SquirrelJME/SquirrelJME

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modules/tool-classfile/src/main/java/net/multiphasicapps/classfile/ByteCode.java

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// -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
// ---------------------------------------------------------------------------
// SquirrelJME
//     Copyright (C) Stephanie Gawroriski <xer@multiphasicapps.net>
// ---------------------------------------------------------------------------
// SquirrelJME is under the Mozilla Public License Version 2.0.
// See license.mkd for licensing and copyright information.
// ---------------------------------------------------------------------------

package net.multiphasicapps.classfile;

import cc.squirreljme.runtime.cldc.debug.Debugging;
import cc.squirreljme.runtime.cldc.debug.ErrorCode;
import cc.squirreljme.runtime.cldc.util.IntegerArrayList;
import cc.squirreljme.runtime.cldc.util.SortedTreeMap;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.lang.ref.Reference;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;

/**
 * This class represents the byte code within a method.
 *
 * @since 2017/10/09
 */
public final class ByteCode
    implements Contexual, Iterable<Instruction>
{
    /** The code is always at this offset. */
    public static final int CODE_OFFSET =
        8;
    
    /** The maximum number of bytes the byte code may be. */
    private static final int _MAX_CODE_LENGTH =
        65535;
    
    /** The maximum number of stack entries. */
    protected final int maxstack;
    
    /** The maximum number of local entries. */
    protected final int maxlocals;
    
    /** The length of the method code in bytes. */
    protected final int codelen;
    
    /** The constant pool. */
    protected final Pool pool;
    
    /** The exceptions within this method. */
    protected final ExceptionHandlerTable exceptions;
    
    /** This type. */
    protected final ClassName thistype;
    
    /** The name of this method. */
    protected final MethodName methodname;
    
    /** Method type. */
    protected final MethodDescriptor methodtype;
    
    /** Is this method synchronized? */
    protected final boolean issynchronized;
    
    /** Is this an instance method? */
    protected final boolean isinstance;
    
    /** Local variable table. */
    protected final LocalVariableTable localVariables;
    
    /** The input attribute code, used for instruction lookup. */
    private final byte[] _rawByteCode;
    
    /** The stack map table data. */
    private final byte[] _smtdata;
    
    /** Is the stack map table data new? */
    private final boolean _newsmtdata;
    
    /** The owning method reference. */
    private final Reference<Method> _methodref;
    
    /** Instruction lengths at each position. */
    private final int[] _lengths;
    
    /** The addresses of every instruction by index. */
    private final int[] _index;
    
    /** The line number table. */
    private final short[] _linenumbertable;
    
    /** The cache of instructions in the byte code. */
    private final Reference<Instruction>[] _icache;
    
    /** String representation of this byte code */
    private Reference<String> _string;
    
    /** The stack map table cache. */
    private Reference<StackMapTable> _smt;
    
    /** Stack map at runtime. */
    private Reference<StackMapTablePairs> _stackMapRunTime;
    
    /**
     * Initializes the byte code.
     *
     * @param __mr The owning method reference.
     * @param __ca The raw code attribute data.
     * @param __tt The current {@code this} type.
     * @param __mf Method flags.
     * @throws InvalidClassFormatException If the byte code is not valid.
     * @throws NullPointerException On null arguments.
     * @since 2017/10/09
     */
    ByteCode(Reference<Method> __mr, byte[] __ca, ClassName __tt,
        MethodFlags __mf)
        throws InvalidClassFormatException, NullPointerException
    {
        if (__mr == null || __ca == null || __tt == null || __mf == null)
            throw new NullPointerException("NARG");
        
        // Needed
        Method method = __mr.get();
        
        // Set
        this._methodref = __mr;
        this._rawByteCode = __ca;
        this.issynchronized = __mf.isSynchronized();
        this.isinstance = !__mf.isStatic();
        
        // Is this an initializer method?
        this.methodname = method.name();
        this.methodtype = method.type();
        
        // If any IOExceptions are generated then the attribute is not valid
        Pool pool = method.pool();
        try (DataInputStream in = new DataInputStream(
            new ByteArrayInputStream(__ca)))
        {
            // The number of variables allocated to the method
            int maxStack = in.readUnsignedShort();
            int maxLocals = in.readUnsignedShort();
                
            /* {@squirreljme.error JC1y The specified code length is not valid.
            (The code length)} */
            int codeLen = in.readInt();
            if (codeLen <= 0 || codeLen > ByteCode._MAX_CODE_LENGTH)
                throw new InvalidClassFormatException(
                    String.format("JC1y %d", codeLen), this);
        
            // Ignore that many bytes
            for (int i = 0; i < codeLen; i++)
                in.readByte();
            
            // Read exception handler table
            ExceptionHandlerTable eht = ExceptionHandlerTable.decode(in, pool,
                codeLen);
            
            // The instruction index is used to lookup using a linear index
            // count rather than the potentially spaced out address lookup
            int[] index = new int[codeLen];
            int indexat = 0;
        
            // Set all lengths initially to invalid positions, this used as a
            // quick marker to determine which positions have valid
            // instructions
            int[] lengths = new int[codeLen];
            for (int i = 0; i < codeLen; i++)
                lengths[i] = -1;
        
            // Determine instruction lengths for each position
            for (int i = 0, li = -1; i < codeLen; li = i)
            {
                // Store address of instruction for an index based lookup
                index[indexat++] = i;
            
                // Store length
                int opLen = ByteCodeUtils.instructionLength(__ca,
                    ByteCode.CODE_OFFSET, i, null);
                lengths[i] = opLen;
            
