Source Code Cross Referenced for LocalVariableTable.java in  » 6.0-JDK-Modules-sun » tools » sun » tools » asm » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » 6.0 JDK Modules sun » tools » sun.tools.asm 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * Copyright 1995-2003 Sun Microsystems, Inc.  All Rights Reserved.
003:         * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004:         *
005:         * This code is free software; you can redistribute it and/or modify it
006:         * under the terms of the GNU General Public License version 2 only, as
007:         * published by the Free Software Foundation.  Sun designates this
008:         * particular file as subject to the "Classpath" exception as provided
009:         * by Sun in the LICENSE file that accompanied this code.
010:         *
011:         * This code is distributed in the hope that it will be useful, but WITHOUT
012:         * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013:         * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
014:         * version 2 for more details (a copy is included in the LICENSE file that
015:         * accompanied this code).
016:         *
017:         * You should have received a copy of the GNU General Public License version
018:         * 2 along with this work; if not, write to the Free Software Foundation,
019:         * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020:         *
021:         * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022:         * CA 95054 USA or visit www.sun.com if you need additional information or
023:         * have any questions.
024:         */
025:
026:        package sun.tools.asm;
027:
028:        import sun.tools.java.*;
029:        import java.io.IOException;
030:        import java.io.DataOutputStream;
031:
032:        /**
033:         * This class is used to assemble the local variable table.
034:         *
035:         * WARNING: The contents of this source file are not part of any
036:         * supported API.  Code that depends on them does so at its own risk:
037:         * they are subject to change or removal without notice.
038:         *
039:         * @author Arthur van Hoff
040:         * @version 	1.26, 05/05/07
041:         */
042:        final class LocalVariableTable {
043:            LocalVariable locals[] = new LocalVariable[8];
044:            int len;
045:
046:            /**
047:             * Define a new local variable. Merge entries where possible.
048:             */
049:            void define(MemberDefinition field, int slot, int from, int to) {
050:                if (from >= to) {
051:                    return;
052:                }
053:                for (int i = 0; i < len; i++) {
054:                    if ((locals[i].field == field) && (locals[i].slot == slot)
055:                            && (from <= locals[i].to) && (to >= locals[i].from)) {
056:                        locals[i].from = Math.min(locals[i].from, from);
057:                        locals[i].to = Math.max(locals[i].to, to);
058:                        return;
059:                    }
060:                }
061:                if (len == locals.length) {
062:                    LocalVariable newlocals[] = new LocalVariable[len * 2];
063:                    System.arraycopy(locals, 0, newlocals, 0, len);
064:                    locals = newlocals;
065:                }
066:                locals[len++] = new LocalVariable(field, slot, from, to);
067:            }
068:
069:            /**
070:             * Trim overlapping local ranges.  Java forbids shadowing of
071:             * locals in nested scopes, but non-nested scopes may still declare
072:             * locals with the same name.  Because local variable ranges are
073:             * computed using flow analysis as part of assembly, it isn't
074:             * possible to simply make sure variable ranges end where the
075:             * enclosing lexical scope ends.  This method makes sure that
076:             * variables with the same name don't overlap, giving priority to
077:             * fields with higher slot numbers that should have appeared later
078:             * in the source.
079:             */
080:            private void trim_ranges() {
081:                for (int i = 0; i < len; i++) {
082:                    for (int j = i + 1; j < len; j++) {
083:                        if ((locals[i].field.getName() == locals[j].field
084:                                .getName())
085:                                && (locals[i].from <= locals[j].to)
086:                                && (locals[i].to >= locals[j].from)) {
087:                            // At this point we know that both ranges are
088:                            // the same name and there is also overlap or they abut
089:                            if (locals[i].slot < locals[j].slot) {
090:                                if (locals[i].from < locals[j].from) {
091:                                    locals[i].to = Math.min(locals[i].to,
092:                                            locals[j].from);
093:                                } else {
094:                                    // We've detected two local variables with the
095:                                    // same name, and the one with the greater slot
096:                                    // number starts before the other.  This order
097:                                    // reversal may happen with locals with the same
098:                                    // name declared in both a try body and an
099:                                    // associated catch clause.  This is rare, and
100:                                    // we give up.
101:                                }
102:                            } else if (locals[i].slot > locals[j].slot) {
103:                                if (locals[i].from > locals[j].from) {
104:                                    locals[j].to = Math.min(locals[j].to,
105:                                            locals[i].from);
106:                                } else {
107:                                    // Same situation as above; just give up.
108:                                }
109:                            } else {
110:                                // This case can happen if there are two variables
111:                                // with the same name and slot numbers, and ranges
112:                                // that abut.  AFAIK the only way this can occur
113:                                // is with multiple static initializers.  Punt.
114:                            }
115:                        }
116:                    }
117:                }
118:            }
119:
120:            /**
121:             * Write out the data.
122:             */
123:            void write(Environment env, DataOutputStream out, ConstantPool tab)
124:                    throws IOException {
125:                trim_ranges();
126:                out.writeShort(len);
127:                for (int i = 0; i < len; i++) {
128:                    //System.out.println("pc=" + locals[i].from + ", len=" + (locals[i].to - locals[i].from) + ", nm=" + locals[i].field.getName() + ", slot=" + locals[i].slot);
129:                    out.writeShort(locals[i].from);
130:                    out.writeShort(locals[i].to - locals[i].from);
131:                    out.writeShort(tab.index(locals[i].field.getName()
132:                            .toString()));
133:                    out.writeShort(tab.index(locals[i].field.getType()
134:                            .getTypeSignature()));
135:                    out.writeShort(locals[i].slot);
136:                }
137:            }
138:        }
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