Java tutorial
// ASM: a very small and fast Java bytecode manipulation framework // Copyright (c) 2000-2011 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 position in the bytecode of a method. Labels are used for jump, goto, and switch instructions, * and for try catch blocks. A label designates the <i>instruction</i> that is just after. Note * however that there can be other elements between a label and the instruction it designates (such * as other labels, stack map frames, line numbers, etc.). * * @author Eric Bruneton */ public class Label { /** * A flag indicating that a label is only used for debug attributes. Such a label is not the start * of a basic block, the target of a jump instruction, or an exception handler. It can be safely * ignored in control flow graph analysis algorithms (for optimization purposes). */ static final int FLAG_DEBUG_ONLY = 1; /** * A flag indicating that a label is the target of a jump instruction, or the start of an * exception handler. */ static final int FLAG_JUMP_TARGET = 2; /** A flag indicating that the bytecode offset of a label is known. */ static final int FLAG_RESOLVED = 4; /** A flag indicating that a label corresponds to a reachable basic block. */ static final int FLAG_REACHABLE = 8; /** * A flag indicating that the basic block corresponding to a label ends with a subroutine call. By * construction in {@link MethodWriter#visitJumpInsn}, labels with this flag set have at least two * outgoing edges: * * <ul> * <li>the first one corresponds to the instruction that follows the jsr instruction in the * bytecode, i.e. where execution continues when it returns from the jsr call. This is a * virtual control flow edge, since execution never goes directly from the jsr to the next * instruction. Instead, it goes to the subroutine and eventually returns to the instruction * following the jsr. This virtual edge is used to compute the real outgoing edges of the * basic blocks ending with a ret instruction, in {@link #addSubroutineRetSuccessors}. * <li>the second one corresponds to the target of the jsr instruction, * </ul> */ static final int FLAG_SUBROUTINE_CALLER = 16; /** * A flag indicating that the basic block corresponding to a label is the start of a subroutine. */ static final int FLAG_SUBROUTINE_START = 32; /** A flag indicating that the basic block corresponding to a label is the end of a subroutine. */ static final int FLAG_SUBROUTINE_END = 64; /** * The number of elements to add to the {@link #otherLineNumbers} array when it needs to be * resized to store a new source line number. */ static final int LINE_NUMBERS_CAPACITY_INCREMENT = 4; /** * The number of elements to add to the {@link #forwardReferences} array when it needs to be * resized to store a new forward reference. */ static final int FORWARD_REFERENCES_CAPACITY_INCREMENT = 6; /** * The bit mask to extract the type of a forward reference to this label. The extracted type is * either {@link #FORWARD_REFERENCE_TYPE_SHORT} or {@link #FORWARD_REFERENCE_TYPE_WIDE}. * * @see #forwardReferences */ static final int FORWARD_REFERENCE_TYPE_MASK = 0xF0000000; /** * The type of forward references stored with two bytes in the bytecode. This is the case, for * instance, of a forward reference from an ifnull instruction. */ static final int FORWARD_REFERENCE_TYPE_SHORT = 0x10000000; /** * The type of forward references stored in four bytes in the bytecode. This is the case, for * instance, of a forward reference from a lookupswitch instruction. */ static final int FORWARD_REFERENCE_TYPE_WIDE = 0x20000000; /** * The bit mask to extract the 'handle' of a forward reference to this label. The extracted handle * is the bytecode offset where the forward reference value is stored (using either 2 or 4 bytes, * as indicated by the {@link #FORWARD_REFERENCE_TYPE_MASK}). * * @see #forwardReferences */ static final int FORWARD_REFERENCE_HANDLE_MASK = 0x0FFFFFFF; /** * A sentinel element used to indicate the end of a list of labels. * * @see #nextListElement */ static final Label EMPTY_LIST = new Label(); /** * A user managed state associated with this label. Warning: this field is used by the ASM tree * package. In order to use it with the ASM tree package you must override the getLabelNode method * in MethodNode. */ public Object info; /** * The type and status of this label or its corresponding basic