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 #include "request.h"
  24
  25 struct user_handle
  26 {
  27     void          *ptr;          /* pointer to object */
  28     unsigned short type;         /* object type (0 if free) */
  29     unsigned short generation;   /* generation counter */
  30 };
  31
  32 static struct user_handle *handles;
  33 static struct user_handle *freelist;
  34 static int nb_handles;
  35 static int allocated_handles;
  36
  37 static struct user_handle *handle_to_entry( user_handle_t handle )
  38 {
  39     unsigned short generation;
  40     int index = ((handle & 0xffff) - FIRST_USER_HANDLE) >> 1;
  41     if (index < 0 || index >= nb_handles) return NULL;
  42     if (!handles[index].type) return NULL;
  43     generation = handle >> 16;
  44     if (generation == handles[index].generation || !generation || generation == 0xffff)
  45         return &handles[index];
  46     return NULL;
  47 }
  48
  49 static inline user_handle_t entry_to_handle( struct user_handle *ptr )
  50 {
  51     unsigned int index = ptr - handles;
  52     return (index << 1) + FIRST_USER_HANDLE + (ptr->generation << 16);
  53 }
  54
  55 static inline struct user_handle *alloc_user_entry(void)
  56 {
  57     struct user_handle *handle;
  58
  59     if (freelist)
  60     {
  61         handle = freelist;
  62         freelist = handle->ptr;
  63         return handle;
  64     }
  65     if (nb_handles >= allocated_handles)  /* need to grow the array */
  66     {
  67         struct user_handle *new_handles;
  68         /* grow array by 50% (but at minimum 32 entries) */
  69         int growth = max( 32, allocated_handles / 2 );
  70         int new_size = min( allocated_handles + growth, (LAST_USER_HANDLE-FIRST_USER_HANDLE+1) >> 1 );
  71         if (new_size <= allocated_handles) return NULL;
  72         if (!(new_handles = realloc( handles, new_size * sizeof(*handles) )))
  73             return NULL;
  74         handles = new_handles;
  75         allocated_handles = new_size;
  76     }
  77     handle = &handles[nb_handles++];
  78     handle->generation = 0;
  79     return handle;
  80 }
  81
  82 static inline void *free_user_entry( struct user_handle *ptr )
  83 {
  84     void *ret;
  85     ret = ptr->ptr;
  86     ptr->ptr  = freelist;
  87     ptr->type = 0;
  88     freelist  = ptr;
  89     return ret;
  90 }
  91
  92 /* allocate a user handle for a given object */
  93 user_handle_t alloc_user_handle( void *ptr, enum user_object type )
  94 {
  95     struct user_handle *entry = alloc_user_entry();
  96     if (!entry) return 0;
  97     entry->ptr  = ptr;
  98     entry->type = type;
  99     if (++entry->generation >= 0xffff) entry->generation = 1;
 100     return entry_to_handle( entry );
 101 }
 102
 103 /* return a pointer to a user object from its handle */
 104 void *get_user_object( user_handle_t handle, enum user_object type )
 105 {
 106     struct user_handle *entry;
 107
 108     if (!(entry = handle_to_entry( handle )) || entry->type != type) return NULL;
 109     return entry->ptr;
 110 }
 111
 112 /* get the full handle for a possibly truncated handle */
 113 user_handle_t get_user_full_handle( user_handle_t handle )
 114 {
 115     struct user_handle *entry;
 116
 117     if (handle >> 16) return handle;
 118     if (!(entry = handle_to_entry( handle ))) return handle;
 119     return entry_to_handle( entry );
 120 }
 121
 122 /* same as get_user_object plus set the handle to the full 32-bit value */
 123 void *get_user_object_handle( user_handle_t *handle, enum user_object type )
 124 {
 125     struct user_handle *entry;
 126
 127     if (!(entry = handle_to_entry( *handle )) || entry->type != type) return NULL;
 128     *handle = entry_to_handle( entry );
 129     return entry->ptr;
 130 }
 131
 132 /* free a user handle and return a pointer to the object */
 133 void *free_user_handle( user_handle_t handle )
 134 {
 135     struct user_handle *entry;
 136
 137     if (!(entry = handle_to_entry( handle )))
 138     {
 139         set_error( STATUS_INVALID_HANDLE );
 140         return NULL;
 141     }
 142     return free_user_entry( entry );
 143 }
 144
 145 /* return the next user handle after 'handle' that is of a given type */
 146 void *next_user_handle( user_handle_t *handle, enum user_object type )
 147 {
 148     struct user_handle *entry;
 149
 150     if (!*handle) entry = handles;
 151     else
 152     {
 153         int index = ((*handle & 0xffff) - FIRST_USER_HANDLE) >> 1;
 154         if (index < 0 || index >= nb_handles) return NULL;
 155         entry = handles + index + 1;  /* start from the next one */
 156     }
 157     while (entry < handles + nb_handles)
 158     {
 159         if (!type || entry->type == type)
 160         {
 161             *handle = entry_to_handle( entry );
 162             return entry->ptr;
 163         }
 164         entry++;
 165     }
 166     return NULL;
 167 }
 168
 169 /* free client-side user handles managed by the process */
 170 void free_process_user_handles( struct process *process )
 171 {
 172     unsigned int i;
 173
 174     for (i = 0; i < nb_handles; i++)
 175         if (handles[i].type == USER_CLIENT && handles[i].ptr == process)
 176             free_user_entry( &handles[i] );
 177 }
 178
 179 /* allocate an arbitrary user handle */
 180 DECL_HANDLER(alloc_user_handle)
 181 {
 182     reply->handle = alloc_user_handle( current->process, USER_CLIENT );
 183 }
 184
 185
 186 /* free an arbitrary user handle */
 187 DECL_HANDLER(free_user_handle)
 188 {
 189     struct user_handle *entry;
 190
 191     if ((entry = handle_to_entry( req->handle )) && entry->type == USER_CLIENT)
 192         free_user_entry( entry );
 193     else
 194         set_error( STATUS_INVALID_HANDLE );
 195 }