/*-------------------------------------------------------------------------
 *
 * shm.c
 *	  System V Shared Memory Emulation
 *
 * Copyright (c) 1999, repas AEG Automation GmbH
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/port/qnx4/Attic/shm.c,v 1.3 2001/03/13 01:17:06 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */

#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/shm.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 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];

	if (cmd == IPC_RMID)
	{
		if (shm_getinfo(shmid, &info) == -1)
		{
			errno = EACCES;
			return -1;
		}
		return shm_unlink(itoa(info.key, name, 16));
	}
	if (cmd == IPC_STAT)
	{
		/* Can we support IPC_STAT?  We only need shm_nattch ...
		 * For now, punt and assume the shm seg does not exist.
		 */
		errno = EINVAL;
		return -1;
	}
	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(itoa(key, name, 16), oflag, MODE);

	/* store shared memory information */
	if (info.shmid != -1)
	{
		info.key = key;
		info.size = size;
		info.addr = NULL;
		if (shm_putinfo(&info) == -1)
			return -1;
	}

	/* The size may only be set once. Ignore errors. */
	ltrunc(info.shmid, size, SEEK_SET);

	return info.shmid;
}
