/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *   https://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  package org.apache.bcel.generic;
  
  import java.util.Arrays;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.bcel.Const;
  import org.apache.bcel.classfile.Constant;
  import org.apache.bcel.classfile.ConstantCP;
  import org.apache.bcel.classfile.ConstantClass;
  import org.apache.bcel.classfile.ConstantDouble;
  import org.apache.bcel.classfile.ConstantDynamic;
  import org.apache.bcel.classfile.ConstantFieldref;
  import org.apache.bcel.classfile.ConstantFloat;
  import org.apache.bcel.classfile.ConstantInteger;
  import org.apache.bcel.classfile.ConstantInterfaceMethodref;
  import org.apache.bcel.classfile.ConstantInvokeDynamic;
  import org.apache.bcel.classfile.ConstantLong;
  import org.apache.bcel.classfile.ConstantMethodref;
  import org.apache.bcel.classfile.ConstantNameAndType;
  import org.apache.bcel.classfile.ConstantPool;
  import org.apache.bcel.classfile.ConstantString;
  import org.apache.bcel.classfile.ConstantUtf8;
  import org.apache.bcel.classfile.Utility;
  
  /**
   * This class is used to build up a constant pool. The user adds constants via 'addXXX' methods, 'addString', 'addClass', and so on. These methods return an
   * index into the constant pool. Finally, 'getFinalConstantPool()' returns the constant pool built up. Intermediate versions of the constant pool can be
   * obtained with 'getConstantPool()'. A constant pool has capacity for Constants.MAX_SHORT entries. Note that the first (0) is used by the JVM and that Double
   * and Long constants need two slots.
   *
   * @see Constant
   */
  public class ConstantPoolGen {
  
      private static final int DEFAULT_BUFFER_SIZE = 256;
  
      private static final String METHODREF_DELIM = ":";
  
      private static final String IMETHODREF_DELIM = "#";
  
      private static final String FIELDREF_DELIM = "&";
  
      /**
       * Builds a lookup key that stays collision-free even when the parts contain the ASCII characters used as
       * delimiters above. Class, member and signature names read from a class file may legally contain those characters
       * (the JVMS only forbids {@code . ; [ /} and, for members, {@code < >}), so each part is prefixed with its length
       * to keep distinct triples distinct.
       *
       * @param parts The key parts.
       * @return A collision-free key.
       */
      private static String toKey(final String... parts) {
          final StringBuilder buf = new StringBuilder();
          for (final String part : parts) {
              buf.append(part.length()).append(':').append(part);
          }
          return buf.toString();
      }
  
      /**
       * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
       */
      @Deprecated
      protected int size;
  
      /**
       * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
       */
      @Deprecated
      protected Constant[] constants;
  
      /**
       * @deprecated (since 6.0) will be made private; do not access directly, use getSize()
       */
      @Deprecated
      protected int index = 1; // First entry (0) used by JVM
  
      private final Map<String, Integer> stringTable = new HashMap<>();
  
      private final Map<String, Integer> classTable = new HashMap<>();
 
     private final Map<String, Integer> utf8Table = new HashMap<>();
 
     private final Map<String, Integer> natTable = new HashMap<>();
 
     private final Map<String, Integer> cpTable = new HashMap<>();
 
     /**
      * Constructs a new empty constant pool.
      */
     public ConstantPoolGen() {
         size = DEFAULT_BUFFER_SIZE;
         constants = new Constant[size];
     }
 
     /**
      * Constructs a new instance with the given array of constants.
      *
      * @param cs array of given constants, new ones will be appended.
      */
     public ConstantPoolGen(final Constant[] cs) {
         size = Math.min(Math.max(DEFAULT_BUFFER_SIZE, cs.length + 64), Const.MAX_CP_ENTRIES + 1);
         constants = Arrays.copyOf(cs, size);
 
