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https://github.com/ioacademy-jikim/debugging
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140 lines
6.5 KiB
C
140 lines
6.5 KiB
C
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/*--------------------------------------------------------------------*/
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/*--- A pool (memory) allocator that avoids duplicated copies. ---*/
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/*--- pub_tool_deduppoolalloc.h ---*/
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/*--------------------------------------------------------------------*/
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/*
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This file is part of Valgrind, a dynamic binary instrumentation
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framework.
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Copyright (C) 2014-2015 Philippe Waroquiers philippe.waroquiers@skynet.be
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307, USA.
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The GNU General Public License is contained in the file COPYING.
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*/
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#ifndef __PUB_TOOL_DEDUPPOOLALLOC_H
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#define __PUB_TOOL_DEDUPPOOLALLOC_H
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#include "pub_tool_basics.h" // UWord
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//-----------------------------------------------------------------------------
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// PURPOSE: Provides a pool allocator for elements, storing only once identical
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// elements. In other words, this can be considered a "dictionary" of elements.
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//
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// This pool allocator manages elements allocation by allocating "pools" of
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// many elements from a lower level allocator (typically pub_tool_mallocfree.h).
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// Single elements are allocated from these pools.
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// Currently, elements can only be allocated, elements cannot be freed
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// individually.
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// Once allocated, an element must not be modified anymore.
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//
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// Elements can be inserted in the pool using VG_(allocEltDedupPA)
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// or using VG_(allocFixedEltDedupPA).
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//
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// Use VG_(allocFixedEltDedupPA) to allocate elements that are all of
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// the same size and that you want to identify with a (small) number:
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// VG_(allocFixedEltDedupPA) will assign a sequence number to each
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// unique allocated element. This unique number can be translated to
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// an address when the element data must be used.
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// The idea is that such small numbers can be used as reference instead
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// of the element address, to spare memory.
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// Elements are numbered starting from 1. The nr 0 can thus be used
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// as 'null element'. The address identified by a nr can change
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// if new elements are inserted in the pool. Once the pool is frozen,
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// an element address does not change.
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//
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// Use VG_(allocEltDedupPA) for variable size elements or when the
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// memory needed to store the element reference is not critical or
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// when performance to access elements is critical.
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// The address of an element allocated with VG_(allocEltDedupPA) does
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// not change, even if new elements are inserted in the pool.
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//
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// In the same pool, you can only use one of the allocate element functions.
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//
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// A dedup pool allocator has significantly less memory overhead than
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// calling directly pub_tool_mallocfree.h if the deduplication factor
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// is big. However, allocating an element incurs a cost for searching
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// if an identical element is already in the pool.
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//
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// Note: the elements of the pool cannot be freed (at least currently).
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// The only way to free the elements is to delete the dedup pool allocator.
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//--------------------------------------------------------------------
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typedef struct _DedupPoolAlloc DedupPoolAlloc;
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/* Create new DedupPoolAlloc, using given allocation and free function.
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alloc_fn must not return NULL (that is, if it returns it must have
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succeeded.)
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poolSzB is the (minimum) size in bytes of the pool of elements allocated
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with alloc.
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eltAlign is the minimum required alignement for the elements allocated
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from the DedupPoolAlloc.
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This function never returns NULL. */
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extern DedupPoolAlloc* VG_(newDedupPA) ( SizeT poolSzB,
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SizeT eltAlign,
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void* (*alloc)(const HChar*, SizeT),
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const HChar* cc,
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void (*free_fn)(void*) );
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/* Allocates a new element from ddpa with eltSzB bytes to store elt.
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This function never returns NULL.
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If ddpa already contains an element equal to elt, then the address of
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the already existing element is returned.
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Equality between elements is done by comparing all bytes.
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So, if void *elt points to a struct, be sure to initialise all components
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and the holes between components. */
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extern const void* VG_(allocEltDedupPA) (DedupPoolAlloc *ddpa,
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SizeT eltSzB, const void *elt);
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/* Allocates a new (fixed size) element from ddpa. Returns the
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unique number identifying this element. This function never returns NULL.
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Similarly to VG_(allocEltDedupPA), this will return the unique number
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of an already existing identical element to elt. */
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extern UInt VG_(allocFixedEltDedupPA) (DedupPoolAlloc *ddpa,
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SizeT eltSzB, const void *elt);
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/* Translate an element number to its address. Note that the address
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corresponding to eltNr can change if new elements are inserted
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in the pool. */
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extern void* VG_(indexEltNumber) (DedupPoolAlloc *ddpa,
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UInt eltNr);
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/* The Dedup Pool Allocator must maintain a data structure to avoid
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duplicates as long as new elements can be allocated from the pool.
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Once no new elements will be allocated, this dedup data structure
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can be released using VG_(freezeDedupPA). Once ddpa has been frozen,
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it is an error to call VG_(allocEltDedupPA) or VG_(allocFixedEltDedupPA).
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If shrink_block is not NULL, the last pool will be shrunk using
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shrink_block. */
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extern void VG_(freezeDedupPA) (DedupPoolAlloc *ddpa,
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void (*shrink_block)(void*, SizeT));
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/* How many (unique) elements are there in this ddpa now? */
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extern UInt VG_(sizeDedupPA) (DedupPoolAlloc *ddpa);
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/* Free all memory associated with a DedupPoolAlloc. */
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extern void VG_(deleteDedupPA) ( DedupPoolAlloc *ddpa);
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#endif // __PUB_TOOL_DEDUPPOOLALLOC_
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/*--------------------------------------------------------------------*/
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/*--- end pub_tool_deduppoolalloc.h ---*/
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/*--------------------------------------------------------------------*/
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