                /* {@squirreljme.error JC1z The operation exceeds the bounds of
                the method byte code. (The operation pointer; The operation
                length; The code length; The last operation pointer)} */
                if ((i += opLen) > codeLen)
                    throw new InvalidClassFormatException(
                        String.format("JC1z %d %d %d %d",
                            i, opLen, codeLen, li), this);
            }
            
            // The stack map table is used for verification
            byte[] smt = null;
            boolean smtnew = false;
            
            // Parse the attribute table
            AttributeTable attrs = AttributeTable.parse(pool, in);
            
            // Try using the newer stack map table, if that does not exist
            // then fallback to the old one
            Attribute attr = attrs.get("StackMapTable");
            if (attr != null)
            {
                smt = attr.bytes();
                smtnew = true;
            }
            else
            {
                attr = attrs.get("StackMap");
                if (attr != null)
                {
                    smt = attr.bytes();
                    smtnew = false;
                }
            }
            
            // If there is no stack map, then use a default one (which has
            // just no entries) which has an assumed state
            if (smt == null)
            {
                smt = new byte[2];
                smtnew = true;
            }
            
            // Initialize a blank line number table
            short[] lnt = new short[codeLen];
            for (int i = 0; i < codeLen; i++)
                lnt[i] = -1;
            
            // Parse the line number table for debug purposes
            attr = attrs.get("LineNumberTable");
            if (attr != null)
                try (DataInputStream ai = attr.open())
                {
                    // Read entry count
                    int n = ai.readUnsignedShort();
                    
                    // Read all the individual entries
                    for (int i = 0; i < n; i++)
                    {
                        int pc = ai.readUnsignedShort(),
                            line = ai.readUnsignedShort();
                        
                        // Failed to read the program address, this could be
                        // a failure but instead just ignore it and continue
                        // on
                        if (pc < 0 || pc >= codeLen)
                            continue;
                        
                        // This gets handled later, but if there is more than
                        // 65534 lines in a file then what is the programmer
                        // even doing
                        lnt[pc] = (short)line;
                    }
                }
            
            // Parse local variables
            LocalVariableTable localVariables =
                LocalVariableTable.parse(pool, attrs);
            
            // Can set fields now
            this.maxstack = maxStack;
            this.maxlocals = maxLocals;
            this.codelen = codeLen;
            this.exceptions = eht;
            this.pool = pool;
            this.thistype = __tt;
            this._smtdata = smt;
            this._newsmtdata = smtnew;
            this._lengths = lengths;
            this._icache = ByteCode.__newCache(codeLen);
            this._linenumbertable = lnt;
            this.localVariables = localVariables;
            
            // Store addresses for all the indexes
            if (indexat == codeLen)
                this._index = index;
            else
                this._index = Arrays.copyOf(index, indexat);
        }
        
        /* {@squirreljme.error JC20 Failed to read from the code attribute.} */
        catch (IOException e)
        {
            throw new InvalidClassFormatException("JC20", e, this);
        }
    }
    
    /**
     * Returns the address of the instruction following the specified one.
     *
     * @param __a The following address.
     * @return The instruction address following the instruction at the
     * specified address, if the next address is at the end then this will
     * return an address after the last operation.
     * @throws InvalidClassFormatException If the specified address
     * is not valid.
     * @since 2017/05/20
     */
    public int addressFollowing(int __a)
        throws InvalidClassFormatException
    {
        /* {@squirreljme.error JC21 The instruction at the specified address is
        not valid. (The address)} */
        if (!this.isValidAddress(__a))
            throw new InvalidClassFormatException(
                String.format("JC21 %d", __a), this);
        
        int result = __a + this._lengths[__a];
        if (result >= this._lengths.length)
            return this._lengths.length;
        
        return result;
    }
    
    /**
     * Translates an address to an index.
     *
     * @param __a The address to translate.
     * @return The index of the instruction or {@code -1} if it is not valid,
     * if the address is the byte code length then the number of indexes is
     * returned.
     * @since 2017/08/02
     */
    public int addressToIndex(int __a)
    {
        // Byte right at the end converts to the last index
        int[] index = this._index;
        if (__a == this.codelen)
            return index.length;
        
        // Not the end
        int rv = Arrays.binarySearch(index, __a);
        if (rv < 0)
            return -1;
        return rv;
    }
    
    /**
     * Returns the exception handler table.
     *
     * @return The exception handler table.
     * @since 2018/10/13
     */
    public final ExceptionHandlerTable exceptions()
    {
        return this.exceptions;
    }
    
    /**
     * Returns the instruction at the specified address.
     *
     * @param __a The address to get the instruction for.
     * @return The represented instruction for the given address.
     * @throws InvalidClassFormatException If the address is not valid.
     * @since 2017/05/18
     */
    public Instruction getByAddress(int __a)
        throws InvalidClassFormatException
    {
        /* {@squirreljme.error JC22 The instruction at the specified address is
        not valid. (The address)} */
        if (!this.isValidAddress(__a))
        {
            Reference<Instruction>[] iCache = this._icache;
            int numCache = iCache.length;
            Instruction[] cache = new Instruction[numCache];
            for (int i = 0; i < numCache; i++)
                if (i == __a || iCache[i] != null ||
                    !this.isValidAddress(i))
                    cache[i] = (iCache[i] != null ? iCache[i].get() : null);
                else
                    try
                    {
                        cache[i] = this.getByAddress(i);
                    }
                    catch (Throwable __ignored)
                    {
                        // Ignored
                    }
            
            throw new InvalidClassFormatException(
                ErrorCode.__error__("JC22", __a,
                    this.__method().inClass(),
                    this.methodname, this.methodtype,
                    new IntegerArrayList(this._lengths),
                    new IntegerArrayList(this._index),
                    Arrays.asList(cache)), this);
        }
        
