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      1 /*
      2  * Copyright (C) 2018 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 #ifndef ANDROID_BUFFER_HUB_METADATA_H_
     18 #define ANDROID_BUFFER_HUB_METADATA_H_
     19 
     20 #include <android-base/unique_fd.h>
     21 #include <ui/BufferHubDefs.h>
     22 
     23 namespace android {
     24 
     25 namespace {
     26 using base::unique_fd;
     27 } // namespace
     28 
     29 class BufferHubMetadata {
     30 public:
     31     // Creates a new BufferHubMetadata backed by an ashmem region.
     32     //
     33     // @param userMetadataSize Size in bytes of the user defined metadata. The entire metadata
     34     //        shared memory region to be allocated is the size of canonical
     35     //        BufferHubDefs::MetadataHeader plus userMetadataSize.
     36     static BufferHubMetadata create(size_t userMetadataSize);
     37 
     38     // Imports an existing BufferHubMetadata from an ashmem FD.
     39     //
     40     // @param ashmemFd Ashmem file descriptor representing an ashmem region.
     41     static BufferHubMetadata import(unique_fd ashmemFd);
     42 
     43     BufferHubMetadata() = default;
     44 
     45     BufferHubMetadata(BufferHubMetadata&& other) { *this = std::move(other); }
     46 
     47     ~BufferHubMetadata();
     48 
     49     BufferHubMetadata& operator=(BufferHubMetadata&& other) {
     50         if (this != &other) {
     51             mUserMetadataSize = other.mUserMetadataSize;
     52             other.mUserMetadataSize = 0;
     53 
     54             mAshmemFd = std::move(other.mAshmemFd);
     55 
     56             // The old raw mMetadataHeader pointer must be cleared, otherwise the destructor will
     57             // automatically mummap() the shared memory.
     58             mMetadataHeader = other.mMetadataHeader;
     59             other.mMetadataHeader = nullptr;
     60         }
     61         return *this;
     62     }
     63 
     64     // Returns true if the metadata is valid, i.e. the metadata has a valid ashmem fd and the ashmem
     65     // has been mapped into virtual address space.
     66     bool isValid() const { return mAshmemFd.get() != -1 && mMetadataHeader != nullptr; }
     67 
     68     size_t userMetadataSize() const { return mUserMetadataSize; }
     69     size_t metadataSize() const { return mUserMetadataSize + BufferHubDefs::kMetadataHeaderSize; }
     70 
     71     const unique_fd& ashmemFd() const { return mAshmemFd; }
     72     BufferHubDefs::MetadataHeader* metadataHeader() { return mMetadataHeader; }
     73 
     74 private:
     75     BufferHubMetadata(size_t userMetadataSize, unique_fd ashmemFd,
     76                       BufferHubDefs::MetadataHeader* metadataHeader);
     77 
     78     BufferHubMetadata(const BufferHubMetadata&) = delete;
     79     void operator=(const BufferHubMetadata&) = delete;
     80 
     81     size_t mUserMetadataSize = 0;
     82     unique_fd mAshmemFd;
     83     BufferHubDefs::MetadataHeader* mMetadataHeader = nullptr;
     84 };
     85 
     86 } // namespace android
     87 
     88 #endif // ANDROID_BUFFER_HUB_METADATA_H_
     89