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 = (handle & 0xffff) - FIRST_USER_HANDLE;
  39     if (index < 0 || index >= nb_handles) return NULL;
  40     if (!handles[index].type) return NULL;
  41     if ((handle >> 16) && (handle >> 16 != handles[index].generation)) return NULL;
  42     return &handles[index];
  43 }
  44
  45 inline static user_handle_t entry_to_handle( struct user_handle *ptr )
  46 {
  47     int index = ptr - handles;
  48     return (index + FIRST_USER_HANDLE) + (ptr->generation << 16);
  49 }
  50
  51 inline static struct user_handle *alloc_user_entry(void)
  52 {
  53     struct user_handle *handle;
  54
  55     if (freelist)
  56     {
  57         handle = freelist;
  58         freelist = handle->ptr;
  59         return handle;
  60     }
  61     if (nb_handles >= allocated_handles)  /* need to grow the array */
  62     {
  63         struct user_handle *new_handles;
  64         /* grow array by 50% (but at minimum 32 entries) */
  65         int growth = max( 32, allocated_handles / 2 );
  66         int new_size = min( allocated_handles + growth, LAST_USER_HANDLE-FIRST_USER_HANDLE+1 );
  67         if (new_size <= allocated_handles) return NULL;
  68         if (!(new_handles = realloc( handles, new_size * sizeof(*handles) )))
  69             return NULL;
  70         handles = new_handles;
  71         allocated_handles = new_size;
  72     }
  73     handle = &handles[nb_handles++];
  74     handle->generation = 0;
  75     return handle;
  76 }
  77
  78 inline static void *free_user_entry( struct user_handle *ptr )
  79 {
  80     void *ret;
  81     ret = ptr->ptr;
  82     ptr->ptr  = freelist;
  83     ptr->type = 0;
  84     freelist  = ptr;
  85     return ret;
  86 }
  87
  88 /* allocate a user handle for a given object */
  89 user_handle_t alloc_user_handle( void *ptr, enum user_object type )
  90 {
  91     struct user_handle *entry = alloc_user_entry();
  92     if (!entry) return 0;
  93     entry->ptr  = ptr;
  94     entry->type = type;
  95     if (++entry->generation >= 0xffff) entry->generation = 1;
  96     return entry_to_handle( entry );
  97 }
  98
  99 /* return a pointer to a user object from its handle */
 100 void *get_user_object( user_handle_t handle, enum user_object type )
 101 {
 102     struct user_handle *entry;
 103
 104     if (!(entry = handle_to_entry( handle )) || entry->type != type) return NULL;
 105     return entry->ptr;
 106 }
 107
 108 /* get the full handle for a possibly truncated handle */
 109 user_handle_t get_user_full_handle( user_handle_t handle )
 110 {
 111     struct user_handle *entry;
 112
 113     if (handle >> 16) return handle;
 114     if (!(entry = handle_to_entry( handle ))) return handle;
 115     return entry_to_handle( entry );
 116 }
 117
 118 /* same as get_user_object plus set the handle to the full 32-bit value */
 119 void *get_user_object_handle( user_handle_t *handle, enum user_object type )
 120 {
 121     struct user_handle *entry;
 122
 123     if (!(entry = handle_to_entry( *handle )) || entry->type != type) return NULL;
 124     *handle = entry_to_handle( entry );
 125     return entry->ptr;
 126 }
 127
 128 /* free a user handle and return a pointer to the object */
 129 void *free_user_handle( user_handle_t handle )
 130 {
 131     struct user_handle *entry;
 132
 133     if (!(entry = handle_to_entry( handle )))
 134     {
 135         set_error( STATUS_INVALID_HANDLE );
 136         return NULL;
 137     }
 138     return free_user_entry( entry );
 139 }
 140
 141 /* return the next user handle after 'handle' that is of a given type */
 142 void *next_user_handle( user_handle_t *handle, enum user_object type )
 143 {
 144     struct user_handle *entry;
 145
 146     if (!*handle) entry = handles;
 147     else
 148     {
 149         if (!(entry = handle_to_entry( *handle ))) return NULL;
 150         entry++;  /* start from the next one */
 151     }
 152     while (entry < handles + nb_handles)
 153     {
 154         if (!type || entry->type == type)
 155         {
 156             *handle = entry_to_handle( entry );
 157             return entry->ptr;
 158         }
 159         entry++;
 160     }
 161     return NULL;
 162 }