         if (cs.length > 0) {
             index = cs.length;
         }
 
         for (int i = 1; i < index; i++) {
             final Constant c = constants[i];
             if (c instanceof ConstantString) {
                 final ConstantString s = (ConstantString) c;
                 final ConstantUtf8 u8 = (ConstantUtf8) constants[s.getStringIndex()];
                 final String key = u8.getBytes();
                 if (!stringTable.containsKey(key)) {
                     stringTable.put(key, Integer.valueOf(i));
                 }
             } else if (c instanceof ConstantClass) {
                 final ConstantClass s = (ConstantClass) c;
                 final ConstantUtf8 u8 = (ConstantUtf8) constants[s.getNameIndex()];
                 final String key = u8.getBytes();
                 if (!classTable.containsKey(key)) {
                     classTable.put(key, Integer.valueOf(i));
                 }
             } else if (c instanceof ConstantNameAndType) {
                 final ConstantNameAndType n = (ConstantNameAndType) c;
                 final ConstantUtf8 u8NameIdx = (ConstantUtf8) constants[n.getNameIndex()];
                 final ConstantUtf8 u8SigIdx = (ConstantUtf8) constants[n.getSignatureIndex()];
                 final String key = toKey(u8NameIdx.getBytes(), u8SigIdx.getBytes());
                 if (!natTable.containsKey(key)) {
                     natTable.put(key, Integer.valueOf(i));
                 }
             } else if (c instanceof ConstantUtf8) {
                 final ConstantUtf8 u = (ConstantUtf8) c;
                 final String key = u.getBytes();
                 if (!utf8Table.containsKey(key)) {
                     utf8Table.put(key, Integer.valueOf(i));
                 }
             } else if (c instanceof ConstantCP) {
                 final ConstantCP m = (ConstantCP) c;
                 final String className;
                 ConstantUtf8 u8;
 
                 if (c instanceof ConstantInvokeDynamic) {
                     className = Integer.toString(((ConstantInvokeDynamic) m).getBootstrapMethodAttrIndex());
                 } else if (c instanceof ConstantDynamic) {
                     className = Integer.toString(((ConstantDynamic) m).getBootstrapMethodAttrIndex());
                 } else {
                     final ConstantClass clazz = (ConstantClass) constants[m.getClassIndex()];
                     u8 = (ConstantUtf8) constants[clazz.getNameIndex()];
                     className = Utility.pathToPackage(u8.getBytes());
                 }
 
                 final ConstantNameAndType n = (ConstantNameAndType) constants[m.getNameAndTypeIndex()];
                 u8 = (ConstantUtf8) constants[n.getNameIndex()];
                 final String methodName = u8.getBytes();
                 u8 = (ConstantUtf8) constants[n.getSignatureIndex()];
                 final String signature = u8.getBytes();
 
                 // Distinguishes the three kinds of reference that share cpTable.
                 String delim = METHODREF_DELIM;
                 if (c instanceof ConstantInterfaceMethodref) {
                     delim = IMETHODREF_DELIM;
                 } else if (c instanceof ConstantFieldref) {
                     delim = FIELDREF_DELIM;
                 }
                 final String key = toKey(delim, className, methodName, signature);
                 if (!cpTable.containsKey(key)) {
                     cpTable.put(key, Integer.valueOf(i));
                 }
             }
 //            else if (c == null) { // entries may be null
 //                // nothing to do
 //            } else if (c instanceof ConstantInteger) {
 //                // nothing to do
 //            } else if (c instanceof ConstantLong) {
 //                // nothing to do
 //            } else if (c instanceof ConstantFloat) {
 //                // nothing to do
 //            } else if (c instanceof ConstantDouble) {
 //                // nothing to do
 //            } else if (c instanceof org.apache.bcel.classfile.ConstantMethodType) {
 //                // TODO should this be handled somehow?
 //            } else if (c instanceof org.apache.bcel.classfile.ConstantMethodHandle) {
 //                // TODO should this be handled somehow?
 //            } else if (c instanceof org.apache.bcel.classfile.ConstantModule) {
 //                // TODO should this be handled somehow?
 //            } else if (c instanceof org.apache.bcel.classfile.ConstantPackage) {
 //                // TODO should this be handled somehow?
 //            } else {
 //                // Not helpful, should throw an exception.
 //                assert false : "Unexpected constant type: " + c.getClass().getName();
 //            }
         }
     }
 
     /**
      * Constructs a new instance with the given constant pool.
      *
      * @param cp The constant pool.
      */
     public ConstantPoolGen(final ConstantPool cp) {
         this(cp.getConstantPool());
     }
 
     /**
      * Add a reference to an array class (for example, String[][]) as needed by MULTIANEWARRAY instruction, for example, to the ConstantPool.
      *
      * @param type type of array class.
      * @return index of entry.
      */
     public int addArrayClass(final ArrayType type) {
         return addClass_(type.getSignature());
     }
 
