server/user.c

   1 /*
   2  * Server-side USER handles
   3  *
   4  * Copyright (C) 2001 Alexandre Julliard
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  */
  20
  21 #include "thread.h"
  22 #include "user.h"
  23
  24 struct user_handle
  25 {
  26     void          *ptr;          /* pointer to object */
  27     unsigned short type;         /* object type (0 if free) */
  28     unsigned short generation;   /* generation counter */
  29 };
  30
  31 static struct user_handle *handles;
  32 static struct user_handle *freelist;
  33 static int nb_handles;
  34 static int allocated_handles;
  35
  36 static struct user_handle *handle_to_entry( user_handle_t handle )
  37 {
  38     int index = (((unsigned int)handle & 0xffff) - FIRST_USER_HANDLE) >> 1;
  39     if (index < 0 || index >= nb_handles) return NULL;
  40     if (!handles[index].type) return NULL;
  41     if (((unsigned int)handle >> 16) && ((unsigned int)handle >> 16 != handles[index].generation))
  42         return NULL;
  43     return &handles[index];
  44 }
  45
  46 inline static user_handle_t entry_to_handle( struct user_handle *ptr )
  47 {
  48     int index = ptr - handles;
  49     return (user_handle_t)(((index << 1) + FIRST_USER_HANDLE) + (ptr->generation << 16));
  50 }
  51
  52 inline static struct user_handle *alloc_user_entry(void)
  53 {
  54     struct user_handle *handle;
  55
  56     if (freelist)
  57     {
  58         handle = freelist;
  59         freelist = handle->ptr;
  60         return handle;
  61     }
  62     if (nb_handles >= allocated_handles)  /* need to grow the array */
  63     {
  64         struct user_handle *new_handles;
  65         /* grow array by 50% (but at minimum 32 entries) */
  66         int growth = max( 32, allocated_handles / 2 );
  67         int new_size = min( allocated_handles + growth, (LAST_USER_HANDLE-FIRST_USER_HANDLE+1) >> 1 );
  68         if (new_size <= allocated_handles) return NULL;
  69         if (!(new_handles = realloc( handles, new_size * sizeof(*handles) )))
  70             return NULL;
  71         handles = new_handles;
  72         allocated_handles = new_size;
  73     }
  74     handle = &handles[nb_handles++];
  75     handle->generation = 0;
  76     return handle;
  77 }
  78
  79 inline static void *free_user_entry( struct user_handle *ptr )
  80 {
  81     void *ret;
  82     ret = ptr->ptr;
  83     ptr->ptr  = freelist;
  84     ptr->type = 0;
  85     freelist  = ptr;
  86     return ret;
  87 }
  88
  89 /* allocate a user handle for a given object */
  90 user_handle_t alloc_user_handle( void *ptr, enum user_object type )
  91 {
  92     struct user_handle *entry = alloc_user_entry();
  93     if (!entry) return 0;
  94     entry->ptr  = ptr;
  95     entry->type = type;
  96     if (++entry->generation >= 0xffff) entry->generation = 1;
  97     return entry_to_handle( entry );
  98 }
  99
 100 /* return a pointer to a user object from its handle */
 101 void *get_user_object( user_handle_t handle, enum user_object type )
 102 {
 103     struct user_handle *entry;
 104
 105     if (!(entry = handle_to_entry( handle )) || entry->type != type) return NULL;
 106     return entry->ptr;
 107 }
 108
 109 /* get the full handle for a possibly truncated handle */
 110 user_handle_t get_user_full_handle( user_handle_t handle )
 111 {
 112     struct user_handle *entry;
 113
 114     if ((unsigned int)handle >> 16) return handle;
 115     if (!(entry = handle_to_entry( handle ))) return handle;
 116     return entry_to_handle( entry );
 117 }
 118
 119 /* same as get_user_object plus set the handle to the full 32-bit value */
 120 void *get_user_object_handle( user_handle_t *handle, enum user_object type )
 121 {
 122     struct user_handle *entry;
 123
 124     if (!(entry = handle_to_entry( *handle )) || entry->type != type) return NULL;
 125     *handle = entry_to_handle( entry );
 126     return entry->ptr;
 127 }
 128
 129 /* free a user handle and return a pointer to the object */
 130 void *free_user_handle( user_handle_t handle )
 131 {
 132     struct user_handle *entry;
 133
 134     if (!(entry = handle_to_entry( handle )))
 135     {
 136         set_error( STATUS_INVALID_HANDLE );
 137         return NULL;
 138     }
 139     return free_user_entry( entry );
 140 }
 141
 142 /* return the next user handle after 'handle' that is of a given type */
 143 void *next_user_handle( user_handle_t *handle, enum user_object type )
 144 {
 145     struct user_handle *entry;
 146
 147     if (!*handle) entry = handles;
 148     else
 149     {
 150         int index = (((unsigned int)*handle & 0xffff) - FIRST_USER_HANDLE) >> 1;
 151         if (index < 0 || index >= nb_handles) return NULL;
 152         entry = handles + index + 1;  /* start from the next one */
 153     }
 154     while (entry < handles + nb_handles)
 155     {
 156         if (!type || entry->type == type)
 157         {
 158             *handle = entry_to_handle( entry );
 159             return entry->ptr;
 160         }
 161         entry++;
 162     }
 163     return NULL;
 164 }