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source: vbox/trunk/src/libs/xpcom18a4/xpcom/ds/nsFixedSizeAllocator.cpp@ 62375

Last change on this file since 62375 was 1, checked in by vboxsync, 55 years ago

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1/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
2/* ***** BEGIN LICENSE BLOCK *****
3 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
4 *
5 * The contents of this file are subject to the Mozilla Public License Version
6 * 1.1 (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 * http://www.mozilla.org/MPL/
9 *
10 * Software distributed under the License is distributed on an "AS IS" basis,
11 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
12 * for the specific language governing rights and limitations under the
13 * License.
14 *
15 * The Original Code is mozilla.org code.
16 *
17 * The Initial Developer of the Original Code is
18 * Netscape Communications Corporation.
19 * Portions created by the Initial Developer are Copyright (C) 1998
20 * the Initial Developer. All Rights Reserved.
21 *
22 * Contributor(s):
23 * Chris Waterson <[email protected]
24 *
25 * Alternatively, the contents of this file may be used under the terms of
26 * either of the GNU General Public License Version 2 or later (the "GPL"),
27 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
28 * in which case the provisions of the GPL or the LGPL are applicable instead
29 * of those above. If you wish to allow use of your version of this file only
30 * under the terms of either the GPL or the LGPL, and not to allow others to
31 * use your version of this file under the terms of the MPL, indicate your
32 * decision by deleting the provisions above and replace them with the notice
33 * and other provisions required by the GPL or the LGPL. If you do not delete
34 * the provisions above, a recipient may use your version of this file under
35 * the terms of any one of the MPL, the GPL or the LGPL.
36 *
37 * ***** END LICENSE BLOCK ***** */
38
39/*
40
41 Implementation for nsFixedSizeAllocator
42
43*/
44
45#include "nsCRT.h"
46#include "nsFixedSizeAllocator.h"
47
48nsFixedSizeAllocator::Bucket *
49nsFixedSizeAllocator::AddBucket(size_t aSize)
50{
51 void* p;
52 PL_ARENA_ALLOCATE(p, &mPool, sizeof(Bucket));
53 if (! p)
54 return nsnull;
55
56 Bucket* bucket = NS_STATIC_CAST(Bucket*, p);
57 bucket->mSize = aSize;
58 bucket->mFirst = nsnull;
59 bucket->mNext = mBuckets;
60
61 mBuckets = bucket;
62 return bucket;
63}
64
65nsresult
66nsFixedSizeAllocator::Init(const char* aName,
67 const size_t* aBucketSizes,
68 PRInt32 aNumBuckets,
69 PRInt32 aInitialSize,
70 PRInt32 aAlign)
71{
72 NS_PRECONDITION(aNumBuckets > 0, "no buckets");
73 if (aNumBuckets <= 0)
74 return NS_ERROR_INVALID_ARG;
75
76 // Blow away the old pool if we're being re-initialized.
77 if (mBuckets)
78 PL_FinishArenaPool(&mPool);
79
80 PRInt32 bucketspace = aNumBuckets * sizeof(Bucket);
81 PL_InitArenaPool(&mPool, aName, bucketspace + aInitialSize, aAlign);
82
83 mBuckets = nsnull;
84 for (PRInt32 i = 0; i < aNumBuckets; ++i)
85 AddBucket(aBucketSizes[i]);
86
87 return NS_OK;
88}
89
90nsFixedSizeAllocator::Bucket *
91nsFixedSizeAllocator::FindBucket(size_t aSize)
92{
93 Bucket** link = &mBuckets;
94 Bucket* bucket;
95
96 while ((bucket = *link) != nsnull) {
97 if (aSize == bucket->mSize) {
98 // Promote to the head of the list, under the assumption
99 // that we'll allocate same-sized object contemporaneously.
100 *link = bucket->mNext;
101 bucket->mNext = mBuckets;
102 mBuckets = bucket;
103 return bucket;
104 }
105
106 link = &bucket->mNext;
107 }
108 return nsnull;
109}
110
111void*
112nsFixedSizeAllocator::Alloc(size_t aSize)
113{
114 Bucket* bucket = FindBucket(aSize);
115 if (! bucket) {
116 // Oops, we don't carry that size. Let's fix that.
117 bucket = AddBucket(aSize);
118 if (! bucket)
119 return nsnull;
120 }
121
122 void* next;
123 if (bucket->mFirst) {
124 next = bucket->mFirst;
125 bucket->mFirst = bucket->mFirst->mNext;
126 }
127 else {
128 PL_ARENA_ALLOCATE(next, &mPool, aSize);
129 if (!next)
130 return nsnull;
131 }
132
133#ifdef DEBUG
134 memset(next, 0xc8, aSize);
135#endif
136
137 return next;
138}
139
140void
141nsFixedSizeAllocator::Free(void* aPtr, size_t aSize)
142{
143 FreeEntry* entry = NS_REINTERPRET_CAST(FreeEntry*, aPtr);
144 Bucket* bucket = FindBucket(aSize);
145
146#ifdef DEBUG
147 NS_ASSERTION(bucket && bucket->mSize == aSize, "ack! corruption! bucket->mSize != aSize!");
148 memset(aPtr, 0xd8, bucket->mSize);
149#endif
150
151 entry->mNext = bucket->mFirst;
152 bucket->mFirst = entry;
153}
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