lib/daybreak/record.rb in daybreak-0.0.4 vs lib/daybreak/record.rb in daybreak-0.1.0

@@ -7,24 +7,32 @@
     # Thrown when there is a CRC mismatch between the data from the disk
     # and what was written to disk previously.
     class CorruptDataError < Exception; end
     include Locking
 
+    # The mask a record uses to check for deletion.
+    DELETION_MASK = (1 << 31)
+
     attr_accessor :key, :data
 
-    def initialize(key = nil, data = nil)
+    def initialize(key = nil, data = nil, deleted = false)
       @key  = key
       @data = data
+      if deleted
+        @deleted = DELETION_MASK
+      else
+        @deleted = 0
+      end
     end
 
     # Read a record from an open io source, check the CRC, and set <tt>@key</tt>
     # and <tt>@data</tt>.
     # @param [#read] io an IO instance to read from
     def read(io)
       lock io do
-        @key  = read_bytes(io)
-        @data = read_bytes(io)
+        @key  = read_key(io)
+        @data = read_data(io)
         crc   = io.read(4)
         raise CorruptDataError, "CRC mismatch #{crc} should be #{crc_string}" unless crc == crc_string
       end
       self
     end
@@ -40,26 +48,40 @@
     # @param [#read] io an IO instance to read from
     def self.read(io)
       new.read(io)
     end
 
+    def deleted?
+      @deleted > 0
+    end
+
     private
 
     def byte_string
-      @byte_string ||= part(@key) + part(@data)
+      @byte_string ||= part(@key, @key.bytesize + @deleted) + part(@data, @data.bytesize)
     end
 
     def crc_string
       [Zlib.crc32(byte_string, 0)].pack('N')
     end
 
-    def read_bytes(io)
+    def read_data(io)
+      io.read read32(io)
+    end
+
+    def read_key(io)
+      masked   = read32 io
+      @deleted = masked & DELETION_MASK
+      length   = masked & (DELETION_MASK - 1)
+      io.read length
+    end
+
+    def read32(io)
       raw = io.read(4)
-      length = raw.unpack('N')[0]
-      io.read(length)
+      raw.unpack('N')[0]
     end
 
-    def part(data)
-      [data.bytesize].pack('N') + data
+    def part(data, length)
+      [length].pack('N') + data
     end
   end
 end