block. Must be zero or more of * {@link #FLAG_DEBUG_ONLY}, {@link #FLAG_JUMP_TARGET}, {@link #FLAG_RESOLVED}, {@link * #FLAG_REACHABLE}, {@link #FLAG_SUBROUTINE_CALLER}, {@link #FLAG_SUBROUTINE_START}, {@link * #FLAG_SUBROUTINE_END}. */ short flags; /** * The source line number corresponding to this label, or 0. If there are several source line * numbers corresponding to this label, the first one is stored in this field, and the remaining * ones are stored in {@link #otherLineNumbers}. */ private short lineNumber; /** * The source line numbers corresponding to this label, in addition to {@link #lineNumber}, or * null. The first element of this array is the number n of source line numbers it contains, which * are stored between indices 1 and n (inclusive). */ private int[] otherLineNumbers; /** * The offset of this label in the bytecode of its method, in bytes. This value is set if and only * if the {@link #FLAG_RESOLVED} flag is set. */ int bytecodeOffset; /** * The forward references to this label. The first element is the number of forward references, * times 2 (this corresponds to the index of the last element actually used in this array). Then, * each forward reference is described with two consecutive integers noted * 'sourceInsnBytecodeOffset' and 'reference': * * <ul> * <li>'sourceInsnBytecodeOffset' is the bytecode offset of the instruction that contains the * forward reference, * <li>'reference' contains the type and the offset in the bytecode where the forward reference * value must be stored, which can be extracted with {@link #FORWARD_REFERENCE_TYPE_MASK} * and {@link #FORWARD_REFERENCE_HANDLE_MASK}. * </ul> * * <p>For instance, for an ifnull instruction at bytecode offset x, 'sourceInsnBytecodeOffset' is * equal to x, and 'reference' is of type {@link #FORWARD_REFERENCE_TYPE_SHORT} with value x + 1 * (because the ifnull instruction uses a 2 bytes bytecode offset operand stored one byte after * the start of the instruction itself). For the default case of a lookupswitch instruction at * bytecode offset x, 'sourceInsnBytecodeOffset' is equal to x, and 'reference' is of type {@link * #FORWARD_REFERENCE_TYPE_WIDE} with value between x + 1 and x + 4 (because the lookupswitch * instruction uses a 4 bytes bytecode offset operand stored one to four bytes after the start of * the instruction itself). */ private int[] forwardReferences; // ----------------------------------------------------------------------------------------------- // Fields for the control flow and data flow graph analysis algorithms (used to compute the // maximum stack size or the stack map frames). 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 with the Label object that corresponds to the first instruction of this // basic block. Each node also stores the list of its successors in the graph, as a linked list of // Edge objects. // // The control flow analysis algorithms used to compute the maximum stack size or the stack map // frames are similar and use two steps. The first step, during the visit of each instruction, // builds information about the state of the local variables and the operand stack at the end of // each basic block, called the "output frame", <i>relatively</i> to the frame state at the // beginning of the basic block, which is called the "input frame", and which is <i>unknown</i> // during this step. The second step, in {@link MethodWriter#computeAllFrames} and {@link // MethodWriter#computeMaxStackAndLocal}, is a fix point algorithm // that computes information about the input frame of each basic block, from the input state of // the first basic block (known from the method signature), and by the using the previously // computed relative output frames. // // The algorithm used to compute the maximum stack size only computes the relative output and // absolute input stack heights, while the algorithm used to compute stack map frames computes // relative output frames and absolute input frames. /** * The number of elements in the input stack of the basic block corresponding to this label. This * field is computed in {@link MethodWriter#computeMaxStackAndLocal}. */ short inputStackSize; /** * The number of elements in the output stack, at the end of the basic block corresponding to this * label. This field is only computed for basic blocks that end with a RET instruction. */ short