obj_map.c

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/* 
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991, 1992 by Xerox Corporation.  All rights reserved.
 * Copyright (c) 1999-2001 by Hewlett-Packard Company. All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program
 * for any purpose,  provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is granted,
 * provided the above notices are retained, and a notice that the code was
 * modified is included with the above copyright notice.
 */
  
/* Routines for maintaining maps describing heap block
 * layouts for various object sizes.  Allows fast pointer validity checks
 * and fast location of object start locations on machines (such as SPARC)
 * with slow division.
 */
 
# include "private/gc_priv.h"

/* Consider pointers that are offset bytes displaced from the beginning */
/* of an object to be valid.                                            */

void GC_register_displacement(size_t offset)
{
    DCL_LOCK_STATE;
    
    LOCK();
    GC_register_displacement_inner(offset);
    UNLOCK();
}

void GC_register_displacement_inner(size_t offset) 
{
    if (offset >= VALID_OFFSET_SZ) {
        ABORT("Bad argument to GC_register_displacement");
    }
    if (!GC_valid_offsets[offset]) {
      GC_valid_offsets[offset] = TRUE;
      GC_modws_valid_offsets[offset % sizeof(word)] = TRUE;
    }
}

#ifdef MARK_BIT_PER_GRANULE
/* Add a heap block map for objects of size granules to obj_map.	*/
/* Return FALSE on failure.						*/
/* A size of 0 granules is used for large objects.			*/
GC_bool GC_add_map_entry(size_t granules)
{
    unsigned displ;
    short * new_map;
    
    if (granules > BYTES_TO_GRANULES(MAXOBJBYTES)) granules = 0;
    if (GC_obj_map[granules] != 0) {
        return(TRUE);
    }
    new_map = (short *)GC_scratch_alloc(MAP_LEN * sizeof(short));
    if (new_map == 0) return(FALSE);
    if (GC_print_stats)
        GC_printf("Adding block map for size of %u granules (%u bytes)\n",
		  (unsigned)granules, (unsigned)(GRANULES_TO_BYTES(granules)));
    if (granules == 0) {
      for (displ = 0; displ < BYTES_TO_GRANULES(HBLKSIZE); displ++) {
        new_map[displ] = 1;  /* Nonzero to get us out of marker fast path. */
      }
    } else {
      for (displ = 0; displ < BYTES_TO_GRANULES(HBLKSIZE); displ++) {
	new_map[displ] = (short)(displ % granules);
      }
    }
    GC_obj_map[granules] = new_map;
    return(TRUE);
}
#endif

static GC_bool offsets_initialized = FALSE;

void GC_initialize_offsets(void)
{
    if (!offsets_initialized) {
      int i;
      if (GC_all_interior_pointers) {
	for (i = 0; i < VALID_OFFSET_SZ; ++i) GC_valid_offsets[i] = TRUE;
      }
      offsets_initialized = TRUE;
    }
}