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  * reserved comment block

  * DO NOT REMOVE OR ALTER!

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 package com.sun.org.apache.bcel.internal.util;

 /*

  * 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

  *

  *      http://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.

  *

  */

 import com.sun.org.apache.bcel.internal.Constants;

 import com.sun.org.apache.bcel.internal.generic.*;

 import java.util.*;

 import java.util.regex.Matcher;

 import java.util.regex.Pattern;

 /**

  * InstructionFinder is a tool to search for given instructions patterns,

  * i.e., match sequences of instructions in an instruction list via

  * regular expressions. This can be used, e.g., in order to implement

  * a peep hole optimizer that looks for code patterns and replaces

  * them with faster equivalents.

  *

  * <p>This class internally uses the <a href="http://jakarta.apache.org/regexp/">

  * Regexp</a> package to search for regular expressions.

  *

  * A typical application would look like this:

 <pre>

     InstructionFinder f   = new InstructionFinder(il);

     String            pat = "IfInstruction ICONST_0 GOTO ICONST_1 NOP (IFEQ|IFNE)";

     for(Iterator i = f.search(pat, constraint); i.hasNext(); ) {

       InstructionHandle[] match = (InstructionHandle[])i.next();

       ...

       il.delete(match[1], match[5]);

       ...

     }

 </pre>

  * @author  <A HREF="http://www.berlin.de/~markus.dahm/">M. Dahm</A>

  * @see Instruction

  * @see InstructionList

  */

 public class InstructionFinder {

   private static final int OFFSET     = 32767; // char + OFFSET is outside of LATIN-1

   private static final int NO_OPCODES = 256;   // Potential number, some are not used

   private static final HashMap map = new HashMap(); // Map<String,Pattern>

   private InstructionList     il;

   private String              il_string;    // instruction list as string

   private InstructionHandle[] handles;      // map instruction list to array

   /**

    * @param il instruction list to search for given patterns

    */

   public InstructionFinder(InstructionList il) {

     this.il = il;

     reread();

   }

   /**

    * Reread the instruction list, e.g., after you've altered the list upon a match.

    */

   public final void reread() {

     int    size  = il.getLength();

     char[] buf   = new char[size]; // Create a string with length equal to il length

     handles      = il.getInstructionHandles();

     // Map opcodes to characters

     for(int i=0; i < size; i++)

       buf[i] = makeChar(handles[i].getInstruction().getOpcode());

     il_string = new String(buf);

   }

   /**

    * Map symbolic instruction names like "getfield" to a single character.

    *

    * @param pattern instruction pattern in lower case

    * @return encoded string for a pattern such as "BranchInstruction".

    */

   private static final String mapName(String pattern) {

     String result = (String)map.get(pattern);

     if(result != null)

       return result;

     for(short i=0; i < NO_OPCODES; i++)

       if(pattern.equals(Constants.OPCODE_NAMES[i]))

         return "" + makeChar(i);

     throw new RuntimeException("Instruction unknown: " + pattern);

   }

   /**

    * Replace symbolic names of instructions with the appropiate character and remove

    * all white space from string. Meta characters such as +, * are ignored.

    *

    * @param pattern The pattern to compile

    * @return translated regular expression string

    */

   private static final String compilePattern(String pattern) {

     String       lower      = pattern.toLowerCase();

     StringBuffer buf        = new StringBuffer();

     int          size       = pattern.length();

     for(int i=0; i < size; i++) {

       char ch = lower.charAt(i);

       if(Character.isLetterOrDigit(ch)) {

         StringBuffer name = new StringBuffer();

         while((Character.isLetterOrDigit(ch) || ch == '_') && i < size) {

           name.append(ch);

           if(++i < size)

             ch = lower.charAt(i);

           else

             break;

         }

         i--;

         buf.append(mapName(name.toString()));

       } else if(!Character.isWhitespace(ch))

         buf.append(ch);

     }

     return buf.toString();

   }

   /**

    * @return the matched piece of code as an array of instruction (handles)

