gecko-dev/xpcom/ds/nsFixedSizeAllocator.cpp

149 строки
3.8 KiB
C++

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* The contents of this file are subject to the Netscape 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/NPL/
*
* 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 Netscape are
* Copyright (C) 1998 Netscape Communications Corporation. All
* Rights Reserved.
*
* Original Author(s):
* Chris Waterson <waterson@netscape.com
*
* Contributor(s):
*/
/*
Implementation for nsFixedSizeAllocator
*/
#include "nsCRT.h"
#include "nsFixedSizeAllocator.h"
nsresult
nsFixedSizeAllocator::AddBucket(size_t aSize)
{
void* p;
PL_ARENA_ALLOCATE(p, &mPool, sizeof(Bucket));
if (! p)
return NS_ERROR_OUT_OF_MEMORY;
Bucket* bucket = NS_STATIC_CAST(Bucket*, p);
bucket->mSize = aSize;
bucket->mFirst = nsnull;
bucket->mNext = mBuckets;
mBuckets = bucket;
return NS_OK;
}
nsresult
nsFixedSizeAllocator::Init(const char* aName,
const size_t* aBucketSizes,
PRInt32 aNumBuckets,
PRInt32 aInitialSize,
PRInt32 aAlign)
{
NS_PRECONDITION(aNumBuckets > 0, "no buckets");
if (aNumBuckets <= 0)
return NS_ERROR_INVALID_ARG;
// Blow away the old pool if we're being re-initialized.
if (mBuckets)
PL_FinishArenaPool(&mPool);
PRInt32 bucketspace = aNumBuckets * sizeof(Bucket);
PL_InitArenaPool(&mPool, aName, bucketspace + aInitialSize, aAlign);
mBuckets = nsnull;
for (PRInt32 i = 0; i < aNumBuckets; ++i)
AddBucket(aBucketSizes[i]);
return NS_OK;
}
void*
nsFixedSizeAllocator::Alloc(size_t aSize)
{
Bucket** link = &mBuckets;
Bucket* bucket = mBuckets;
while (bucket != nsnull) {
if (aSize == bucket->mSize) {
// Promote to the head of the list, under the assumption
// that we'll allocate same-sized object cotemporaneously.
*link = bucket->mNext;
bucket->mNext = mBuckets;
mBuckets = bucket;
break;
}
link = &bucket->mNext;
bucket = bucket->mNext;
}
if (! bucket) {
// Oops, we don't carry that size. Let's fix that.
nsresult rv = AddBucket(aSize);
if (NS_FAILED(rv))
return nsnull;
bucket = mBuckets;
}
void* next;
if (bucket->mFirst) {
next = bucket->mFirst;
bucket->mFirst = bucket->mFirst->mNext;
}
else {
// Allocate headroom so we can have a backpointer. Use
// 'sizeof double' so that the block stays well-aligned
PL_ARENA_ALLOCATE(next, &mPool, aSize + sizeof(double));
FreeEntry* entry = NS_STATIC_CAST(FreeEntry*, next);
entry->mBucket = bucket;
}
next = NS_STATIC_CAST(void*, NS_STATIC_CAST(char*, next) + sizeof(double));
#ifdef DEBUG
nsCRT::memset(next, 0xc8, bucket->mSize);
#endif
return next;
}
void
nsFixedSizeAllocator::Free(void* aPtr, size_t aSize)
{
FreeEntry* entry = NS_REINTERPRET_CAST(FreeEntry*, NS_STATIC_CAST(char*, aPtr) - sizeof(double));
Bucket* bucket = entry->mBucket;
#ifdef DEBUG
NS_ASSERTION(bucket->mSize == aSize, "ack! corruption! bucket->mSize != aSize!");
nsCRT::memset(aPtr, 0xd8, bucket->mSize);
#endif
entry->mNext = bucket->mFirst;
bucket->mFirst = entry;
}