        Reference<Instruction>[] icache = this._icache;
        Reference<Instruction> ref = icache[__a];
        Instruction rv;
        
        if (ref == null || null == (rv = ref.get()))
            icache[__a] = new SoftReference<>((rv = new Instruction(
                this._rawByteCode, this.pool, __a, this.exceptions,
                this.stackMapTable(), this.addressFollowing(__a),
                this.addressToIndex(__a))));
        
        return rv;
    }
    
    /**
     * Returns the instruction based on an index in the order it appears within
     * the byte code rather than by address.
     *
     * @param __i The instruction index to get.
     * @return The instruction at this index.
     * @throws IndexOutOfBoundsException If the index is not within bounds.
     * @throws InvalidClassFormatException If the instruction is not valid.
     * @since 2017/08/01
     */
    public Instruction getByIndex(int __i)
        throws IndexOutOfBoundsException
    {
        // Check
        int[] index = this._index;
        if (__i < 0 || __i >= index.length)
            throw new IndexOutOfBoundsException("IOOB");
        
        return this.getByAddress(index[__i]);
    }
    
    /**
     * Translates an index to an address.
     *
     * @param __i The index to translate.
     * @return The address of the index or {@code -1} if it is not valid, if
     * the index is the number of indexes then the length of the byte code in
     * addresses is returned.
     * @since 2017/08/02
     */
    public int indexToAddress(int __i)
    {
        // Last index translates to the length of the byte code
        int[] index = this._index;
        int n = index.length;
        if (__i == n)
            return this.codelen;
        
        // Normal position
        if (__i < 0 || __i >= n)
            return -1;
        return index[__i];
    }
    
    /**
     * Returns the number of instructions (valid addresses) which are within
     * this method. This will not match the byte code length unless all
     * byte codes were to be single-byte in length.
     *
     * @return The number of instructions which are in the method.
     * @since 2017/08/01
     */
    public int instructionCount()
    {
        return this._index.length;
    }
    
    /**
     * This returns an iterator over the instructions which are defined within
     * this method.
     *
     * @return The iterator over byte code instructions.
     * @since 2017/05/20
     */
    public Iterator<Instruction> instructionIterator()
    {
        return new __InstructionIterator__();
    }
    
    /**
     * Returns if this is an instance or not.
     *
     * @return If this is an instance.
     * @since 2019/04/26
     */
    public final boolean isInstance()
    {
        return this.isinstance;
    }
    
    /**
     * Returns whether this is a constructor or not.
     *
     * @return Whether this is a constructor or not.
     * @since 2019/03/24
     */
    public final boolean isInstanceInitializer()
    {
        return this.methodname.isInstanceInitializer();
    }
    
    /**
     * Returns whether this is a static initializer or not.
     *
     * @return Whether this is a static initializer or not.
     * @since 2019/03/24
     */
    public final boolean isStaticInitializer()
    {
        return this.methodname.isStaticInitializer();
    }
    
    /**
     * Is this method synchronized?
     *
     * @return If this is synchronized.
     * @since 2019/04/26
     */
    public final boolean isSynchronized()
    {
        return this.issynchronized;
    }
    
    /**
     * Checks whether the given address is a valid instruction address.
     *
     * @param __a The address to check.
     * @return {@code true} if the address is valid.
     * @since 2017/05/18
     */
    public boolean isValidAddress(int __a)
    {
        // Out of range
        if (__a < 0 || __a >= this.codelen)
            return false;
        
        // Has to have a positive non-zero length
        return (this._lengths[__a] > 0);
    }
    
    /**
     * {@inheritDoc}
     * @since 2019/02/17
     */
    @Override
    public final Iterator<Instruction> iterator()
    {
        return this.instructionIterator();
    }
    
    /**
     * Returns the jump targets for this byte code.
     *
     * @return The jump targets.
     * @since 2019/03/30
     */
    public final Map<Integer, InstructionJumpTargets> jumpTargets()
    {
        Map<Integer, InstructionJumpTargets> rv = new LinkedHashMap<>();
        
        // Just fill addresses with instruction info
        for (Instruction i : this)
            rv.put(i.address(), i.jumpTargets());
        
        return rv;
    }
    
    /**
     * Returns the length of the byte code.
     *
     * @return The byte code length.
     * @since 2017/05/20
     */
    public int length()
    {
        return this.codelen;
    }
    
    /**
     * Returns the line that the address is on, assuming the address is valid
     * and there is line number information available.
     *
     * @param __a The address to lookup.
     * @return The line of the address or a negative value if it is not valid
     * or it is unknown.
     * @since 2018/09/08
     */
    public final int lineOfAddress(int __a)
    {
        // Scan through the table and try to find the line number for the given
        // address, the table is negative padded for unknown locations
        int codelen = this.codelen;
        short[] linenumbertable = this._linenumbertable;
        int negscandx = __a;
        for (int pc = __a; pc >= 0 && pc < codelen; pc--)
        {
            // Do not use this value if the line is not valid, scan backwards
            short clip = linenumbertable[pc];
            if (clip == -1)
                continue;
            
            // If the address we started at is not valid then a bunch of source
            // code is probably on the same line for a bunch of area so to
            // prevent any extra backscanning when this information is needed
            // cache it back into the table so it is used
            // Fill the entire table to our PC address so that way the entire
            // section is filled
            while (negscandx > pc)
                linenumbertable[negscandx--] = clip;
            
            // Sign extends to int, then removes the negative part so we can
            // recover the full 0-65534 range of the line table
            return (clip & 0xFFFF);
        }
        
        // Not known
        return -1;
    }
    
    /**
     * Returns the local variable table.
     *
     * @return The local variable table.
     * @since 2022/09/21
     */
    public LocalVariableTable localVariables()
    {
        return this.localVariables;
    }
    
