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/*-------------------------------------------------------------------------
*
* shm.c
* System V Shared Memory Emulation
*
* Copyright (c) 1999, repas AEG Automation GmbH
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/port/qnx4/shm.c,v 1.9 2003/11/29 19:51:54 pgsql Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/shm.h>
#include <sys/stat.h>
#define MODE 0777
#define SHMMAX 1024
struct shm_info
{
int shmid;
key_t key;
size_t size;
void *addr;
};
static struct shm_info *ShmInfo;
static int shm_putinfo(struct shm_info * info);
static int shm_updinfo(int i, struct shm_info * info);
static int shm_getinfo(int shmid, struct shm_info * info);
static int shm_getinfobyaddr(const void *addr, struct shm_info * info);
static char *
keytoname(key_t key, char *name)
{
sprintf(name, "PgShm%x", key);
return name;
}
static int
shm_putinfo(struct shm_info * info)
{
int i;
if (ShmInfo == NULL)
{
ShmInfo = calloc(SHMMAX, sizeof(struct shm_info));
if (ShmInfo == NULL)
return -1;
/* initialize ShmInfo */
for (i = 0; i < SHMMAX; i++)
ShmInfo[i].shmid = -1;
}
/* search first free element */
i = 0;
while (i < SHMMAX && ShmInfo[i].shmid != -1)
i++;
if (i >= SHMMAX)
{
errno = ENOSPC;
return -1;
}
memcpy(&ShmInfo[i], info, sizeof(struct shm_info));
return i;
}
static int
shm_updinfo(int i, struct shm_info * info)
{
if (i >= SHMMAX)
return -1;
if (ShmInfo == NULL)
return -1;
memcpy(&ShmInfo[i], info, sizeof(struct shm_info));
return i;
}
static int
shm_getinfo(int shmid, struct shm_info * info)
{
int i;
if (ShmInfo == NULL)
return -1;
/* search element */
i = 0;
while (i < SHMMAX && ShmInfo[i].shmid != shmid)
i++;
if (i >= SHMMAX)
return -1;
memcpy(info, &ShmInfo[i], sizeof(struct shm_info));
return i;
}
static int
shm_getinfobyaddr(const void *addr, struct shm_info * info)
{
int i;
if (ShmInfo == (struct shm_info *) - 1)
return -1;
/* search element */
i = 0;
while (i < SHMMAX && ShmInfo[i].addr != addr)
i++;
if (i >= SHMMAX)
return -1;
memcpy(info, &ShmInfo[i], sizeof(struct shm_info));
return i;
}
void *
shmat(int shmid, const void *shmaddr, int shmflg)
{
struct shm_info info;
int i;
i = shm_getinfo(shmid, &info);
if (i == -1)
{
errno = EACCES;
return (void *) -1;
}
info.addr = mmap((void *) shmaddr, info.size,
PROT_READ | PROT_WRITE, MAP_SHARED, shmid, 0);
if (info.addr == MAP_FAILED)
return info.addr;
if (shm_updinfo(i, &info) == -1)
{
errno = EACCES;
return (void *) -1;
}
return info.addr;
}
int
shmdt(const void *addr)
{
struct shm_info info;
if (shm_getinfobyaddr(addr, &info) == -1)
{
errno = EACCES;
return -1;
}
return munmap((void *) addr, info.size);
}
int
shmctl(int shmid, int cmd, struct shmid_ds * buf)
{
struct shm_info info;
char name[NAME_MAX + 1];
int result;
int fd;
struct stat statbuf;
switch (cmd)
{
case IPC_RMID:
if (shm_getinfo(shmid, &info) == -1)
{
errno = EACCES;
return -1;
}
close(info.shmid);
keytoname(info.key, name);
return shm_unlink(name);
case IPC_STAT:
/*
* we have to open it first. stat() does no prefix tracking ->
* the call would go to fsys instead of proc
*/
keytoname(shmid, name);
fd = shm_open(name, 0, MODE);
if (fd >= 0)
{
result = fstat(fd, &statbuf);
/*
* if the file exists, subtract 2 from linkcount : one for
* our own open and one for the dir entry
*/
if (!result)
buf->shm_nattch = statbuf.st_nlink - 2;
close(fd);
return result;
}
else
{
/*
* if there's no entry for this key it doesn't matter the
* next shmget() would get a different shm anyway
*/
buf->shm_nattch = 0;
return 0;
}
}
errno = EINVAL;
return -1;
}
int
shmget(key_t key, size_t size, int flags)
{
char name[NAME_MAX + 1];
int oflag = 0;
struct shm_info info;
if (flags & IPC_CREAT)
oflag |= O_CREAT;
if (flags & IPC_EXCL)
oflag |= O_EXCL;
if (flags & SHM_R)
{
if (flags & SHM_W)
oflag |= O_RDWR;
else
oflag |= O_RDONLY;
}
info.shmid = shm_open(keytoname(key, name), oflag, MODE);
/* store shared memory information */
if (info.shmid != -1)
{
info.key = key;
info.size = size;
info.addr = NULL;
if (shm_putinfo(&info) == -1)
{
close(info.shmid);
if ((oflag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
shm_unlink(name);
return -1;
}
}
/* The size may only be set once. Ignore errors. */
ltrunc(info.shmid, size, SEEK_SET);
return info.shmid;
}
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