/*
    * 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. 
   *
   */
  package org.apache.bcel.util;
  
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Locale;
  import java.util.Map;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import org.apache.bcel.Constants;
  import org.apache.bcel.generic.ClassGenException;
  import org.apache.bcel.generic.Instruction;
  import org.apache.bcel.generic.InstructionHandle;
  import org.apache.bcel.generic.InstructionList;
  
  /**
   * 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 java.util.regex
   * package to search for regular expressions.
   * 
   * A typical application would look like this:
   * 
   * <pre>
   * 
   *  
   *   InstructionFinder f   = new InstructionFinder(il);
   *   String            pat = &quot;IfInstruction ICONST_0 GOTO ICONST_1 NOP (IFEQ|IFNE)&quot;;
   *   
   *   for(Iterator i = f.search(pat, constraint); i.hasNext(); ) {
   *   InstructionHandle[] match = (InstructionHandle[])i.next();
   *   ...
   *   il.delete(match[1], match[5]);
   *   ...
   *   }
   *   
   *  
   * </pre>
   * 
   * @version $Id: InstructionFinder.java 1152077 2011-07-29 02:29:42Z dbrosius $
   * @author <A HREF="mailto:m.dahm@gmx.de">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 Map<String, String> map = new HashMap<String, String>();
      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 = 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 ) {
         //Bug: 38787 - Instructions are assumed to be english, to avoid odd Locale issues
         String lower = pattern.toLowerCase(Locale.ENGLISH);
         StringBuilder buf = new StringBuilder();
         int size = pattern.length();
         for (int i = 0; i < size; i++) {
             char ch = lower.charAt(i);
             if (Character.isLetterOrDigit(ch)) {
                 StringBuilder name = new StringBuilder();
                 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(&quot;BranchInstruction NOP ((IfInstruction|GOTO)+ ISTORE Instruction)*&quot;);
      * </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<InstructionHandle[]> 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<InstructionHandle[]>();
         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<InstructionHandle[]> 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<InstructionHandle[]> 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<InstructionHandle[]> 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 static 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 (String key : map.keySet()) {
 			String value = 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
 		StringBuilder buf = new StringBuilder("(");
 		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 ) {
         StringBuilder buf = new StringBuilder("(");
         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((ch - OFFSET));
 //                }
 //            } else {
 //                buf.append(ch);
 //            }
 //        }
 //        return buf.toString();
 //    }
 }