server/user.c

   1 /*
   2  * Server-side USER handles
   3  *
   4  * Copyright (C) 2001 Alexandre Julliard
   5  */
   6
   7 #include "thread.h"
   8 #include "user.h"
   9
  10 struct user_handle
  11 {
  12     void          *ptr;          /* pointer to object */
  13     unsigned short type;         /* object type (0 if free) */
  14     unsigned short generation;   /* generation counter */
  15 };
  16
  17 static struct user_handle *handles;
  18 static struct user_handle *freelist;
  19 static int nb_handles;
  20 static int allocated_handles;
  21
  22 static struct user_handle *handle_to_entry( user_handle_t handle )
  23 {
  24     int index = (handle & 0xffff) - FIRST_USER_HANDLE;
  25     if (index < 0 || index >= nb_handles) return NULL;
  26     if (!handles[index].type) return NULL;
  27     if ((handle >> 16) && (handle >> 16 != handles[index].generation)) return NULL;
  28     return &handles[index];
  29 }
  30
  31 inline static user_handle_t entry_to_handle( struct user_handle *ptr )
  32 {
  33     int index = ptr - handles;
  34     return (index + FIRST_USER_HANDLE) + (ptr->generation << 16);
  35 }
  36
  37 inline static struct user_handle *alloc_user_entry(void)
  38 {
  39     struct user_handle *handle;
  40
  41     if (freelist)
  42     {
  43         handle = freelist;
  44         freelist = handle->ptr;
  45         return handle;
  46     }
  47     if (nb_handles >= allocated_handles)  /* need to grow the array */
  48     {
  49         struct user_handle *new_handles;
  50         /* grow array by 50% (but at minimum 32 entries) */
  51         int growth = max( 32, allocated_handles / 2 );
  52         int new_size = min( allocated_handles + growth, LAST_USER_HANDLE-FIRST_USER_HANDLE+1 );
  53         if (new_size <= allocated_handles) return NULL;
  54         if (!(new_handles = realloc( handles, new_size * sizeof(*handles) )))
  55             return NULL;
  56         handles = new_handles;
  57         allocated_handles = new_size;
  58     }
  59     handle = &handles[nb_handles++];
  60     handle->generation = 0;
  61     return handle;
  62 }
  63
  64 inline static void *free_user_entry( struct user_handle *ptr )
  65 {
  66     void *ret;
  67     ret = ptr->ptr;
  68     ptr->ptr  = freelist;
  69     ptr->type = 0;
  70     freelist  = ptr;
  71     return ret;
  72 }
  73
  74 /* allocate a user handle for a given object */
  75 user_handle_t alloc_user_handle( void *ptr, enum user_object type )
  76 {
  77     struct user_handle *entry = alloc_user_entry();
  78     if (!entry) return 0;
  79     entry->ptr  = ptr;
  80     entry->type = type;
  81     if (++entry->generation >= 0xffff) entry->generation = 1;
  82     return entry_to_handle( entry );
  83 }
  84
  85 /* return a pointer to a user object from its handle */
  86 void *get_user_object( user_handle_t handle, enum user_object type )
  87 {
  88     struct user_handle *entry;
  89
  90     if (!(entry = handle_to_entry( handle )) || entry->type != type) return NULL;
  91     return entry->ptr;
  92 }
  93
  94 /* get the full handle for a possibly truncated handle */
  95 user_handle_t get_user_full_handle( user_handle_t handle )
  96 {
  97     struct user_handle *entry;
  98
  99     if (handle >> 16) return handle;
 100     if (!(entry = handle_to_entry( handle ))) return handle;
 101     return entry_to_handle( entry );
 102 }
 103
 104 /* same as get_user_object plus set the handle to the full 32-bit value */
 105 void *get_user_object_handle( user_handle_t *handle, enum user_object type )
 106 {
 107     struct user_handle *entry;
 108
 109     if (!(entry = handle_to_entry( *handle )) || entry->type != type) return NULL;
 110     *handle = entry_to_handle( entry );
 111     return entry->ptr;
 112 }
 113
 114 /* free a user handle and return a pointer to the object */
 115 void *free_user_handle( user_handle_t handle )
 116 {
 117     struct user_handle *entry;
 118
 119     if (!(entry = handle_to_entry( handle )))
 120     {
 121         set_error( STATUS_INVALID_HANDLE );
 122         return NULL;
 123     }
 124     return free_user_entry( entry );
 125 }
 126
 127 /* return the next user handle after 'handle' that is of a given type */
 128 void *next_user_handle( user_handle_t *handle, enum user_object type )
 129 {
 130     struct user_handle *entry;
 131
 132     if (!*handle) entry = handles;
 133     else
 134     {
 135         if (!(entry = handle_to_entry( *handle ))) return NULL;
 136         entry++;  /* start from the next one */
 137     }
 138     while (entry < handles + nb_handles)
 139     {
 140         if (!type || entry->type == type)
 141         {
 142             *handle = entry_to_handle( entry );
 143             return entry->ptr;
 144         }
 145         entry++;
 146     }
 147     return NULL;
 148 }