outputStackSize; /** * The maximum height reached by the output stack, relatively to the top of the input stack, in * the basic block corresponding to this label. This maximum is always positive or {@literal * null}. */ short outputStackMax; /** * The id of the subroutine to which this basic block belongs, or 0. If the basic block belongs to * several subroutines, this is the id of the "oldest" subroutine that contains it (with the * convention that a subroutine calling another one is "older" than the callee). This field is * computed in {@link MethodWriter#computeMaxStackAndLocal}, if the method contains JSR * instructions. */ short subroutineId; /** * The input and output stack map frames of the basic block corresponding to this label. This * field is only used when the {@link MethodWriter#COMPUTE_ALL_FRAMES} or {@link * MethodWriter#COMPUTE_INSERTED_FRAMES} option is used. */ Frame frame; /** * The successor of this label, in the order they are visited in {@link MethodVisitor#visitLabel}. * This linked list does not include labels used for debug info only. If the {@link * MethodWriter#COMPUTE_ALL_FRAMES} or {@link MethodWriter#COMPUTE_INSERTED_FRAMES} option is used * then it does not contain either successive labels that denote the same bytecode offset (in this * case only the first label appears in this list). */ Label nextBasicBlock; /** * The outgoing edges of the basic block corresponding to this label, in the control flow graph of * its method. These edges are stored in a linked list of {@link Edge} objects, linked to each * other by their {@link Edge#nextEdge} field. */ Edge outgoingEdges; /** * The next element in the list of labels to which this label belongs, or {@literal null} if it * does not belong to any list. All lists of labels must end with the {@link #EMPTY_LIST} * sentinel, in order to ensure that this field is null if and only if this label does not belong * to a list of labels. Note that there can be several lists of labels at the same time, but that * a label can belong to at most one list at a time (unless some lists share a common tail, but * this is not used in practice). * * <p>List of labels are used in {@link MethodWriter#computeAllFrames} and {@link * MethodWriter#computeMaxStackAndLocal} to compute stack map frames and the maximum stack size, * respectively, as well as in {@link #markSubroutine} and {@link #addSubroutineRetSuccessors} to * compute the basic blocks belonging to subroutines and their outgoing edges. Outside of these * methods, this field should be null (this property is a precondition and a postcondition of * these methods). */ Label nextListElement; // ----------------------------------------------------------------------------------------------- // Constructor and accessors // ----------------------------------------------------------------------------------------------- /** Constructs a new label. */ public Label() { // Nothing to do. } /** * Returns the bytecode 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 bytecode offset corresponding to this label. * @throws IllegalStateException if this label is not resolved yet. */ public int getOffset() { if ((flags & FLAG_RESOLVED) == 0) { throw new IllegalStateException("Label offset position has not been resolved yet"); } return bytecodeOffset; } /** * Returns the "canonical" {@link Label} instance corresponding to this label's bytecode offset, * if known, otherwise the label itself. The canonical instance is the first label (in the order * of their visit by {@link MethodVisitor#visitLabel}) corresponding to this bytecode offset. It * cannot be known for labels which have not been visited yet. * * <p><i>This method should only be used when the {@link MethodWriter#COMPUTE_ALL_FRAMES} option * is used.