AU: delta compress the kernel partition

src/platform/update_engine/delta_performer.h

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_DELTA_PERFORMER_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_DELTA_PERFORMER_H__
 
 #include <inttypes.h>
 #include <vector>
 #include <google/protobuf/repeated_field.h>
 #include "update_engine/file_writer.h"
 #include "update_engine/update_metadata.pb.h"
 
 namespace chromeos_update_engine {
 
 // This class performs the actions in a delta update synchronously. The delta
 // update itself should be passed in in chunks as it is received.
 
 class DeltaPerformer : public FileWriter {
  public:
   DeltaPerformer()
       : fd_(-1),
+        kernel_fd_(-1),
         manifest_valid_(false),
-        next_operation_(0),
+        next_operation_num_(0),
         buffer_offset_(0),
         block_size_(0) {}
+  
+  // Opens the kernel. Should be called before or after Open(), but before
+  // Write(). The kernel file will be close()d when Close() is called.
+  bool OpenKernel(const char* kernel_path);
+
   // flags and mode ignored. Once Close()d, a DeltaPerformer can't be
   // Open()ed again.
   int Open(const char* path, int flags, mode_t mode);
 
   // Wrapper around write. Returns bytes written on success or
   // -errno on error.
   ssize_t Write(const void* bytes, size_t count);
 
   // Wrapper around close. Returns 0 on success or -errno on error.
+  // Closes both 'path' given to Open() and the kernel path.
   int Close();
   
   // Converts an ordered collection of Extent objects which contain data of
   // length full_length to a comma-separated string. For each Extent, the
   // string will have the start offset and then the length in bytes.
   // The length value of the last extent in the string may be short, since
   // the full length of all extents in the string is capped to full_length.
   // Also, an extent starting at kSparseHole, appears as -1 in the string.
   // For example, if the Extents are {1, 1}, {4, 2}, {kSparseHole, 1},
   // {0, 1}, block_size is 4096, and full_length is 5 * block_size - 13,
   // the resulting string will be: "4096:4096,16384:8192,-1:4096,0:4083"
   static bool ExtentsToBsdiffPositionsString(
       const google::protobuf::RepeatedPtrField<Extent>& extents,
       uint64_t block_size,
       uint64_t full_length,
       std::string* positions_string);
 
  private:
   // Returns true if enough of the delta file has been passed via Write()
   // to be able to perform a given install operation.
   bool CanPerformInstallOperation(
       const DeltaArchiveManifest_InstallOperation& operation);
   
   // Returns true on success.
   bool PerformInstallOperation(
       const DeltaArchiveManifest_InstallOperation& operation);
   
   // These perform a specific type of operation and return true on success.
   bool PerformReplaceOperation(
-      const DeltaArchiveManifest_InstallOperation& operation);
+      const DeltaArchiveManifest_InstallOperation& operation,
+      bool is_kernel_partition);
   bool PerformMoveOperation(
-      const DeltaArchiveManifest_InstallOperation& operation);
+      const DeltaArchiveManifest_InstallOperation& operation,
+      bool is_kernel_partition);
   bool PerformBsdiffOperation(
-      const DeltaArchiveManifest_InstallOperation& operation);
+      const DeltaArchiveManifest_InstallOperation& operation,
+      bool is_kernel_partition);
 
   // File descriptor of open device.
   int fd_;
   
-  std::string path_;  // Path that fd_ refers to
+  // File descriptor of the kernel device
+  int kernel_fd_;
+  
+  std::string path_;  // Path that fd_ refers to.
+  std::string kernel_path_;  // Path that kernel_fd_ refers to.
   
   DeltaArchiveManifest manifest_;
   bool manifest_valid_;
   
   // Index of the next operation to perform in the manifest.
-  int next_operation_;
+  int next_operation_num_;
 
   // buffer_ is a window of the data that's been downloaded. At first,
   // it contains the beginning of the download, but after the protobuf
   // has been downloaded and parsed, it contains a sliding window of
   // data blobs.
   std::vector<char> buffer_;
   // Offset of buffer_ in the binary blobs section of the update.
   uint64_t buffer_offset_;
   
   // The block size (parsed from the manifest).
   uint32_t block_size_;
   
   DISALLOW_COPY_AND_ASSIGN(DeltaPerformer);
 };
 
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_DELTA_PERFORMER_H__