1 // Copyright (C) 2021 The Android Open Source Project 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #pragma once 16 17 #include <linux/types.h> 18 #include <stdint.h> 19 #include <stdlib.h> 20 21 #include <iostream> 22 23 #include <libsnapshot/cow_reader.h> 24 25 namespace android { 26 namespace snapshot { 27 28 class BufferSink final { 29 public: 30 // Do not reserve any space of header by default Initialize(size_t size)31 void Initialize(size_t size) { return Initialize(0, size); }; 32 // This allows to set const header_size_ to be used if caller needs it 33 // for example, while working with dm_user 34 void Initialize(size_t header_size, size_t size); GetBufPtr()35 void* GetBufPtr() { return buffer_.get(); } Clear()36 void Clear() { memset(GetBufPtr(), 0, buffer_size_); } 37 void* GetPayloadBuffer(size_t size); 38 void* GetBuffer(size_t requested, size_t* actual); UpdateBufferOffset(size_t size)39 void UpdateBufferOffset(size_t size) { buffer_offset_ += size; } 40 void* GetHeaderPtr(); ResetBufferOffset()41 void ResetBufferOffset() { buffer_offset_ = 0; } 42 void* GetPayloadBufPtr(); GetPayloadBytesWritten()43 loff_t GetPayloadBytesWritten() { return buffer_offset_; } 44 45 // Same as calling GetPayloadBuffer and then UpdateBufferOffset. 46 // 47 // This is preferred over GetPayloadBuffer as it does not require a 48 // separate call to UpdateBufferOffset. AcquireBuffer(size_t size)49 void* AcquireBuffer(size_t size) { return AcquireBuffer(size, size); } 50 51 // Same as AcquireBuffer, but separates the requested size from the buffer 52 // offset. This is useful for a situation where a full run of data will be 53 // read, but only a partial amount will be returned. 54 // 55 // If size != to_write, the excess bytes may be reallocated by the next 56 // call to AcquireBuffer. 57 void* AcquireBuffer(size_t size, size_t to_write); 58 59 private: 60 std::unique_ptr<uint8_t[]> buffer_; 61 loff_t buffer_offset_; 62 size_t buffer_size_; 63 size_t header_size_; 64 }; 65 66 } // namespace snapshot 67 } // namespace android 68