    */

   private InstructionHandle[] getMatch(int matched_from, int match_length) {

     InstructionHandle[] match = new InstructionHandle[match_length];

     System.arraycopy(handles, matched_from, match, 0, match_length);

     return match;

   }

   /**

    * Search for the given pattern in the instruction list. You can search for any valid

    * opcode via its symbolic name, e.g. "istore". You can also use a super class or

    * an interface name to match a whole set of instructions, e.g. "BranchInstruction" or

    * "LoadInstruction". "istore" is also an alias for all "istore_x" instructions. Additional

    * aliases are "if" for "ifxx", "if_icmp" for "if_icmpxx", "if_acmp" for "if_acmpxx".

    *

    * Consecutive instruction names must be separated by white space which will be removed

    * during the compilation of the pattern.

    *

    * For the rest the usual pattern matching rules for regular expressions apply.<P>

    * Example pattern:

    * <pre>

      search("BranchInstruction NOP ((IfInstruction|GOTO)+ ISTORE Instruction)*");

    * </pre>

    *

    * <p>If you alter the instruction list upon a match such that other

    * matching areas are affected, you should call reread() to update

    * the finder and call search() again, because the matches are cached.

    *

    * @param pattern the instruction pattern to search for, where case is ignored

    * @param from where to start the search in the instruction list

    * @param constraint optional CodeConstraint to check the found code pattern for

    * user-defined constraints

    * @return iterator of matches where e.nextElement() returns an array of instruction handles

    * describing the matched area

    */

   public final Iterator search(String pattern, InstructionHandle from,

                                CodeConstraint constraint)

   {

     String search = compilePattern(pattern);

     int  start    = -1;

     for(int i=0; i < handles.length; i++) {

       if(handles[i] == from) {

         start = i; // Where to start search from (index)

         break;

       }

     }

     if(start == -1)

       throw new ClassGenException("Instruction handle " + from +

                                   " not found in instruction list.");

     Pattern regex = Pattern.compile(search);

     List<InstructionHandle[]> matches = new ArrayList<>();

     Matcher matcher = regex.matcher(il_string);

     while(start < il_string.length() && matcher.find(start)) {

       int startExpr = matcher.start();

       int endExpr   = matcher.end();

       int lenExpr   = endExpr - startExpr;

       InstructionHandle[] match = getMatch(startExpr, lenExpr);

       if((constraint == null) || constraint.checkCode(match))

         matches.add(match);

       start = endExpr;

     }

     return matches.iterator();

   }

   /**

    * Start search beginning from the start of the given instruction list.

    *

    * @param pattern the instruction pattern to search for, where case is ignored

    * @return iterator of matches where e.nextElement()

    * returns an array of instruction handles describing the matched

    * area

    */

   public final Iterator search(String pattern) {

     return search(pattern, il.getStart(), null);

   }

   /**

    * Start search beginning from `from'.

    *

    * @param pattern the instruction pattern to search for, where case is ignored

    * @param from where to start the search in the instruction list

    * @return  iterator of matches where e.nextElement() returns an array of instruction handles

    * describing the matched area

    */

   public final Iterator search(String pattern, InstructionHandle from) {

     return search(pattern, from, null);

   }

   /**

    * Start search beginning from the start of the given instruction list.

    * Check found matches with the constraint object.

    *

    * @param pattern the instruction pattern to search for, case is ignored

    * @param constraint constraints to be checked on matching code

    * @return instruction handle or `null' if the match failed

    */

   public final Iterator search(String pattern, CodeConstraint constraint) {

     return search(pattern, il.getStart(), constraint);

   }

   /**

    * Convert opcode number to char.

    */

   private static final char makeChar(short opcode) {

     return (char)(opcode + OFFSET);

   }

   /**

    * @return the inquired instruction list

    */

   public final InstructionList getInstructionList() { return il; }

   /**

    * Code patterns found may be checked using an additional

    * user-defined constraint object whether they really match the needed criterion.

    * I.e., check constraints that can not expressed with regular expressions.

