e1731a4f2e
Fixes -Wzero-as-null-pointer-constant warning. Test: m Bug: 68236239 Change-Id: I5e89ec8c42151875439d2656475a8739ab9cb7dc
146 lines
4.5 KiB
C++
146 lines
4.5 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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/*
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* DEPRECATED. DO NOT USE FOR NEW CODE.
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*/
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#ifndef ANDROID_SHARED_BUFFER_H
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#define ANDROID_SHARED_BUFFER_H
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#include <atomic>
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#include <stdint.h>
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#include <sys/types.h>
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// ---------------------------------------------------------------------------
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namespace android {
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class SharedBuffer
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{
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public:
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/* flags to use with release() */
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enum {
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eKeepStorage = 0x00000001
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};
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/*! allocate a buffer of size 'size' and acquire() it.
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* call release() to free it.
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*/
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static SharedBuffer* alloc(size_t size);
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/*! free the memory associated with the SharedBuffer.
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* Fails if there are any users associated with this SharedBuffer.
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* In other words, the buffer must have been release by all its
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* users.
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*/
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static void dealloc(const SharedBuffer* released);
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//! access the data for read
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inline const void* data() const;
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//! access the data for read/write
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inline void* data();
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//! get size of the buffer
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inline size_t size() const;
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//! get back a SharedBuffer object from its data
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static inline SharedBuffer* bufferFromData(void* data);
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//! get back a SharedBuffer object from its data
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static inline const SharedBuffer* bufferFromData(const void* data);
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//! get the size of a SharedBuffer object from its data
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static inline size_t sizeFromData(const void* data);
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//! edit the buffer (get a writtable, or non-const, version of it)
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SharedBuffer* edit() const;
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//! edit the buffer, resizing if needed
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SharedBuffer* editResize(size_t size) const;
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//! like edit() but fails if a copy is required
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SharedBuffer* attemptEdit() const;
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//! resize and edit the buffer, loose it's content.
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SharedBuffer* reset(size_t size) const;
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//! acquire/release a reference on this buffer
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void acquire() const;
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/*! release a reference on this buffer, with the option of not
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* freeing the memory associated with it if it was the last reference
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* returns the previous reference count
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*/
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int32_t release(uint32_t flags = 0) const;
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//! returns wether or not we're the only owner
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inline bool onlyOwner() const;
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private:
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inline SharedBuffer() { }
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inline ~SharedBuffer() { }
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SharedBuffer(const SharedBuffer&);
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SharedBuffer& operator = (const SharedBuffer&);
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// Must be sized to preserve correct alignment.
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mutable std::atomic<int32_t> mRefs;
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size_t mSize;
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uint32_t mReserved[2];
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};
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static_assert(sizeof(SharedBuffer) % 8 == 0
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&& (sizeof(size_t) > 4 || sizeof(SharedBuffer) == 16),
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"SharedBuffer has unexpected size");
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// ---------------------------------------------------------------------------
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const void* SharedBuffer::data() const {
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return this + 1;
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}
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void* SharedBuffer::data() {
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return this + 1;
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}
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size_t SharedBuffer::size() const {
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return mSize;
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}
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SharedBuffer* SharedBuffer::bufferFromData(void* data) {
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return data ? static_cast<SharedBuffer *>(data)-1 : nullptr;
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}
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const SharedBuffer* SharedBuffer::bufferFromData(const void* data) {
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return data ? static_cast<const SharedBuffer *>(data)-1 : nullptr;
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}
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size_t SharedBuffer::sizeFromData(const void* data) {
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return data ? bufferFromData(data)->mSize : 0;
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}
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bool SharedBuffer::onlyOwner() const {
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return (mRefs.load(std::memory_order_acquire) == 1);
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}
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} // namespace android
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// ---------------------------------------------------------------------------
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#endif // ANDROID_VECTOR_H
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