fix: fix btree iterate for empty db

internal/btree/btree.go

@@ -528,9 +528,11 @@ func (d *DB) Delete(hash *byte) error {
 
 // Foreach iterates over all items in the database file.
 func (d *DB) Foreach(iter func(key [16]byte, value []byte)) {
+	if d.top != 0 {
 		top := d.get(d.top)
 		d.iterate(top, iter)
 	}
+}
 
 func (d *DB) iterate(table *table, iter func(key [16]byte, value []byte)) {
 	for i := 0; i < table.size; i++ {

internal/btree/btree_test.go

@@ -27,7 +27,8 @@ func TestBtree(t *testing.T) {
 	f := tempfile(t)
 	defer os.Remove(f)
 	bt, err := Create(f)
-	assert2.NoError(t, err)
+	assert := assert2.New(t)
+	assert.NoError(err)
 
 	tests := []string{
 		"hello world",
@@ -42,51 +43,55 @@ func TestBtree(t *testing.T) {
 		sha[i] = &hash.Sum(nil)[0]
 		bt.Insert(sha[i], []byte(tt))
 	}
-	assert2.NoError(t, bt.Close())
+	assert.NoError(bt.Close())
 
 	bt, err = Open(f)
-	assert2.NoError(t, err)
+	assert.NoError(err)
 	var ss []string
 	bt.Foreach(func(key [16]byte, value []byte) {
 		ss = append(ss, string(value))
 	})
-	assert2.ElementsMatch(t, tests, ss)
+	assert.ElementsMatch(tests, ss)
 
 	for i, tt := range tests {
-		assert2.Equal(t, []byte(tt), bt.Get(sha[i]))
+		assert.Equal([]byte(tt), bt.Get(sha[i]))
 	}
 
 	for i := range tests {
-		assert2.NoError(t, bt.Delete(sha[i]))
+		assert.NoError(bt.Delete(sha[i]))
 	}
 
 	for i := range tests {
-		assert2.Equal(t, []byte(nil), bt.Get(sha[i]))
+		assert.Equal([]byte(nil), bt.Get(sha[i]))
+	}
+	assert.NoError(bt.Close())
 }
 
-	assert2.NoError(t, bt.Close())
+func testForeach(t *testing.T, elemSize int) {
-}
+	expected := make([]string, elemSize)
-
-func TestDB_Foreach(t *testing.T) {
-	const elemSize = 100
-	set := make([]string, elemSize)
 	for i := 0; i < elemSize; i++ {
-		set[i] = utils.RandomString(20)
+		expected[i] = utils.RandomString(20)
 	}
 	f := tempfile(t)
 	defer os.Remove(f)
 	bt, err := Create(f)
 	defer bt.Close()
 	assert2.NoError(t, err)
-	for _, v := range set {
+	for _, v := range expected {
 		hash := sha1.New()
 		hash.Write([]byte(v))
 		bt.Insert(&hash.Sum(nil)[0], []byte(v))
 	}
-
+	var got []string
-	var ss []string
 	bt.Foreach(func(key [16]byte, value []byte) {
-		ss = append(ss, string(value))
+		got = append(got, string(value))
 	})
-	assert2.ElementsMatch(t, set, ss)
+	assert2.ElementsMatch(t, expected, got)
+}
+
+func TestDB_Foreach(t *testing.T) {
+	elemSizes := []int{0, 5, 100, 200}
+	for _, size := range elemSizes {
+		testForeach(t, size)
+	}
 }