1 /*
2 * Copyright (C) 2005 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <stdlib.h>
18 #include <string.h>
19
20 #include <log/log.h>
21
22 #include "SharedBuffer.h"
23
24 // ---------------------------------------------------------------------------
25
26 namespace android {
27
alloc(size_t size)28 SharedBuffer* SharedBuffer::alloc(size_t size)
29 {
30 // Don't overflow if the combined size of the buffer / header is larger than
31 // size_max.
32 LOG_ALWAYS_FATAL_IF((size >= (SIZE_MAX - sizeof(SharedBuffer))),
33 "Invalid buffer size %zu", size);
34
35 SharedBuffer* sb = static_cast<SharedBuffer *>(malloc(sizeof(SharedBuffer) + size));
36 if (sb) {
37 // Should be std::atomic_init(&sb->mRefs, 1);
38 // But that generates a warning with some compilers.
39 // The following is OK on Android-supported platforms.
40 sb->mRefs.store(1, std::memory_order_relaxed);
41 sb->mSize = size;
42 }
43 return sb;
44 }
45
46
dealloc(const SharedBuffer * released)47 void SharedBuffer::dealloc(const SharedBuffer* released)
48 {
49 free(const_cast<SharedBuffer*>(released));
50 }
51
edit() const52 SharedBuffer* SharedBuffer::edit() const
53 {
54 if (onlyOwner()) {
55 return const_cast<SharedBuffer*>(this);
56 }
57 SharedBuffer* sb = alloc(mSize);
58 if (sb) {
59 memcpy(sb->data(), data(), size());
60 release();
61 }
62 return sb;
63 }
64
editResize(size_t newSize) const65 SharedBuffer* SharedBuffer::editResize(size_t newSize) const
66 {
67 if (onlyOwner()) {
68 SharedBuffer* buf = const_cast<SharedBuffer*>(this);
69 if (buf->mSize == newSize) return buf;
70 // Don't overflow if the combined size of the new buffer / header is larger than
71 // size_max.
72 LOG_ALWAYS_FATAL_IF((newSize >= (SIZE_MAX - sizeof(SharedBuffer))),
73 "Invalid buffer size %zu", newSize);
74
75 buf = (SharedBuffer*)realloc(buf, sizeof(SharedBuffer) + newSize);
76 if (buf != NULL) {
77 buf->mSize = newSize;
78 return buf;
79 }
80 }
81 SharedBuffer* sb = alloc(newSize);
82 if (sb) {
83 const size_t mySize = mSize;
84 memcpy(sb->data(), data(), newSize < mySize ? newSize : mySize);
85 release();
86 }
87 return sb;
88 }
89
attemptEdit() const90 SharedBuffer* SharedBuffer::attemptEdit() const
91 {
92 if (onlyOwner()) {
93 return const_cast<SharedBuffer*>(this);
94 }
95 return 0;
96 }
97
reset(size_t new_size) const98 SharedBuffer* SharedBuffer::reset(size_t new_size) const
99 {
100 // cheap-o-reset.
101 SharedBuffer* sb = alloc(new_size);
102 if (sb) {
103 release();
104 }
105 return sb;
106 }
107
acquire() const108 void SharedBuffer::acquire() const {
109 mRefs.fetch_add(1, std::memory_order_relaxed);
110 }
111
release(uint32_t flags) const112 int32_t SharedBuffer::release(uint32_t flags) const
113 {
114 int32_t prev = 1;
115 if (onlyOwner() || ((prev = mRefs.fetch_sub(1, std::memory_order_release) == 1)
116 && (atomic_thread_fence(std::memory_order_acquire), true))) {
117 mRefs.store(0, std::memory_order_relaxed);
118 if ((flags & eKeepStorage) == 0) {
119 free(const_cast<SharedBuffer*>(this));
120 }
121 }
122 return prev;
123 }
124
125
126 }; // namespace android
127