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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, 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     unsigned short generation;
  39     int index = (((unsigned int)handle & 0xffff) - FIRST_USER_HANDLE) >> 1;
  40     if (index < 0 || index >= nb_handles) return NULL;
  41     if (!handles[index].type) return NULL;
  42     generation = (unsigned int)handle >> 16;
  43     if (generation == handles[index].generation || !generation || generation == 0xffff)
  44         return &handles[index];
  45     return NULL;
  46 }
  47
  48 inline static user_handle_t entry_to_handle( struct user_handle *ptr )
  49 {
  50     int index = ptr - handles;
  51     return (user_handle_t)(((index << 1) + FIRST_USER_HANDLE) + (ptr->generation << 16));
  52 }
  53
  54 inline static struct user_handle *alloc_user_entry(void)
  55 {
  56     struct user_handle *handle;
  57
  58     if (freelist)
  59     {
  60         handle = freelist;
  61         freelist = handle->ptr;
  62         return handle;
  63     }
  64     if (nb_handles >= allocated_handles)  /* need to grow the array */
  65     {
  66         struct user_handle *new_handles;
  67         /* grow array by 50% (but at minimum 32 entries) */
  68         int growth = max( 32, allocated_handles / 2 );
  69         int new_size = min( allocated_handles + growth, (LAST_USER_HANDLE-FIRST_USER_HANDLE+1) >> 1 );
  70         if (new_size <= allocated_handles) return NULL;
  71         if (!(new_handles = realloc( handles, new_size * sizeof(*handles) )))
  72             return NULL;
  73         handles = new_handles;
  74         allocated_handles = new_size;
  75     }
  76     handle = &handles[nb_handles++];
  77     handle->generation = 0;
  78     return handle;
  79 }
  80
  81 inline static void *free_user_entry( struct user_handle *ptr )
  82 {
  83     void *ret;
  84     ret = ptr->ptr;
  85     ptr->ptr  = freelist;
  86     ptr->type = 0;
  87     freelist  = ptr;
  88     return ret;
  89 }
  90
  91 /* allocate a user handle for a given object */
  92 user_handle_t alloc_user_handle( void *ptr, enum user_object type )
  93 {
  94     struct user_handle *entry = alloc_user_entry();
  95     if (!entry) return 0;
  96     entry->ptr  = ptr;
  97     entry->type = type;
  98     if (++entry->generation >= 0xffff) entry->generation = 1;
  99     return entry_to_handle( entry );
 100 }
 101
 102 /* return a pointer to a user object from its handle */
 103 void *get_user_object( user_handle_t handle, enum user_object type )
 104 {
 105     struct user_handle *entry;
 106
 107     if (!(entry = handle_to_entry( handle )) || entry->type != type) return NULL;
 108     return entry->ptr;
 109 }
 110
 111 /* get the full handle for a possibly truncated handle */
 112 user_handle_t get_user_full_handle( user_handle_t handle )
 113 {
 114     struct user_handle *entry;
 115
 116     if ((unsigned int)handle >> 16) return handle;
 117     if (!(entry = handle_to_entry( handle ))) return handle;
 118     return entry_to_handle( entry );
 119 }
 120
 121 /* same as get_user_object plus set the handle to the full 32-bit value */
 122 void *get_user_object_handle( user_handle_t *handle, enum user_object type )
 123 {
 124     struct user_handle *entry;
 125
 126     if (!(entry = handle_to_entry( *handle )) || entry->type != type) return NULL;
 127     *handle = entry_to_handle( entry );
 128     return entry->ptr;
 129 }
 130
 131 /* free a user handle and return a pointer to the object */
 132 void *free_user_handle( user_handle_t handle )
 133 {
 134     struct user_handle *entry;
 135
 136     if (!(entry = handle_to_entry( handle )))
 137     {
 138         set_error( STATUS_INVALID_HANDLE );
 139         return NULL;
 140     }
 141     return free_user_entry( entry );
 142 }
 143
 144 /* return the next user handle after 'handle' that is of a given type */
 145 void *next_user_handle( user_handle_t *handle, enum user_object type )
 146 {
 147     struct user_handle *entry;
 148
 149     if (!*handle) entry = handles;
 150     else
 151     {
 152         int index = (((unsigned int)*handle & 0xffff) - FIRST_USER_HANDLE) >> 1;
 153         if (index < 0 || index >= nb_handles) return NULL;
 154         entry = handles + index + 1;  /* start from the next one */
 155     }
 156     while (entry < handles + nb_handles)
 157     {
 158         if (!type || entry->type == type)
 159         {
 160             *handle = entry_to_handle( entry );
 161             return entry->ptr;
 162         }
 163         entry++;
 164     }
 165     return NULL;
 166 }