/* IBM_PROLOG_BEGIN_TAG */
/* This is an automatically generated prolog. */
/* */
/* bos720 src/bos/kernext/rcm/inc/sys/rcm_wg.h 1.2 */
/* */
/* Licensed Materials - Property of IBM */
/* */
/* COPYRIGHT International Business Machines Corp. 1991,1999 */
/* All Rights Reserved */
/* */
/* US Government Users Restricted Rights - Use, duplication or */
/* disclosure restricted by GSA ADP Schedule Contract with IBM Corp. */
/* */
/* IBM_PROLOG_END_TAG */
/* @(#)14 1.2 src/bos/kernext/rcm/inc/sys/rcm_wg.h, rcm, bos720 5/3/99 17:39:00 */
/*
* COMPONENT_NAME: (rcm) AIX Rendering Context Manager structure definitions
*
* FUNCTIONS: none
*
* ORIGINS: 27
*
* (C) COPYRIGHT International Business Machines Corp. 1991-1993
* All Rights Reserved
* Licensed Materials - Property of IBM
*
* US Government Users Restricted Rights - Use, duplication or
* disclosure restricted by GSA ADP Schedule Contract with IBM Corp.
*/
#ifndef _H_RCX_WG
#define _H_RCX_WG
/* -----------------------------------------------------------------
Define the WG hash table entry here
-------------------------------------------------------------- */
typedef struct _rcm_wg_hash
{
void *pWG ; /* Pointer to the window geom (chain) */
} rcm_wg_hash_t ;
/* ----------------------------------------------------------------
Define the entire hash table here:
The value RCM_WG_HASH_SIZE was pick somewhat arbitrarily.
Although very few hash collisions were observed during
development, this value could be evaluated later for
performance reasons.
---------------------------------------------------------------*/
#define RCM_WG_HASH_SIZE 1024
#define RCM_WG_HASH_SHIFT 6
#define RCM_WG_HASH_MASK ((RCM_WG_HASH_SIZE-1)<<RCM_WG_HASH_SHIFT)
typedef struct _wg_hash_table
{
rcm_wg_hash_t entry[RCM_WG_HASH_SIZE] ;
} rcm_wg_hash_table_t ;
/* ----------------------------------------------------------------
Macro to perform the hashing function
Because of the way that the WG pointers are allocated, the
6 low-order bits of a given WG pointer may be the same as
any other. Therefore, shift out the 6 low-order bits
(RCM_WG_HASH_SHIFT) and use the next 10 bits as an index
into the hash table. These 10 bits should be the most
likely to vary between WG pointers.
---------------------------------------------------------------*/
#define RCM_WG_HASH(pWG) \
( ((uint)pWG & RCM_WG_HASH_MASK) >> RCM_WG_HASH_SHIFT)
#endif /* _H_RCX_WG */