| /*** |
| * ASM: a very small and fast Java bytecode manipulation framework |
| * Copyright (c) 2000-2005 INRIA, France Telecom |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. Neither the name of the copyright holders nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
| * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
| * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF |
| * THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| package org.objectweb.asm; |
| |
| /** |
| * A label represents a position in the bytecode of a method. Labels are used |
| * for jump, goto, and switch instructions, and for try catch blocks. |
| * |
| * @author Eric Bruneton |
| */ |
| public class Label { |
| |
| /** |
| * The line number corresponding to this label, if known. |
| */ |
| int line; |
| |
| /** |
| * Indicates if the position of this label is known. |
| */ |
| boolean resolved; |
| |
| /** |
| * The position of this label in the code, if known. |
| */ |
| int position; |
| |
| /** |
| * If the label position has been updated, after instruction resizing. |
| */ |
| boolean resized; |
| |
| /** |
| * Number of forward references to this label, times two. |
| */ |
| private int referenceCount; |
| |
| /** |
| * Informations about forward references. Each forward reference is |
| * described by two consecutive integers in this array: the first one is the |
| * position of the first byte of the bytecode instruction that contains the |
| * forward reference, while the second is the position of the first byte of |
| * the forward reference itself. In fact the sign of the first integer |
| * indicates if this reference uses 2 or 4 bytes, and its absolute value |
| * gives the position of the bytecode instruction. |
| */ |
| private int[] srcAndRefPositions; |
| |
| /* |
| * Fields for the control flow graph analysis algorithm (used to compute the |
| * maximum stack size). A control flow graph contains one node per "basic |
| * block", and one edge per "jump" from one basic block to another. Each |
| * node (i.e., each basic block) is represented by the Label object that |
| * corresponds to the first instruction of this basic block. Each node also |
| * stores the list of it successors in the graph, as a linked list of Edge |
| * objects. |
| */ |
| |
| /** |
| * The stack size at the beginning of this basic block. This size is |
| * initially unknown. It is computed by the control flow analysis algorithm |
| * (see {@link MethodWriter#visitMaxs visitMaxs}). |
| */ |
| int beginStackSize; |
| |
| /** |
| * The (relative) maximum stack size corresponding to this basic block. This |
| * size is relative to the stack size at the beginning of the basic block, |
| * i.e., the true maximum stack size is equal to {@link #beginStackSize |
| * beginStackSize} + {@link #maxStackSize maxStackSize}. |
| */ |
| int maxStackSize; |
| |
| /** |
| * The successors of this node in the control flow graph. These successors |
| * are stored in a linked list of {@link Edge Edge} objects, linked to each |
| * other by their {@link Edge#next} field. |
| */ |
| Edge successors; |
| |
| /** |
| * The next basic block in the basic block stack. See |
| * {@link MethodWriter#visitMaxs visitMaxs}. |
| */ |
| Label next; |
| |
| /** |
| * <tt>true</tt> if this basic block has been pushed in the basic block |
| * stack. See {@link MethodWriter#visitMaxs visitMaxs}. |
| */ |
| boolean pushed; |
| |
| // ------------------------------------------------------------------------ |
| // Constructor |
| // ------------------------------------------------------------------------ |
| |
| /** |
| * Constructs a new label. |
| */ |
| public Label() { |
| } |
| |
| // ------------------------------------------------------------------------ |
| // Methods to compute offsets and to manage forward references |
| // ------------------------------------------------------------------------ |
| |
| /** |
| * Returns the offset corresponding to this label. This offset is computed |
| * from the start of the method's bytecode. <i>This method is intended for |
| * {@link Attribute} sub classes, and is normally not needed by class |
| * generators or adapters.</i> |
| * |
| * @return the offset corresponding to this label. |
| * @throws IllegalStateException if this label is not resolved yet. |
| */ |
| public int getOffset() { |
| if (!resolved) { |
| throw new IllegalStateException("Label offset position has not been resolved yet"); |
| } |
| return position; |
| } |
| |
| /** |
| * Puts a reference to this label in the bytecode of a method. If the |
| * position of the label is known, the offset is computed and written |
| * directly. Otherwise, a null offset is written and a new forward reference |
| * is declared for this label. |
| * |
| * @param owner the code writer that calls this method. |
| * @param out the bytecode of the method. |
| * @param source the position of first byte of the bytecode instruction that |