    /**
     * Returns the maximum number of locals.
     *
     * @return The maximum number of locals.
     * @since 2017/05/20
     */
    public int maxLocals()
    {
        return this.maxlocals;
    }
    
    /**
     * Returns the maximum size of the stack.
     *
     * @return The maximum stack size.
     * @since 2017/05/20
     */
    public int maxStack()
    {
        return this.maxstack;
    }
    
    /**
     * Returns the name of this method.
     *
     * @return The method name.
     * @since 2019/04/22
     */
    public final MethodName name()
    {
        return this.methodname;
    }
    
    /**
     * Returns the constant pool being used.
     *
     * @return The constant pool the method uses.
     * @since 2017/05/20
     */
    public Pool pool()
    {
        return this.pool;
    }
    
    /**
     * Returns the raw byte code array.
     * 
     * @return The byte code as an array.
     * @since 2021/03/21
     */
    public byte[] rawByteCode()
    {
        byte[] rawCode = this._rawByteCode;
        int rawLen = rawCode.length;
        
        // It is the actual code attribute, so it needs to be stripped
        int len = Math.min(rawLen - ByteCode.CODE_OFFSET,
            this.codelen);
        byte[] result = new byte[len];
        System.arraycopy(rawCode, ByteCode.CODE_OFFSET,
            result, 0, len);
        
        return result;
    }
    
    /**
     * Reads an unsigned short from the raw byte code at the given address.
     *
     * @param __addr The address to read from.
     * @return The read unsigned short.
     * @throws IndexOutOfBoundsException If the address is out of bounds.
     * @since 2018/09/28
     */
    public final int readRawCodeUnsignedShort(int __addr)
        throws IndexOutOfBoundsException
    {
        /* {@squirreljme.error JC23 Out of bounds read of unsigned short from
        raw byte code. (The address)} */
        if (__addr < 0 || __addr >= this.codelen - 1)
            throw new IndexOutOfBoundsException(
                String.format("JC23 %d", __addr));
        
        byte[] rad = this._rawByteCode;
        int d = __addr + ByteCode.CODE_OFFSET;
        return ((rad[d] & 0xFF) << 8) |
            (rad[d + 1] & 0xFF);
    }
    
    /**
     * Returns the reverse jump targets, this essentially specifies the
     * instructions and exception handlers at given points jump to the
     * key addresses.
     *
     * @return The reverse jump targets.
     * @since 2019/03/30
     */
    public final Map<Integer, InstructionJumpTargets> reverseJumpTargets()
    {
        // Get the original jump table
        Map<Integer, InstructionJumpTargets> jumpmap = this.jumpTargets();
        
        // The target jump table has both normals and exceptions, so it must
        // remember that state accordingly
        class Working
        {
            Set<InstructionJumpTarget> normal =
                new LinkedHashSet<>();
            
            Set<InstructionJumpTarget> exception =
                new LinkedHashSet<>();
        }
        Map<Integer, Working> works = new LinkedHashMap<>();
        
        // Go through all the original jump targets and add them
        for (Map.Entry<Integer, InstructionJumpTargets> e : jumpmap.entrySet())
        {
            InstructionJumpTarget addr = new InstructionJumpTarget(e.getKey());
            InstructionJumpTargets jumps = e.getValue();
            
            for (int i = 0, n = jumps.size(); i < n; i++)
            {
                int targ = jumps.get(i).target();
                boolean isex = jumps.isException(i);
                
                // Create work if missing
                Working work = works.get(targ);
                if (work == null)
                    works.put(targ, (work = new Working()));
                
                // Add
                if (isex)
                    work.exception.add(addr);
                else
                    work.normal.add(addr);
            }
        }
        
        // Finalize for returning
        Map<Integer, InstructionJumpTargets> rv = new LinkedHashMap<>();
        for (Map.Entry<Integer, Working> e : works.entrySet())
        {
            Working work = e.getValue();
            Set<InstructionJumpTarget> nrm = work.normal,
                exe = work.exception;
            
            // Convert
            rv.put(e.getKey(), new InstructionJumpTargets(
                nrm.<InstructionJumpTarget>toArray(
                    new InstructionJumpTarget[nrm.size()]),
                exe.<InstructionJumpTarget>toArray(
                    new InstructionJumpTarget[exe.size()])));
        }
        
        return rv;
    }
    
    /**
     * Returns the stack map table.
     *
     * @return The stack map table.
     * @since 2017/10/15
     */
    public StackMapTable stackMapTable()
    {
        Reference<StackMapTable> ref = this._smt;
        StackMapTable rv;
        
        if (ref == null || null == (rv = ref.get()))
            this._smt = new SoftReference<>(rv = new __StackMapParser__(
                this.pool, this.__method(), this._newsmtdata, this._smtdata,
                this, new JavaType(this.thistype)).get());
        
        return rv;
    }
    
    /**
     * Returns a fully filled in {@link StackMapTable} for each instruction
     * as it would occur at runtime.
     * 
     * @return The stack map table at runtime.
     * @since 2023/07/03
     */
    public StackMapTablePairs stackMapTableFull()
    {
        Reference<StackMapTablePairs> ref = this._stackMapRunTime;
        StackMapTablePairs rv;
        
        if (ref == null || (rv = ref.get()) == null)
            try
            {
                rv = this.__calcStackMapTableFull();
                this._stackMapRunTime = new WeakReference<>(rv);
            }
            catch (InvalidClassFormatException __e)
            {
                /* {@squirreljme.error JC9a Could not calculate the full stack
                map in method. (The class; The method)} */
                Method method = this.__method();
                throw new InvalidClassFormatException(
                    String.format("JC9a %s %s",
                        method.inClass(),
                        method.nameAndType()), __e, this);
            }
        
        return rv;
    }
    
    /**
     * Returns the name of the current class.
     *
     * @return The current class name.
     * @since 2019/03/24
     */
    public final ClassName thisType()
    {
        return this.thistype;
    }
    
