| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.mrql.gen; |
| |
| import java.io.*; |
| import java.util.Iterator; |
| |
| |
| /* A symbol in the symbol table */ |
| class SymbolCell { |
| String name; |
| Tree binding; |
| SymbolCell next; |
| SymbolCell ( String n, Tree v, SymbolCell r ) { name=n; binding=v; next=r; } |
| } |
| |
| |
| final class SymbolTableIterator implements Iterator<String> { |
| SymbolTable table; |
| SymbolTable original_table; |
| |
| SymbolTableIterator ( SymbolTable t ) { |
| table = new SymbolTable(); |
| original_table = t; |
| for ( int i = 0; i < t.symbol_table_size; i++ ) |
| table.symbol_table[i] = t.symbol_table[i]; |
| for ( int i = 0; i < t.scope_stack.length; i++ ) |
| table.scope_stack[i] = t.scope_stack[i]; |
| table.scope_stack_top = t.scope_stack_top; |
| } |
| |
| public boolean hasNext () { |
| if (table.scope_stack_top <= 0) |
| return false; |
| int n = table.scope_stack[table.scope_stack_top-1]; |
| if (n < 0 || !table.symbol_table[n].binding.equals(original_table.lookup(table.symbol_table[n].name))) { |
| table.scope_stack_top--; |
| return hasNext(); |
| }; |
| return true; |
| } |
| |
| public String next () { |
| int n = table.scope_stack[--table.scope_stack_top]; |
| String var = table.symbol_table[n].name; |
| table.symbol_table[n] = table.symbol_table[n].next; |
| return var; |
| } |
| |
| public void remove () {} |
| } |
| |
| |
| public class SymbolTable implements Iterable<String> { |
| final static int symbol_table_size = 997; |
| final static int initial_scope_stack_length = 1000; |
| |
| SymbolCell[] symbol_table; |
| int[] scope_stack; |
| int scope_stack_top = 0; |
| |
| public SymbolTable () { |
| symbol_table = new SymbolCell[symbol_table_size]; |
| scope_stack = new int[initial_scope_stack_length]; |
| scope_stack_top = 0; |
| for (int i = 0; i < symbol_table_size; i++) |
| symbol_table[i] = null; |
| } |
| |
| public Iterator<String> iterator () { |
| return new SymbolTableIterator(this); |
| } |
| |
| /* a hashing function for strings */ |
| int hash ( String s ) { |
| return Math.abs(s.hashCode()) % symbol_table_size; |
| } |
| |
| /* insert a new item in the symbol table */ |
| public void insert ( String key, Tree binding ) { |
| int loc = hash(key); |
| symbol_table[loc] = new SymbolCell(key,binding,symbol_table[loc]); |
| if (scope_stack_top >= scope_stack.length) { |
| int[] v = new int[scope_stack.length*2]; |
| for ( int i = 0; i < scope_stack.length; i++ ) |
| v[i] = scope_stack[i]; |
| scope_stack = v; |
| }; |
| scope_stack[scope_stack_top++] = loc; |
| } |
| |
| /* replace an item with a given name in the symbol table */ |
| public void replace ( String key, Tree binding ) { |
| int loc = hash(key); |
| for (SymbolCell s = symbol_table[loc]; s != null; s=s.next) |
| if (s.name.equals(key)) |
| s.binding = binding; |
| } |
| |
| /* remove an item with a given name from the symbol table */ |
| public boolean remove ( String key ) { |
| int loc = hash(key); |
| SymbolCell prev = symbol_table[loc]; |
| if (prev == null) |
| return false; |
| if (prev.name.equals(key)) { |
| symbol_table[loc] = prev.next; |
| return true; |
| }; |
| for (SymbolCell s = prev.next; s != null; s=s.next, prev=prev.next) |
| if (s.name.equals(key)) { |
| prev.next = s.next; |
| return true; |
| }; |
| return false; |
| } |
| |
| /* lookup for an item in the symbol table */ |
| public Tree lookup ( String key ) { |
| int loc = hash(key); |
| for (SymbolCell s = symbol_table[loc]; s != null; s=s.next) |
| if (s.name.equals(key)) |
| return s.binding; |
| return null; // if not found |
| } |
| |
| /* return true if key is local */ |
| public boolean is_local ( String key ) { |
| int loc = hash(key); |
| int i = 0; |
| for ( SymbolCell s = symbol_table[loc]; s != null; s = s.next, i++ ) |
| if (s.name.equals(key)) { |
| int k = 0; |
| for ( int j = scope_stack_top-1; j >= 0 && scope_stack[j] >= 0; j--) |
| if (scope_stack[j] == loc) |
| if (k++ == i) |
| return true; |
| return false; |
| }; |
| return false; // if not found |
| } |
| |
| /* start a new environment */ |
| public void begin_scope () { |
| if (scope_stack_top >= scope_stack.length) { |
| int[] v = new int[scope_stack.length*2]; |
| for ( int i = 0; i < scope_stack.length; i++ ) |
| v[i] = scope_stack[i]; |
| scope_stack = v; |
| }; |
| scope_stack[scope_stack_top++] = -1; |
| } |
| |
| /* pop the last environment */ |
| public void end_scope () { |
| int i = scope_stack_top-1; |
| for (; scope_stack[i]>=0 && i>0; i--) { |
| int loc = scope_stack[i]; |
| symbol_table[loc] = symbol_table[loc].next; |
| }; |
| scope_stack_top = i; |
| } |
| |
| /* display the content of the symbol table */ |
| public void display () { |
| SymbolCell[] s = new SymbolCell[symbol_table_size]; |
| for (int i = 0; i<symbol_table_size; i++) |
| s[i] = symbol_table[i]; |
| for (int i = scope_stack_top-1; i>=0; i--) |
| if (scope_stack[i] == -1) |
| System.out.println("----------------"); |
| else { |
| SymbolCell c = s[scope_stack[i]]; |
| s[scope_stack[i]] = c.next; |
| System.out.println(c.name + ": " + c.binding); |
| } |
| } |
| } |