</i> * * @return the label itself if {@link #frame} is null, otherwise the Label's frame owner. This * corresponds to the "canonical" label instance described above thanks to the way the label * frame is set in {@link MethodWriter#visitLabel}. */ final Label getCanonicalInstance() { return frame == null ? this : frame.owner; } // ----------------------------------------------------------------------------------------------- // Methods to manage line numbers // ----------------------------------------------------------------------------------------------- /** * Adds a source line number corresponding to this label. * * @param lineNumber a source line number (which should be strictly positive). */ final void addLineNumber(final int lineNumber) { if (this.lineNumber == 0) { this.lineNumber = (short) lineNumber; } else { if (otherLineNumbers == null) { otherLineNumbers = new int[LINE_NUMBERS_CAPACITY_INCREMENT]; } int otherLineNumberIndex = ++otherLineNumbers[0]; if (otherLineNumberIndex >= otherLineNumbers.length) { int[] newLineNumbers = new int[otherLineNumbers.length + LINE_NUMBERS_CAPACITY_INCREMENT]; System.arraycopy(otherLineNumbers, 0, newLineNumbers, 0, otherLineNumbers.length); otherLineNumbers = newLineNumbers; } otherLineNumbers[otherLineNumberIndex] = lineNumber; } } /** * Makes the given visitor visit this label and its source line numbers, if applicable. * * @param methodVisitor a method visitor. * @param visitLineNumbers whether to visit of the label's source line numbers, if any. */ final void accept(final MethodVisitor methodVisitor, final boolean visitLineNumbers) { methodVisitor.visitLabel(this); if (visitLineNumbers && lineNumber != 0) { methodVisitor.visitLineNumber(lineNumber & 0xFFFF, this); if (otherLineNumbers != null) { for (int i = 1; i <= otherLineNumbers[0]; ++i) { methodVisitor.visitLineNumber(otherLineNumbers[i], this); } } } } // ----------------------------------------------------------------------------------------------- // Methods to compute offsets and to manage forward references // ----------------------------------------------------------------------------------------------- /** * Puts a reference to this label in the bytecode of a method. If the bytecode offset of the label * is known, the relative bytecode offset between the label and the instruction referencing it is * computed and written directly. Otherwise, a null relative offset is written and a new forward * reference is declared for this label. * * @param code the bytecode of the method. This is where the reference is appended. * @param sourceInsnBytecodeOffset the bytecode offset of the instruction that contains the * reference to be appended. * @param wideReference whether the reference must be stored in 4 bytes (instead of 2 bytes). */ final void put(final ByteVector code, final int sourceInsnBytecodeOffset, final boolean wideReference) { if ((flags & FLAG_RESOLVED) == 0) { if (wideReference) { addForwardReference(sourceInsnBytecodeOffset, FORWARD_REFERENCE_TYPE_WIDE, code.length); code.putInt(-1); } else { addForwardReference(sourceInsnBytecodeOffset, FORWARD_REFERENCE_TYPE_SHORT, code.length); code.putShort(-1); } } else { if (wideReference) { code.putInt(bytecodeOffset - sourceInsnBytecodeOffset); } else { code.putShort(bytecodeOffset - sourceInsnBytecodeOffset); } } } /** * 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 relative * bytecode offset of the reference can be, and must be, computed and stored directly. * * @param sourceInsnBytecodeOffset the bytecode offset of the instruction that contains the * reference stored at referenceHandle. * @param referenceType either {@link #FORWARD_REFERENCE_TYPE_SHORT} or {@link * #FORWARD_REFERENCE_TYPE_WIDE}. * @param referenceHandle the offset in the bytecode where the forward reference value must be * stored. */ private void addForwardReference(final int sourceInsnBytecodeOffset, final int referenceType, final int referenceHandle) { if (forwardReferences == null) { forwardReferences = new int[FORWARD_REFERENCES_CAPACITY_INCREMENT]; } int lastElementIndex = forwardReferences[0]; if (lastElementIndex + 2 >= forwardReferences.length) { int[] newValues = new int[forwardReferences.length + FORWARD_REFERENCES_CAPACITY_INCREMENT]; System.arraycopy(forwardReferences, 0, newValues, 0, forwardReferences.length); forwardReferences = newValues; } forwardReferences[++lastElementIndex] = sourceInsnBytecodeOffset; forwardReferences[++lastElementIndex] = referenceType | referenceHandle; forwardReferences[0] = lastElementIndex; } /** * Sets the bytecode offset of this label to the given value and resolves the forward references * to this label, if any. This method must be called when this label is added to the bytecode of * the method, i.e. when its bytecode offset becomes known. This method fills in the blanks that * where left in the bytecode by each forward reference previously added to this label. * * @param code the bytecode of