Added global management of user handles in the server.
Very preliminary support for shared window handles.
diff --git a/server/user.c b/server/user.c
new file mode 100644
index 0000000..ec0584c
--- /dev/null
+++ b/server/user.c
@@ -0,0 +1,149 @@
+/*
+ * Server-side USER handles
+ *
+ * Copyright (C) 2001 Alexandre Julliard
+ */
+
+#include "thread.h"
+#include "user.h"
+
+struct user_handle
+{
+ void *ptr; /* pointer to object */
+ unsigned short type; /* object type (0 if free) */
+ unsigned short generation; /* generation counter */
+};
+
+static struct user_handle *handles;
+static struct user_handle *freelist;
+static int nb_handles;
+static int allocated_handles;
+
+#define FIRST_HANDLE 32 /* handle value for first table entry */
+#define MAX_HANDLES (65536-FIRST_HANDLE)
+
+static struct user_handle *handle_to_entry( user_handle_t handle )
+{
+ int index = (handle & 0xffff) - FIRST_HANDLE;
+ if (index < 0 || index >= nb_handles) return NULL;
+ if (!handles[index].type) return NULL;
+ if ((handle >> 16) && (handle >> 16 != handles[index].generation)) return NULL;
+ return &handles[index];
+}
+
+inline static user_handle_t entry_to_handle( struct user_handle *ptr )
+{
+ int index = ptr - handles;
+ return (index + FIRST_HANDLE) + (ptr->generation << 16);
+}
+
+inline static struct user_handle *alloc_user_entry(void)
+{
+ struct user_handle *handle;
+
+ if (freelist)
+ {
+ handle = freelist;
+ freelist = handle->ptr;
+ return handle;
+ }
+ if (nb_handles >= allocated_handles) /* need to grow the array */
+ {
+ struct user_handle *new_handles;
+ /* grow array by 50% (but at minimum 32 entries) */
+ int growth = max( 32, allocated_handles / 2 );
+ int new_size = min( allocated_handles + growth, MAX_HANDLES );
+ if (new_size <= allocated_handles) return NULL;
+ if (!(new_handles = realloc( handles, new_size * sizeof(*handles) )))
+ return NULL;
+ handles = new_handles;
+ allocated_handles = new_size;
+ }
+ handle = &handles[nb_handles++];
+ handle->generation = 0;
+ return handle;
+}
+
+inline static void *free_user_entry( struct user_handle *ptr )
+{
+ void *ret;
+ ret = ptr->ptr;
+ ptr->ptr = freelist;
+ ptr->type = 0;
+ freelist = ptr;
+ return ret;
+}
+
+/* allocate a user handle for a given object */
+user_handle_t alloc_user_handle( void *ptr, enum user_object type )
+{
+ struct user_handle *entry = alloc_user_entry();
+ if (!entry) return 0;
+ entry->ptr = ptr;
+ entry->type = type;
+ if (++entry->generation >= 0xffff) entry->generation = 1;
+ return entry_to_handle( entry );
+}
+
+/* return a pointer to a user object from its handle */
+void *get_user_object( user_handle_t handle, enum user_object type )
+{
+ struct user_handle *entry;
+
+ if (!(entry = handle_to_entry( handle )) || entry->type != type)
+ {
+ set_error( STATUS_INVALID_HANDLE );
+ return NULL;
+ }
+ return entry->ptr;
+}
+
+/* same as get_user_object plus set the handle to the full 32-bit value */
+void *get_user_object_handle( user_handle_t *handle, enum user_object type )
+{
+ struct user_handle *entry;
+
+ if (!(entry = handle_to_entry( *handle )) || entry->type != type)
+ {
+ set_error( STATUS_INVALID_HANDLE );
+ return NULL;
+ }
+ *handle = entry_to_handle( entry );
+ return entry->ptr;
+}
+
+/* free a user handle and return a pointer to the object */
+void *free_user_handle( user_handle_t handle )
+{
+ struct user_handle *entry;
+
+ if (!(entry = handle_to_entry( handle )))
+ {
+ set_error( STATUS_INVALID_HANDLE );
+ return NULL;
+ }
+ return free_user_entry( entry );
+}
+
+/* return the next user handle after 'handle' that is of a given type */
+void *next_user_handle( user_handle_t *handle, enum user_object type )
+{
+ struct user_handle *entry;
+
+ if (!*handle) entry = handles;
+ else
+ {
+ if (!(entry = handle_to_entry( *handle ))) return NULL;
+ entry++; /* start from the next one */
+ }
+ while (entry < handles + nb_handles)
+ {
+ if (!type || entry->type == type)
+ {
+ *handle = entry_to_handle( entry );
+ return entry->ptr;
+ }
+ entry++;
+ }
+ return NULL;
+}
