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/*-------------------------------------------------------------------------
*
* shmem.c
* Microsoft Windows Win32 Shared Memory Emulation
*
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <stdio.h>
#include <errno.h>
static DWORD s_segsize = 0;
/* Detach from a shared mem area based on its address */
int
shmdt(const void *shmaddr)
{
if (UnmapViewOfFile(shmaddr))
return 0;
else
return -1;
}
/* Attach to an existing area */
void *
shmat(int memId, void *shmaddr, int flag)
{
/* TODO -- shmat needs to count # attached to shared mem */
void *lpmem = MapViewOfFileEx((HANDLE) memId,
FILE_MAP_WRITE | FILE_MAP_READ,
0, 0, /* (DWORD)pshmdsc->segsize */ 0 /* s_segsize */, shmaddr);
if (lpmem == NULL)
{
lpmem = (void *) -1;
errno = GetLastError();
}
return lpmem;
}
/* Control a shared mem area */
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 */
errno = EINVAL;
return -1;
}
else
{
/* Shared memory does exist and must be in use */
shmctl(hmap, IPC_RMID, NULL); /* Release our hold on it */
errno = 0;
return 0;
}
}
errno = EINVAL;
return -1;
}
/* Get an area based on the IPC key */
int
shmget(int memKey, int size, int flag)
{
HANDLE hmap;
char szShareMem[32];
DWORD dwRet;
s_segsize = size;
sprintf(szShareMem, "sharemem.%d", memKey);
if (flag & IPC_CREAT)
{
hmap = CreateFileMapping((HANDLE) 0xFFFFFFFF, /* Use the swap file */
NULL,
PAGE_READWRITE, /* Memory is Read/Write */
0L, /* Size Upper 32 Bits */
(DWORD) s_segsize, /* Size Lower 32 bits */
szShareMem);
}
else
{
hmap = OpenFileMapping(FILE_MAP_ALL_ACCESS,
FALSE,
szShareMem);
if (!hmap)
{
errno = ENOENT;
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);
errno = EEXIST;
return -1;
}
else if (!hmap)
{
/* Unable to get shared memory */
return -1;
}
return (int) hmap;
}
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