    *

    */

   public interface CodeConstraint {

     /**

      * @param match array of instructions matching the requested pattern

      * @return true if the matched area is really useful

      */

     public boolean checkCode(InstructionHandle[] match);

   }

   // Initialize pattern map

   static {

     map.put("arithmeticinstruction", "(irem|lrem|iand|ior|ineg|isub|lneg|fneg|fmul|ldiv|fadd|lxor|frem|idiv|land|ixor|ishr|fsub|lshl|fdiv|iadd|lor|dmul|lsub|ishl|imul|lmul|lushr|dneg|iushr|lshr|ddiv|drem|dadd|ladd|dsub)");

     map.put("invokeinstruction", "(invokevirtual|invokeinterface|invokestatic|invokespecial)");

     map.put("arrayinstruction", "(baload|aastore|saload|caload|fastore|lastore|iaload|castore|iastore|aaload|bastore|sastore|faload|laload|daload|dastore)");

     map.put("gotoinstruction", "(goto|goto_w)");

     map.put("conversioninstruction", "(d2l|l2d|i2s|d2i|l2i|i2b|l2f|d2f|f2i|i2d|i2l|f2d|i2c|f2l|i2f)");

     map.put("localvariableinstruction", "(fstore|iinc|lload|dstore|dload|iload|aload|astore|istore|fload|lstore)");

     map.put("loadinstruction", "(fload|dload|lload|iload|aload)");

     map.put("fieldinstruction", "(getfield|putstatic|getstatic|putfield)");

     map.put("cpinstruction", "(ldc2_w|invokeinterface|multianewarray|putstatic|instanceof|getstatic|checkcast|getfield|invokespecial|ldc_w|invokestatic|invokevirtual|putfield|ldc|new|anewarray)");

     map.put("stackinstruction", "(dup2|swap|dup2_x2|pop|pop2|dup|dup2_x1|dup_x2|dup_x1)");

     map.put("branchinstruction", "(ifle|if_acmpne|if_icmpeq|if_acmpeq|ifnonnull|goto_w|iflt|ifnull|if_icmpne|tableswitch|if_icmple|ifeq|if_icmplt|jsr_w|if_icmpgt|ifgt|jsr|goto|ifne|ifge|lookupswitch|if_icmpge)");

     map.put("returninstruction", "(lreturn|ireturn|freturn|dreturn|areturn|return)");

     map.put("storeinstruction", "(istore|fstore|dstore|astore|lstore)");

     map.put("select", "(tableswitch|lookupswitch)");

     map.put("ifinstruction", "(ifeq|ifgt|if_icmpne|if_icmpeq|ifge|ifnull|ifne|if_icmple|if_icmpge|if_acmpeq|if_icmplt|if_acmpne|ifnonnull|iflt|if_icmpgt|ifle)");

     map.put("jsrinstruction", "(jsr|jsr_w)");

     map.put("variablelengthinstruction", "(tableswitch|jsr|goto|lookupswitch)");

     map.put("unconditionalbranch", "(goto|jsr|jsr_w|athrow|goto_w)");

     map.put("constantpushinstruction", "(dconst|bipush|sipush|fconst|iconst|lconst)");

     map.put("typedinstruction", "(imul|lsub|aload|fload|lor|new|aaload|fcmpg|iand|iaload|lrem|idiv|d2l|isub|dcmpg|dastore|ret|f2d|f2i|drem|iinc|i2c|checkcast|frem|lreturn|astore|lushr|daload|dneg|fastore|istore|lshl|ldiv|lstore|areturn|ishr|ldc_w|invokeinterface|aastore|lxor|ishl|l2d|i2f|return|faload|sipush|iushr|caload|instanceof|invokespecial|putfield|fmul|ireturn|laload|d2f|lneg|ixor|i2l|fdiv|lastore|multianewarray|i2b|getstatic|i2d|putstatic|fcmpl|saload|ladd|irem|dload|jsr_w|dconst|dcmpl|fsub|freturn|ldc|aconst_null|castore|lmul|ldc2_w|dadd|iconst|f2l|ddiv|dstore|land|jsr|anewarray|dmul|bipush|dsub|sastore|d2i|i2s|lshr|iadd|l2i|lload|bastore|fstore|fneg|iload|fadd|baload|fconst|ior|ineg|dreturn|l2f|lconst|getfield|invokevirtual|invokestatic|iastore)");

