/*
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991-1994 by Xerox Corporation.  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.
 */

#ifndef GC_HEADERS_H
#define GC_HEADERS_H

typedef struct hblkhdr hdr;

#if CPP_WORDSZ != 32 && CPP_WORDSZ < 36
        --> Get a real machine.
#endif

/*
 * The 2 level tree data structure that is used to find block headers.
 * If there are more than 32 bits in a pointer, the top level is a hash
 * table.
 *
 * This defines HDR, GET_HDR, and SET_HDR, the main macros used to
 * retrieve and set object headers.
 *
 * We take advantage of a header lookup
 * cache.  This is a locally declared direct mapped cache, used inside
 * the marker.  The HC_GET_HDR macro uses and maintains this
 * cache.  Assuming we get reasonable hit rates, this shaves a few
 * memory references from each pointer validation.
 */

#if CPP_WORDSZ > 32
# define HASH_TL
#endif

/* Define appropriate out-degrees for each of the two tree levels       */
#if defined(LARGE_CONFIG) || !defined(SMALL_CONFIG)
# define LOG_BOTTOM_SZ 10
#else
# define LOG_BOTTOM_SZ 11
        /* Keep top index size reasonable with smaller blocks.  */
#endif
#define BOTTOM_SZ (1 << LOG_BOTTOM_SZ)

#ifndef HASH_TL
# define LOG_TOP_SZ (WORDSZ - LOG_BOTTOM_SZ - LOG_HBLKSIZE)
#else
# define LOG_TOP_SZ 11
#endif
#define TOP_SZ (1 << LOG_TOP_SZ)

/* #define COUNT_HDR_CACHE_HITS  */

#ifdef COUNT_HDR_CACHE_HITS
  extern word GC_hdr_cache_hits; /* used for debugging/profiling */
  extern word GC_hdr_cache_misses;
# define HC_HIT() ++GC_hdr_cache_hits
# define HC_MISS() ++GC_hdr_cache_misses
#else
# define HC_HIT()
# define HC_MISS()
#endif

typedef struct hce {
  word block_addr;    /* right shifted by LOG_HBLKSIZE */
  hdr * hce_hdr;
} hdr_cache_entry;

#define HDR_CACHE_SIZE 8  /* power of 2 */

#define DECLARE_HDR_CACHE \
        hdr_cache_entry hdr_cache[HDR_CACHE_SIZE]

#define INIT_HDR_CACHE BZERO(hdr_cache, sizeof(hdr_cache))

#define HCE(h) hdr_cache + (((word)(h) >> LOG_HBLKSIZE) & (HDR_CACHE_SIZE-1))

#define HCE_VALID_FOR(hce,h) ((hce) -> block_addr == \
                                ((word)(h) >> LOG_HBLKSIZE))

#define HCE_HDR(h) ((hce) -> hce_hdr)

#ifdef PRINT_BLACK_LIST
  GC_INNER hdr * GC_header_cache_miss(ptr_t p, hdr_cache_entry *hce,
                                      ptr_t source);
# define HEADER_CACHE_MISS(p, hce, source) \
          GC_header_cache_miss(p, hce, source)
#else
  GC_INNER hdr * GC_header_cache_miss(ptr_t p, hdr_cache_entry *hce);
# define HEADER_CACHE_MISS(p, hce, source) GC_header_cache_miss(p, hce)
#endif

/* Set hhdr to the header for p.  Analogous to GET_HDR below,           */
/* except that in the case of large objects, it                         */
/* gets the header for the object beginning, if GC_all_interior_ptrs    */
/* is set.                                                              */
/* Returns zero if p points to somewhere other than the first page      */
/* of an object, and it is not a valid pointer to the object.           */
#define HC_GET_HDR(p, hhdr, source, exit_label) \
        do { \
          hdr_cache_entry * hce = HCE(p); \
          if (EXPECT(HCE_VALID_FOR(hce, p), TRUE)) { \
            HC_HIT(); \
            hhdr = hce -> hce_hdr; \
          } else { \
            hhdr = HEADER_CACHE_MISS(p, hce, source); \
            if (0 == hhdr) goto exit_label; \
          } \
        } while (0)

