db2/os/db_os_mmap.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[] = "@(#)db_os_mmap.c  10.4 (Sleepycat) 6/28/97";
  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 #include "os_ext.h"
  23
  24 /*
  25  * __db_mmap --
  26  *      Map in some shared memory backed by a file descriptor.
  27  *
  28  * PUBLIC: int __db_mmap __P((int, size_t, int, int, void *));
  29  */
  30 int
  31 __db_mmap(fd, len, is_private, rdonly, addr)
  32         int fd, is_private, rdonly;
  33         size_t len;
  34         void *addr;
  35 {
  36 #ifdef _WIN32
  37         /* We have not implemented copy-on-write here */
  38         void * pMemory = 0;
  39         HANDLE hFile = (HANDLE)_get_osfhandle(fd);
  40         HANDLE hMemory = CreateFileMapping(
  41               hFile,
  42               0,
  43               (rdonly ? PAGE_READONLY : PAGE_READWRITE),
  44               0,
  45               len, /* This code fails if the library is ever compiled on a 64-bit machine */
  46               0
  47               );
  48         if (NULL == hMemory)
  49         {
  50               return errno;
  51         }
  52         pMemory = MapViewOfFile(
  53               hMemory,
  54               (rdonly ? FILE_MAP_READ : FILE_MAP_ALL_ACCESS),
  55               0,
  56               0,
  57               len
  58               );
  59         CloseHandle(hMemory);
  60         *(void **)addr = pMemory;
  61         return 0;
  62
  63 #else /* !_WIN32 */
  64
  65         void *p;
  66         int flags, prot;
  67
  68         flags = is_private ? MAP_PRIVATE : MAP_SHARED;
  69 #ifdef MAP_HASSEMAPHORE
  70         flags += MAP_HASSEMAPHORE;
  71 #endif
  72         prot = PROT_READ | (rdonly ? 0 : PROT_WRITE);
  73
  74 #ifndef MAP_FAILED                      /* XXX: Mmap(2) failure return. */
  75 #define MAP_FAILED      -1
  76 #endif
  77         if ((p =
  78             mmap(NULL, len, prot, flags, fd, (off_t)0)) == (void *)MAP_FAILED)
  79                 return (errno);
  80
  81         *(void **)addr = p;
  82         return (0);
  83 #endif /* _WIN32 */
  84 }
  85
  86 /*
  87  * __db_unmap --
  88  *      Release the specified shared memory.
  89  *
  90  * PUBLIC: int __db_munmap __P((void *, size_t));
  91  */
  92 int
  93 __db_munmap(addr, len)
  94         void *addr;
  95         size_t len;
  96 {
  97         /*
  98          * !!!
  99          * The argument len is always the same length as was mapped.
 100          */
 101 #ifdef _WIN32
 102         return (!UnmapViewOfFile(addr) ? errno : 0);
 103 #else
 104         return (munmap(addr, len) ? errno : 0);
 105 #endif
 106 }