     /**
      * Add a new Class reference to the ConstantPool for a given type.
      *
      * @param type Class to add.
      * @return index of entry.
      */
     public int addClass(final ObjectType type) {
         return addClass(type.getClassName());
     }
 
     /**
      * Add a new Class reference to the ConstantPool, if it is not already in there.
      *
      * @param str Class to add.
      * @return index of entry.
      */
     public int addClass(final String str) {
         return addClass_(Utility.packageToPath(str));
     }
 
     private int addClass_(final String clazz) {
         final int cpRet;
         if ((cpRet = lookupClass(clazz)) != -1) {
             return cpRet; // Already in CP
         }
         adjustSize();
         final ConstantClass c = new ConstantClass(addUtf8(clazz));
         final int ret = index;
         constants[index++] = c;
         return computeIfAbsent(classTable, clazz, ret);
     }
 
     /**
      * Adds a constant from another ConstantPool and returns the new index.
      *
      * @param constant The constant to add.
      * @param cpGen Source pool.
      * @return index of entry.
      */
     public int addConstant(final Constant constant, final ConstantPoolGen cpGen) {
         final Constant[] constants = cpGen.getConstantPool().getConstantPool();
         switch (constant.getTag()) {
         case Const.CONSTANT_String: {
             final ConstantString s = (ConstantString) constant;
             final ConstantUtf8 u8 = (ConstantUtf8) constants[s.getStringIndex()];
             return addString(u8.getBytes());
         }
         case Const.CONSTANT_Class: {
             final ConstantClass s = (ConstantClass) constant;
             final ConstantUtf8 u8 = (ConstantUtf8) constants[s.getNameIndex()];
             return addClass(u8.getBytes());
         }
         case Const.CONSTANT_NameAndType: {
             final ConstantNameAndType n = (ConstantNameAndType) constant;
             final ConstantUtf8 u8 = (ConstantUtf8) constants[n.getNameIndex()];
             final ConstantUtf8 u8_2 = (ConstantUtf8) constants[n.getSignatureIndex()];
             return addNameAndType(u8.getBytes(), u8_2.getBytes());
         }
         case Const.CONSTANT_Utf8:
             return addUtf8(((ConstantUtf8) constant).getBytes());
         case Const.CONSTANT_Double:
             return addDouble(((ConstantDouble) constant).getBytes());
         case Const.CONSTANT_Float:
             return addFloat(((ConstantFloat) constant).getBytes());
         case Const.CONSTANT_Long:
             return addLong(((ConstantLong) constant).getBytes());
         case Const.CONSTANT_Integer:
             return addInteger(((ConstantInteger) constant).getBytes());
         case Const.CONSTANT_InterfaceMethodref:
         case Const.CONSTANT_Methodref:
         case Const.CONSTANT_Fieldref: {
             final ConstantCP m = (ConstantCP) constant;
             final ConstantClass clazz = (ConstantClass) constants[m.getClassIndex()];
             final ConstantNameAndType n = (ConstantNameAndType) constants[m.getNameAndTypeIndex()];
             ConstantUtf8 u8 = (ConstantUtf8) constants[clazz.getNameIndex()];
             final String className = Utility.pathToPackage(u8.getBytes());
             u8 = (ConstantUtf8) constants[n.getNameIndex()];
             final String name = u8.getBytes();
             u8 = (ConstantUtf8) constants[n.getSignatureIndex()];
             final String signature = u8.getBytes();
             switch (constant.getTag()) {
             case Const.CONSTANT_InterfaceMethodref:
                 return addInterfaceMethodref(className, name, signature);
             case Const.CONSTANT_Methodref:
                 return addMethodref(className, name, signature);
             case Const.CONSTANT_Fieldref:
                 return addFieldref(className, name, signature);
             default: // Never reached
                 throw new IllegalArgumentException("Unknown constant type " + constant);
             }
         }
         default: // Never reached
             throw new IllegalArgumentException("Unknown constant type " + constant);
         }
     }
 
     /**
      * Add a new double constant to the ConstantPool, if it is not already in there.
      *
      * @param n Double number to add.
      * @return index of entry.
      */
     public int addDouble(final double n) {
         int ret;
         if ((ret = lookupDouble(n)) != -1) {
             return ret; // Already in CP
         }
         adjustSize();
         ret = index;
         constants[index] = new ConstantDouble(n);
         index += 2; // Wastes one entry according to spec
         return ret;
     }
 
