myvtm/Framework/libtoolkit/shm.c

#include "precompile.h"
#include "shm.h"

#include <stdio.h>

/* Detach from a shared mem area based on its address */
TOOLKIT_API int
shmdt(const void *shmaddr)
{
	if (UnmapViewOfFile((LPCVOID *) shmaddr))
		return 0;
	else
		return -1;
}

/* Attach to an existing area */
TOOLKIT_API void *
shmat(int memId, void *shmaddr, int flag)
{
	DWORD dwAccessFlag = (flag & SHM_RDONLY) ? FILE_MAP_READ : (FILE_MAP_WRITE | FILE_MAP_READ);
	/* TODO -- shmat needs to count # attached to shared mem */
	void	   *lpmem = MapViewOfFileEx((HANDLE) memId,
										dwAccessFlag,
			0, 0, /* (DWORD)pshmdsc->segsize */ 0, shmaddr);

	if (lpmem == NULL)
	{
		DWORD dwError = GetLastError();
		lpmem = (void *) -1;
	}

	return lpmem;
}

/* Control a shared mem area */
TOOLKIT_API int shmctl(int shmid, int flag, struct shmid_ds * dummy)
{
	if (flag == IPC_RMID)
	{
		/* Delete the area */
		CloseHandle((HANDLE) shmid);
		return 0;
	}
	if (flag == IPC_STAT)
	{
		/* Can only test for if exists */
		int			hmap = shmget(shmid, 0, 0);

		if (hmap < 0)
		{
			/* Shared memory does not exist */
			return -1;
		}
		else
		{
			/* Shared memory does exist and must be in use */
			shmctl(hmap, IPC_RMID, NULL);		/* Release our hold on it */
			return 0;
		}
	}

	return -1;
}

static int shmget_str(const char *szShareMem, int size, int flag)
{
	HANDLE		hmap;
	DWORD		dwRet;

	if (flag & IPC_CREAT)
	{
		hmap = CreateFileMappingA((HANDLE) 0xFFFFFFFF,	/* Use the swap file	*/
			NULL,
			PAGE_READWRITE,		/* Memory is Read/Write */
			0L,	/* Size Upper 32 Bits	*/
			(DWORD) size,		/* Size Lower 32 bits */
			szShareMem);
	}
	else
	{
		hmap = OpenFileMappingA(FILE_MAP_ALL_ACCESS,
			FALSE,
			szShareMem);
		if (!hmap)
		{
			return -1;
		}
	}

	dwRet = GetLastError();
	if (dwRet == ERROR_ALREADY_EXISTS && hmap && (flag & IPC_CREAT & IPC_EXCL))
	{
		/* Caller wanted to create the segment -- error if already exists */
		CloseHandle(hmap);
		return -1;
	}
	else if (!hmap)
	{
		/* Unable to get shared memory */
		return -1;
	}

	return (int) hmap;
}

/* Get an area based on the IPC key */
TOOLKIT_API int shmget(int memKey, int size, int flag)
{
	char		szShareMem[32];

	sprintf(szShareMem, "shm.%d", memKey);

	return shmget_str(szShareMem, size, flag);
}