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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 <memory>
     21 #include <utility>
     22 
     23 #include <base/logging.h>
     24 #include <brillo/secure_blob.h>
     25 
     26 #include "update_engine/common/utils.h"
     27 #include "update_engine/payload_consumer/file_descriptor.h"
     28 #include "update_engine/update_metadata.pb.h"
     29 
     30 // ExtentWriter is an abstract class which synchronously writes to a given
     31 // file descriptor at the extents given.
     32 
     33 namespace chromeos_update_engine {
     34 
     35 class ExtentWriter {
     36  public:
     37   ExtentWriter() = default;
     38   virtual ~ExtentWriter() {
     39     LOG_IF(ERROR, !end_called_) << "End() not called on ExtentWriter.";
     40   }
     41 
     42   // Returns true on success.
     43   virtual bool Init(FileDescriptorPtr fd,
     44                     const google::protobuf::RepeatedPtrField<Extent>& extents,
     45                     uint32_t block_size) = 0;
     46 
     47   // Returns true on success.
     48   virtual bool Write(const void* bytes, size_t count) = 0;
     49 
     50   // Should be called when all writing is complete. Returns true on success.
     51   // The fd is not closed. Caller is responsible for closing it.
     52   bool End() {
     53     end_called_ = true;
     54     return EndImpl();
     55   }
     56   virtual bool EndImpl() = 0;
     57  private:
     58   bool end_called_{false};
     59 };
     60 
     61 // DirectExtentWriter is probably the simplest ExtentWriter implementation.
     62 // It writes the data directly into the extents.
     63 
     64 class DirectExtentWriter : public ExtentWriter {
     65  public:
     66   DirectExtentWriter() = default;
     67   ~DirectExtentWriter() override = default;
     68 
     69   bool Init(FileDescriptorPtr fd,
     70             const google::protobuf::RepeatedPtrField<Extent>& extents,
     71             uint32_t block_size) override {
     72     fd_ = fd;
     73     block_size_ = block_size;
     74     extents_ = extents;
     75     cur_extent_ = extents_.begin();
     76     return true;
     77   }
     78   bool Write(const void* bytes, size_t count) override;
     79   bool EndImpl() override { return true; }
     80 
     81  private:
     82   FileDescriptorPtr fd_{nullptr};
     83 
     84   size_t block_size_{0};
     85   // Bytes written into |cur_extent_| thus far.
     86   uint64_t extent_bytes_written_{0};
     87   google::protobuf::RepeatedPtrField<Extent> extents_;
     88   // The next call to write should correspond to |cur_extents_|.
     89   google::protobuf::RepeatedPtrField<Extent>::iterator cur_extent_;
     90 };
     91 
     92 // Takes an underlying ExtentWriter to which all operations are delegated.
     93 // When End() is called, ZeroPadExtentWriter ensures that the total number
     94 // of bytes written is a multiple of block_size_. If not, it writes zeros
     95 // to pad as needed.
     96 
     97 class ZeroPadExtentWriter : public ExtentWriter {
     98  public:
     99   explicit ZeroPadExtentWriter(
    100       std::unique_ptr<ExtentWriter> underlying_extent_writer)
    101       : underlying_extent_writer_(std::move(underlying_extent_writer)) {}
    102   ~ZeroPadExtentWriter() override = default;
    103 
    104   bool Init(FileDescriptorPtr fd,
    105             const google::protobuf::RepeatedPtrField<Extent>& extents,
    106             uint32_t block_size) override {
    107     block_size_ = block_size;
    108     return underlying_extent_writer_->Init(fd, extents, block_size);
    109   }
    110   bool Write(const void* bytes, size_t count) override {
    111     if (underlying_extent_writer_->Write(bytes, count)) {
    112       bytes_written_mod_block_size_ += count;
    113       bytes_written_mod_block_size_ %= block_size_;
    114       return true;
    115     }
    116     return false;
    117   }
    118   bool EndImpl() override {
    119     if (bytes_written_mod_block_size_) {
    120       const size_t write_size = block_size_ - bytes_written_mod_block_size_;
    121       brillo::Blob zeros(write_size, 0);
    122       TEST_AND_RETURN_FALSE(underlying_extent_writer_->Write(zeros.data(),
    123                                                              write_size));
    124     }
    125     return underlying_extent_writer_->End();
    126   }
    127 
    128  private:
    129   std::unique_ptr<ExtentWriter> underlying_extent_writer_;
    130   size_t block_size_{0};
    131   size_t bytes_written_mod_block_size_{0};
    132 };
    133 
    134 }  // namespace chromeos_update_engine
    135 
    136 #endif  // UPDATE_ENGINE_PAYLOAD_CONSUMER_EXTENT_WRITER_H_
    137