AU: Start checkpointing update progress.

omaha_hash_calculator.h

Index: omaha_hash_calculator.h
diff --git a/omaha_hash_calculator.h b/omaha_hash_calculator.h
index 52ac1b75fd5a9227195bb9f535f5a19513a92f35..7aa37e4338f71ba1eb1a4545d93a89c03761789a 100644
--- a/omaha_hash_calculator.h
+++ b/omaha_hash_calculator.h
@@ -11,11 +11,11 @@
 #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 {
 
@@ -45,6 +45,15 @@ class OmahaHashCalculator {
     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);