gecko/layout/base/nsPresArena.cpp

198 lines
5.5 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=2 sw=2 et tw=78:
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 1998
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Steve Clark <buster@netscape.com>
* HÃ¥kan Waara <hwaara@chello.se>
* Dan Rosen <dr@netscape.com>
* Daniel Glazman <glazman@netscape.com>
* Mats Palmgren <mats.palmgren@bredband.net>
*
* Alternatively, the contents of this file may be used under the terms of
* either of the GNU General Public License Version 2 or later (the "GPL"),
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK *****
*/
/* arena allocation for the frame tree and closely-related objects */
#include "nsPresArena.h"
#include "nsCRT.h"
#include "nsDebug.h"
#include "prmem.h"
// Uncomment this to disable arenas, instead forwarding to
// malloc for every allocation.
//#define DEBUG_TRACEMALLOC_PRESARENA 1
#ifndef DEBUG_TRACEMALLOC_PRESARENA
// Even on 32-bit systems, we allocate objects from the frame arena
// that require 8-byte alignment. The cast to PRUword is needed
// because plarena isn't as careful about mask construction as it
// ought to be.
#define ALIGN_SHIFT 3
#define PL_ARENA_CONST_ALIGN_MASK ((PRUword(1) << ALIGN_SHIFT) - 1)
#include "plarena.h"
// Largest chunk size we recycle
static const size_t MAX_RECYCLED_SIZE = 400;
// Recycler array entry N (0 <= N < NUM_RECYCLERS) holds chunks of
// size (N+1) << ALIGN_SHIFT, thus we need this many array entries.
static const size_t NUM_RECYCLERS = MAX_RECYCLED_SIZE >> ALIGN_SHIFT;
// Size to use for PLArena block allocations.
static const size_t ARENA_PAGE_SIZE = 4096;
struct nsPresArena::State {
void* mRecyclers[NUM_RECYCLERS];
PLArenaPool mPool;
State()
{
PL_INIT_ARENA_POOL(&mPool, "PresArena", ARENA_PAGE_SIZE);
memset(mRecyclers, 0, sizeof(mRecyclers));
}
~State()
{
PL_FinishArenaPool(&mPool);
}
void* Allocate(size_t aSize)
{
void* result = nsnull;
// Recycler lists are indexed by aligned size
aSize = PL_ARENA_ALIGN(&mPool, aSize);
// Check recyclers first
if (aSize <= MAX_RECYCLED_SIZE) {
const size_t index = (aSize >> ALIGN_SHIFT) - 1;
result = mRecyclers[index];
if (result) {
// Need to move to the next object
void* next = *((void**)result);
mRecyclers[index] = next;
}
}
if (!result) {
// Allocate a new chunk from the arena
PL_ARENA_ALLOCATE(result, &mPool, aSize);
}
return result;
}
void Free(size_t aSize, void* aPtr)
{
// Recycler lists are indexed by aligned size
aSize = PL_ARENA_ALIGN(&mPool, aSize);
// See if it's a size that we recycle
if (aSize <= MAX_RECYCLED_SIZE) {
const size_t index = (aSize >> ALIGN_SHIFT) - 1;
void* currentTop = mRecyclers[index];
mRecyclers[index] = aPtr;
*((void**)aPtr) = currentTop;
}
#if defined DEBUG_dbaron || defined DEBUG_zack
else {
fprintf(stderr,
"WARNING: nsPresArena::FreeFrame leaking chunk of %lu bytes.\n",
aSize);
}
#endif
}
};
#else
// Stub implementation that just forwards everything to malloc.
struct nsPresArena::State
{
void* Allocate(size_t aSize)
{
return PR_Malloc(aSize);
}
void Free(size_t /*unused*/, void* aPtr)
{
PR_Free(aPtr);
}
};
#endif // DEBUG_TRACEMALLOC_PRESARENA
// Public interface
nsPresArena::nsPresArena()
: mState(new nsPresArena::State())
#ifdef DEBUG
, mAllocCount(0)
#endif
{}
nsPresArena::~nsPresArena()
{
#ifdef DEBUG
NS_ASSERTION(mAllocCount == 0,
"Some PresArena objects were not freed");
#endif
delete mState;
}
void*
nsPresArena::Allocate(size_t aSize)
{
NS_ABORT_IF_FALSE(aSize > 0, "PresArena cannot allocate zero bytes");
void* result = mState->Allocate(aSize);
#ifdef DEBUG
if (result)
mAllocCount++;
#endif
return result;
}
void
nsPresArena::Free(size_t aSize, void* aPtr)
{
NS_ABORT_IF_FALSE(aSize > 0, "PresArena cannot free zero bytes");
#ifdef DEBUG
// Mark the memory with 0xdd in DEBUG builds so that there will be
// problems if someone tries to access memory that they've freed.
memset(aPtr, 0xdd, aSize);
mAllocCount--;
#endif
mState->Free(aSize, aPtr);
}