AU: Start checkpointing update progress.

omaha_hash_calculator.h

 // Copyright (c) 2009 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_OMAHA_HASH_CALCULATOR_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_OMAHA_HASH_CALCULATOR_H__
 
 #include <string>
 #include <vector>
 #include <openssl/sha.h>
 #include "base/basictypes.h"
 #include "base/logging.h"
 
-// Omaha uses base64 encoded SHA-1 as the hash. This class provides a simple
+// Omaha uses base64 encoded SHA-256 as the hash. This class provides a simple
 // wrapper around OpenSSL providing such a formatted hash of data passed in.
-// The methods of this class must be called in a very specific order:
-// First the ctor (of course), then 0 or more calls to Update(), then
-// Finalize(), then 0 or more calls to hash().
+// The methods of this class must be called in a very specific order: First the
+// ctor (of course), then 0 or more calls to Update(), then Finalize(), then 0
+// or more calls to hash().
 
 namespace chromeos_update_engine {
 
 class OmahaHashCalculator {
  public:
   OmahaHashCalculator();
 
   // Update is called with all of the data that should be hashed in order.
   // Update will read |length| bytes of |data|.
   // Returns true on success.
   bool Update(const char* data, size_t length);
 
   // Call Finalize() when all data has been passed in. This method tells
   // OpenSSl that no more data will come in and base64 encodes the resulting
   // hash.
   // Returns true on success.
   bool Finalize();
 
   // Gets the hash. Finalize() must have been called.
   const std::string& hash() const {
     DCHECK(!hash_.empty()) << "Call Finalize() first";
     return hash_;
   }
 
   const std::vector<char>& raw_hash() const {
     DCHECK(!raw_hash_.empty()) << "Call Finalize() first";
     return raw_hash_;
   }
 
+  // Gets the current hash context. Note that the string will contain binary
+  // data (including \0 characters).
+  std::string GetContext() const;
+
+  // Sets the current hash context. |context| must the string returned by a
+  // previous OmahaHashCalculator::GetContext method call. Returns true on
+  // success, and false otherwise.
+  bool SetContext(const std::string& context);
+
   static bool RawHashOfData(const std::vector<char>& data,
                             std::vector<char>* out_hash);
 
   // Used by tests
   static std::string OmahaHashOfBytes(const void* data, size_t length);
   static std::string OmahaHashOfString(const std::string& str);
   static std::string OmahaHashOfData(const std::vector<char>& data);
 
  private:
   // If non-empty, the final base64 encoded hash and the raw hash. Will only be
   // set to non-empty when Finalize is called.
   std::string hash_;
   std::vector<char> raw_hash_;
 
   // Init success
   bool valid_;
 
   // The hash state used by OpenSSL
   SHA256_CTX ctx_;
   DISALLOW_COPY_AND_ASSIGN(OmahaHashCalculator);
 };
 
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_OMAHA_HASH_CALCULATOR_H__