commons-bcel-master/src/examples/Mini/ASTExpr.java
/*
 * 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.
 */
/* Generated By:JJTree: Do not edit this line. ASTExpr.java */
/* JJT: 0.3pre1 */

package Mini;

import org.apache.bcel.Const;
import org.apache.bcel.generic.BranchHandle;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.GOTO;
import org.apache.bcel.generic.IF_ICMPEQ;
import org.apache.bcel.generic.IF_ICMPGE;
import org.apache.bcel.generic.IF_ICMPGT;
import org.apache.bcel.generic.IF_ICMPLE;
import org.apache.bcel.generic.IF_ICMPLT;
import org.apache.bcel.generic.IF_ICMPNE;
import org.apache.bcel.generic.InstructionConst;
import org.apache.bcel.generic.InstructionList;
import org.apache.bcel.generic.MethodGen;
import org.apache.bcel.generic.PUSH;

/**
 * Represents arithmetic expressions such as '(a + 12 == b) OR c'. The parse tree is built initially by the parser and
 * modified, i.e. compacted with 'traverse()'. Each (Expr, Term, Factor) node with kind == -1 is replaced which its
 * successor node, which is converted to type 'Expr'
 *
 * A node with kind == -1 denotes the fact that this expression node has just one child branch and thus may be replaced
 * by this branch (or leaf) directly without altering the expression semantics. Term and Factor nodes are used only to
 * build the parse tree obeying the aritmetical precedences (* stronger than +, etc.) and are discarded in the first
 * pass.
 */
public class ASTExpr extends SimpleNode implements MiniParserConstants, MiniParserTreeConstants {
    public static Node jjtCreate(final MiniParser p, final int id) {
        return new ASTExpr(p, id);
    }

    private static String toBool(final String i) {
        return "(" + i + " != 0)";
    }

    private static String toInt(final String i) {
        return "((" + i + ")? 1 : 0)";
    }

    protected int kind = -1; // Single twig to leaf?
    private int unop = -1; // Special case: Unary operand applied
    protected ASTExpr[] exprs; // Sub expressions

    protected Environment env; // Needed in all passes

    protected int line, column;

    protected boolean is_simple; // true, if simple expression like '12 + f(a)'

    /*
     * Not all children shall inherit this, exceptions are ASTIdent and ASTFunAppl, which look up the type in the
     * corresponding environment entry.
     */
    protected int type = Const.T_UNKNOWN;

    /*
     * Special constructor, called from ASTTerm.traverse() and ASTFactor.traverse(), when traverse()ing the parse tree
     * replace themselves with Expr nodes.
     */
    ASTExpr(final ASTExpr[] children, final int kind, final int line, final int column) {
        this(line, column, kind, JJTEXPR);
        exprs = children;
    }

    // Generated methods
    ASTExpr(final int id) {
        super(id);
    }

    ASTExpr(final int line, final int column, final int id) {
        super(id);
        this.line = line;
        this.column = column;
    }

    ASTExpr(final int line, final int column, final int kind, final int id) {
        this(line, column, id);
        this.kind = kind;
    }

    ASTExpr(final MiniParser p, final int id) {
        super(p, id);
    }

    /**
     * Fifth pass, produce Java byte code.
     */
    public void byte_code(final InstructionList il, final MethodGen method, final ConstantPoolGen cp) {
        exprs[0].byte_code(il, method, cp);

        if (unop != -1) { // Apply unary operand
            if (unop == MINUS) {
                il.append(InstructionConst.INEG);
            } else { // == NOT
                il.append(new PUSH(cp, 1));
                ASTFunDecl.push(); // Push TRUE
                il.append(InstructionConst.IXOR);
                ASTFunDecl.pop();
            }
        } else { // Apply binary operand
            BranchHandle bh = null;

            exprs[1].byte_code(il, method, cp);

            switch (kind) {
            case PLUS:
                il.append(InstructionConst.IADD);
                ASTFunDecl.pop();
                break;
            case MINUS:
                il.append(InstructionConst.ISUB);
                ASTFunDecl.pop();
                break;
            case MULT:
                il.append(InstructionConst.IMUL);
                ASTFunDecl.pop();
                break;
            case DIV:
                il.append(InstructionConst.IDIV);
                ASTFunDecl.pop();
                break;
            case AND:
                il.append(InstructionConst.IAND);
                ASTFunDecl.pop();
                break;
            case OR:
                il.append(InstructionConst.IOR);
                ASTFunDecl.pop();
                break;

            /* Use negated operands */
            case EQ:
                bh = il.append(new IF_ICMPNE(null));
                ASTFunDecl.pop(2);
                break;
            case LEQ:
                bh = il.append(new IF_ICMPGT(null));
                ASTFunDecl.pop(2);
                break;
            case GEQ:
                bh = il.append(new IF_ICMPLT(null));
                ASTFunDecl.pop(2);
                break;
            case NEQ:
                bh = il.append(new IF_ICMPEQ(null));
                ASTFunDecl.pop(2);
                break;
            case LT:
                bh = il.append(new IF_ICMPGE(null));
                ASTFunDecl.pop(2);
                break;
            case GT:
                bh = il.append(new IF_ICMPLE(null));
                ASTFunDecl.pop(2);
                break;
            default:
                System.err.println("Unhandled case: " + kind);
            }

            switch (kind) {
            case EQ:
            case LEQ:
            case GEQ:
            case NEQ:
            case LT:
            case GT:
                BranchHandle g;

                il.append(new PUSH(cp, 1));
                g = il.append(new GOTO(null));
                bh.setTarget(il.append(new PUSH(cp, 0)));
                g.setTarget(il.append(InstructionConst.NOP)); // May be optimized away later
                ASTFunDecl.push();
                break;

            default:
                break;
            }
        }
    }

    /**
     * Overrides SimpleNode.closeNode(). Overridden by some subclasses.
     *
     * Called by the parser when the construction of this node is finished. Casts children Node[] to precise ASTExpr[] type.
     */
    @Override
    public void closeNode() {
        if (children != null) {
            exprs = new ASTExpr[children.length];
            System.arraycopy(children, 0, exprs, 0, children.length);
            children = null; // Throw away old reference
        }
    }

