SquirrelJME/SquirrelJME

// -*- 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 java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.util.Arrays;

/**
 * This class represents a lookup switch which is used to lookup indexes as a
 * jump table.
 *
 * @since 2018/09/20
 */
public final class LookupSwitch
    implements IntMatchingJumpTable
{
    /** The default target. */
    protected final InstructionJumpTarget defaultjump;
    
    /** The keys. */
    private final int[] _keys;
    
    /** The jump targets. */
    private final InstructionJumpTarget[] _jumps;
    
    /** String representation. */
    private Reference<String> _string;
    
    /**
     * Initializes the lookup switch.
     *
     * @param __def The default address if no values match at all.
     * @param __keys The keys to check, must be sorted.
     * @param __jumps The jump targets.
     * @throws IllegalArgumentException If the key and jump table length are
     * difference lengths.
     * @throws InvalidClassFormatException If the key table is not sorted.
     * @throws NullPointerException On null arguments.
     * @since 2018/09/20
     */
    public LookupSwitch(InstructionJumpTarget __def,
        int[] __keys, InstructionJumpTarget[] __jumps)
        throws IllegalArgumentException, InvalidClassFormatException,
            NullPointerException
    {
        if (__def == null || __keys == null || __jumps == null)
            throw new NullPointerException("NARG");
        
        /* {@squirreljme.error JC3c Key and jump table for lookup switch
        table is of different lengths.} */
        if (__keys.length != __jumps.length)
            throw new IllegalArgumentException("JC3c");
        
        // Defensive copy
        __keys = __keys.clone();
        __jumps = __jumps.clone();
        
        // Check for sorted
        long last = ((long)Integer.MIN_VALUE) - 1;
        for (int i = 0, n = __keys.length; i < n; i++)
        {
            /* {@squirreljme.error JC3d Lookup switch key is not in sorted
            order. (The index; The current key; The last key)} */
            int k = __keys[i];
            if (k < last)
                throw new InvalidClassFormatException(
                    String.format("JC3d %d %d %d", i, k, last));
            last = k;
            
            if (__jumps[i] == null)
                throw new NullPointerException("NARG");
        }
        
        this.defaultjump = __def;
        this._keys = __keys;
        this._jumps = __jumps;
    }
    
    /**
     * Returns the default jump.
     *
     * @return The default jump.
     * @since 2019/04/16
     */
    public final InstructionJumpTarget defaultJump()
    {
        return this.defaultjump;
    }
    
    /**
     * Returns the jumps.
     *
     * @return The jumps.
     * @since 2019/04/16
     */
    public final InstructionJumpTarget[] jumps()
    {
        return this._jumps.clone();
    }
    
    /**
     * Returns the keys.
     *
     * @return The keys.
     * @since 2019/04/16
     */
    public final int[] keys()
    {
        return this._keys.clone();
    }
    
    /**
     * {@inheritDoc}
     * @since 2018/09/20
     */
    @Override
    public final InstructionJumpTarget match(int __k)
    {
        // Use binary search since all entries are sorted
        int dx = Arrays.binarySearch(this._keys, __k);
        
        // Match was found, use that result
        if (dx >= 0)
            return this._jumps[dx];
        
        // Not found
        return this.defaultjump;
    }
    
    /**
     * Returns the size of the switch.
     *
     * @return The size.
     * @since 2019/04/16
     */
    public final int size()
    {
        return this._jumps.length;
    }
    
    /**
     * {@inheritDoc}
     * @since 2019/03/31
     */
    @Override
    public final InstructionJumpTarget[] targets()
    {
        InstructionJumpTarget[] jumps = this._jumps;
        int n = jumps.length;
        
        // Start off array with the default jump
        InstructionJumpTarget[] rv = new InstructionJumpTarget[n + 1];
        rv[0] = this.defaultjump;
        
        // Add all the others
        for (int i = 0, o = 1; i < n; i++, o++)
            rv[o] = jumps[i];
        
        return rv;
    }
    
    /**
     * {@inheritDoc}
     * @since 2018/09/20
     */
    @Override
    public final String toString()
    {
        Reference<String> ref = this._string;
        String rv;
        
        if (ref == null || null == (rv = ref.get()))
        {
            // Set with default first
            StringBuilder sb = new StringBuilder("{default=");
            sb.append(this.defaultjump);
            
            // Add all matches and their targets
            int[] keys = this._keys;
            InstructionJumpTarget[] jumps = this._jumps;
            for (int i = 0, n = keys.length; i < n; i++)
            {
                sb.append(", ");
                
                sb.append(keys[i]);
                sb.append('=');
                sb.append(jumps[i]);
            }
            
            // Cleans
            sb.append('}');
            
            this._string = new WeakReference<>((rv = sb.toString()));
        }
        
        return rv;
    }
}