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|
package symbol
import (
"fmt"
"sort"
)
type symbolKind string
const (
symbolKindNonTerminal = symbolKind("non-terminal")
symbolKindTerminal = symbolKind("terminal")
)
func (t symbolKind) String() string {
return string(t)
}
type SymbolNum uint16
func (n SymbolNum) Int() int {
return int(n)
}
type Symbol uint16
func (s Symbol) String() string {
kind, isStart, isEOF, num := s.describe()
var prefix string
switch {
case isStart:
prefix = "s"
case isEOF:
prefix = "e"
case kind == symbolKindNonTerminal:
prefix = "n"
case kind == symbolKindTerminal:
prefix = "t"
default:
prefix = "?"
}
return fmt.Sprintf("%v%v", prefix, num)
}
const (
maskKindPart = uint16(0x8000) // 1000 0000 0000 0000
maskNonTerminal = uint16(0x0000) // 0000 0000 0000 0000
maskTerminal = uint16(0x8000) // 1000 0000 0000 0000
maskSubKindpart = uint16(0x4000) // 0100 0000 0000 0000
maskNonStartAndEOF = uint16(0x0000) // 0000 0000 0000 0000
maskStartOrEOF = uint16(0x4000) // 0100 0000 0000 0000
maskNumberPart = uint16(0x3fff) // 0011 1111 1111 1111
symbolNumStart = uint16(0x0001) // 0000 0000 0000 0001
symbolNumEOF = uint16(0x0001) // 0000 0000 0000 0001
SymbolNil = Symbol(0) // 0000 0000 0000 0000
symbolStart = Symbol(maskNonTerminal | maskStartOrEOF | symbolNumStart) // 0100 0000 0000 0001
SymbolEOF = Symbol(maskTerminal | maskStartOrEOF | symbolNumEOF) // 1100 0000 0000 0001: The EOF symbol is treated as a terminal symbol.
// The symbol name contains `<` and `>` to avoid conflicting with user-defined symbols.
symbolNameEOF = "<eof>"
nonTerminalNumMin = SymbolNum(2) // The number 1 is used by a start symbol.
terminalNumMin = SymbolNum(2) // The number 1 is used by the EOF symbol.
symbolNumMax = SymbolNum(0xffff) >> 2 // 0011 1111 1111 1111
)
func newSymbol(kind symbolKind, isStart bool, num SymbolNum) (Symbol, error) {
if num > symbolNumMax {
return SymbolNil, fmt.Errorf("a symbol number exceeds the limit; limit: %v, passed: %v", symbolNumMax, num)
}
if kind == symbolKindTerminal && isStart {
return SymbolNil, fmt.Errorf("a start symbol must be a non-terminal symbol")
}
kindMask := maskNonTerminal
if kind == symbolKindTerminal {
kindMask = maskTerminal
}
startMask := maskNonStartAndEOF
if isStart {
startMask = maskStartOrEOF
}
return Symbol(kindMask | startMask | uint16(num)), nil
}
func (s Symbol) Num() SymbolNum {
_, _, _, num := s.describe()
return num
}
func (s Symbol) Byte() []byte {
if s.IsNil() {
return []byte{0, 0}
}
return []byte{byte(uint16(s) >> 8), byte(uint16(s) & 0x00ff)}
}
func (s Symbol) IsNil() bool {
_, _, _, num := s.describe()
return num == 0
}
func (s Symbol) IsStart() bool {
if s.IsNil() {
return false
}
_, isStart, _, _ := s.describe()
return isStart
}
func (s Symbol) isEOF() bool {
if s.IsNil() {
return false
}
_, _, isEOF, _ := s.describe()
return isEOF
}
func (s Symbol) isNonTerminal() bool {
if s.IsNil() {
return false
}
kind, _, _, _ := s.describe()
return kind == symbolKindNonTerminal
}
func (s Symbol) IsTerminal() bool {
if s.IsNil() {
return false
}
return !s.isNonTerminal()
}
func (s Symbol) describe() (symbolKind, bool, bool, SymbolNum) {
kind := symbolKindNonTerminal
if uint16(s)&maskKindPart > 0 {
kind = symbolKindTerminal
}
isStart := false
isEOF := false
