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