+static int
+mdb_env_map(MDB_env *env, void *addr, int newsize)
+{
+ MDB_page *p;
+ unsigned int flags = env->me_flags;
+#ifdef _WIN32
+ int rc;
+ HANDLE mh;
+ LONG sizelo, sizehi;
+ sizelo = env->me_mapsize & 0xffffffff;
+ sizehi = env->me_mapsize >> 16 >> 16; /* only needed on Win64 */
+
+ /* Windows won't create mappings for zero length files.
+ * Just allocate the maxsize right now.
+ */
+ if (newsize) {
+ if (SetFilePointer(env->me_fd, sizelo, &sizehi, 0) != (DWORD)sizelo
+ || !SetEndOfFile(env->me_fd)
+ || SetFilePointer(env->me_fd, 0, NULL, 0) != 0)
+ return ErrCode();
+ }
+ mh = CreateFileMapping(env->me_fd, NULL, flags & MDB_WRITEMAP ?
+ PAGE_READWRITE : PAGE_READONLY,
+ sizehi, sizelo, NULL);
+ if (!mh)
+ return ErrCode();
+ env->me_map = MapViewOfFileEx(mh, flags & MDB_WRITEMAP ?
+ FILE_MAP_WRITE : FILE_MAP_READ,
+ 0, 0, env->me_mapsize, addr);
+ rc = env->me_map ? 0 : ErrCode();
+ CloseHandle(mh);
+ if (rc)
+ return rc;
+#else
+ int prot = PROT_READ;
+ if (flags & MDB_WRITEMAP) {
+ prot |= PROT_WRITE;
+ if (ftruncate(env->me_fd, env->me_mapsize) < 0)
+ return ErrCode();
+ }
+ env->me_map = mmap(addr, env->me_mapsize, prot, MAP_SHARED,
+ env->me_fd, 0);
+ if (env->me_map == MAP_FAILED) {
+ env->me_map = NULL;
+ return ErrCode();
+ }
+
+ if (flags & MDB_NORDAHEAD) {
+ /* Turn off readahead. It's harmful when the DB is larger than RAM. */
+#ifdef MADV_RANDOM
+ madvise(env->me_map, env->me_mapsize, MADV_RANDOM);
+#else
+#ifdef POSIX_MADV_RANDOM
+ posix_madvise(env->me_map, env->me_mapsize, POSIX_MADV_RANDOM);
+#endif /* POSIX_MADV_RANDOM */
+#endif /* MADV_RANDOM */
+ }
+#endif /* _WIN32 */
+
+ /* Can happen because the address argument to mmap() is just a
+ * hint. mmap() can pick another, e.g. if the range is in use.
+ * The MAP_FIXED flag would prevent that, but then mmap could
+ * instead unmap existing pages to make room for the new map.
+ */
+ if (addr && env->me_map != addr)
+ return EBUSY; /* TODO: Make a new MDB_* error code? */
+
+ p = (MDB_page *)env->me_map;
+ env->me_metas[0] = METADATA(p);
+ env->me_metas[1] = (MDB_meta *)((char *)env->me_metas[0] + env->me_psize);
+
+ return MDB_SUCCESS;
+}
+