    /**
     * {@inheritDoc}
     * @since 2017/05/20
     */
    @Override
    public String toString()
    {
        Reference<String> ref = this._string;
        String rv;
        
        if (ref == null || null == (rv = ref.get()))
        {
            StringBuilder sb = new StringBuilder("[");
            
            // Fill in instructions
            boolean comma = false;
            for (Iterator<Instruction> it = this.instructionIterator();
                 it.hasNext();)
            {
                if (comma)
                    sb.append(", ");
                else
                    comma = true;
                
                sb.append(it.next());
            }
            
            sb.append(']');
            this._string = new WeakReference<>((rv = sb.toString()));
        }
        
        return rv;
    }
    
    /**
     * Returns the method type.
     *
     * @return The method type.
     * @since 2019/04/22
     */
    public final MethodDescriptor type()
    {
        return this.methodtype;
    }
    
    /**
     * Returns all of the valid addresses within this code.
     * 
     * @return The list of valid addresses.
     * @since 2021/03/14
     */
    public final int[] validAddresses()
    {
        return this._index.clone();
    }
    
    /**
     * Returns all the local variables which are written to.
     *
     * @return The local variables which are written to.
     * @since 2019/03/30
     */
    public final int[] writtenLocals()
    {
        Set<Integer> written = new LinkedHashSet<>();
        
        // Go through all instructions and count anything which is written to
        for (Instruction inst : this)
        {
            // Anything which is wide hits the adjacent local as well
            boolean wide = false;
            
            // Only specific instructions will do so
            int hit, op;
            switch ((op = inst.operation()))
            {
                case InstructionIndex.ASTORE:
                case InstructionIndex.WIDE_ASTORE:
                case InstructionIndex.FSTORE:
                case InstructionIndex.WIDE_FSTORE:
                case InstructionIndex.IINC:
                case InstructionIndex.WIDE_IINC:
                case InstructionIndex.ISTORE:
                case InstructionIndex.WIDE_ISTORE:
                    hit = inst.intArgument(0);
                    break;
                
                case InstructionIndex.ASTORE_0:
                case InstructionIndex.ASTORE_1:
                case InstructionIndex.ASTORE_2:
                case InstructionIndex.ASTORE_3:
                    hit = op - InstructionIndex.ASTORE_0;
                    break;
                
                case InstructionIndex.DSTORE:
                case InstructionIndex.WIDE_DSTORE:
                case InstructionIndex.LSTORE:
                case InstructionIndex.WIDE_LSTORE:
                    hit = inst.intArgument(0);
                    wide = true;
                    break;
                
                case InstructionIndex.DSTORE_0:
                case InstructionIndex.DSTORE_1:
                case InstructionIndex.DSTORE_2:
                case InstructionIndex.DSTORE_3:
                    hit = op - InstructionIndex.DSTORE_0;
                    wide = true;
                    break;
                
                case InstructionIndex.FSTORE_0:
                case InstructionIndex.FSTORE_1:
                case InstructionIndex.FSTORE_2:
                case InstructionIndex.FSTORE_3:
                    hit = op - InstructionIndex.FSTORE_0;
                    break;
                
                case InstructionIndex.ISTORE_0:
                case InstructionIndex.ISTORE_1:
                case InstructionIndex.ISTORE_2:
                case InstructionIndex.ISTORE_3:
                    hit = op - InstructionIndex.ISTORE_0;
                    break;
                
                case InstructionIndex.LSTORE_0:
                case InstructionIndex.LSTORE_1:
                case InstructionIndex.LSTORE_2:
                case InstructionIndex.LSTORE_3:
                    hit = op - InstructionIndex.LSTORE_0;
                    wide = true;
                    break;
                
                default:
                    continue;
            }
            
            // Set local as being written to, handle wides as well
            written.add(hit);
            if (wide)
                written.add(hit + 1);
        }
        
        // Convert to array
        Integer[] from = written.<Integer>toArray(new Integer[written.size()]);
        int n = from.length;
        int[] rv = new int[n];
        for (int i = 0; i < n; i++)
            rv[i] = from[i];
        return rv;
    }
    
    /**
     * Calculates the full stack map.
     * 
     * @return The full stack map.
     * @since 2023/07/16
     */
    private StackMapTablePairs __calcStackMapTableFull()
    {
        // We need to get the base table
        StackMapTable base = this.stackMapTable();
        
        // Resultant tables, will get big!
        Map<Integer, StackMapTableState> inputs = new SortedTreeMap<>();
        Map<Integer, StackMapTableState> outputs = new SortedTreeMap<>();
        
        // Working pop set
        List<StackMapTableEntry> popped = new ArrayList<>();
        
        // Go through each instruction and build the mapping
        StackMapTableState current = null;
        for (int logicalAddr = 0, numAddrs = this.instructionCount();
             logicalAddr < numAddrs; logicalAddr++)
        {
            int actualAddr = this.indexToAddress(logicalAddr);
            Instruction instruction = this.getByIndex(logicalAddr)
                .normalize();
            
            // Wipe popped state
            popped.clear();
            
            // Use pre-existing table? At entry point that is
            if (inputs.containsKey(actualAddr))
                current = inputs.get(actualAddr);
            else
            {
                StackMapTableState exist = instruction.stackMapTableState();
                if (exist != null)
                {
                    current = exist;
                    
                    // Overwrite input with the one from the actual stack map
                    // table
                    inputs.put(actualAddr, current);
                }
            }
            
