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      1 //
      2 // Copyright (C) 2009 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 UPDATE_ENGINE_PAYLOAD_CONSUMER_EXTENT_WRITER_H_
     18 #define UPDATE_ENGINE_PAYLOAD_CONSUMER_EXTENT_WRITER_H_
     19 
     20 #include <vector>
     21 
     22 #include <base/logging.h>
     23 #include <brillo/secure_blob.h>
     24 
     25 #include "update_engine/common/utils.h"
     26 #include "update_engine/payload_consumer/file_descriptor.h"
     27 #include "update_engine/update_metadata.pb.h"
     28 
     29 // ExtentWriter is an abstract class which synchronously writes to a given
     30 // file descriptor at the extents given.
     31 
     32 namespace chromeos_update_engine {
     33 
     34 class ExtentWriter {
     35  public:
     36   ExtentWriter() = default;
     37   virtual ~ExtentWriter() {
     38     LOG_IF(ERROR, !end_called_) << "End() not called on ExtentWriter.";
     39   }
     40 
     41   // Returns true on success.
     42   virtual bool Init(FileDescriptorPtr fd,
     43                     const std::vector<Extent>& extents,
     44                     uint32_t block_size) = 0;
     45 
     46   // Returns true on success.
     47   virtual bool Write(const void* bytes, size_t count) = 0;
     48 
     49   // Should be called when all writing is complete. Returns true on success.
     50   // The fd is not closed. Caller is responsible for closing it.
     51   bool End() {
     52     end_called_ = true;
     53     return EndImpl();
     54   }
     55   virtual bool EndImpl() = 0;
     56  private:
     57   bool end_called_{false};
     58 };
     59 
     60 // DirectExtentWriter is probably the simplest ExtentWriter implementation.
     61 // It writes the data directly into the extents.
     62 
     63 class DirectExtentWriter : public ExtentWriter {
     64  public:
     65   DirectExtentWriter() = default;
     66   ~DirectExtentWriter() override = default;
     67 
     68   bool Init(FileDescriptorPtr fd,
     69             const std::vector<Extent>& extents,
     70             uint32_t block_size) override {
     71     fd_ = fd;
     72     block_size_ = block_size;
     73     extents_ = extents;
     74     return true;
     75   }
     76   bool Write(const void* bytes, size_t count) override;
     77   bool EndImpl() override { return true; }
     78 
     79  private:
     80   FileDescriptorPtr fd_{nullptr};
     81 
     82   size_t block_size_{0};
     83   // Bytes written into next_extent_index_ thus far
     84   uint64_t extent_bytes_written_{0};
     85   std::vector<Extent> extents_;
     86   // The next call to write should correspond to extents_[next_extent_index_]
     87   std::vector<Extent>::size_type next_extent_index_{0};
     88 };
     89 
     90 // Takes an underlying ExtentWriter to which all operations are delegated.
     91 // When End() is called, ZeroPadExtentWriter ensures that the total number
     92 // of bytes written is a multiple of block_size_. If not, it writes zeros
     93 // to pad as needed.
     94 
     95 class ZeroPadExtentWriter : public ExtentWriter {
     96  public:
     97   explicit ZeroPadExtentWriter(
     98       std::unique_ptr<ExtentWriter> underlying_extent_writer)
     99       : underlying_extent_writer_(std::move(underlying_extent_writer)) {}
    100   ~ZeroPadExtentWriter() override = default;
    101 
    102   bool Init(FileDescriptorPtr fd,
    103             const std::vector<Extent>& extents,
    104             uint32_t block_size) override {
    105     block_size_ = block_size;
    106     return underlying_extent_writer_->Init(fd, extents, block_size);
    107   }
    108   bool Write(const void* bytes, size_t count) override {
    109     if (underlying_extent_writer_->Write(bytes, count)) {
    110       bytes_written_mod_block_size_ += count;
    111       bytes_written_mod_block_size_ %= block_size_;
    112       return true;
    113     }
    114     return false;
    115   }
    116   bool EndImpl() override {
    117     if (bytes_written_mod_block_size_) {
    118       const size_t write_size = block_size_ - bytes_written_mod_block_size_;
    119       brillo::Blob zeros(write_size, 0);
    120       TEST_AND_RETURN_FALSE(underlying_extent_writer_->Write(zeros.data(),
    121                                                              write_size));
    122     }
    123     return underlying_extent_writer_->End();
    124   }
    125 
    126  private:
    127   std::unique_ptr<ExtentWriter> underlying_extent_writer_;
    128   size_t block_size_{0};
    129   size_t bytes_written_mod_block_size_{0};
    130 };
    131 
    132 }  // namespace chromeos_update_engine
    133 
    134 #endif  // UPDATE_ENGINE_PAYLOAD_CONSUMER_EXTENT_WRITER_H_
    135