/* * 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 */finalclass 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);        }    }}