     map.put("popinstruction", "(fstore|dstore|pop|pop2|astore|putstatic|istore|lstore)");

     map.put("allocationinstruction", "(multianewarray|new|anewarray|newarray)");

     map.put("indexedinstruction", "(lload|lstore|fload|ldc2_w|invokeinterface|multianewarray|astore|dload|putstatic|instanceof|getstatic|checkcast|getfield|invokespecial|dstore|istore|iinc|ldc_w|ret|fstore|invokestatic|iload|putfield|invokevirtual|ldc|new|aload|anewarray)");

     map.put("pushinstruction", "(dup|lload|dup2|bipush|fload|ldc2_w|sipush|lconst|fconst|dload|getstatic|ldc_w|aconst_null|dconst|iload|ldc|iconst|aload)");

     map.put("stackproducer", "(imul|lsub|aload|fload|lor|new|aaload|fcmpg|iand|iaload|lrem|idiv|d2l|isub|dcmpg|dup|f2d|f2i|drem|i2c|checkcast|frem|lushr|daload|dneg|lshl|ldiv|ishr|ldc_w|invokeinterface|lxor|ishl|l2d|i2f|faload|sipush|iushr|caload|instanceof|invokespecial|fmul|laload|d2f|lneg|ixor|i2l|fdiv|getstatic|i2b|swap|i2d|dup2|fcmpl|saload|ladd|irem|dload|jsr_w|dconst|dcmpl|fsub|ldc|arraylength|aconst_null|tableswitch|lmul|ldc2_w|iconst|dadd|f2l|ddiv|land|jsr|anewarray|dmul|bipush|dsub|d2i|newarray|i2s|lshr|iadd|lload|l2i|fneg|iload|fadd|baload|fconst|lookupswitch|ior|ineg|lconst|l2f|getfield|invokevirtual|invokestatic)");

     map.put("stackconsumer", "(imul|lsub|lor|iflt|fcmpg|if_icmpgt|iand|ifeq|if_icmplt|lrem|ifnonnull|idiv|d2l|isub|dcmpg|dastore|if_icmpeq|f2d|f2i|drem|i2c|checkcast|frem|lreturn|astore|lushr|pop2|monitorexit|dneg|fastore|istore|lshl|ldiv|lstore|areturn|if_icmpge|ishr|monitorenter|invokeinterface|aastore|lxor|ishl|l2d|i2f|return|iushr|instanceof|invokespecial|fmul|ireturn|d2f|lneg|ixor|pop|i2l|ifnull|fdiv|lastore|i2b|if_acmpeq|ifge|swap|i2d|putstatic|fcmpl|ladd|irem|dcmpl|fsub|freturn|ifgt|castore|lmul|dadd|f2l|ddiv|dstore|land|if_icmpne|if_acmpne|dmul|dsub|sastore|ifle|d2i|i2s|lshr|iadd|l2i|bastore|fstore|fneg|fadd|ior|ineg|ifne|dreturn|l2f|if_icmple|getfield|invokevirtual|invokestatic|iastore)");

     map.put("exceptionthrower", "(irem|lrem|laload|putstatic|baload|dastore|areturn|getstatic|ldiv|anewarray|iastore|castore|idiv|saload|lastore|fastore|putfield|lreturn|caload|getfield|return|aastore|freturn|newarray|instanceof|multianewarray|athrow|faload|iaload|aaload|dreturn|monitorenter|checkcast|bastore|arraylength|new|invokevirtual|sastore|ldc_w|ireturn|invokespecial|monitorexit|invokeinterface|ldc|invokestatic|daload)");

     map.put("loadclass", "(multianewarray|invokeinterface|instanceof|invokespecial|putfield|checkcast|putstatic|invokevirtual|new|getstatic|invokestatic|getfield|anewarray)");

     map.put("instructiontargeter", "(ifle|if_acmpne|if_icmpeq|if_acmpeq|ifnonnull|goto_w|iflt|ifnull|if_icmpne|tableswitch|if_icmple|ifeq|if_icmplt|jsr_w|if_icmpgt|ifgt|jsr|goto|ifne|ifge|lookupswitch|if_icmpge)");