            // Debug
            /*Debugging.debugNote("I### %s: %s -> ...",
                instruction, current);*/
            
            // Should not occur
            StackMapTableState input = current;
            if (current == null)
                throw Debugging.oops();
            
            // At an input state currently, if not set already
            if (!inputs.containsKey(actualAddr))
                inputs.put(actualAddr, current);
            
            // Depends on the instruction what happens
            try
            {
                int op = instruction.op;
                switch (op)
                {
                        // No changes to the stack
                    case InstructionIndex.NOP:
                    case InstructionIndex.GOTO:
                    case InstructionIndex.GOTO_W:
                    case InstructionIndex.WIDE_IINC:
                    case InstructionIndex.RETURN:
                        break;
                        
                        // Push null object
                    case InstructionIndex.ACONST_NULL:
                        current = current.deriveStackPush(
                            StackMapTableEntry.INITIALIZED_OBJECT);
                        break;
                        
                        // Load local variables
                    case InstructionIndex.WIDE_ALOAD:
                    case InstructionIndex.WIDE_ILOAD:
                    case InstructionIndex.WIDE_FLOAD:
                    case InstructionIndex.WIDE_LLOAD:
                    case InstructionIndex.WIDE_DLOAD:
                        current = current.deriveLocalLoad(
                            instruction.intArgument(0));
                        break;
                    
                        // Store local variable
                    case InstructionIndex.WIDE_ASTORE:
                    case InstructionIndex.WIDE_ISTORE:
                    case InstructionIndex.WIDE_FSTORE:
                    case InstructionIndex.WIDE_LSTORE:
                    case InstructionIndex.WIDE_DSTORE:
                        current = current.deriveLocalStore(
                            instruction.intArgument(0));
                        break;
                        
                        // Load constant value
                    case InstructionIndex.LDC:
                    case InstructionIndex.LDC_W:
                    case InstructionIndex.LDC2_W:
                        current = current.deriveStackPush(
                            ByteCode.__deriveLdc(instruction));
                        break;
                        
                        // Load from reference array
                    case InstructionIndex.AALOAD:
                        current = current.deriveStackPop(popped, 2);
                        current = current.deriveStackPush(
                            ByteCode.__deriveComponentType(popped.get(0)));
                        break;
                        
                        // Load from array, note that the input could be
                        // Object, so we have to assume it is the right array
                    case InstructionIndex.IALOAD:
                    case InstructionIndex.LALOAD:
                    case InstructionIndex.FALOAD:
                    case InstructionIndex.DALOAD:
                    case InstructionIndex.BALOAD:
                    case InstructionIndex.CALOAD:
                    case InstructionIndex.SALOAD:
                        current = current.deriveStackPop(popped, 2);
                        current = current.deriveStackPush(
                            ByteCode.__deriveComponentTypeViaOp(op));
                        break;
                        
                        // Store into array
                    case InstructionIndex.IASTORE:
                    case InstructionIndex.LASTORE:
                    case InstructionIndex.FASTORE:
                    case InstructionIndex.DASTORE:
                    case InstructionIndex.AASTORE:
                    case InstructionIndex.BASTORE:
                    case InstructionIndex.CASTORE:
                    case InstructionIndex.SASTORE:
                        current = current.deriveStackPop(null,
                            3);
                        break;
                        
                        // Push/pop operations
                    case InstructionIndex.POP:
                    case InstructionIndex.POP2:
                    case InstructionIndex.DUP:
                    case InstructionIndex.DUP_X1:
                    case InstructionIndex.DUP_X2:
                    case InstructionIndex.DUP2:
                    case InstructionIndex.DUP2_X1:
                    case InstructionIndex.DUP2_X2:
                    case InstructionIndex.SWAP:
                        current = current.deriveStackShuffle(
                            JavaStackShuffleType.ofOperation(op));
                        break;
                        
                        // Pop two, push first type
                    case InstructionIndex.IADD:
                    case InstructionIndex.LADD:
                    case InstructionIndex.FADD:
                    case InstructionIndex.DADD:
                    case InstructionIndex.ISUB:
                    case InstructionIndex.LSUB:
                    case InstructionIndex.FSUB:
                    case InstructionIndex.DSUB:
                    case InstructionIndex.IMUL:
                    case InstructionIndex.LMUL:
                    case InstructionIndex.FMUL:
                    case InstructionIndex.DMUL:
                    case InstructionIndex.IDIV:
                    case InstructionIndex.LDIV:
                    case InstructionIndex.FDIV:
                    case InstructionIndex.DDIV:
                    case InstructionIndex.IREM:
                    case InstructionIndex.LREM:
                    case InstructionIndex.FREM:
                    case InstructionIndex.DREM:
                    case InstructionIndex.IAND:
                    case InstructionIndex.LAND:
                    case InstructionIndex.IOR:
                    case InstructionIndex.LOR:
                    case InstructionIndex.IXOR:
                    case InstructionIndex.LXOR:
                    case InstructionIndex.ISHL:
                    case InstructionIndex.LSHL:
                    case InstructionIndex.ISHR:
                    case InstructionIndex.LSHR:
                    case InstructionIndex.IUSHR:
                    case InstructionIndex.LUSHR:
                        current = current.deriveStackPop(popped, 2);
                        current = current.deriveStackPush(popped.get(0));
                        break;
                        
                        // Pop then push same type
                    case InstructionIndex.INEG:
                    case InstructionIndex.LNEG:
                    case InstructionIndex.FNEG:
                    case InstructionIndex.DNEG:
                    case InstructionIndex.CHECKCAST:
                        current = current.deriveStackPop(popped, 1);
                        current = current.deriveStackPush(popped.get(0));
                        break;
                        
