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jeremybenn |
/*
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* Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
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* Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
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* Copyright 1996 Silicon Graphics. All rights reserved.
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*
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* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
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* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
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*
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* Permission is hereby granted to use or copy this program
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* for any purpose, provided the above notices are retained on all copies.
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* Permission to modify the code and to distribute modified code is granted,
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* provided the above notices are retained, and a notice that the code was
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* modified is included with the above copyright notice.
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*/
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/*
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* Some simple primitives for allocation with explicit type information.
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* Facilities for dynamic type inference may be added later.
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* Should be used only for extremely performance critical applications,
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* or if conservative collector leakage is otherwise a problem (unlikely).
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* Note that this is implemented completely separately from the rest
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* of the collector, and is not linked in unless referenced.
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* This does not currently support GC_DEBUG in any interesting way.
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*/
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/* Boehm, May 19, 1994 2:13 pm PDT */
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#ifndef _GC_TYPED_H
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# define _GC_TYPED_H
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# ifndef _GC_H
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# include "gc.h"
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# endif
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#ifdef __cplusplus
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extern "C" {
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#endif
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typedef GC_word * GC_bitmap;
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/* The least significant bit of the first word is one if */
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/* the first word in the object may be a pointer. */
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# define GC_WORDSZ (8*sizeof(GC_word))
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# define GC_get_bit(bm, index) \
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(((bm)[index/GC_WORDSZ] >> (index%GC_WORDSZ)) & 1)
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# define GC_set_bit(bm, index) \
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(bm)[index/GC_WORDSZ] |= ((GC_word)1 << (index%GC_WORDSZ))
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# define GC_WORD_OFFSET(t, f) (offsetof(t,f)/sizeof(GC_word))
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# define GC_WORD_LEN(t) (sizeof(t)/ sizeof(GC_word))
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# define GC_BITMAP_SIZE(t) ((GC_WORD_LEN(t) + GC_WORDSZ-1)/GC_WORDSZ)
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typedef GC_word GC_descr;
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GC_API GC_descr GC_make_descriptor GC_PROTO((GC_bitmap bm, size_t len));
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/* Return a type descriptor for the object whose layout */
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/* is described by the argument. */
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/* The least significant bit of the first word is one */
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/* if the first word in the object may be a pointer. */
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/* The second argument specifies the number of */
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/* meaningful bits in the bitmap. The actual object */
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/* may be larger (but not smaller). Any additional */
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/* words in the object are assumed not to contain */
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/* pointers. */
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/* Returns a conservative approximation in the */
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/* (unlikely) case of insufficient memory to build */
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/* the descriptor. Calls to GC_make_descriptor */
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/* may consume some amount of a finite resource. This */
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/* is intended to be called once per type, not once */
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/* per allocation. */
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/* It is possible to generate a descriptor for a C type T with */
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/* word aligned pointer fields f1, f2, ... as follows: */
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/* */
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/* GC_descr T_descr; */
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/* GC_word T_bitmap[GC_BITMAP_SIZE(T)] = {0}; */
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/* GC_set_bit(T_bitmap, GC_WORD_OFFSET(T,f1)); */
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/* GC_set_bit(T_bitmap, GC_WORD_OFFSET(T,f2)); */
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/* ... */
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/* T_descr = GC_make_descriptor(T_bitmap, GC_WORD_LEN(T)); */
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GC_API GC_PTR GC_malloc_explicitly_typed
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GC_PROTO((size_t size_in_bytes, GC_descr d));
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/* Allocate an object whose layout is described by d. */
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/* The resulting object MAY NOT BE PASSED TO REALLOC. */
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/* The returned object is cleared. */
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GC_API GC_PTR GC_malloc_explicitly_typed_ignore_off_page
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GC_PROTO((size_t size_in_bytes, GC_descr d));
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GC_API GC_PTR GC_calloc_explicitly_typed
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GC_PROTO((size_t nelements,
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size_t element_size_in_bytes,
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GC_descr d));
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/* Allocate an array of nelements elements, each of the */
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/* given size, and with the given descriptor. */
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/* The elemnt size must be a multiple of the byte */
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/* alignment required for pointers. E.g. on a 32-bit */
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/* machine with 16-bit aligned pointers, size_in_bytes */
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/* must be a multiple of 2. */
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/* Returned object is cleared. */
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#ifdef GC_DEBUG
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# define GC_MALLOC_EXPLICITLY_TYPED(bytes, d) GC_MALLOC(bytes)
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# define GC_CALLOC_EXPLICITLY_TYPED(n, bytes, d) GC_MALLOC(n*bytes)
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#else
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# define GC_MALLOC_EXPLICITLY_TYPED(bytes, d) \
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GC_malloc_explicitly_typed(bytes, d)
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# define GC_CALLOC_EXPLICITLY_TYPED(n, bytes, d) \
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GC_calloc_explicitly_typed(n, bytes, d)
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#endif /* !GC_DEBUG */
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#ifdef __cplusplus
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} /* matches extern "C" */
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#endif
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#endif /* _GC_TYPED_H */
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