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package driver
import (
"fmt"
"io"
mldriver "github.com/nihei9/maleeni/driver"
"github.com/nihei9/vartan/spec"
)
type CST struct {
KindName string
Text string
Children []*CST
}
func printCST(cst *CST, depth int) {
for i := 0; i < depth; i++ {
fmt.Printf(" ")
}
fmt.Printf("%v", cst.KindName)
if cst.Text != "" {
fmt.Printf(` "%v"`, cst.Text)
}
fmt.Printf("\n")
for _, c := range cst.Children {
printCST(c, depth+1)
}
}
type semanticFrame struct {
cst *CST
}
type Parser struct {
gram *spec.CompiledGrammar
lex *mldriver.Lexer
stateStack []int
semStack []*semanticFrame
cst *CST
}
func NewParser(gram *spec.CompiledGrammar, src io.Reader) (*Parser, error) {
lex, err := mldriver.NewLexer(gram.LexicalSpecification.Maleeni.Spec, src)
if err != nil {
return nil, err
}
return &Parser{
gram: gram,
lex: lex,
stateStack: []int{},
semStack: []*semanticFrame{},
}, nil
}
func (p *Parser) Parse() error {
termCount := p.gram.ParsingTable.TerminalCount
p.push(p.gram.ParsingTable.InitialState)
tok, err := p.nextToken()
if err != nil {
return err
}
for {
var tsym int
if tok.EOF {
tsym = p.gram.ParsingTable.EOFSymbol
} else {
tsym = p.gram.LexicalSpecification.Maleeni.KindToTerminal[tok.Mode.Int()][tok.Kind]
}
act := p.gram.ParsingTable.Action[p.top()*termCount+tsym]
switch {
case act < 0: // Shift
tokText := tok.Text()
tok, err = p.shift(act * -1)
if err != nil {
return err
}
// semantic action
p.semStack = append(p.semStack, &semanticFrame{
cst: &CST{
KindName: p.gram.ParsingTable.Terminals[tsym],
Text: tokText,
},
})
case act > 0: // Reduce
accepted := p.reduce(act)
if accepted {
p.cst = p.semStack[len(p.semStack)-1].cst
return nil
}
// semantic action
prodNum := act
lhs := p.gram.ParsingTable.LHSSymbols[prodNum]
n := p.gram.ParsingTable.AlternativeSymbolCounts[prodNum]
children := []*CST{}
for _, f := range p.semStack[len(p.semStack)-n:] {
children = append(children, f.cst)
}
p.semStack = p.semStack[:len(p.semStack)-n]
p.semStack = append(p.semStack, &semanticFrame{
cst: &CST{
KindName: p.gram.ParsingTable.NonTerminals[lhs],
Children: children,
},
})
default:
return fmt.Errorf("unexpected token: %v", tok)
}
}
}
func (p *Parser) nextToken() (*mldriver.Token, error) {
skip := p.gram.LexicalSpecification.Maleeni.Skip
for {
tok, err := p.lex.Next()
if err != nil {
return nil, err
}
if tok.Invalid {
return nil, fmt.Errorf("invalid token: %+v", tok)
}
if skip[tok.Mode.Int()][tok.Kind] > 0 {
continue
}
return tok, nil
}
}
func (p *Parser) shift(nextState int) (*mldriver.Token, error) {
p.push(nextState)
return p.nextToken()
}
func (p *Parser) reduce(prodNum int) bool {
tab := p.gram.ParsingTable
lhs := tab.LHSSymbols[prodNum]
if lhs == tab.LHSSymbols[tab.StartProduction] {
return true
}
n := tab.AlternativeSymbolCounts[prodNum]
p.pop(n)
nextState := tab.GoTo[p.top()*tab.NonTerminalCount+lhs]
p.push(nextState)
return false
}
func (p *Parser) top() int {
return p.stateStack[len(p.stateStack)-1]
}
func (p *Parser) push(state int) {
p.stateStack = append(p.stateStack, state)
}
func (p *Parser) pop(n int) {
p.stateStack = p.stateStack[:len(p.stateStack)-n]
}
func (p *Parser) GetCST() *CST {
return p.cst
}
|
