| /* |
| * Copyright (C) 2005 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #define LOG_TAG "sharedbuffer" |
| |
| #include <stdlib.h> |
| #include <string.h> |
| |
| #include <android/log.h> |
| |
| #include "SharedBuffer.h" |
| |
| // --------------------------------------------------------------------------- |
| |
| namespace android { |
| |
| SharedBuffer* SharedBuffer::alloc(size_t size) |
| { |
| // Don't overflow if the combined size of the buffer / header is larger than |
| // size_max. |
| LOG_ALWAYS_FATAL_IF((size >= (SIZE_MAX - sizeof(SharedBuffer))), |
| "Invalid buffer size %zu", size); |
| |
| SharedBuffer* sb = static_cast<SharedBuffer *>(malloc(sizeof(SharedBuffer) + size)); |
| if (sb) { |
| // Should be std::atomic_init(&sb->mRefs, 1); |
| // But that generates a warning with some compilers. |
| // The following is OK on Android-supported platforms. |
| sb->mRefs.store(1, std::memory_order_relaxed); |
| sb->mSize = size; |
| } |
| return sb; |
| } |
| |
| |
| void SharedBuffer::dealloc(const SharedBuffer* released) |
| { |
| free(const_cast<SharedBuffer*>(released)); |
| } |
| |
| SharedBuffer* SharedBuffer::edit() const |
| { |
| if (onlyOwner()) { |
| return const_cast<SharedBuffer*>(this); |
| } |
| SharedBuffer* sb = alloc(mSize); |
| if (sb) { |
| memcpy(sb->data(), data(), size()); |
| release(); |
| } |
| return sb; |
| } |
| |
| SharedBuffer* SharedBuffer::editResize(size_t newSize) const |
| { |
| if (onlyOwner()) { |
| SharedBuffer* buf = const_cast<SharedBuffer*>(this); |
| if (buf->mSize == newSize) return buf; |
| // Don't overflow if the combined size of the new buffer / header is larger than |
| // size_max. |
| LOG_ALWAYS_FATAL_IF((newSize >= (SIZE_MAX - sizeof(SharedBuffer))), |
| "Invalid buffer size %zu", newSize); |
| |
| buf = (SharedBuffer*)realloc(buf, sizeof(SharedBuffer) + newSize); |
| if (buf != NULL) { |
| buf->mSize = newSize; |
| return buf; |
| } |
| } |
| SharedBuffer* sb = alloc(newSize); |
| if (sb) { |
| const size_t mySize = mSize; |
| memcpy(sb->data(), data(), newSize < mySize ? newSize : mySize); |
| release(); |
| } |
| return sb; |
| } |
| |
| SharedBuffer* SharedBuffer::attemptEdit() const |
| { |
| if (onlyOwner()) { |
| return const_cast<SharedBuffer*>(this); |
| } |
| return 0; |
| } |
| |
| SharedBuffer* SharedBuffer::reset(size_t new_size) const |
| { |
| // cheap-o-reset. |
| SharedBuffer* sb = alloc(new_size); |
| if (sb) { |
| release(); |
| } |
| return sb; |
| } |
| |
| void SharedBuffer::acquire() const { |
| mRefs.fetch_add(1, std::memory_order_relaxed); |
| } |
| |
| int32_t SharedBuffer::release(uint32_t flags) const |
| { |
| const bool useDealloc = ((flags & eKeepStorage) == 0); |
| if (onlyOwner()) { |
| // Since we're the only owner, our reference count goes to zero. |
| mRefs.store(0, std::memory_order_relaxed); |
| if (useDealloc) { |
| dealloc(this); |
| } |
| // As the only owner, our previous reference count was 1. |
| return 1; |
| } |
| // There's multiple owners, we need to use an atomic decrement. |
| int32_t prevRefCount = mRefs.fetch_sub(1, std::memory_order_release); |
| if (prevRefCount == 1) { |
| // We're the last reference, we need the acquire fence. |
| atomic_thread_fence(std::memory_order_acquire); |
| if (useDealloc) { |
| dealloc(this); |
| } |
| } |
| return prevRefCount; |
| } |
| |
| |
| }; // namespace android |