/*

 * Copyright (c) 1995, 2003, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.tools.asm;

import sun.tools.java.*;

import java.io.IOException;

import java.io.DataOutputStream;

/**

 * This class is used to assemble the local variable table.

 *

 * WARNING: The contents of this source file are not part of any

 * supported API.  Code that depends on them does so at its own risk:

 * they are subject to change or removal without notice.

 *

 * @author Arthur van Hoff

 */

final

class LocalVariableTable {

    LocalVariable locals[] = new LocalVariable[8];

    int len;

    /**

     * Define a new local variable. Merge entries where possible.

     */

    void define(MemberDefinition field, int slot, int from, int to) {

        if (from >= to) {

            return;

        }

        for (int i = 0 ; i < len ; i++) {

            if ((locals[i].field == field) && (locals[i].slot == slot) &&

                (from <= locals[i].to) && (to >= locals[i].from)) {

                locals[i].from = Math.min(locals[i].from, from);

                locals[i].to = Math.max(locals[i].to, to);

                return;

            }

        }

        if (len == locals.length) {

            LocalVariable newlocals[] = new LocalVariable[len * 2];

            System.arraycopy(locals, 0, newlocals, 0, len);

            locals = newlocals;

        }

        locals[len++] = new LocalVariable(field, slot, from, to);

    }

    /**

     * Trim overlapping local ranges.  Java forbids shadowing of

     * locals in nested scopes, but non-nested scopes may still declare

     * locals with the same name.  Because local variable ranges are

     * computed using flow analysis as part of assembly, it isn't

     * possible to simply make sure variable ranges end where the

     * enclosing lexical scope ends.  This method makes sure that

     * variables with the same name don't overlap, giving priority to

     * fields with higher slot numbers that should have appeared later

     * in the source.

     */

    private void trim_ranges() {

        for (int i=0; i<len; i++) {

            for (int j=i+1; j<len; j++) {

                if ((locals[i].field.getName()==locals[j].field.getName())

                        && (locals[i].from <= locals[j].to)

                        && (locals[i].to >= locals[j].from)) {

                    // At this point we know that both ranges are

                    // the same name and there is also overlap or they abut

                    if (locals[i].slot < locals[j].slot) {

                        if (locals[i].from < locals[j].from) {

                          locals[i].to = Math.min(locals[i].to, locals[j].from);

                        } else {

                          // We've detected two local variables with the

                          // same name, and the one with the greater slot

                          // number starts before the other.  This order

                          // reversal may happen with locals with the same

                          // name declared in both a try body and an

                          // associated catch clause.  This is rare, and

                          // we give up.

                        }

                    } else if (locals[i].slot > locals[j].slot) {

                        if (locals[i].from > locals[j].from) {

                          locals[j].to = Math.min(locals[j].to, locals[i].from);

                        } else {

                          // Same situation as above; just give up.

                        }

                    } else {

                        // This case can happen if there are two variables

                        // with the same name and slot numbers, and ranges

                        // that abut.  AFAIK the only way this can occur

                        // is with multiple static initializers.  Punt.

                    }

                }

            }

        }

    }

    /**

     * Write out the data.

     */

    void write(Environment env, DataOutputStream out, ConstantPool tab) throws IOException {

        trim_ranges();

        out.writeShort(len);

        for (int i = 0 ; i < len ; i++) {

            //System.out.println("pc=" + locals[i].from + ", len=" + (locals[i].to - locals[i].from) + ", nm=" + locals[i].field.getName() + ", slot=" + locals[i].slot);

            out.writeShort(locals[i].from);

            out.writeShort(locals[i].to - locals[i].from);

            out.writeShort(tab.index(locals[i].field.getName().toString()));

            out.writeShort(tab.index(locals[i].field.getType().getTypeSignature()));

            out.writeShort(locals[i].slot);

        }

    }

}