     /**
      * Add a new Fieldref constant to the ConstantPool, if it is not already in there.
      *
      * @param className class name string to add.
      * @param fieldName field name string to add.
      * @param signature signature string to add.
      * @return index of entry.
      */
     public int addFieldref(final String className, final String fieldName, final String signature) {
         final int cpRet;
         if ((cpRet = lookupFieldref(className, fieldName, signature)) != -1) {
             return cpRet; // Already in CP
         }
         adjustSize();
         final int classIndex = addClass(className);
         final int nameAndTypeIndex = addNameAndType(fieldName, signature);
         final int ret = index;
         constants[index++] = new ConstantFieldref(classIndex, nameAndTypeIndex);
         return computeIfAbsent(cpTable, toKey(FIELDREF_DELIM, className, fieldName, signature), ret);
     }
 
     /**
      * Add a new Float constant to the ConstantPool, if it is not already in there.
      *
      * @param n Float number to add.
      * @return index of entry.
      */
     public int addFloat(final float n) {
         int ret;
         if ((ret = lookupFloat(n)) != -1) {
             return ret; // Already in CP
         }
         adjustSize();
         ret = index;
         constants[index++] = new ConstantFloat(n);
         return ret;
     }
 
     /**
      * Add a new Integer constant to the ConstantPool, if it is not already in there.
      *
      * @param n integer number to add.
      * @return index of entry.
      */
     public int addInteger(final int n) {
         int ret;
         if ((ret = lookupInteger(n)) != -1) {
             return ret; // Already in CP
         }
         adjustSize();
         ret = index;
         constants[index++] = new ConstantInteger(n);
         return ret;
     }
 
     /**
      * Adds a new InterfaceMethodref constant to the ConstantPool.
      *
      * @param method The method to add.
      * @return index of entry.
      */
     public int addInterfaceMethodref(final MethodGen method) {
         return addInterfaceMethodref(method.getClassName(), method.getName(), method.getSignature());
     }
 
     /**
      * Add a new InterfaceMethodref constant to the ConstantPool, if it is not already in there.
      *
      * @param className class name string to add.
      * @param methodName method name string to add.
      * @param signature signature string to add.
      * @return index of entry.
      */
     public int addInterfaceMethodref(final String className, final String methodName, final String signature) {
         final int cpRet;
         if ((cpRet = lookupInterfaceMethodref(className, methodName, signature)) != -1) {
             return cpRet; // Already in CP
         }
         adjustSize();
         final int classIndex = addClass(className);
         final int nameAndTypeIndex = addNameAndType(methodName, signature);
         final int ret = index;
         constants[index++] = new ConstantInterfaceMethodref(classIndex, nameAndTypeIndex);
         return computeIfAbsent(cpTable, toKey(IMETHODREF_DELIM, className, methodName, signature), ret);
     }
 
     /**
      * Add a new long constant to the ConstantPool, if it is not already in there.
      *
      * @param n Long number to add.
      * @return index of entry.
      */
     public int addLong(final long n) {
         int ret;
         if ((ret = lookupLong(n)) != -1) {
             return ret; // Already in CP
         }
         adjustSize();
         ret = index;
         constants[index] = new ConstantLong(n);
         index += 2; // Wastes one entry according to spec
         return ret;
     }
 
     /**
      * Adds a new Methodref constant to the ConstantPool.
      *
      * @param method The method to add.
      * @return index of entry.
      */
     public int addMethodref(final MethodGen method) {
         return addMethodref(method.getClassName(), method.getName(), method.getSignature());
     }
 
     /**
      * Add a new Methodref constant to the ConstantPool, if it is not already in there.
      *
      * @param className class name string to add.
      * @param methodName method name string to add.
      * @param signature method signature string to add.
      * @return index of entry.
      */
     public int addMethodref(final String className, final String methodName, final String signature) {
         final int cpRet;
         if ((cpRet = lookupMethodref(className, methodName, signature)) != -1) {
             return cpRet; // Already in CP
         }
         adjustSize();
         final int nameAndTypeIndex = addNameAndType(methodName, signature);
         final int classIndex = addClass(className);
         final int ret = index;
         constants[index++] = new ConstantMethodref(classIndex, nameAndTypeIndex);
         return computeIfAbsent(cpTable, toKey(METHODREF_DELIM, className, methodName, signature), ret);
     }
 