if uint16(s)&maskSubKindpart > 0 {
if kind == symbolKindNonTerminal {
isStart = true
} else {
isEOF = true
}
}
num := SymbolNum(uint16(s) & maskNumberPart)
return kind, isStart, isEOF, num
}
type SymbolTable struct {
text2Sym map[string]Symbol
sym2Text map[Symbol]string
nonTermTexts []string
termTexts []string
nonTermNum SymbolNum
termNum SymbolNum
}
type SymbolTableWriter struct {
*SymbolTable
}
type SymbolTableReader struct {
*SymbolTable
}
func NewSymbolTable() *SymbolTable {
return &SymbolTable{
text2Sym: map[string]Symbol{
symbolNameEOF: SymbolEOF,
},
sym2Text: map[Symbol]string{
SymbolEOF: symbolNameEOF,
},
termTexts: []string{
"", // Nil
symbolNameEOF, // EOF
},
nonTermTexts: []string{
"", // Nil
"", // Start Symbol
},
nonTermNum: nonTerminalNumMin,
termNum: terminalNumMin,
}
}
func (t *SymbolTable) Writer() *SymbolTableWriter {
return &SymbolTableWriter{
SymbolTable: t,
}
}
func (t *SymbolTable) Reader() *SymbolTableReader {
return &SymbolTableReader{
SymbolTable: t,
}
}
func (w *SymbolTableWriter) RegisterStartSymbol(text string) (Symbol, error) {
w.text2Sym[text] = symbolStart
w.sym2Text[symbolStart] = text
w.nonTermTexts[symbolStart.Num().Int()] = text
return symbolStart, nil
}
func (w *SymbolTableWriter) RegisterNonTerminalSymbol(text string) (Symbol, error) {
if sym, ok := w.text2Sym[text]; ok {
return sym, nil
}
sym, err := newSymbol(symbolKindNonTerminal, false, w.nonTermNum)
if err != nil {
return SymbolNil, err
}
w.nonTermNum++
w.text2Sym[text] = sym
w.sym2Text[sym] = text
w.nonTermTexts = append(w.nonTermTexts, text)
return sym, nil
}
func (w *SymbolTableWriter) RegisterTerminalSymbol(text string) (Symbol, error) {
if sym, ok := w.text2Sym[text]; ok {
return sym, nil
}
sym, err := newSymbol(symbolKindTerminal, false, w.termNum)
if err != nil {
return SymbolNil, err
}
w.termNum++
w.text2Sym[text] = sym
w.sym2Text[sym] = text
w.termTexts = append(w.termTexts, text)
return sym, nil
}
func (r *SymbolTableReader) ToSymbol(text string) (Symbol, bool) {
if sym, ok := r.text2Sym[text]; ok {
return sym, true
}
return SymbolNil, false
}
func (r *SymbolTableReader) ToText(sym Symbol) (string, bool) {
text, ok := r.sym2Text[sym]
return text, ok
}
func (r *SymbolTableReader) TerminalSymbols() []Symbol {
syms := make([]Symbol, 0, r.termNum.Int()-terminalNumMin.Int())
for sym := range r.sym2Text {
if !sym.IsTerminal() || sym.IsNil() {
continue
}
syms = append(syms, sym)
}
sort.Slice(syms, func(i, j int) bool {
return syms[i] < syms[j]
})
return syms
}
func (r *SymbolTableReader) TerminalTexts() ([]string, error) {
if r.termNum == terminalNumMin {
return nil, fmt.Errorf("symbol table has no terminals")
}
return r.termTexts, nil
}
func (r *SymbolTableReader) NonTerminalSymbols() []Symbol {
syms := make([]Symbol, 0, r.nonTermNum.Int()-nonTerminalNumMin.Int())
for sym := range r.sym2Text {
if !sym.isNonTerminal() || sym.IsNil() {
continue
}
syms = append(syms, sym)
}
sort.Slice(syms, func(i, j int) bool {
return syms[i] < syms[j]
})
return syms
}
func (r *SymbolTableReader) NonTerminalTexts() ([]string, error) {
if r.nonTermNum == nonTerminalNumMin || r.nonTermTexts[symbolStart.Num().Int()] == "" {
return nil, fmt.Errorf("symbol table has no terminals or no start symbol")
}
return r.nonTermTexts, nil
}
|
