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|
package compiler
import (
"encoding/binary"
"fmt"
"strings"
)
type symbolPosition uint16
const (
symbolPositionNil = symbolPosition(0x0000) // 0000 0000 0000 0000
symbolPositionMin = uint16(0x0001) // 0000 0000 0000 0001
symbolPositionMax = uint16(0x7fff) // 0111 1111 1111 1111
symbolPositionMaskSymbol = uint16(0x0000) // 0000 0000 0000 0000
symbolPositionMaskEndMark = uint16(0x8000) // 1000 0000 0000 0000
symbolPositionMaskValue = uint16(0x7fff) // 0111 1111 1111 1111
)
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 {
if uint16(p)&symbolPositionMaskEndMark > 1 {
return true
}
return false
}
func (p symbolPosition) describe() (uint16, bool) {
v := uint16(p) & symbolPositionMaskValue
if p.isEndMark() {
return v, true
}
return v, false
}
type symbolPositionSet map[symbolPosition]struct{}
func newSymbolPositionSet() symbolPositionSet {
return map[symbolPosition]struct{}{}
}
func (s symbolPositionSet) String() string {
if len(s) <= 0 {
return "{}"
}
ps := s.sort()
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) add(pos symbolPosition) symbolPositionSet {
s[pos] = struct{}{}
return s
}
func (s symbolPositionSet) merge(t symbolPositionSet) symbolPositionSet {
for p := range t {
s.add(p)
}
return s
}
func (s symbolPositionSet) intersect(set symbolPositionSet) symbolPositionSet {
in := newSymbolPositionSet()
for p1 := range s {
for p2 := range set {
if p1 != p2 {
continue
}
in.add(p1)
}
}
return in
}
func (s symbolPositionSet) hash() string {
if len(s) <= 0 {
return ""
}
sorted := s.sort()
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) sort() []symbolPosition {
sorted := make([]symbolPosition, len(s))
i := 0
for p := range s {
sorted[i] = p
i++
}
sortSymbolPositions(sorted, 0, len(sorted)-1)
return sorted
}
// 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 = p3, p2
if p1 > p2 {
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)
}
|
