boehm-gc/gc_typed.h

   1 /*
   2  * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
   3  * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   4  * Copyright 1996 Silicon Graphics.  All rights reserved.
   5  *
   6  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   7  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   8  *
   9  * Permission is hereby granted to use or copy this program
  10  * for any purpose,  provided the above notices are retained on all copies.
  11  * Permission to modify the code and to distribute modified code is granted,
  12  * provided the above notices are retained, and a notice that the code was
  13  * modified is included with the above copyright notice.
  14  */
  15 /*
  16  * Some simple primitives for allocation with explicit type information.
  17  * Facilities for dynamic type inference may be added later.
  18  * Should be used only for extremely performance critical applications,
  19  * or if conservative collector leakage is otherwise a problem (unlikely).
  20  * Note that this is implemented completely separately from the rest
  21  * of the collector, and is not linked in unless referenced.
  22  * This does not currently support GC_DEBUG in any interesting way.
  23  */
  24 /* Boehm, May 19, 1994 2:13 pm PDT */
  25
  26 #ifndef _GC_TYPED_H
  27 # define _GC_TYPED_H
  28 # ifndef _GC_H
  29 #   include "gc.h"
  30 # endif
  31
  32 typedef GC_word * GC_bitmap;
  33         /* The least significant bit of the first word is one if        */
  34         /* the first word in the object may be a pointer.               */
  35
  36 # define GC_get_bit(bm, index) \
  37                 (((bm)[divWORDSZ(index)] >> modWORDSZ(index)) & 1)
  38 # define GC_set_bit(bm, index) \
  39                 (bm)[divWORDSZ(index)] |= (word)1 << modWORDSZ(index)
  40
  41 typedef GC_word GC_descr;
  42
  43 GC_API GC_descr GC_make_descriptor GC_PROTO((GC_bitmap bm, size_t len));
  44                 /* Return a type descriptor for the object whose layout */
  45                 /* is described by the argument.                        */
  46                 /* The least significant bit of the first word is one   */
  47                 /* if the first word in the object may be a pointer.    */
  48                 /* The second argument specifies the number of          */
  49                 /* meaningful bits in the bitmap.  The actual object    */
  50                 /* may be larger (but not smaller).  Any additional     */
  51                 /* words in the object are assumed not to contain       */
  52                 /* pointers.                                            */
  53                 /* Returns a conservative approximation in the          */
  54                 /* (unlikely) case of insufficient memory to build      */
  55                 /* the descriptor.  Calls to GC_make_descriptor         */
  56                 /* may consume some amount of a finite resource.  This  */
  57                 /* is intended to be called once per type, not once     */
  58                 /* per allocation.                                      */
  59
  60 GC_API GC_PTR GC_malloc_explicitly_typed
  61                         GC_PROTO((size_t size_in_bytes, GC_descr d));
  62                 /* Allocate an object whose layout is described by d.   */
  63                 /* The resulting object MAY NOT BE PASSED TO REALLOC.   */
  64
  65 GC_API GC_PTR GC_malloc_explicitly_typed_ignore_off_page
  66                         GC_PROTO((size_t size_in_bytes, GC_descr d));
  67
  68 GC_API GC_PTR GC_calloc_explicitly_typed
  69                         GC_PROTO((size_t nelements,
  70                                   size_t element_size_in_bytes,
  71                                   GC_descr d));
  72         /* Allocate an array of nelements elements, each of the */
  73         /* given size, and with the given descriptor.           */
  74         /* The elemnt size must be a multiple of the byte       */
  75         /* alignment required for pointers.  E.g. on a 32-bit   */
  76         /* machine with 16-bit aligned pointers, size_in_bytes  */
  77         /* must be a multiple of 2.                             */
  78
  79 #ifdef GC_DEBUG
  80 #   define GC_MALLOC_EXPLICTLY_TYPED(bytes, d) GC_MALLOC(bytes)
  81 #   define GC_CALLOC_EXPLICTLY_TYPED(n, bytes, d) GC_MALLOC(n*bytes)
  82 #else
  83 #  define GC_MALLOC_EXPLICTLY_TYPED(bytes, d) \
  84         GC_malloc_explicitly_typed(bytes, d)
  85 #  define GC_CALLOC_EXPLICTLY_TYPED(n, bytes, d) \
  86         GC_calloc_explicitly_typed(n, bytes, d)
  87 #endif /* !GC_DEBUG */
  88
  89
  90 #endif /* _GC_TYPED_H */
  91