iterator add offset and limit, reviterator bug fix

leveldb/db.go

@@ -116,7 +116,7 @@ func (db *DB) Destroy() {
 }
 
 func (db *DB) Clear() {
-	it := db.Iterator(nil, nil, 0, -1)
+	it := db.Iterator(nil, nil, 0, 0, -1)
 	for ; it.Valid(); it.Next() {
 		db.Delete(it.Key())
 	}
@@ -142,13 +142,15 @@ func (db *DB) NewWriteBatch() *WriteBatch {
 }
 
 //limit < 0, unlimit
-func (db *DB) Iterator(min []byte, max []byte, rangeType uint8, limit int) *Iterator {
+//offset must >= 0, if < 0, will get nothing
-	return newIterator(db, db.iteratorOpts, NewRange(min, max, rangeType), limit, IteratorForward)
+func (db *DB) Iterator(min []byte, max []byte, rangeType uint8, offset int, limit int) *Iterator {
+	return newIterator(db, db.iteratorOpts, NewRange(min, max, rangeType), offset, limit, IteratorForward)
 }
 
 //limit < 0, unlimit
-func (db *DB) RevIterator(min []byte, max []byte, rangeType uint8, limit int) *Iterator {
+//offset must >= 0, if < 0, will get nothing
-	return newIterator(db, db.iteratorOpts, NewRange(min, max, rangeType), limit, IteratorBackward)
+func (db *DB) RevIterator(min []byte, max []byte, rangeType uint8, offset int, limit int) *Iterator {
+	return newIterator(db, db.iteratorOpts, NewRange(min, max, rangeType), offset, limit, IteratorBackward)
 }
 
 func (db *DB) NewSnapshot() *Snapshot {

leveldb/iterator.go

@@ -39,6 +39,7 @@ type Iterator struct {
 
 	r *Range
 
+	offset int
 	limit  int
 
 	step int
@@ -47,16 +48,21 @@ type Iterator struct {
 	direction uint8
 }
 
-func newIterator(db *DB, opts *levigo.ReadOptions, r *Range, limit int, direction uint8) *Iterator {
+func newIterator(db *DB, opts *levigo.ReadOptions, r *Range, offset int, limit int, direction uint8) *Iterator {
 	it := new(Iterator)
 	it.it = db.db.NewIterator(opts)
 
 	it.r = r
+	it.offset = offset
 	it.limit = limit
 	it.direction = direction
 
 	it.step = 0
 
+	if offset < 0 {
+		return it
+	}
+
 	if direction == IteratorForward {
 		if r.Min == nil {
 			it.it.SeekToFirst()
@@ -64,7 +70,7 @@ func newIterator(db *DB, opts *levigo.ReadOptions, r *Range, limit int, directio
 			it.it.Seek(r.Min)
 
 			if r.Type&RangeLOpen > 0 {
-				if it.Valid() && bytes.Equal(it.Key(), r.Min) {
+				if it.it.Valid() && bytes.Equal(it.it.Key(), r.Min) {
 					it.it.Next()
 				}
 			}
@@ -74,10 +80,14 @@ func newIterator(db *DB, opts *levigo.ReadOptions, r *Range, limit int, directio
 			it.it.SeekToLast()
 		} else {
 			it.it.Seek(r.Max)
-			if it.Valid() && !bytes.Equal(it.Key(), r.Max) {
+
-				//key must bigger than max, so we must go prev
+			if !it.it.Valid() {
+				it.it.SeekToLast()
+			} else {
+				if !bytes.Equal(it.it.Key(), r.Max) {
 					it.it.Prev()
 				}
+			}
 
 			if r.Type&RangeROpen > 0 {
 				if it.Valid() && bytes.Equal(it.Key(), r.Max) {
@@ -87,15 +97,21 @@ func newIterator(db *DB, opts *levigo.ReadOptions, r *Range, limit int, directio
 		}
 	}
 
+	for i := 0; i < offset; i++ {
+		if it.Valid() {
+			it.Next()
+		}
+	}
+
 	return it
 }
 
 func (it *Iterator) Valid() bool {
-	if !it.it.Valid() {
+	if it.offset < 0 {
 		return false
-	}
+	} else if !it.it.Valid() {
-
+		return false
-	if it.limit >= 0 && it.step >= it.limit {
+	} else if it.limit >= 0 && it.step >= it.limit {
 		return false
 	}
 