typedef struct bi {
    hdr * index[BOTTOM_SZ];
        /*
         * The bottom level index contains one of three kinds of values:
         * 0 means we're not responsible for this block,
         *   or this is a block other than the first one in a free block.
         * 1 < (long)X <= MAX_JUMP means the block starts at least
         *        X * HBLKSIZE bytes before the current address.
         * A valid pointer points to a hdr structure. (The above can't be
         * valid pointers due to the GET_MEM return convention.)
         */
    struct bi * asc_link;       /* All indices are linked in    */
                                /* ascending order...           */
    struct bi * desc_link;      /* ... and in descending order. */
    word key;                   /* high order address bits.     */
# ifdef HASH_TL
    struct bi * hash_link;      /* Hash chain link.             */
# endif
} bottom_index;

/* bottom_index GC_all_nils; - really part of GC_arrays */

/* extern bottom_index * GC_top_index []; - really part of GC_arrays */
                                /* Each entry points to a bottom_index. */
                                /* On a 32 bit machine, it points to    */
                                /* the index for a set of high order    */
                                /* bits equal to the index.  For longer */
                                /* addresses, we hash the high order    */
                                /* bits to compute the index in         */
                                /* GC_top_index, and each entry points  */
                                /* to a hash chain.                     */
                                /* The last entry in each chain is      */
                                /* GC_all_nils.                         */


#define MAX_JUMP (HBLKSIZE - 1)

#define HDR_FROM_BI(bi, p) \
                ((bi)->index[((word)(p) >> LOG_HBLKSIZE) & (BOTTOM_SZ - 1)])
#ifndef HASH_TL
# define BI(p) (GC_top_index \
              [(word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE)])
# define HDR_INNER(p) HDR_FROM_BI(BI(p),p)
# ifdef SMALL_CONFIG
#     define HDR(p) GC_find_header((ptr_t)(p))
# else
#     define HDR(p) HDR_INNER(p)
# endif
# define GET_BI(p, bottom_indx) (void)((bottom_indx) = BI(p))
# define GET_HDR(p, hhdr) (void)((hhdr) = HDR(p))
# define SET_HDR(p, hhdr) (void)(HDR_INNER(p) = (hhdr))
# define GET_HDR_ADDR(p, ha) (void)((ha) = &HDR_INNER(p))
#else /* hash */
  /* Hash function for tree top level */
# define TL_HASH(hi) ((hi) & (TOP_SZ - 1))
  /* Set bottom_indx to point to the bottom index for address p */
# define GET_BI(p, bottom_indx) \
        do { \
          register word hi = \
              (word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE); \
          register bottom_index * _bi = GC_top_index[TL_HASH(hi)]; \
          while (_bi -> key != hi && _bi != GC_all_nils) \
              _bi = _bi -> hash_link; \
          (bottom_indx) = _bi; \
        } while (0)
# define GET_HDR_ADDR(p, ha) \
        do { \
          register bottom_index * bi; \
          GET_BI(p, bi); \
          (ha) = &HDR_FROM_BI(bi, p); \
        } while (0)
# define GET_HDR(p, hhdr) \
        do { \
          register hdr ** _ha; \
          GET_HDR_ADDR(p, _ha); \
          (hhdr) = *_ha; \
        } while (0)
# define SET_HDR(p, hhdr) \
        do { \
          register hdr ** _ha; \
          GET_HDR_ADDR(p, _ha); \
          *_ha = (hhdr); \
        } while (0)
# define HDR(p) GC_find_header((ptr_t)(p))
#endif

/* Is the result a forwarding address to someplace closer to the        */
/* beginning of the block or NULL?                                      */
#define IS_FORWARDING_ADDR_OR_NIL(hhdr) ((size_t) (hhdr) <= MAX_JUMP)

/* Get an HBLKSIZE aligned address closer to the beginning of the block */
/* h.  Assumes hhdr == HDR(h) and IS_FORWARDING_ADDR(hhdr).             */
#define FORWARDED_ADDR(h, hhdr) ((struct hblk *)(h) - (size_t)(hhdr))

#endif /* GC_HEADERS_H */