    /**
     * Fourth pass, produce Java code.
     */
    public void code(final StringBuffer buf) {
        if (unop != -1) {
            exprs[0].code(buf);
            final String top = ASTFunDecl.pop();
            if (unop == MINUS) {
                ASTFunDecl.push(buf, "-" + top);
            } else {
                ASTFunDecl.push(buf, "(" + top + " == 1)? 0 : 1)");
            }
        } else {
            exprs[0].code(buf);
            exprs[1].code(buf);
            final String _body_int2 = ASTFunDecl.pop();
            final String _body_int = ASTFunDecl.pop();

            switch (kind) {
            case PLUS:
                ASTFunDecl.push(buf, _body_int + " + " + _body_int2);
                break;
            case MINUS:
                ASTFunDecl.push(buf, _body_int + " - " + _body_int2);
                break;
            case MULT:
                ASTFunDecl.push(buf, _body_int + " * " + _body_int2);
                break;
            case DIV:
                ASTFunDecl.push(buf, _body_int + " / " + _body_int2);
                break;

            case AND:
                ASTFunDecl.push(buf, toInt(toBool(_body_int) + " && " + toBool(_body_int2)));
                break;
            case OR:
                ASTFunDecl.push(buf, toInt(toBool(_body_int) + " || " + toBool(_body_int2)));
                break;

            case EQ:
                ASTFunDecl.push(buf, toInt(_body_int + " == " + _body_int2));
                break;
            case LEQ:
                ASTFunDecl.push(buf, toInt(_body_int + " <= " + _body_int2));
                break;
            case GEQ:
                ASTFunDecl.push(buf, toInt(_body_int + " >= " + _body_int2));
                break;
            case NEQ:
                ASTFunDecl.push(buf, toInt(_body_int + " != " + _body_int2));
                break;
            case LT:
                ASTFunDecl.push(buf, toInt(_body_int + " < " + _body_int2));
                break;
            case GT:
                ASTFunDecl.push(buf, toInt(_body_int + " > " + _body_int2));
                break;

            default:
                System.err.println("Unhandled case: " + kind);
            }
        }
    }

    @Override
    public void dump(final String prefix) {
        System.out.println(toString(prefix));

        if (exprs != null) {
            for (final ASTExpr expr : exprs) {
                expr.dump(prefix + " ");
            }
        }
    }

    /**
     * Second and third pass
     *
     * @return type of expression
     * @param expected type
     */
    public int eval(final int expected) {
        int childType = Const.T_UNKNOWN, t;

        is_simple = true;

        // Determine expected node type depending on used operator.
        if (unop != -1) {
            if (unop == MINUS) {
                childType = type = Const.T_INT; // -
            } else {
                childType = type = Const.T_BOOLEAN; // !
            }
        } else // Compute expected type
        if (kind == PLUS || kind == MINUS || kind == MULT || kind == MOD || kind == DIV) {
            childType = type = Const.T_INT;
        } else if (kind == AND || kind == OR) {
            childType = type = Const.T_BOOLEAN;
        } else { // LEQ, GT, etc.
            childType = Const.T_INT;
            type = Const.T_BOOLEAN;
        }

        // Get type of subexpressions
        for (final ASTExpr expr : exprs) {
            t = expr.eval(childType);

            if (t != childType) {
                MiniC.addError(expr.getLine(), expr.getColumn(),
                        "Expression has not expected type " + Const.getTypeName(childType) + " but " + Const.getTypeName(t) + ".");
            }

            is_simple = is_simple && expr.isSimple();
        }

        return type;
    }

    public int getColumn() {
        return column;
    }

    public int getKind() {
        return kind;
    }

    public int getLine() {
        return line;
    }

    public int getType() {
        return type;
    }

    public int getUnOp() {
        return unop;
    }

    public boolean isSimple() {
        return is_simple;
    }

    public void setColumn(final int column) {
        this.column = column;
    }

    public void setKind(final int kind) {
        this.kind = kind;
    }

    public void setLine(final int line) {
        this.line = line;
    }

    public void setPosition(final int line, final int column) {
        this.line = line;
        this.column = column;
    }

    public void setType(final int type) {
        this.type = type;
    }

    public void setUnOp(final int unop) {
        this.unop = unop;
    }

    /**
     * @return name of node, its kind and the number of children.
     */
    @Override
    public String toString() {
        String op = "";
        final int len = children != null ? children.length : 0;
        if (unop != -1) {
            op = tokenImage[unop];
        } else if (kind != -1) {
            op = tokenImage[kind];
        }

        return jjtNodeName[id] + "(" + op + ")[" + len + "]<" + Const.getTypeName(type) + "> @" + line + ", " + column;
    }

    /**
     * First pass Overridden by subclasses. Traverse the whole parse tree recursively and drop redundant nodes.
     */
    public ASTExpr traverse(final Environment env) {
        this.env = env;

        if (kind == -1 && unop == -1) {
            return exprs[0].traverse(env); // --> Replaced by successor
        }
        for (int i = 0; i < exprs.length; i++) {
            exprs[i] = exprs[i].traverse(env); // References may change
        }

        return this;
    }
}