     /**
      * Add a new NameAndType constant to the ConstantPool if it is not already in there.
      *
      * @param name Name string to add.
      * @param signature signature string to add.
      * @return index of entry.
      */
     public int addNameAndType(final String name, final String signature) {
         int ret;
         if ((ret = lookupNameAndType(name, signature)) != -1) {
             return ret; // Already in CP
         }
         adjustSize();
         final int nameIndex = addUtf8(name);
         final int signatureIndex = addUtf8(signature);
         ret = index;
         constants[index++] = new ConstantNameAndType(nameIndex, signatureIndex);
         return computeIfAbsent(natTable, toKey(name, signature), ret);
     }
 
     /**
      * Add a new String constant to the ConstantPool, if it is not already in there.
      *
      * @param str String to add.
      * @return index of entry.
      */
     public int addString(final String str) {
         int ret;
         if ((ret = lookupString(str)) != -1) {
             return ret; // Already in CP
         }
         final int utf8 = addUtf8(str);
         adjustSize();
         final ConstantString s = new ConstantString(utf8);
         ret = index;
         constants[index++] = s;
         return computeIfAbsent(stringTable, str, ret);
     }
 
     /**
      * Add a new Utf8 constant to the ConstantPool, if it is not already in there.
      *
      * @param n Utf8 string to add.
      * @return index of entry.
      */
     public int addUtf8(final String n) {
         int ret;
         if ((ret = lookupUtf8(n)) != -1) {
             return ret; // Already in CP
         }
         adjustSize();
         ret = index;
         constants[index++] = new ConstantUtf8(n);
         return computeIfAbsent(utf8Table, n, ret);
     }
 
     /**
      * Resize internal array of constants.
      */
     protected void adjustSize() {
         // 3 extra spaces are needed as some entries may take 3 slots
         if (index + 3 >= Const.MAX_CP_ENTRIES + 1) {
             throw new IllegalStateException("The number of constants " + (index + 3)
                     + " is over the size of the constant pool: "
                     + Const.MAX_CP_ENTRIES);
         }
 
         if (index + 3 >= size) {
             final Constant[] tmp = constants;
             size *= 2;
             // the constant array shall not exceed the size of the constant pool
             size = Math.min(size, Const.MAX_CP_ENTRIES + 1);
             constants = new Constant[size];
             System.arraycopy(tmp, 0, constants, 0, index);
         }
     }
 
     private int computeIfAbsent(final Map<String, Integer> map, final String key, final int value) {
         return map.computeIfAbsent(key, k -> Integer.valueOf(value));
     }
 
     /**
      * Gets a constant pool entry at the specified index.
      *
      * @param i index in constant pool.
      * @return constant pool entry at index i.
      */
     public Constant getConstant(final int i) {
         return constants[i];
     }
 
     /**
      * Gets the intermediate constant pool.
      *
      * @return intermediate constant pool.
      */
     public ConstantPool getConstantPool() {
         return new ConstantPool(constants);
     }
 
     /**
      * Gets the constant pool with proper length.
      *
      * @return constant pool with proper length.
      */
     public ConstantPool getFinalConstantPool() {
         return new ConstantPool(Arrays.copyOf(constants, index));
     }
 
     private int getIndex(final Map<String, Integer> map, final String key) {
         return toIndex(map.get(key));
     }
 
     /**
      * Gets the current size of constant pool.
      *
      * @return current size of constant pool.
      */
     public int getSize() {
         return index;
     }
 
     /**
      * Look for ConstantClass in ConstantPool named 'str'.
      *
      * @param str String to search for.
      * @return index on success, -1 otherwise.
      */
     public int lookupClass(final String str) {
         return getIndex(classTable, Utility.packageToPath(str));
     }
 
     /**
      * Look for ConstantDouble in ConstantPool.
      *
      * @param n Double number to look for.
      * @return index on success, -1 otherwise.
      */
     public int lookupDouble(final double n) {
         final long bits = Double.doubleToLongBits(n);
         for (int i = 1; i < index; i++) {
             if (constants[i] instanceof ConstantDouble) {
                 final ConstantDouble c = (ConstantDouble) constants[i];
                 if (Double.doubleToLongBits(c.getBytes()) == bits) {
                     return i;
                 }
             }
         }
         return -1;
     }
 
     /**
      * Look for ConstantFieldref in ConstantPool.
      *
      * @param className Where to find method.
      * @param fieldName Guess what.
      * @param signature return and argument types.
      * @return index on success, -1 otherwise.
      */
     public int lookupFieldref(final String className, final String fieldName, final String signature) {
         return getIndex(cpTable, toKey(FIELDREF_DELIM, className, fieldName, signature));
     }
 