| * contains this label. |
| * @param wideOffset <tt>true</tt> if the reference must be stored in 4 |
| * bytes, or <tt>false</tt> if it must be stored with 2 bytes. |
| * @throws IllegalArgumentException if this label has not been created by |
| * the given code writer. |
| */ |
| void put( |
| final MethodWriter owner, |
| final ByteVector out, |
| final int source, |
| final boolean wideOffset) |
| { |
| if (resolved) { |
| if (wideOffset) { |
| out.putInt(position - source); |
| } else { |
| out.putShort(position - source); |
| } |
| } else { |
| if (wideOffset) { |
| addReference(-1 - source, out.length); |
| out.putInt(-1); |
| } else { |
| addReference(source, out.length); |
| out.putShort(-1); |
| } |
| } |
| } |
| |
| /** |
| * Adds a forward reference to this label. This method must be called only |
| * for a true forward reference, i.e. only if this label is not resolved |
| * yet. For backward references, the offset of the reference can be, and |
| * must be, computed and stored directly. |
| * |
| * @param sourcePosition the position of the referencing instruction. This |
| * position will be used to compute the offset of this forward |
| * reference. |
| * @param referencePosition the position where the offset for this forward |
| * reference must be stored. |
| */ |
| private void addReference( |
| final int sourcePosition, |
| final int referencePosition) |
| { |
| if (srcAndRefPositions == null) { |
| srcAndRefPositions = new int[6]; |
| } |
| if (referenceCount >= srcAndRefPositions.length) { |
| int[] a = new int[srcAndRefPositions.length + 6]; |
| System.arraycopy(srcAndRefPositions, |
| 0, |
| a, |
| 0, |
| srcAndRefPositions.length); |
| srcAndRefPositions = a; |
| } |
| srcAndRefPositions[referenceCount++] = sourcePosition; |
| srcAndRefPositions[referenceCount++] = referencePosition; |
| } |
| |
| /** |
| * Resolves all forward references to this label. This method must be called |
| * when this label is added to the bytecode of the method, i.e. when its |
| * position becomes known. This method fills in the blanks that where left |
| * in the bytecode by each forward reference previously added to this label. |
| * |
| * @param owner the code writer that calls this method. |
| * @param position the position of this label in the bytecode. |
| * @param data the bytecode of the method. |
| * @return <tt>true</tt> if a blank that was left for this label was to |
| * small to store the offset. In such a case the corresponding jump |
| * instruction is replaced with a pseudo instruction (using unused |
| * opcodes) using an unsigned two bytes offset. These pseudo |
| * instructions will need to be replaced with true instructions with |
| * wider offsets (4 bytes instead of 2). This is done in |
| * {@link MethodWriter#resizeInstructions}. |
| * @throws IllegalArgumentException if this label has already been resolved, |
| * or if it has not been created by the given code writer. |
| */ |
| boolean resolve( |
| final MethodWriter owner, |
| final int position, |
| final byte[] data) |
| { |
| boolean needUpdate = false; |
| this.resolved = true; |
| this.position = position; |
| int i = 0; |
| while (i < referenceCount) { |
| int source = srcAndRefPositions[i++]; |
| int reference = srcAndRefPositions[i++]; |
| int offset; |
| if (source >= 0) { |
| offset = position - source; |
| if (offset < Short.MIN_VALUE || offset > Short.MAX_VALUE) { |
| /* |
| * changes the opcode of the jump instruction, in order to |
| * be able to find it later (see resizeInstructions in |
| * MethodWriter). These temporary opcodes are similar to |
| * jump instruction opcodes, except that the 2 bytes offset |
| * is unsigned (and can therefore represent values from 0 to |
| * 65535, which is sufficient since the size of a method is |
| * limited to 65535 bytes). |
| */ |
| int opcode = data[reference - 1] & 0xFF; |
| if (opcode <= Opcodes.JSR) { |
| // changes IFEQ ... JSR to opcodes 202 to 217 |
| data[reference - 1] = (byte) (opcode + 49); |
| } else { |
| // changes IFNULL and IFNONNULL to opcodes 218 and 219 |
| data[reference - 1] = (byte) (opcode + 20); |
| } |
| needUpdate = true; |
| } |
| data[reference++] = (byte) (offset >>> 8); |
| data[reference] = (byte) offset; |
| } else { |
| offset = position + source + 1; |
| data[reference++] = (byte) (offset >>> 24); |
| data[reference++] = (byte) (offset >>> 16); |
| data[reference++] = (byte) (offset >>> 8); |
| data[reference] = (byte) offset; |
| } |
| } |
| return needUpdate; |
| } |
| |
| // ------------------------------------------------------------------------ |
| // Overriden Object methods |
| // ------------------------------------------------------------------------ |
| |
| /** |
| * Returns a string representation of this label. |
| * |
| * @return a string representation of this label. |
| */ |
| public String toString() { |
| return "L" + System.identityHashCode(this); |
| } |
| } |
