add SetIterateLowerBound and testcase

go.mod

@@ -0,0 +1,10 @@
+module github.com/yiyanwannian/gorocksdb
+
+go 1.16
+
+require (
+	github.com/facebookgo/ensure v0.0.0-20200202191622-63f1cf65ac4c
+	github.com/facebookgo/stack v0.0.0-20160209184415-751773369052 // indirect
+	github.com/facebookgo/subset v0.0.0-20200203212716-c811ad88dec4 // indirect
+	github.com/stretchr/testify v1.7.0
+)

iterator_test.go

@@ -29,3 +29,36 @@ func TestIterator(t *testing.T) {
 	ensure.Nil(t, iter.Err())
 	ensure.DeepEqual(t, actualKeys, givenKeys)
 }
+
+func TestIteratorWithRange(t *testing.T) {
+	db := newTestDB(t, "TestIterator", nil)
+	defer db.Close()
+
+	// insert keys
+	givenKeys := [][]byte{
+		[]byte("key1"),
+		[]byte("key2"),
+		[]byte("key3"),
+		[]byte("key4"),
+		[]byte("key5"),
+	}
+	wo := NewDefaultWriteOptions()
+	for _, k := range givenKeys {
+		ensure.Nil(t, db.Put(wo, k, []byte("val")))
+	}
+
+	ro := NewDefaultReadOptions()
+	ro.SetIterateLowerBound([]byte("key2"))
+	ro.SetIterateUpperBound([]byte("key4"))
+
+	iter := db.NewIterator(ro)
+	defer iter.Close()
+	var actualKeys [][]byte
+	for iter.SeekToFirst(); iter.Valid(); iter.Next() {
+		key := make([]byte, 4)
+		copy(key, iter.Key().Data())
+		actualKeys = append(actualKeys, key)
+	}
+	ensure.Nil(t, iter.Err())
+	ensure.DeepEqual(t, len(actualKeys), 2)
+}

options_read.go

@@ -93,6 +93,22 @@ func (opts *ReadOptions) SetTailing(value bool) {
 	C.rocksdb_readoptions_set_tailing(opts.c, boolToChar(value))
 }
 
+// SetIterateLowerBound specifies "iterate_lower_bound", which defines
+// the extent upto which the forward iterator can returns entries.
+// Once the bound is reached, Valid() will be false.
+// "iterate_lower_bound" is exclusive ie the bound value is
+// not a valid entry.  If iterator_extractor is not null, the Seek target
+// and iterator_lower_bound need to have the same prefix.
+// This is because ordering is not guaranteed outside of prefix domain.
+// There is no lower bound on the iterator. If needed, that can be easily
+// implemented.
+// Default: nullptr
+func (opts *ReadOptions) SetIterateLowerBound(key []byte) {
+	cKey := byteToChar(key)
+	cKeyLen := C.size_t(len(key))
+	C.rocksdb_readoptions_set_iterate_lower_bound(opts.c, cKey, cKeyLen)
+}
+
 // SetIterateUpperBound specifies "iterate_upper_bound", which defines
 // the extent upto which the forward iterator can returns entries.
 // Once the bound is reached, Valid() will be false.