NULL, MAXBUFFNUM, MAXBUFFNUM, "ChenDanweiOsClassSemP");
		hSemC = CreateSemaphore(NULL, 0, MAXBUFFNUM, "ChenDanweiOsClassSemC");
	}

	__except(EXCEPTION_EXECUTE_HANDLER)
	{
		printf(" exception in creatting mutex or semphore !!\n");

		__try
		{
			CloseHandle(hMutex);
			CloseHandle(hSemP);
			CloseHandle(hSemC);
		}

		__finally
		{
			exit(0);
		}
	
	}

	return;
}


int WriteBuffer( IN long & aData)
{
	int ret = 0 ;
	
	__try 
	{
        WaitForSingleObject(hSemP,INFINITE);     
		WaitForSingleObject(hMutex,INFINITE);    //simlar to P operate
       
		glBuffer[pWriter] = aData;
		pWriter = (pWriter + 1) %  MAXBUFFNUM;

     }

	__finally   //whatever condition, we should re
	{
		ReleaseMutex(hMutex);
		ReleaseSemaphore(hSemC, 1, NULL);

	}

	return ret;

}


int ReadBuffer( OUT long & aData)
{
	int ret = 0;

	__try 
	{
		WaitForSingleObject(hSemC,INFINITE);     //simlar to P operate
		WaitForSingleObject(hMutex,INFINITE);    
        
		aData = glBuffer[pReader];
		pReader = (pReader + 1) %  MAXBUFFNUM;
     }

	__finally   //whatever condition, we should release
	{
		ReleaseMutex(hMutex);                  //simlar to V oprerate
		ReleaseSemaphore(hSemP, 1, NULL);
	}

	return ret;
}