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package main
import (
"encoding/json"
"fmt"
"os"
"github.com/nihei9/vartan/grammar"
"github.com/nihei9/vartan/spec"
"github.com/spf13/cobra"
)
var compileFlags = struct {
grammar *string
output *string
}{}
func init() {
cmd := &cobra.Command{
Use: "compile",
Short: "Compile a grammar into a parsing table",
Example: ` cat grammar | vartan compile -o grammar.json`,
RunE: runCompile,
}
compileFlags.grammar = cmd.Flags().StringP("grammar", "g", "", "grammar file path (default stdin)")
compileFlags.output = cmd.Flags().StringP("output", "o", "", "output file path (default stdout)")
rootCmd.AddCommand(cmd)
}
func runCompile(cmd *cobra.Command, args []string) (retErr error) {
gram, err := readGrammar(*compileFlags.grammar)
if err != nil {
return err
}
cgram, err := grammar.Compile(gram)
if err != nil {
return err
}
err = writeCompiledGrammar(cgram, *compileFlags.output)
if err != nil {
return fmt.Errorf("Cannot write a compiled grammar: %w", err)
}
return nil
}
func readGrammar(path string) (*grammar.Grammar, error) {
r := os.Stdin
if path != "" {
f, err := os.Open(path)
if err != nil {
return nil, fmt.Errorf("Cannot open the grammar file %s: %w", path, err)
}
defer f.Close()
r = f
}
ast, err := spec.Parse(r)
if err != nil {
return nil, err
}
return grammar.NewGrammar(ast)
}
func writeCompiledGrammar(cgram *spec.CompiledGrammar, path string) error {
out, err := json.Marshal(cgram)
if err != nil {
return err
}
w := os.Stdout
if path != "" {
f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
if err != nil {
return fmt.Errorf("Cannot open the output file %s: %w", path, err)
}
defer f.Close()
w = f
}
fmt.Fprintf(w, "%v\n", string(out))
return nil
}
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