001 /* 002 * Copyright (C) 2010 eXo Platform SAS. 003 * 004 * This is free software; you can redistribute it and/or modify it 005 * under the terms of the GNU Lesser General Public License as 006 * published by the Free Software Foundation; either version 2.1 of 007 * the License, or (at your option) any later version. 008 * 009 * This software is distributed in the hope that it will be useful, 010 * but WITHOUT ANY WARRANTY; without even the implied warranty of 011 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 012 * Lesser General Public License for more details. 013 * 014 * You should have received a copy of the GNU Lesser General Public 015 * License along with this software; if not, write to the Free 016 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 017 * 02110-1301 USA, or see the FSF site: http://www.fsf.org. 018 */ 019 020 package org.crsh.shell.impl; 021 022 import org.crsh.command.SyntaxException; 023 024 /** 025 * @author <a href="mailto:julien.viet@exoplatform.com">Julien Viet</a> 026 * @version $Revision$ 027 */ 028 class Parser { 029 030 /** . */ 031 private Tokenizer tokenizer; 032 033 /** . */ 034 private Token token; 035 036 public Parser(CharSequence s) { 037 this.tokenizer = new Tokenizer(s); 038 this.token = tokenizer.nextToken(); 039 } 040 041 042 /* 043 044 grammar 045 046 expr -> term | term "|" expr 047 term -> cmd | cmd "+" term 048 049 */ 050 051 public AST parse() { 052 if (token == Token.EOF) { 053 return null; 054 } else { 055 return parseExpr(); 056 } 057 } 058 059 private AST.Expr parseExpr() { 060 AST.Term term = parseTerm(); 061 if (token == Token.EOF) { 062 return new AST.Expr(term); 063 } else if (token == Token.PIPE) { 064 token = tokenizer.nextToken(); 065 AST.Expr next = parseExpr(); 066 return new AST.Expr(term, next); 067 } else { 068 throw new SyntaxException("Syntax error"); 069 } 070 } 071 072 private AST.Term parseTerm() { 073 if (token instanceof Token.Command) { 074 Token.Command command = (Token.Command)token; 075 token = tokenizer.nextToken(); 076 if (token == Token.PLUS) { 077 token = tokenizer.nextToken(); 078 AST.Term next = parseTerm(); 079 return new AST.Term(command.line, next); 080 } else { 081 return new AST.Term(command.line); 082 } 083 } else { 084 throw new SyntaxException("Syntax error"); 085 } 086 } 087 }