db2/os/os_map.c

   1 /*-
   2  * See the file LICENSE for redistribution information.
   3  *
   4  * Copyright (c) 1996, 1997
   5  *      Sleepycat Software.  All rights reserved.
   6  */
   7
   8 #include "config.h"
   9
  10 #ifndef lint
  11 static const char sccsid[] = "@(#)os_map.c      10.7 (Sleepycat) 10/25/97";
  12 #endif /* not lint */
  13
  14 #ifndef NO_SYSTEM_INCLUDES
  15 #include <sys/types.h>
  16 #include <sys/mman.h>
  17
  18 #include <errno.h>
  19 #endif
  20
  21 #include "db_int.h"
  22
  23 /*
  24  * __os_map --
  25  *      Map in some shared memory backed by a file descriptor.
  26  *
  27  * PUBLIC: int __os_map __P((int, size_t, int, int, void **));
  28  */
  29 int
  30 __os_map(fd, len, is_private, is_rdonly, addr)
  31         int fd, is_private, is_rdonly;
  32         size_t len;
  33         void **addr;
  34 {
  35         void *p;
  36         int flags, prot;
  37
  38         flags = is_private ? MAP_PRIVATE : MAP_SHARED;
  39 #ifdef MAP_HASSEMAPHORE
  40         flags |= MAP_HASSEMAPHORE;
  41 #endif
  42         prot = PROT_READ | (is_rdonly ? 0 : PROT_WRITE);
  43
  44 #ifndef MAP_FAILED                      /* XXX: Mmap(2) failure return. */
  45 #define MAP_FAILED      -1
  46 #endif
  47         if ((p =
  48             mmap(NULL, len, prot, flags, fd, (off_t)0)) == (void *)MAP_FAILED)
  49                 return (errno);
  50
  51         *addr = p;
  52         return (0);
  53 }
  54
  55 /*
  56  * __os_unmap --
  57  *      Release the specified shared memory.
  58  *
  59  * PUBLIC: int __os_unmap __P((void *, size_t));
  60  */
  61 int
  62 __os_unmap(addr, len)
  63         void *addr;
  64         size_t len;
  65 {
  66         /*
  67          * !!!
  68          * The argument len is always the same length as was mapped.
  69          */
  70         return (munmap(addr, len) ? errno : 0);
  71 }