1 files changed, 180 insertions, 0 deletions
diff --git a/src/proguard/classfile/instruction/BranchInstruction.java b/src/proguard/classfile/instruction/BranchInstruction.java
new file mode 100644
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+++ b/src/proguard/classfile/instruction/BranchInstruction.java
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+/*
+ * ProGuard -- shrinking, optimization, obfuscation, and preverification
+ *             of Java bytecode.
+ *
+ * Copyright (c) 2002-2009 Eric Lafortune (eric@graphics.cornell.edu)
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program 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 for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+package proguard.classfile.instruction;
+
+import proguard.classfile.*;
+import proguard.classfile.attribute.CodeAttribute;
+import proguard.classfile.instruction.visitor.InstructionVisitor;
+
+/**
+ * This interface describes an instruction that branches to a given offset in
+ * the code.
+ *
+ * @author Eric Lafortune
+ */
+public class BranchInstruction extends Instruction
+{
+    public int branchOffset;
+
+
+    /**
+     * Creates an uninitialized BranchInstruction.
+     */
+    public BranchInstruction() {}
+
+
+    public BranchInstruction(byte opcode, int branchOffset)
+    {
+        this.opcode       = opcode;
+        this.branchOffset = branchOffset;
+    }
+
+
+    /**
+     * Copies the given instruction into this instruction.
+     * @param branchInstruction the instruction to be copied.
+     * @return this instruction.
+     */
+    public BranchInstruction copy(BranchInstruction branchInstruction)
+    {
+        this.opcode       = branchInstruction.opcode;
+        this.branchOffset = branchInstruction.branchOffset;
+
+        return this;
+    }
+
+
+    // Implementations for Instruction.
+
+    public byte canonicalOpcode()
+    {
+        // Remove the _w extension, if any.
+        switch (opcode)
+        {
+            case InstructionConstants.OP_GOTO_W: return InstructionConstants.OP_GOTO;
+
+            case InstructionConstants.OP_JSR_W: return InstructionConstants.OP_JSR;
+
+            default: return opcode;
+        }
+    }
+
+    public Instruction shrink()
+    {
+        // Do we need an ordinary branch or a wide branch?
+        if (requiredBranchOffsetSize() == 2)
+        {
+            // Can we replace the wide branch by an ordinary branch?
+            if      (opcode == InstructionConstants.OP_GOTO_W)
+            {
+                opcode = InstructionConstants.OP_GOTO;
+            }
+            else if (opcode == InstructionConstants.OP_JSR_W)
+            {
+                opcode = InstructionConstants.OP_JSR;
+            }
+        }
+        else
+        {
+            // Should we replace the ordinary branch by a wide branch?
+            if      (opcode == InstructionConstants.OP_GOTO)
+            {
+                opcode = InstructionConstants.OP_GOTO_W;
+            }
+            else if (opcode == InstructionConstants.OP_JSR)
+            {
+                opcode = InstructionConstants.OP_JSR_W;
+            }
+            else
+            {
+                throw new IllegalArgumentException("Branch instruction can't be widened ("+this.toString()+")");
+            }
+        }
+
+        return this;
+    }
+
+    protected void readInfo(byte[] code, int offset)
+    {
+        branchOffset = readSignedValue(code, offset, branchOffsetSize());
+    }
+
+
+    protected void writeInfo(byte[] code, int offset)
+    {
+        if (requiredBranchOffsetSize() > branchOffsetSize())
+        {
+            throw new IllegalArgumentException("Instruction has invalid branch offset size ("+this.toString(offset)+")");
+        }
+
+        writeSignedValue(code, offset, branchOffset, branchOffsetSize());
+    }
+
+
+    public int length(int offset)
+    {
+        return 1 + branchOffsetSize();
+    }
+
+
+    public void accept(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, InstructionVisitor instructionVisitor)
+    {
+        instructionVisitor.visitBranchInstruction(clazz, method, codeAttribute, offset, this);
+    }
+
+
+    public String toString(int offset)
+    {
+        return "["+offset+"] "+toString()+" (target="+(offset+branchOffset)+")";
+    }
+
+
+    // Implementations for Object.
+
+    public String toString()
+    {
+        return getName()+" "+(branchOffset >= 0 ? "+" : "")+branchOffset;
+    }
+
+
+    // Small utility methods.
+
+    /**
+     * Returns the branch offset size for this instruction.
+     */
+    private int branchOffsetSize()
+    {
+        return opcode == InstructionConstants.OP_GOTO_W ||
+               opcode == InstructionConstants.OP_JSR_W  ? 4 :
+                                                          2;
+    }
+
+
+    /**
+     * Computes the required branch offset size for this instruction's branch
+     * offset.
+     */
+    private int requiredBranchOffsetSize()
+    {
+        return branchOffset << 16 >> 16 == branchOffset ? 2 :
+                                                          4;
+    }
+}