Adding bitcask#each_key iterator and ability to skip tombstones

lib/bitcask.rb

@@ -44,11 +44,23 @@ def data_files
     end
   end
 
+  # Iterates over all keys in keydir. Yields key.
+  def each_key(skip_tombstones=false)
+    @keydir.each do |key, index|
+      if skip_tombstones
+        key, is_tombstone = @keydir.data_files[index.file_id].read_key(index.value_pos)
+        yield key unless is_tombstone
+      else
+        yield key
+      end
+    end
+  end
+
   # Iterates over all keys in keydir. Yields key, value pairs.
-  def each
+  def each(skip_tombstones=false)
     @keydir.each do |key, index|
       entry = @keydir.data_files[index.file_id][index.value_pos, index.value_sz]
-      yield [entry.key, entry.value]
+      yield [entry.key, entry.value] unless skip_tombstones and entry.value == TOMBSTONE
     end
   end
 

lib/bitcask/data_file.rb

@@ -63,6 +63,29 @@ def pos
   end
   alias tell pos
 
+  def read_key(offset)
+    seek offset
+
+    f = @file
+
+    # Parse header
+    header = f.read(14) or return
+    crc, tstamp, ksz, value_sz = header.unpack "NNnN"
+
+    # Read key
+    key = f.read ksz
+
+    if value_sz != Bitcask::TOMBSTONE.size
+      is_tombstone = false
+    else
+      value = f.read value_sz
+      raise Bitcask::ChecksumError unless crc == Zlib.crc32(header[4..-1] + key + value)
+      is_tombstone = value == Bitcask::TOMBSTONE
+    end
+
+    return key, is_tombstone
+  end
+
   # Returns a single Entry read from the current offset, and advances to the
   # next.
   #