     // Some aliases

     map.put("if_icmp", "(if_icmpne|if_icmpeq|if_icmple|if_icmpge|if_icmplt|if_icmpgt)");

     map.put("if_acmp", "(if_acmpeq|if_acmpne)");

     map.put("if", "(ifeq|ifne|iflt|ifge|ifgt|ifle)");

     // Precompile some aliases first

     map.put("iconst", precompile(Constants.ICONST_0, Constants.ICONST_5, Constants.ICONST_M1));

     map.put("lconst", new String(new char[] { '(', makeChar(Constants.LCONST_0), '|',

                                               makeChar(Constants.LCONST_1), ')' }));

     map.put("dconst", new String(new char[] { '(', makeChar(Constants.DCONST_0), '|',

                                               makeChar(Constants.DCONST_1), ')' }));

     map.put("fconst", new String(new char[] { '(', makeChar(Constants.FCONST_0), '|',

                                               makeChar(Constants.FCONST_1), ')' }));

     map.put("iload", precompile(Constants.ILOAD_0, Constants.ILOAD_3, Constants.ILOAD));

     map.put("dload", precompile(Constants.DLOAD_0, Constants.DLOAD_3, Constants.DLOAD));

     map.put("fload", precompile(Constants.FLOAD_0, Constants.FLOAD_3, Constants.FLOAD));

     map.put("aload", precompile(Constants.ALOAD_0, Constants.ALOAD_3, Constants.ALOAD));

     map.put("istore", precompile(Constants.ISTORE_0, Constants.ISTORE_3, Constants.ISTORE));

     map.put("dstore", precompile(Constants.DSTORE_0, Constants.DSTORE_3, Constants.DSTORE));

     map.put("fstore", precompile(Constants.FSTORE_0, Constants.FSTORE_3, Constants.FSTORE));

     map.put("astore", precompile(Constants.ASTORE_0, Constants.ASTORE_3, Constants.ASTORE));

     // Compile strings

     for(Iterator i = map.keySet().iterator(); i.hasNext(); ) {

       String key   = (String)i.next();

       String value = (String)map.get(key);

       char ch = value.charAt(1); // Omit already precompiled patterns

       if(ch < OFFSET) {

         map.put(key, compilePattern(value)); // precompile all patterns

       }

     }

     // Add instruction alias to match anything

     StringBuffer buf = new StringBuffer("(");

     for(short i=0; i < NO_OPCODES; i++) {

       if(Constants.NO_OF_OPERANDS[i] != Constants.UNDEFINED) { // Not an invalid opcode

         buf.append(makeChar(i));

         if(i < NO_OPCODES - 1)

           buf.append('|');

       }

     }

     buf.append(')');

     map.put("instruction", buf.toString());

   }

   private static String precompile(short from, short to, short extra) {

     StringBuffer buf = new StringBuffer("(");

     for(short i=from; i <= to; i++) {

       buf.append(makeChar(i));

       buf.append('|');

     }

     buf.append(makeChar(extra));

     buf.append(")");

     return buf.toString();

   }

   /*

    * Internal debugging routines.

    */

   private static final String pattern2string(String pattern) {

     return pattern2string(pattern, true);

   }

   private static final String pattern2string(String pattern, boolean make_string) {

     StringBuffer buf = new StringBuffer();

     for(int i=0; i < pattern.length(); i++) {

       char ch = pattern.charAt(i);

       if(ch >= OFFSET) {

         if(make_string)

           buf.append(Constants.OPCODE_NAMES[ch - OFFSET]);

         else

           buf.append((int)(ch - OFFSET));

       } else

         buf.append(ch);

     }

     return buf.toString();

   }

 }