1 /*
2  * Copyright (C) 2019 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 #pragma once
18 
19 #include <stdint.h>
20 
21 #include <string>
22 
23 #include <android-base/unique_fd.h>
24 
25 // This is the base class to read data from source and provide the data to FUSE.
26 class FuseDataProvider {
27  public:
FuseDataProvider(uint64_t file_size,uint32_t block_size)28   FuseDataProvider(uint64_t file_size, uint32_t block_size)
29       : file_size_(file_size), fuse_block_size_(block_size) {}
30 
31   virtual ~FuseDataProvider() = default;
32 
file_size()33   uint64_t file_size() const {
34     return file_size_;
35   }
fuse_block_size()36   uint32_t fuse_block_size() const {
37     return fuse_block_size_;
38   }
39 
40   // Reads |fetch_size| bytes data starting from |start_block|. Puts the result in |buffer|.
41   virtual bool ReadBlockAlignedData(uint8_t* buffer, uint32_t fetch_size,
42                                     uint32_t start_block) const = 0;
43 
Close()44   virtual void Close() {}
45 
46  protected:
47   FuseDataProvider() = default;
48 
49   // Size in bytes of the file to read.
50   uint64_t file_size_ = 0;
51   // Block size passed to the fuse, this is different from the block size of the block device.
52   uint32_t fuse_block_size_ = 0;
53 };
54 
55 // This class reads data from a file.
56 class FuseFileDataProvider : public FuseDataProvider {
57  public:
58   FuseFileDataProvider(const std::string& path, uint32_t block_size);
59 
60   bool ReadBlockAlignedData(uint8_t* buffer, uint32_t fetch_size,
61                             uint32_t start_block) const override;
62 
Valid()63   bool Valid() const {
64     return fd_ != -1;
65   }
66 
67   void Close() override;
68 
69  private:
70   // The underlying source to read data from.
71   android::base::unique_fd fd_;
72 };
73