the method. * @param bytecodeOffset the bytecode offset of this label. * @return {@literal true} if a blank that was left for this label was too small to store the * offset. In such a case the corresponding jump instruction is replaced with an equivalent * ASM specific instruction using an unsigned two bytes offset. These ASM specific * instructions are later replaced with standard bytecode instructions with wider offsets (4 * bytes instead of 2), in ClassReader. */ final boolean resolve(final byte[] code, final int bytecodeOffset) { this.flags |= FLAG_RESOLVED; this.bytecodeOffset = bytecodeOffset; if (forwardReferences == null) { return false; } boolean hasAsmInstructions = false; for (int i = forwardReferences[0]; i > 0; i -= 2) { final int sourceInsnBytecodeOffset = forwardReferences[i - 1]; final int reference = forwardReferences[i]; final int relativeOffset = bytecodeOffset - sourceInsnBytecodeOffset; int handle = reference & FORWARD_REFERENCE_HANDLE_MASK; if ((reference & FORWARD_REFERENCE_TYPE_MASK) == FORWARD_REFERENCE_TYPE_SHORT) { if (relativeOffset < Short.MIN_VALUE || relativeOffset > Short.MAX_VALUE) { // Change the opcode of the jump instruction, in order to be able to find it later in // ClassReader. These ASM specific 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 = code[sourceInsnBytecodeOffset] & 0xFF; if (opcode < Opcodes.IFNULL) { // Change IFEQ ... JSR to ASM_IFEQ ... ASM_JSR. code[sourceInsnBytecodeOffset] = (byte) (opcode + Constants.ASM_OPCODE_DELTA); } else { // Change IFNULL and IFNONNULL to ASM_IFNULL and ASM_IFNONNULL. code[sourceInsnBytecodeOffset] = (byte) (opcode + Constants.ASM_IFNULL_OPCODE_DELTA); } hasAsmInstructions = true; } code[handle++] = (byte) (relativeOffset >>> 8); code[handle] = (byte) relativeOffset; } else { code[handle++] = (byte) (relativeOffset >>> 24); code[handle++] = (byte) (relativeOffset >>> 16); code[handle++] = (byte) (relativeOffset >>> 8); code[handle] = (byte) relativeOffset; } } return hasAsmInstructions; } // ----------------------------------------------------------------------------------------------- // Methods related to subroutines // ----------------------------------------------------------------------------------------------- /** * Finds the basic blocks that belong to the subroutine starting with the basic block * corresponding to this label, and marks these blocks as belonging to this subroutine. This * method follows the control flow graph to find all the blocks that are reachable from the * current basic block WITHOUT following any jsr target. * * <p>Note: a precondition and postcondition of this method is that all labels must have a null * {@link #nextListElement}. * * @param subroutineId the id of the subroutine starting with the basic block corresponding to * this label. */ final void markSubroutine(final short subroutineId) { // Data flow algorithm: put this basic block in a list of blocks to process (which are blocks // belonging to subroutine subroutineId) and, while there are blocks to process, remove one from // the list, mark it as belonging to the subroutine, and add its successor basic blocks in the // control flow graph to the list of blocks to process (if not already done). Label listOfBlocksToProcess = this; listOfBlocksToProcess.nextListElement = EMPTY_LIST; while (listOfBlocksToProcess != EMPTY_LIST) { // Remove a basic block from the list of blocks to process. Label basicBlock = listOfBlocksToProcess; listOfBlocksToProcess = listOfBlocksToProcess.nextListElement; basicBlock.nextListElement = null; // If it is not already marked as belonging to a subroutine, mark it as belonging to // subroutineId and add its successors to the list of blocks to process (unless already done). if (basicBlock.subroutineId == 0) { basicBlock.subroutineId = subroutineId; listOfBlocksToProcess = basicBlock.pushSuccessors(listOfBlocksToProcess); } } } /** * Finds the basic blocks that end a subroutine starting with the basic block corresponding to * this label and, for each one of them, adds an outgoing edge to the basic block following the * given subroutine call. In other words, completes the control flow graph by adding the edges * corresponding to the return from this subroutine, when called from the given caller basic * block. * * <p>Note: a precondition and postcondition of this method is that all labels