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77 lines
3.2 KiB
C
77 lines
3.2 KiB
C
/* sa.h: SPARSE ARRAY INTERFACE
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*
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* $Id$
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* Copyright (c) 2014-2020 Ravenbrook Limited. See end of file for license.
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*
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* A sparse array is an array whose storage is partially mapped from a VM.
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* Each element in the array is its own "mapped" status, and may only
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* be used if it is mapped.
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*
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* The main use of sparse arrays is partially mapped page tables in the
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* VM arena, where they provide a fast lookup from an address within
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* a chunk to a page descriptor, while avoiding mapping memory for
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* page descriptors for unused areas of address space, such as unused
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* zone stripes or gaps between those stripes.
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*/
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#ifndef sa_h
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#define sa_h
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#include "mpmtypes.h"
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typedef struct SparseArrayStruct *SparseArray;
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#define SparseArraySig ((Sig)0x5195BA66) /* SIGnature SParse ARRay */
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typedef struct SparseArrayStruct {
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Sig sig;
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void *base; /* base of array, page aligned */
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Size elementSize; /* size of array elements, <= page size */
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Index length; /* number of elements in the array */
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BT mapped; /* whether elements exist in the array */
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BT pages; /* whether underlying pages are mapped */
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VM vm; /* where pages are mapped from */
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Shift shift; /* SizeLog2(VMPageSize(vm)) TODO: VMShift(vm) */
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} SparseArrayStruct;
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extern void SparseArrayInit(SparseArray sa,
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void *base, Size elementSize, Index length,
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BT mapped, BT pages, VM vm);
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extern void SparseArrayFinish(SparseArray sa);
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extern Bool SparseArrayCheck(SparseArray sa);
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#define SparseArrayIsMapped(sa, i) BTGet((sa)->mapped, i)
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extern Res SparseArrayMap(SparseArray sa, Index baseEI, Index limitEI);
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extern void SparseArrayUnmap(SparseArray sa, Index baseEI, Index limitEI);
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#endif /* sa_h */
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/* C. COPYRIGHT AND LICENSE
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*
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* Copyright (C) 2014-2020 Ravenbrook Limited <https://www.ravenbrook.com/>.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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