Add LFU w/ Tests

internal/data/datafile.go

@@ -25,6 +25,7 @@ var (
 type Datafile interface {
 	FileID() int
 	Name() string
+	Open() error
 	Close() error
 	Sync() error
 	Size() int64
@@ -97,6 +98,22 @@ func NewDatafile(path string, id int, readonly bool, maxKeySize uint32, maxValue
 	}, nil
 }
 
+func (df *datafile) Open() error {
+	var err error
+
+	df.r, err = os.Open(df.Name())
+	if err != nil {
+		return err
+	}
+
+	df.ra, err = mmap.Open(df.Name())
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
 func (df *datafile) FileID() int {
 	return df.id
 }

internal/mocks/datafile.go

@@ -2,8 +2,10 @@
 
 package mocks
 
-import internal "github.com/prologic/bitcask/internal"
-import mock "github.com/stretchr/testify/mock"
+import (
+	internal "github.com/prologic/bitcask/internal"
+	mock "github.com/stretchr/testify/mock"
+)
 
 // Datafile is an autogenerated mock type for the Datafile type
 type Datafile struct {
@@ -52,6 +54,20 @@ func (_m *Datafile) Name() string {
 	return r0
 }
 
+// Open provides a mock function with given fields:
+func (_m *Datafile) Open() error {
+	ret := _m.Called()
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func() error); ok {
+		r0 = rf()
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}
+
 // Read provides a mock function with given fields:
 func (_m *Datafile) Read() (internal.Entry, int64, error) {
 	ret := _m.Called()

internal/mocks/indexer.go

@@ -2,9 +2,11 @@
 
 package mocks
 
-import art "github.com/plar/go-adaptive-radix-tree"
+import (
+	art "github.com/plar/go-adaptive-radix-tree"
 
-import mock "github.com/stretchr/testify/mock"
+	mock "github.com/stretchr/testify/mock"
+)
 
 // Indexer is an autogenerated mock type for the Indexer type
 type Indexer struct {