must have a null * {@link #nextListElement}. * * @param subroutineCaller a basic block that ends with a jsr to the basic block corresponding to * this label. This label is supposed to correspond to the start of a subroutine. */ final void addSubroutineRetSuccessors(final Label subroutineCaller) { // Data flow algorithm: put this basic block in a list blocks to process (which are blocks // belonging to a subroutine starting with this label) and, while there are blocks to process, // remove one from the list, put it in a list of blocks that have been processed, add a return // edge to the successor of subroutineCaller if applicable, and add its successor basic blocks // in the control flow graph to the list of blocks to process (if not already done). Label listOfProcessedBlocks = EMPTY_LIST; Label listOfBlocksToProcess = this; listOfBlocksToProcess.nextListElement = EMPTY_LIST; while (listOfBlocksToProcess != EMPTY_LIST) { // Move a basic block from the list of blocks to process to the list of processed blocks. Label basicBlock = listOfBlocksToProcess; listOfBlocksToProcess = basicBlock.nextListElement; basicBlock.nextListElement = listOfProcessedBlocks; listOfProcessedBlocks = basicBlock; // Add an edge from this block to the successor of the caller basic block, if this block is // the end of a subroutine and if this block and subroutineCaller do not belong to the same // subroutine. if ((basicBlock.flags & FLAG_SUBROUTINE_END) != 0 && basicBlock.subroutineId != subroutineCaller.subroutineId) { basicBlock.outgoingEdges = new Edge(basicBlock.outputStackSize, // By construction, the first outgoing edge of a basic block that ends with a jsr // instruction leads to the jsr continuation block, i.e. where execution continues // when ret is called (see {@link #FLAG_SUBROUTINE_CALLER}). subroutineCaller.outgoingEdges.successor, basicBlock.outgoingEdges); } // Add its successors to the list of blocks to process. Note that {@link #pushSuccessors} does // not push basic blocks which are already in a list. Here this means either in the list of // blocks to process, or in the list of already processed blocks. This second list is // important to make sure we don't reprocess an already processed block. listOfBlocksToProcess = basicBlock.pushSuccessors(listOfBlocksToProcess); } // Reset the {@link #nextListElement} of all the basic blocks that have been processed to null, // so that this method can be called again with a different subroutine or subroutine caller. while (listOfProcessedBlocks != EMPTY_LIST) { Label newListOfProcessedBlocks = listOfProcessedBlocks.nextListElement; listOfProcessedBlocks.nextListElement = null; listOfProcessedBlocks = newListOfProcessedBlocks; } } /** * Adds the successors of this label in the method's control flow graph (except those * corresponding to a jsr target, and those already in a list of labels) to the given list of * blocks to process, and returns the new list. * * @param listOfLabelsToProcess a list of basic blocks to process, linked together with their * {@link #nextListElement} field. * @return the new list of blocks to process. */ private Label pushSuccessors(final Label listOfLabelsToProcess) { Label newListOfLabelsToProcess = listOfLabelsToProcess; Edge outgoingEdge = outgoingEdges; while (outgoingEdge != null) { // By construction, the second outgoing edge of a basic block that ends with a jsr instruction // leads to the jsr target (see {@link #FLAG_SUBROUTINE_CALLER}). boolean isJsrTarget = (flags & Label.FLAG_SUBROUTINE_CALLER) != 0 && outgoingEdge == outgoingEdges.nextEdge; if (!isJsrTarget && outgoingEdge.successor.nextListElement == null) { // Add this successor to the list of blocks to process, if it does not already belong to a // list of labels. outgoingEdge.successor.nextListElement = newListOfLabelsToProcess; newListOfLabelsToProcess = outgoingEdge.successor; } outgoingEdge = outgoingEdge.nextEdge; } return newListOfLabelsToProcess; } // ----------------------------------------------------------------------------------------------- // Overridden Object methods // ----------------------------------------------------------------------------------------------- /** * Returns a string representation of this label. * * @return a string representation of this label. */ @Override public String toString() { return "L" + System.identityHashCode(this); } }