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package dfa
import (
"encoding/binary"
"fmt"
"strings"
)
type symbolPosition uint16
const (
symbolPositionNil symbolPosition = 0x0000
symbolPositionMin uint16 = 0x0001
symbolPositionMax uint16 = 0x7fff
symbolPositionMaskSymbol uint16 = 0x0000
symbolPositionMaskEndMark uint16 = 0x8000
symbolPositionMaskValue uint16 = 0x7fff
)
func newSymbolPosition(n uint16, endMark bool) (symbolPosition, error) {
if n < symbolPositionMin || n > symbolPositionMax {
return symbolPositionNil, fmt.Errorf("symbol position must be within %v to %v: n: %v, endMark: %v", symbolPositionMin, symbolPositionMax, n, endMark)
}
if endMark {
return symbolPosition(n | symbolPositionMaskEndMark), nil
}
return symbolPosition(n | symbolPositionMaskSymbol), nil
}
func (p symbolPosition) String() string {
if p.isEndMark() {
return fmt.Sprintf("end#%v", uint16(p)&symbolPositionMaskValue)
}
return fmt.Sprintf("sym#%v", uint16(p)&symbolPositionMaskValue)
}
func (p symbolPosition) isEndMark() bool {
return uint16(p)&symbolPositionMaskEndMark > 1
}
func (p symbolPosition) describe() (uint16, bool) {
v := uint16(p) & symbolPositionMaskValue
if p.isEndMark() {
return v, true
}
return v, false
}
type symbolPositionSet struct {
// `s` represents a set of symbol positions.
// However, immediately after adding a symbol position, the elements may be duplicated.
// When you need an aligned set with no duplicates, you can get such value via the set function.
s []symbolPosition
sorted bool
}
func newSymbolPositionSet() *symbolPositionSet {
return &symbolPositionSet{
s: []symbolPosition{},
sorted: false,
}
}
func (s *symbolPositionSet) String() string {
if len(s.s) <= 0 {
return "{}"
}
ps := s.sortAndRemoveDuplicates()
var b strings.Builder
fmt.Fprintf(&b, "{")
for i, p := range ps {
if i <= 0 {
fmt.Fprintf(&b, "%v", p)
continue
}
fmt.Fprintf(&b, ", %v", p)
}
fmt.Fprintf(&b, "}")
return b.String()
}
func (s *symbolPositionSet) set() []symbolPosition {
s.sortAndRemoveDuplicates()
return s.s
}
func (s *symbolPositionSet) add(pos symbolPosition) *symbolPositionSet {
s.s = append(s.s, pos)
s.sorted = false
return s
}
func (s *symbolPositionSet) merge(t *symbolPositionSet) *symbolPositionSet {
s.s = append(s.s, t.s...)
s.sorted = false
return s
}
func (s *symbolPositionSet) hash() string {
if len(s.s) <= 0 {
return ""
}
sorted := s.sortAndRemoveDuplicates()
var buf []byte
for _, p := range sorted {
b := make([]byte, 8)
binary.PutUvarint(b, uint64(p))
buf = append(buf, b...)
}
// Convert to a string to be able to use it as a key of a map.
// But note this byte sequence is made from values of symbol positions,
// so this is not a well-formed UTF-8 sequence.
return string(buf)
}
func (s *symbolPositionSet) sortAndRemoveDuplicates() []symbolPosition {
if s.sorted {
return s.s
}
sortSymbolPositions(s.s, 0, len(s.s)-1)
// Remove duplicates.
lastV := s.s[0]
nextIdx := 1
for _, v := range s.s[1:] {
if v == lastV {
continue
}
s.s[nextIdx] = v
nextIdx++
lastV = v
}
s.s = s.s[:nextIdx]
s.sorted = true
return s.s
}
// sortSymbolPositions sorts a slice of symbol positions as it uses quick sort.
func sortSymbolPositions(ps []symbolPosition, left, right int) {
if left >= right {
return
}
var pivot symbolPosition
{
// Use a median as a pivot.
p1 := ps[left]
p2 := ps[(left+right)/2]
p3 := ps[right]
if p1 > p2 {
p1, p2 = p2, p1
}
if p2 > p3 {
p2 = p3
if p1 > p2 {
p2 = p1
}
}
pivot = p2
}
i := left
j := right
for i <= j {
for ps[i] < pivot {
i++
}
for ps[j] > pivot {
j--
}
if i <= j {
ps[i], ps[j] = ps[j], ps[i]
i++
j--
}
}
sortSymbolPositions(ps, left, j)
sortSymbolPositions(ps, i, right)
}
|
