|
1 package ro.infoiasi.donald.compiler.parser.runtime;
2
3 import java.util.Stack  ;
4
5 public abstract class SkeletonLRParser {
6 private Lexer lex;
7
8 protected StackSymbol currentToken;
9 protected Stack parseStack = new Stack ();
10 protected boolean doneParsing = false;
11 protected boolean DEBUG = false;
12
13 protected short[][] productionTable;
14 protected short[][] actionTable;
15 protected short[][] gotoTable;
16
17 public SkeletonLRParser() {
18 }
20
21 public SkeletonLRParser(Lexer lex) {
22 this();
23 setLexer(lex);
24 }
25
26 public void setLexer(Lexer lex) {
27 this.lex = lex;
28 }
29
30 public Lexer getLexer() {
31 return lex;
32 }
33
34 public abstract short[][] getProductionTable();
35 public abstract short[][] getActionTable();
36 public abstract short[][] getGotoTable();
37 public abstract int getStartState();
38 public abstract int getStartProduction();
39 public abstract int getEOF();
40 public abstract int getTokenOffset();
41 protected abstract void initActions() throws Exception ;
42
43 public abstract StackSymbol doAction(int actNo,
44 SkeletonLRParser parser, Stack stack)
45 throws Exception ;
46
47 public void initCode() throws Exception {
48 }
50 public StackSymbol scan()
51 throws Exception {
52 StackSymbol sym = getLexer().nextStackSymbol();
53 if (sym != null) {
54 return sym;
55 } else {
56 return new StackSymbol(getEOF());
57 }
58 }
59
60 public void doneParsing() {
61 doneParsing = true;
62 }
63
64 public StackSymbol parse() throws Exception {
65 int action;
66 StackSymbol lhs = null;
67 short rhsCount, lhsSID;
68
69 productionTable = getProductionTable();
70 actionTable = getActionTable();
71 gotoTable = getGotoTable();
72
73 initActions();
74 initCode();
75
76 currentToken = scan();
77 trace("# Current Symbol is " + currentToken.sym);
78
79 parseStack.removeAllElements();
80 parseStack.push(new StackSymbol(0, getStartState()));
81
82 while (!doneParsing) {
83 int state = ((StackSymbol)parseStack.peek()).parseState;
84 action = actionTable[state][currentToken.sym-getTokenOffset()];
85 if (action > 0) { currentToken.parseState = action-1;
87 parseStack.push(currentToken);
88 currentToken = scan();
89 } else if (action < 0) { int prod = (-action)-1;
91 lhs = doAction(prod, this, parseStack);
92 lhsSID = productionTable[prod][0];
93 rhsCount = productionTable[prod][1];
94 for (int i = 0; i<rhsCount; i++) {
95 parseStack.pop();
96 }
97
98 state = ((StackSymbol)parseStack.peek()).parseState;
99 action = gotoTable[state][lhsSID];
100
101 lhs.parseState = action;
102 parseStack.push(lhs);
103 } else { syntaxError(currentToken);
105 }
106 }
107 return lhs;
108 }
109
110 public void syntaxError(StackSymbol sym)
111 throws Exception {
112 reportFatalError("Syntax Error", sym);
114 }
115
116 public void reportError(String message, Object info) {
117 System.err.print(message);
118 if (info instanceof StackSymbol) {
119 StackSymbol sym = (StackSymbol)info;
120 if (sym.line != -1) {
121 System.err.print(" at line "+sym.line);
122 if (sym.column != -1) {
123 System.err.print(", column "+sym.column);
124 }
125 System.err.println(" of input");
126 }
127 } else {
128 System.err.println();
129 }
130 }
131
132 public void reportFatalError(String message, Object info)
133 throws java.lang.Exception {
134 doneParsing();
135 reportError(message, info);
136 throw new Exception ("Can't recover from previous error(s)");
137 }
138
139 private void trace(String message) {
140 if (DEBUG) {
141 System.out.println(message);
142 }
143 }
144
145 protected static short[][] unpackFromStrings(String [] sa) {
146 StringBuffer sb = new StringBuffer (sa[0]);
148 for (int i = 1; i<sa.length; i++) {
149 sb.append(sa[i]);
150 }
151 int n = 0; int size1 = (((int)sb.charAt(n))<<16) | ((int)sb.charAt(n+1)); n+=2;
153 short[][] result = new short[size1][];
154 for (int i=0; i<size1; i++) {
155 int size2 = (((int)sb.charAt(n))<<16) | ((int)sb.charAt(n+1)); n+=2;
156 result[i] = new short[size2];
157 for (int j=0; j<size2; j++)
158 result[i][j] = (short) (sb.charAt(n++)-2);
159 }
160 return result;
161 }
162 }
163 |
Popular Tags |
Java API By Example, From Geeks To Geeks.