sync with upstream @ 21409451

Check the NEWS file for details of what changed.

git-svn-id: https://leveldb.googlecode.com/svn/trunk@28 62dab493-f737-651d-591e-8d6aee1b9529

1 files changed, 13 insertions, 7 deletions

diff --git a/include/leveldb/db.h b/include/leveldb/db.h
index f18ded3..79bd283 100644
--- a/include/leveldb/db.h
+++ b/include/leveldb/db.h
@@ -13,26 +13,32 @@
 namespace leveldb {
 
 static const int kMajorVersion = 1;
-static const int kMinorVersion = 1;
+static const int kMinorVersion = 2;
 
 struct Options;
 struct ReadOptions;
 struct WriteOptions;
-
-class Snapshot;
 class WriteBatch;
 
-// Some internal types.  Clients should ignore.
-class WriteBatchInternal;
+// Abstract handle to particular state of a DB.
+// A Snapshot is an immutable object and can therefore be safely
+// accessed from multiple threads without any external synchronization.
+class Snapshot {
+ protected:
+  virtual ~Snapshot();
+};
 
+// A range of keys
 struct Range {
-  Slice start;
-  Slice limit;
+  Slice start;          // Included in the range
+  Slice limit;          // Not included in the range
 
   Range(const Slice& s, const Slice& l) : start(s), limit(l) { }
 };
 
 // A DB is a persistent ordered map from keys to values.
+// A DB is safe for concurrent access from multiple threads without
+// any external synchronization.
 class DB {
  public:
   // Open the database with the specified "name".