                        // Pop one then push integer
                    case InstructionIndex.INSTANCEOF:
                    case InstructionIndex.L2I:
                    case InstructionIndex.F2I:
                    case InstructionIndex.D2I:
                    case InstructionIndex.I2B:
                    case InstructionIndex.I2C:
                    case InstructionIndex.I2S:
                        current = current.deriveStackPop(popped, 1);
                        current = current.deriveStackPush(
                            StackMapTableEntry.INTEGER);
                        break;
                        
                        // Pop two then push integer
                    case InstructionIndex.LCMP:
                    case InstructionIndex.FCMPL:
                    case InstructionIndex.FCMPG:
                    case InstructionIndex.DCMPL:
                    case InstructionIndex.DCMPG:
                        current = current.deriveStackPop(popped, 2);
                        current = current.deriveStackPush(
                            StackMapTableEntry.INTEGER);
                        break;
                    
                    // Pop single value, push nothing
                    case InstructionIndex.IFEQ:
                    case InstructionIndex.IFNE:
                    case InstructionIndex.IFLT:
                    case InstructionIndex.IFGE:
                    case InstructionIndex.IFGT:
                    case InstructionIndex.IFLE:
                    case InstructionIndex.TABLESWITCH:
                    case InstructionIndex.LOOKUPSWITCH:
                    case InstructionIndex.ATHROW:
                    case InstructionIndex.IRETURN:
                    case InstructionIndex.LRETURN:
                    case InstructionIndex.FRETURN:
                    case InstructionIndex.DRETURN:
                    case InstructionIndex.ARETURN:
                    case InstructionIndex.MONITORENTER:
                    case InstructionIndex.MONITOREXIT:
                    case InstructionIndex.IFNULL:
                    case InstructionIndex.IFNONNULL:
                    case InstructionIndex.PUTSTATIC:
                        current = current.deriveStackPop(popped, 1);
                        break;
                        
                        // Pop value, push integer
                    case InstructionIndex.ARRAYLENGTH:
                        current = current.deriveStackPopThenPush(popped,
                            1, StackMapTableEntry.INTEGER);
                        break;
                        
                        // Pop two values, push nothing
                    case InstructionIndex.IF_ICMPEQ:
                    case InstructionIndex.IF_ICMPNE:
                    case InstructionIndex.IF_ICMPLT:
                    case InstructionIndex.IF_ICMPGE:
                    case InstructionIndex.IF_ICMPGT:
                    case InstructionIndex.IF_ICMPLE:
                    case InstructionIndex.IF_ACMPEQ:
                    case InstructionIndex.IF_ACMPNE:
                    case InstructionIndex.PUTFIELD:
                        current = current.deriveStackPop(popped, 2);
                        break;
                        
                        // Method invocation
                    case InstructionIndex.INVOKEVIRTUAL:
                    case InstructionIndex.INVOKESPECIAL:
                    case InstructionIndex.INVOKESTATIC:
                    case InstructionIndex.INVOKEINTERFACE:
                        current = current.deriveMethodCall(
                            op == InstructionIndex.INVOKESTATIC,
                            instruction.argument(0,
                                MethodReference.class));
                        break;
                        
                        // Pop one then push long
                    case InstructionIndex.I2L:
                    case InstructionIndex.F2L:
                    case InstructionIndex.D2L:
                        current = current.deriveStackPop(popped, 1);
                        current = current.deriveStackPush(
                            StackMapTableEntry.LONG);
                        break;
                        
                        // Pop one then push float
                    case InstructionIndex.I2F:
                    case InstructionIndex.L2F:
                    case InstructionIndex.D2F:
                        current = current.deriveStackPop(popped, 1);
                        current = current.deriveStackPush(
                            StackMapTableEntry.FLOAT);
                        break;
                        
                        // Pop one then push double
                    case InstructionIndex.I2D:
                    case InstructionIndex.L2D:
                    case InstructionIndex.F2D:
                        current = current.deriveStackPop(popped, 1);
                        current = current.deriveStackPush(
                            StackMapTableEntry.DOUBLE);
                        break;
                        
                        // Push new object of given type
                    case InstructionIndex.NEW:
                        current = current.deriveStackPush(
                            instruction.argument(0, ClassName.class)
                                .field());
                        break;
                        
                        // Pop one, push specified array
                    case InstructionIndex.ANEWARRAY:
                        current = current.deriveStackPop(null,
                            1);
                        current = current.deriveStackPush(
                            instruction.argument(0, ClassName.class)
                                .field().addDimensions(1));
                        break;
                        
                        // Pop one, push specified array as primitive
                    case InstructionIndex.NEWARRAY:
                        current = current.deriveStackPop(null,
                            1);
                        current = current.deriveStackPush(
                            instruction.argument(0, PrimitiveType.class)
                                .field().addDimensions(1));
                        break;
                        
                        // Pop count in arg 1, push an array
                    case InstructionIndex.MULTIANEWARRAY:
                        current = current.deriveStackPop(null,
                            instruction.intArgument(1));
                        current = current.deriveStackPush(
                            instruction.argument(0, ClassName.class)
                                .field().addDimensions(
                                    instruction.intArgument(1)));
                        break;
                        
                        // Push referred reference type
                    case InstructionIndex.GETSTATIC:
                        current = current.deriveStackPush(
                            instruction.argument(0,
                                FieldReference.class).memberType());
                        break;
                        
                        // Pop one, push referred type
                    case InstructionIndex.GETFIELD:
                        current = current.deriveStackPop(null,
                            1);
                        current = current.deriveStackPush(
                            instruction.argument(0,
                                FieldReference.class).memberType());
                        break;
                        
