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|
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)
}
|
