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Diffstat (limited to 'tools/external/asm/org/objectweb/asm/Label.java')
| -rw-r--r-- | tools/external/asm/org/objectweb/asm/Label.java | 299 |
1 files changed, 299 insertions, 0 deletions
diff --git a/tools/external/asm/org/objectweb/asm/Label.java b/tools/external/asm/org/objectweb/asm/Label.java new file mode 100644 index 000000000..79291f27c --- /dev/null +++ b/tools/external/asm/org/objectweb/asm/Label.java @@ -0,0 +1,299 @@ +/*** + * 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); + } +} |