127 lines
3.5 KiB
C++
127 lines
3.5 KiB
C++
/*
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* Copyright (C) 2005 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <stdlib.h>
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#include <string.h>
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#include <log/log.h>
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#include "SharedBuffer.h"
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// ---------------------------------------------------------------------------
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namespace android {
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SharedBuffer* SharedBuffer::alloc(size_t size)
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{
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// Don't overflow if the combined size of the buffer / header is larger than
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// size_max.
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LOG_ALWAYS_FATAL_IF((size >= (SIZE_MAX - sizeof(SharedBuffer))),
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"Invalid buffer size %zu", size);
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SharedBuffer* sb = static_cast<SharedBuffer *>(malloc(sizeof(SharedBuffer) + size));
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if (sb) {
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// Should be std::atomic_init(&sb->mRefs, 1);
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// But that generates a warning with some compilers.
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// The following is OK on Android-supported platforms.
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sb->mRefs.store(1, std::memory_order_relaxed);
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sb->mSize = size;
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}
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return sb;
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}
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void SharedBuffer::dealloc(const SharedBuffer* released)
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{
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free(const_cast<SharedBuffer*>(released));
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}
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SharedBuffer* SharedBuffer::edit() const
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{
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if (onlyOwner()) {
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return const_cast<SharedBuffer*>(this);
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}
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SharedBuffer* sb = alloc(mSize);
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if (sb) {
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memcpy(sb->data(), data(), size());
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release();
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}
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return sb;
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}
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SharedBuffer* SharedBuffer::editResize(size_t newSize) const
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{
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if (onlyOwner()) {
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SharedBuffer* buf = const_cast<SharedBuffer*>(this);
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if (buf->mSize == newSize) return buf;
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// Don't overflow if the combined size of the new buffer / header is larger than
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// size_max.
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LOG_ALWAYS_FATAL_IF((newSize >= (SIZE_MAX - sizeof(SharedBuffer))),
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"Invalid buffer size %zu", newSize);
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buf = (SharedBuffer*)realloc(buf, sizeof(SharedBuffer) + newSize);
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if (buf != NULL) {
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buf->mSize = newSize;
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return buf;
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}
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}
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SharedBuffer* sb = alloc(newSize);
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if (sb) {
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const size_t mySize = mSize;
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memcpy(sb->data(), data(), newSize < mySize ? newSize : mySize);
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release();
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}
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return sb;
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}
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SharedBuffer* SharedBuffer::attemptEdit() const
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{
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if (onlyOwner()) {
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return const_cast<SharedBuffer*>(this);
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}
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return 0;
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}
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SharedBuffer* SharedBuffer::reset(size_t new_size) const
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{
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// cheap-o-reset.
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SharedBuffer* sb = alloc(new_size);
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if (sb) {
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release();
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}
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return sb;
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}
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void SharedBuffer::acquire() const {
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mRefs.fetch_add(1, std::memory_order_relaxed);
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}
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int32_t SharedBuffer::release(uint32_t flags) const
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{
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int32_t prev = 1;
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if (onlyOwner()
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|| (((prev = mRefs.fetch_sub(1, std::memory_order_release)) == 1)
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&& (atomic_thread_fence(std::memory_order_acquire), true))) {
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mRefs.store(0, std::memory_order_relaxed);
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if ((flags & eKeepStorage) == 0) {
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free(const_cast<SharedBuffer*>(this));
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}
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}
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return prev;
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}
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}; // namespace android
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