@@ -136,14 +152,6 @@ func (it *Iterator) Next() {
 	}
 }
 
-func (it *Iterator) Skip(offset int64) {
-	for i := int64(0); i < offset; i++ {
-		if it.Valid() {
-			it.Next()
-		}
-	}
-}
-
 func (it *Iterator) Key() []byte {
 	return it.it.Key()
 }

leveldb/leveldb_test.go

@@ -146,52 +146,52 @@ func TestIterator(t *testing.T) {
 		return []byte(fmt.Sprintf("key_%d", i))
 	}
 
-	it = db.Iterator(k(1), k(5), RangeClose, -1)
+	it = db.Iterator(k(1), k(5), RangeClose, 0, -1)
 	if err := checkIterator(it, 1, 2, 3, 4, 5); err != nil {
 		t.Fatal(err)
 	}
 
-	it = db.Iterator(k(1), k(5), RangeClose, 3)
+	it = db.Iterator(k(1), k(5), RangeClose, 1, 3)
-	if err := checkIterator(it, 1, 2, 3); err != nil {
+	if err := checkIterator(it, 2, 3); err != nil {
 		t.Fatal(err)
 	}
 
-	it = db.Iterator(k(1), k(5), RangeLOpen, -1)
+	it = db.Iterator(k(1), k(5), RangeLOpen, 0, -1)
 	if err := checkIterator(it, 2, 3, 4, 5); err != nil {
 		t.Fatal(err)
 	}
 
-	it = db.Iterator(k(1), k(5), RangeROpen, -1)
+	it = db.Iterator(k(1), k(5), RangeROpen, 0, -1)
 	if err := checkIterator(it, 1, 2, 3, 4); err != nil {
 		t.Fatal(err)
 	}
 
-	it = db.Iterator(k(1), k(5), RangeOpen, -1)
+	it = db.Iterator(k(1), k(5), RangeOpen, 0, -1)
 	if err := checkIterator(it, 2, 3, 4); err != nil {
 		t.Fatal(err)
 	}
 
-	it = db.RevIterator(k(1), k(5), RangeClose, -1)
+	it = db.RevIterator(k(1), k(5), RangeClose, 0, -1)
 	if err := checkIterator(it, 5, 4, 3, 2, 1); err != nil {
 		t.Fatal(err)
 	}
 
-	it = db.RevIterator(k(1), k(5), RangeClose, 3)
+	it = db.RevIterator(k(1), k(5), RangeClose, 1, 3)
-	if err := checkIterator(it, 5, 4, 3); err != nil {
+	if err := checkIterator(it, 4, 3); err != nil {
 		t.Fatal(err)
 	}
 
-	it = db.RevIterator(k(1), k(5), RangeLOpen, -1)
+	it = db.RevIterator(k(1), k(5), RangeLOpen, 0, -1)
 	if err := checkIterator(it, 5, 4, 3, 2); err != nil {
 		t.Fatal(err)
 	}
 
-	it = db.RevIterator(k(1), k(5), RangeROpen, -1)
+	it = db.RevIterator(k(1), k(5), RangeROpen, 0, -1)
 	if err := checkIterator(it, 4, 3, 2, 1); err != nil {
 		t.Fatal(err)
 	}
 
-	it = db.RevIterator(k(1), k(5), RangeOpen, -1)
+	it = db.RevIterator(k(1), k(5), RangeOpen, 0, -1)
 	if err := checkIterator(it, 4, 3, 2); err != nil {
 		t.Fatal(err)
 	}

leveldb/snapshot.go

@@ -37,12 +37,12 @@ func (s *Snapshot) Get(key []byte) ([]byte, error) {
 	return s.db.db.Get(s.readOpts, key)
 }
 
-func (s *Snapshot) Iterator(min []byte, max []byte, rangeType uint8, limit int) *Iterator {
+func (s *Snapshot) Iterator(min []byte, max []byte, rangeType uint8, offset int, limit int) *Iterator {
-	return newIterator(s.db, s.iteratorOpts, NewRange(min, max, rangeType), limit, IteratorForward)
+	return newIterator(s.db, s.iteratorOpts, NewRange(min, max, rangeType), offset, limit, IteratorForward)
 }
 
-func (s *Snapshot) RevIterator(min []byte, max []byte, rangeType uint8, limit int) *Iterator {
+func (s *Snapshot) RevIterator(min []byte, max []byte, rangeType uint8, offset int, limit int) *Iterator {
-	return newIterator(s.db, s.iteratorOpts, NewRange(min, max, rangeType), limit, IteratorBackward)
+	return newIterator(s.db, s.iteratorOpts, NewRange(min, max, rangeType), offset, limit, IteratorBackward)
 }
 
 func (s *Snapshot) GetInt(key []byte) (int64, error) {