package match import ( "fmt" "unicode/utf8" ) type BTree struct { Value Matcher Left Matcher Right Matcher ValueLengthRunes int LeftLengthRunes int RightLengthRunes int LengthRunes int } func NewBTree(Value, Left, Right Matcher) (tree BTree) { tree.Value = Value tree.Left = Left tree.Right = Right lenOk := true if tree.ValueLengthRunes = Value.Len(); tree.ValueLengthRunes == -1 { lenOk = false } if Left != nil { if tree.LeftLengthRunes = Left.Len(); tree.LeftLengthRunes == -1 { lenOk = false } } if Right != nil { if tree.RightLengthRunes = Right.Len(); tree.RightLengthRunes == -1 { lenOk = false } } if lenOk { tree.LengthRunes = tree.LeftLengthRunes + tree.ValueLengthRunes + tree.RightLengthRunes } else { tree.LengthRunes = -1 } return tree } func (self BTree) Len() int { return self.LengthRunes } // todo? func (self BTree) Index(s string) (int, []int) { return -1, nil } func (self BTree) Match(s string) bool { inputLen := len(s) // self.Length, self.RLen and self.LLen are values meaning the length of runes for each part // here we manipulating byte length for better optimizations // but these checks still works, cause minLen of 1-rune string is 1 byte. if self.LengthRunes != -1 && self.LengthRunes > inputLen { return false } // try to cut unnecessary parts // by knowledge of length of right and left part var offset, limit int if self.LeftLengthRunes >= 0 { offset = self.LeftLengthRunes } if self.RightLengthRunes >= 0 { limit = inputLen - self.RightLengthRunes } else { limit = inputLen } for offset < limit { // search for matching part in substring index, segments := self.Value.Index(s[offset:limit]) if index == -1 { releaseSegments(segments) return false } l := s[:offset+index] var left bool if self.Left != nil { left = self.Left.Match(l) } else { left = l == "" } if left { for i := len(segments) - 1; i >= 0; i-- { length := segments[i] var right bool var r string // if there is no string for the right branch if inputLen <= offset+index+length { r = "" } else { r = s[offset+index+length:] } if self.Right != nil { right = self.Right.Match(r) } else { right = r == "" } if right { releaseSegments(segments) return true } } } _, step := utf8.DecodeRuneInString(s[offset+index:]) offset += index + step releaseSegments(segments) } return false } func (self BTree) String() string { const n string = "<nil>" var l, r string if self.Left == nil { l = n } else { l = self.Left.String() } if self.Right == nil { r = n } else { r = self.Right.String() } return fmt.Sprintf("<btree:[%s<-%s->%s]>", l, self.Value, r) }