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 #ifdef __cplusplus 33 extern "C" { 34 #endif 35 typedef GC_word * GC_bitmap; 36 /* The least significant bit of the first word is one if */ 37 /* the first word in the object may be a pointer. */ 38 39 # define GC_WORDSZ (8*sizeof(GC_word)) 40 # define GC_get_bit(bm, index) \ 41 (((bm)[index/GC_WORDSZ] >> (index%GC_WORDSZ)) & 1) 42 # define GC_set_bit(bm, index) \ 43 (bm)[index/GC_WORDSZ] |= ((GC_word)1 << (index%GC_WORDSZ)) 44 # define GC_WORD_OFFSET(t, f) (offsetof(t,f)/sizeof(GC_word)) 45 # define GC_WORD_LEN(t) (sizeof(t)/ sizeof(GC_word)) 46 # define GC_BITMAP_SIZE(t) ((GC_WORD_LEN(t) + GC_WORDSZ-1)/GC_WORDSZ) 47 48 typedef GC_word GC_descr; 49 50 GC_API GC_descr GC_make_descriptor GC_PROTO((GC_bitmap bm, size_t len)); 51 /* Return a type descriptor for the object whose layout */ 52 /* is described by the argument. */ 53 /* The least significant bit of the first word is one */ 54 /* if the first word in the object may be a pointer. */ 55 /* The second argument specifies the number of */ 56 /* meaningful bits in the bitmap. The actual object */ 57 /* may be larger (but not smaller). Any additional */ 58 /* words in the object are assumed not to contain */ 59 /* pointers. */ 60 /* Returns a conservative approximation in the */ 61 /* (unlikely) case of insufficient memory to build */ 62 /* the descriptor. Calls to GC_make_descriptor */ 63 /* may consume some amount of a finite resource. This */ 64 /* is intended to be called once per type, not once */ 65 /* per allocation. */ 66 67 /* It is possible to generate a descriptor for a C type T with */ 68 /* word aligned pointer fields f1, f2, ... as follows: */ 69 /* */ 70 /* GC_descr T_descr; */ 71 /* GC_word T_bitmap[GC_BITMAP_SIZE(T)] = {0}; */ 72 /* GC_set_bit(T_bitmap, GC_WORD_OFFSET(T,f1)); */ 73 /* GC_set_bit(T_bitmap, GC_WORD_OFFSET(T,f2)); */ 74 /* ... */ 75 /* T_descr = GC_make_descriptor(T_bitmap, GC_WORD_LEN(T)); */ 76 77 GC_API GC_PTR GC_malloc_explicitly_typed 78 GC_PROTO((size_t size_in_bytes, GC_descr d)); 79 /* Allocate an object whose layout is described by d. */ 80 /* The resulting object MAY NOT BE PASSED TO REALLOC. */ 81 /* The returned object is cleared. */ 82 83 GC_API GC_PTR GC_malloc_explicitly_typed_ignore_off_page 84 GC_PROTO((size_t size_in_bytes, GC_descr d)); 85 86 GC_API GC_PTR GC_calloc_explicitly_typed 87 GC_PROTO((size_t nelements, 88 size_t element_size_in_bytes, 89 GC_descr d)); 90 /* Allocate an array of nelements elements, each of the */ 91 /* given size, and with the given descriptor. */ 92 /* The elemnt size must be a multiple of the byte */ 93 /* alignment required for pointers. E.g. on a 32-bit */ 94 /* machine with 16-bit aligned pointers, size_in_bytes */ 95 /* must be a multiple of 2. */ 96 /* Returned object is cleared. */ 97 98 #ifdef GC_DEBUG 99 # define GC_MALLOC_EXPLICITLY_TYPED(bytes, d) GC_MALLOC(bytes) 100 # define GC_CALLOC_EXPLICITLY_TYPED(n, bytes, d) GC_MALLOC(n*bytes) 101 #else 102 # define GC_MALLOC_EXPLICITLY_TYPED(bytes, d) \ 103 GC_malloc_explicitly_typed(bytes, d) 104 # define GC_CALLOC_EXPLICITLY_TYPED(n, bytes, d) \ 105 GC_calloc_explicitly_typed(n, bytes, d) 106 #endif /* !GC_DEBUG */ 107 108 #ifdef __cplusplus 109 } /* matches extern "C" */ 110 #endif 111 112 #endif /* _GC_TYPED_H */ 113 114