Arena.h   [plain text]

 * Copyright (C) 1998-2000 Netscape Communications Corporation.
 * Copyright (C) 2003-6 Apple Computer
 * Copyright (C) Research In Motion Limited 2010. All rights reserved.
 * Other contributors:
 *   Nick Blievers <>
 *   Jeff Hostetler <>
 *   Tom Rini <>
 *   Raffaele Sena <>
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * Lesser General Public License for more details.
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 * Alternatively, the contents of this file may be used under the terms
 * of either the Mozilla Public License Version 1.1, found at
 * (the "MPL") or the GNU General Public
 * License Version 2.0, found at
 * (the "GPL"), in which case the provisions of the MPL or the GPL are
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#ifndef Arena_h
#define Arena_h

// FIXME: We'd always like to use AllocAlignmentInteger for Arena alignment
// but there is concern over the memory growth this may cause.
#define ARENA_ALIGN_MASK (sizeof(WTF::AllocAlignmentInteger) - 1)

namespace WebCore {

typedef uintptr_t uword;

struct Arena {
    Arena* next;        // next arena
    uword base;         // aligned base address
    uword limit;        // end of arena (1+last byte)
    uword avail;        // points to next available byte in arena

struct ArenaPool {
    Arena first;        // first arena in pool list.
    Arena* current;     // current arena.
    unsigned int arenasize;
    uword mask;         // Mask (power-of-2 - 1)

void InitArenaPool(ArenaPool*, const char* name, unsigned int size, unsigned int align);
void FinishArenaPool(ArenaPool*);
void* ArenaAllocate(ArenaPool*, unsigned int numBytes, unsigned int& bytesAllocated);

#define ARENA_ALIGN(n) (((uword)(n) + ARENA_ALIGN_MASK) & ~ARENA_ALIGN_MASK)
#define INIT_ARENA_POOL(pool, name, size) InitArenaPool(pool, name, size, ARENA_ALIGN_MASK + 1)
#define ARENA_ALLOCATE(p, pool, nb, bytesAllocated) \
    Arena* _a = (pool)->current; \
    unsigned int _nb = ARENA_ALIGN(nb); \
    uword _p = _a->avail; \
    uword _q = _p + _nb; \
    if (_q > _a->limit) \
        _p = (uword)ArenaAllocate(pool, _nb, *bytesAllocated); \
    else \
        _a->avail = _q; \
    p = (void*)_p;