                        // Unhandled?
                    default:
                        throw Debugging.todo(
                            InstructionMnemonics.toString(op));
                }
            }
            catch (InvalidClassFormatException|IllegalArgumentException|
                IllegalStateException __e)
            {
                /* {@squirreljme.error JC9b Could not process for instruction.
                (The instruction; The input; The output (may be partial)} */
                throw new InvalidClassFormatException(
                    String.format("JC9b %s L#%d %s ?(%s)?",
                        instruction,
                        this.lineOfAddress(instruction.address()),
                        input,
                        current), __e, this);
            }
            
            // Debug
            /*Debugging.debugNote("... -> %s",
                current);*/
            
            // Store output of the instruction
            if (!outputs.containsKey(actualAddr))
                outputs.put(actualAddr, current);
            
            // Set inputs for all jump targets
            InstructionJumpTargets jumps = instruction.jumpTargets();
            for (int i = 0, n = jumps.size(); i < n; i++)
            {
                // Get the designated jump target
                InstructionJumpTarget jump = jumps.get(i);
                boolean isException = jumps.isException(i);
                
                // Set input if it does not exist
                if (!inputs.containsKey(jump.target))
                {
                    if (!isException)
                        inputs.put(jump.target, current);
                }
            }
        }
        
        // Setup table pair
        return new StackMapTablePairs(inputs, outputs);
    }
    
    /**
     * Returns the method which owns this byte code.
     *
     * @return The owning method.
     * @since 2017/10/15
     */
    private Method __method()
    {
        /* {@squirreljme.error JC24 The method owning this byte code has been
        garbage collected.} */
        Method rv = this._methodref.get();
        if (rv == null)
            throw new IllegalStateException("JC24");
        return rv;
    }
    
    /**
     * Derives the component type.
     * 
     * @param __entry The entry to derive.
     * @return The derived type.
     * @throws NullPointerException On null arguments.
     * @since 2023/07/03
     */
    private static StackMapTableEntry __deriveComponentType(
        StackMapTableEntry __entry)
        throws NullPointerException
    {
        if (__entry == null)
            throw new NullPointerException("NARG");
        
        // Get the component type, if it is not found, assume object
        FieldDescriptor type = __entry.type().type().componentType();
        if (type == null)
            return StackMapTableEntry.INITIALIZED_OBJECT;
        
        // Promote smaller than int primitives
        if (type.isPrimitive())
            switch (type.primitiveType())
            {
                case BOOLEAN:
                case BYTE:
                case SHORT:
                case CHARACTER:
                    type = FieldDescriptor.INTEGER;
                    break;
            }
        
        return new StackMapTableEntry(type, true);
    }
    
    /**
     * Derives the component type for primitive arrays.
     *
     * @param __op The operation to check.
     * @return The entry for the type.
     * @throws InvalidClassFormatException If the operation is not valid.
     * @since 2023/07/17
     */
    private static StackMapTableEntry __deriveComponentTypeViaOp(int __op)
        throws InvalidClassFormatException
    {
        switch (__op)
        {
            case InstructionIndex.BALOAD:
            case InstructionIndex.CALOAD:
            case InstructionIndex.SALOAD:
            case InstructionIndex.IALOAD:
                return StackMapTableEntry.INTEGER;
            
            case InstructionIndex.LALOAD:
                return StackMapTableEntry.LONG;
                
            case InstructionIndex.FALOAD:
                return StackMapTableEntry.FLOAT;
                
            case InstructionIndex.DALOAD:
                return StackMapTableEntry.DOUBLE;
        }
            
        /* {@squirreljme.error JCl1 Could not derive primitive type of the
        array instruction. (The instruction)} */
        throw new InvalidClassFormatException(
            String.format("JCl1 %s", InstructionMnemonics.toString(__op)));
    }
    
    /**
     * Derives the LDC instruction.
     *
     * @param __instruction The instruction.
     * @return The derived entry.
     * @throws NullPointerException On null arguments.
     * @since 2023/07/03
     */
    private static FieldDescriptor __deriveLdc(Instruction __instruction)
        throws NullPointerException
    {
        if (__instruction == null)
            throw new NullPointerException("NARG");
        
        return __instruction.argument(0, ConstantValue.class)
            .type.javaType().type;
    }
    
    /**
     * Initializes a new cache array.
     *
     * @param __l The length of the array.
     * @return The cache array.
     * @since 2017/05/18
     */
    @SuppressWarnings({"unchecked"})
    private static Reference<Instruction>[] __newCache(int __l)
    {
        return (Reference<Instruction>[])new Reference[__l];
    }
    
    /**
     * This iterates over each byte code instruction.
     *
     * @since 2017/05/20
     */
    private final class __InstructionIterator__
        implements Iterator<Instruction>
    {
        /** The code length. */
        protected final int codelen =
            ByteCode.this.codelen;
        
        /** The read address. */
        private int _at;
        
        /**
         * {@inheritDoc}
         * @since 2017/05/20
         */
        @Override
        public boolean hasNext()
        {
            return this._at < this.codelen;
        }
        
        /**
         * {@inheritDoc}
         * @since 2017/05/20
         */
        @Override
        public Instruction next()
            throws NoSuchElementException
        {
            // No more?
            if (!this.hasNext())
                throw new NoSuchElementException("NSEE");
            
            // Instruction at current pointer
            int at = this._at;
            Instruction rv = ByteCode.this.getByAddress(at);
            
            // Skip length of instruction
            this._at += ByteCode.this._lengths[at];
            
            return rv;
        }
        
        /**
         * {@inheritDoc}
         * @since 2017/05/20
         */
        @Override
        public void remove()
            throws UnsupportedOperationException
        {
            throw new UnsupportedOperationException("RORO");
        }
    }
}