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Diffstat (limited to 'gc/nursery.h')
| -rwxr-xr-x | gc/nursery.h | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/gc/nursery.h b/gc/nursery.h new file mode 100755 index 0000000..d109ff0 --- /dev/null +++ b/gc/nursery.h @@ -0,0 +1,90 @@ + +/* + * Copyright (c) 1999 by Silicon Graphics. 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. + */ + +/* + * THIS IMPLEMENTATION FOR THIS INTERFACE IS INCOMPLETE. + * NONE OF THIS HAS BEEN TESTED. DO NOT USE. + * + * Comments on the interface are appreciated, especially from + * potential users of the interface. + * + * This is a Bartlett style copying collector for young objects. + * We assume for now that all objects allocated through this + * mechanism have pointers only in the first BITMAP_BITS words. + * (On a 32-bit machine, BITMAP_BITS is 30.) + * Objects allocated in this manner should be rarely referenced + * by objects not allocated either through this interface, or through + * the typed allocation interface. + * If this interface is used, we assume that type information provided + * through either this or the typed allocation interface is valid + * in a stronger sense: + * + * 1) No pointers are stored in fields not marked as such. + * (Otherwise it is only necessary that objects referenced by + * fields marked as nonpointers are also reachable via another + * path.) + * 2) Values stored in pointer fields are either not addresses in + * the heap, or they really are pointers. In the latter case, it + * is acceptable to move the object they refer to, and to update + * the pointer. + * + * GC_free may not be invoked on objects allocated with GC_copying_malloc. + * + * No extra space is added to the end of objects allocated through this + * interface. If the client needs to maintain pointers past the + * end, the size should be explicitly padded. + * + * We assume that calls to this will usually be compiler generated. + * Hence the interface is allowed to be a bit ugly in return for speed. + */ + +#include "gc_copy_descr.h" + +/* GC_copy_descr.h must define */ +/* GC_SIZE_FROM_DESCRIPTOR(descr) and */ +/* GC_BIT_MAP_FROM_DESCRIPTOR(descr). */ +/* It may either be the GC supplied version of the header file, or a */ +/* client specific one that derives the information from a client- */ +/* specific type descriptor. */ + +typedef GC_PTR GC_copy_alloc_state; + /* Current allocator state. */ + /* Multiple allocation states */ + /* may be used for concurrent */ + /* allocation, or to enhance */ + /* locality. */ + /* Should be treated as opaque. */ + +/* Allocate a memory block of size given in the descriptor, and with */ +/* pointer layout given by the descriptor. The resulting block may not */ +/* be cleared, and should immediately be initialized by the client. */ +/* (A concurrent GC may see an uninitialized pointer field. If it */ +/* points outside the nursery, that's fine. If it points inside, it */ +/* may retain an object, and be relocated. But that's also fine, since */ +/* the new value will be immediately overwritten. */ +/* This variant acquires the allocation lock, and uses a default */ +/* global allocation state. */ +GC_PTR GC_copying_malloc(GC_copy_descriptor); + +/* A variant of the above that does no locking on the fast path, */ +/* and passes an explicit pointer to an allocation state. */ +/* The allocation state is updated. */ +/* There will eventually need to be a macro or inline function version */ +/* of this. */ +GC_PTR GC_copying_malloc2(GC_copy_descriptor, GC_copy_alloc_state *); + +/* Initialize an allocation state so that it can be used for */ +/* allocation. This implicitly reserves a small section of the */ +/* nursery for use with this allocator. */ +void GC_init_copy_alloc_state(GC_copy_alloc_state *); |