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 #define FIRST_HANDLE 32  /* handle value for first table entry */
  23 #define LAST_HANDLE  (65536 - 16)
  24 #define MAX_HANDLES  (LAST_HANDLE - FIRST_HANDLE)
  25
  26 static struct user_handle *handle_to_entry( user_handle_t handle )
  27 {
  28     int index = (handle & 0xffff) - FIRST_HANDLE;
  29     if (index < 0 || index >= nb_handles) return NULL;
  30     if (!handles[index].type) return NULL;
  31     if ((handle >> 16) && (handle >> 16 != handles[index].generation)) return NULL;
  32     return &handles[index];
  33 }
  34
  35 inline static user_handle_t entry_to_handle( struct user_handle *ptr )
  36 {
  37     int index = ptr - handles;
  38     return (index + FIRST_HANDLE) + (ptr->generation << 16);
  39 }
  40
  41 inline static struct user_handle *alloc_user_entry(void)
  42 {
  43     struct user_handle *handle;
  44
  45     if (freelist)
  46     {
  47         handle = freelist;
  48         freelist = handle->ptr;
  49         return handle;
  50     }
  51     if (nb_handles >= allocated_handles)  /* need to grow the array */
  52     {
  53         struct user_handle *new_handles;
  54         /* grow array by 50% (but at minimum 32 entries) */
  55         int growth = max( 32, allocated_handles / 2 );
  56         int new_size = min( allocated_handles + growth, MAX_HANDLES );
  57         if (new_size <= allocated_handles) return NULL;
  58         if (!(new_handles = realloc( handles, new_size * sizeof(*handles) )))
  59             return NULL;
  60         handles = new_handles;
  61         allocated_handles = new_size;
  62     }
  63     handle = &handles[nb_handles++];
  64     handle->generation = 0;
  65     return handle;
  66 }
  67
  68 inline static void *free_user_entry( struct user_handle *ptr )
  69 {
  70     void *ret;
  71     ret = ptr->ptr;
  72     ptr->ptr  = freelist;
  73     ptr->type = 0;
  74     freelist  = ptr;
  75     return ret;
  76 }
  77
  78 /* allocate a user handle for a given object */
  79 user_handle_t alloc_user_handle( void *ptr, enum user_object type )
  80 {
  81     struct user_handle *entry = alloc_user_entry();
  82     if (!entry) return 0;
  83     entry->ptr  = ptr;
  84     entry->type = type;
  85     if (++entry->generation >= 0xffff) entry->generation = 1;
  86     return entry_to_handle( entry );
  87 }
  88
  89 /* return a pointer to a user object from its handle */
  90 void *get_user_object( user_handle_t handle, enum user_object type )
  91 {
  92     struct user_handle *entry;
  93
  94     if (!(entry = handle_to_entry( handle )) || entry->type != type)
  95     {
  96         set_error( STATUS_INVALID_HANDLE );
  97         return NULL;
  98     }
  99     return entry->ptr;
 100 }
 101
 102 /* get the full handle for a possibly truncated handle */
 103 user_handle_t get_user_full_handle( user_handle_t handle )
 104 {
 105     struct user_handle *entry;
 106
 107     if (handle >> 16) return handle;
 108     if (!(entry = handle_to_entry( handle ))) return handle;
 109     return entry_to_handle( entry );
 110 }
 111
 112 /* same as get_user_object plus set the handle to the full 32-bit value */
 113 void *get_user_object_handle( user_handle_t *handle, enum user_object type )
 114 {
 115     struct user_handle *entry;
 116
 117     if (!(entry = handle_to_entry( *handle )) || entry->type != type)
 118     {
 119         set_error( STATUS_INVALID_HANDLE );
 120         return NULL;
 121     }
 122     *handle = entry_to_handle( entry );
 123     return entry->ptr;
 124 }
 125
 126 /* free a user handle and return a pointer to the object */
 127 void *free_user_handle( user_handle_t handle )
 128 {
 129     struct user_handle *entry;
 130
 131     if (!(entry = handle_to_entry( handle )))
 132     {
 133         set_error( STATUS_INVALID_HANDLE );
 134         return NULL;
 135     }
 136     return free_user_entry( entry );
 137 }
 138
 139 /* return the next user handle after 'handle' that is of a given type */
 140 void *next_user_handle( user_handle_t *handle, enum user_object type )
 141 {
 142     struct user_handle *entry;
 143
 144     if (!*handle) entry = handles;
 145     else
 146     {
 147         if (!(entry = handle_to_entry( *handle ))) return NULL;
 148         entry++;  /* start from the next one */
 149     }
 150     while (entry < handles + nb_handles)
 151     {
 152         if (!type || entry->type == type)
 153         {
 154             *handle = entry_to_handle( entry );
 155             return entry->ptr;
 156         }
 157         entry++;
 158     }
 159     return NULL;
 160 }