/*

 * Copyright (c) 2017, 2021, Oracle and/or its affiliates. All rights reserved.

 */

/*

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

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

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

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

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

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;

/**

 * 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 = "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>

 *

 * @see com.sun.org.apache.bcel.internal.generic.Instruction

 * @see InstructionList

 * @LastModified: May 2021

 */

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<>();

    private final InstructionList il;

    private String ilString; // instruction list as string

    private InstructionHandle[] handles; // map instruction

    // list to array

    /**

     * @param il

     *          instruction list to search for given patterns

     */

    public InstructionFinder(final 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() {

        final int size = il.getLength();

        final 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());

        }

        ilString = 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 String mapName( final String pattern ) {

        final String result = map.get(pattern);

        if (result != null) {

            return result;

        }

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

            if (pattern.equals(Const.getOpcodeName(i))) {

                return "" + makeChar(i);

            }

        }

        throw new IllegalArgumentException("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 String compilePattern( final String pattern ) {

        //Bug: BCEL-77 - Instructions are assumed to be english, to avoid odd Locale issues

        final String lower = pattern.toLowerCase(Locale.ENGLISH);

        final StringBuilder buf = new StringBuilder();

        final int size = pattern.length();

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

            char ch = lower.charAt(i);

            if (Character.isLetterOrDigit(ch)) {

                final 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( final int matched_from, final int match_length ) {

        final 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<InstructionHandle[]> search( final String pattern,

            final InstructionHandle from, final CodeConstraint constraint ) {

        final 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.");

        }

        final Pattern regex = Pattern.compile(search);

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

        final Matcher matcher = regex.matcher(ilString);

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

            final int startExpr = matcher.start();

            final int endExpr = matcher.end();

            final int lenExpr = endExpr - startExpr;

            final 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( final 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( final String pattern,

            final 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( final String pattern,

            final CodeConstraint constraint ) {

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

    }

    /**

     * Convert opcode number to char.

     */

    private static char makeChar( final 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

         */

        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|invokedynamic)");

        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|invokedynamic|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|invokedynamic|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|invokedynamic|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|invokedynamic|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|invokedynamic|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|invokedynamic|ldc|invokestatic|daload)");

        map.put("loadclass", "(multianewarray|invokeinterface|invokedynamic|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(Const.ICONST_0, Const.ICONST_5, Const.ICONST_M1));

        map.put("lconst", new String(new char[] { '(', makeChar(Const.LCONST_0), '|', makeChar(Const.LCONST_1), ')' }));

        map.put("dconst", new String(new char[] { '(', makeChar(Const.DCONST_0), '|', makeChar(Const.DCONST_1), ')' }));

        map.put("fconst", new String(new char[] { '(', makeChar(Const.FCONST_0), '|', makeChar(Const.FCONST_1), '|', makeChar(Const.FCONST_2), ')' }));

        map.put("lload", precompile(Const.LLOAD_0, Const.LLOAD_3, Const.LLOAD));

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

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

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

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

        map.put("lstore", precompile(Const.LSTORE_0, Const.LSTORE_3, Const.LSTORE));

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

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

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

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

        // Compile strings

        for (final Map.Entry<String, String> entry : map.entrySet()) {

            final String key = entry.getKey();

            final String value = entry.getValue();

            final 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

        final StringBuilder buf = new StringBuilder("(");

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

            if (Const.getNoOfOperands(i) != Const.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( final short from, final short to, final short extra ) {

        final 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.getOpcodeName(ch - OFFSET));

//                } else {

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

//                }

//            } else {

//                buf.append(ch);

//            }

//        }

//        return buf.toString();

//    }

}