package internal import ( "bytes" "github.com/boltdb/bolt" ) // Cursor that can be reversed type Cursor struct { C *bolt.Cursor Reverse bool } // First element func (c *Cursor) First() ([]byte, []byte) { if c.Reverse { return c.C.Last() } return c.C.First() } // Next element func (c *Cursor) Next() ([]byte, []byte) { if c.Reverse { return c.C.Prev() } return c.C.Next() } // RangeCursor that can be reversed type RangeCursor struct { C *bolt.Cursor Reverse bool Min []byte Max []byte CompareFn func([]byte, []byte) int } // First element func (c *RangeCursor) First() ([]byte, []byte) { if c.Reverse { return c.C.Seek(c.Max) } return c.C.Seek(c.Min) } // Next element func (c *RangeCursor) Next() ([]byte, []byte) { if c.Reverse { return c.C.Prev() } return c.C.Next() } // Continue tells if the loop needs to continue func (c *RangeCursor) Continue(val []byte) bool { if c.Reverse { return val != nil && c.CompareFn(val, c.Min) >= 0 } return val != nil && c.CompareFn(val, c.Max) <= 0 } // PrefixCursor that can be reversed type PrefixCursor struct { C *bolt.Cursor Reverse bool Prefix []byte } // First element func (c *PrefixCursor) First() ([]byte, []byte) { var k, v []byte for k, v = c.C.First(); k != nil && !bytes.HasPrefix(k, c.Prefix); k, v = c.C.Next() { } if k == nil { return nil, nil } if c.Reverse { kc, vc := k, v for ; kc != nil && bytes.HasPrefix(kc, c.Prefix); kc, vc = c.C.Next() { k, v = kc, vc } if kc != nil { k, v = c.C.Prev() } } return k, v } // Next element func (c *PrefixCursor) Next() ([]byte, []byte) { if c.Reverse { return c.C.Prev() } return c.C.Next() } // Continue tells if the loop needs to continue func (c *PrefixCursor) Continue(val []byte) bool { return val != nil && bytes.HasPrefix(val, c.Prefix) }