     /**
      * Look for ConstantFloat in ConstantPool.
      *
      * @param n Float number to look for.
      * @return index on success, -1 otherwise.
      */
     public int lookupFloat(final float n) {
         final int bits = Float.floatToIntBits(n);
         for (int i = 1; i < index; i++) {
             if (constants[i] instanceof ConstantFloat) {
                 final ConstantFloat c = (ConstantFloat) constants[i];
                 if (Float.floatToIntBits(c.getBytes()) == bits) {
                     return i;
                 }
             }
         }
         return -1;
     }
 
     /**
      * Look for ConstantInteger in ConstantPool.
      *
      * @param n integer number to look for.
      * @return index on success, -1 otherwise.
      */
     public int lookupInteger(final int n) {
         for (int i = 1; i < index; i++) {
             if (constants[i] instanceof ConstantInteger) {
                 final ConstantInteger c = (ConstantInteger) constants[i];
                 if (c.getBytes() == n) {
                     return i;
                 }
             }
         }
         return -1;
     }
 
     /**
      * Looks up an InterfaceMethodref in the ConstantPool.
      *
      * @param method The method to look for.
      * @return index on success, -1 otherwise.
      */
     public int lookupInterfaceMethodref(final MethodGen method) {
         return lookupInterfaceMethodref(method.getClassName(), method.getName(), method.getSignature());
     }
 
     /**
      * Look for ConstantInterfaceMethodref in ConstantPool.
      *
      * @param className Where to find method.
      * @param methodName Guess what.
      * @param signature return and argument types.
      * @return index on success, -1 otherwise.
      */
     public int lookupInterfaceMethodref(final String className, final String methodName, final String signature) {
         return getIndex(cpTable, toKey(IMETHODREF_DELIM, className, methodName, signature));
     }
 
     /**
      * Look for ConstantLong in ConstantPool.
      *
      * @param n Long number to look for.
      * @return index on success, -1 otherwise.
      */
     public int lookupLong(final long n) {
         for (int i = 1; i < index; i++) {
             if (constants[i] instanceof ConstantLong) {
                 final ConstantLong c = (ConstantLong) constants[i];
                 if (c.getBytes() == n) {
                     return i;
                 }
             }
         }
         return -1;
     }
 
     /**
      * Looks up a Methodref in the ConstantPool.
      *
      * @param method The method to look for.
      * @return index on success, -1 otherwise.
      */
     public int lookupMethodref(final MethodGen method) {
         return lookupMethodref(method.getClassName(), method.getName(), method.getSignature());
     }
 
     /**
      * Look for ConstantMethodref in ConstantPool.
      *
      * @param className Where to find method.
      * @param methodName Guess what.
      * @param signature return and argument types.
      * @return index on success, -1 otherwise.
      */
     public int lookupMethodref(final String className, final String methodName, final String signature) {
         return getIndex(cpTable, toKey(METHODREF_DELIM, className, methodName, signature));
     }
 
     /**
      * Look for ConstantNameAndType in ConstantPool.
      *
      * @param name of variable/method.
      * @param signature of variable/method.
      * @return index on success, -1 otherwise.
      */
     public int lookupNameAndType(final String name, final String signature) {
         return getIndex(natTable, toKey(name, signature));
     }
 
     /**
      * Look for ConstantString in ConstantPool containing String 'str'.
      *
      * @param str String to search for.
      * @return index on success, -1 otherwise.
      */
     public int lookupString(final String str) {
         return getIndex(stringTable, str);
     }
 
     /**
      * Look for ConstantUtf8 in ConstantPool.
      *
      * @param n Utf8 string to look for.
      * @return index on success, -1 otherwise.
      */
     public int lookupUtf8(final String n) {
         return getIndex(utf8Table, n);
     }
 
     /**
      * Use with care!
      *
      * @param i index in constant pool.
      * @param c new constant pool entry at index i.
      */
     public void setConstant(final int i, final Constant c) {
         constants[i] = c;
     }
 
     private int toIndex(final Integer index) {
         return index != null ? index.intValue() : -1;
     }
 
     /**
      * @return String representation.
      */
     @Override
     public String toString() {
         final StringBuilder buf = new StringBuilder();
         for (int i = 1; i < index; i++) {
             buf.append(i).append(")").append(constants[i]).append("\n");
         }
         return buf.toString();
     }
 }