/*-------------------------------------------------------------------------
 *
 * 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 1.1 1999/12/16 16:52:52 momjian 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];

  /* IPC_RMID supported only */
  if( cmd != IPC_RMID )  {
    errno = EINVAL;
    return -1;
  }

  if( shm_getinfo( shmid, &info ) == -1 )  {
    errno = EACCES;
    return -1;
  }

  return shm_unlink( itoa( info.key, name, 16 ) );
}

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;
}