org.eolang.opeo.decompilation.DecompilerState Maven / Gradle / Ivy

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Bytecode decompiler to eolang and back
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/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2016-2023 Objectionary.com
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package org.eolang.opeo.decompilation;

import java.util.Deque;
import java.util.LinkedList;
import java.util.stream.Collectors;
import lombok.EqualsAndHashCode;
import lombok.ToString;
import org.eolang.opeo.ast.AstNode;
import org.eolang.opeo.ast.Opcode;
import org.objectweb.asm.Type;

/**
 * Internal state of decompiler.
 * This state changes all the time between instruction handlers.
 * @since 0.2
 */
@ToString
@EqualsAndHashCode
public final class DecompilerState {

    /**
     * Remaining opcodes.
     * Each method has an original list of opcodes which we decompile.
     * When some agent decompiles an instruction, it removes it from this list.
     */
    private final Deque opcodes;

    /**
     * Current operand stack.
     * It might have some values inside.
     */
    private final OperandStack ostack;

    /**
     * Method local variables.
     */
    private final LocalVariables vars;

    /**
     * Constructor.
     */
    public DecompilerState() {
        this(new LocalVariables());
    }

    /**
     * Constructor.
     * @param vars Method local variables.
     */
    public DecompilerState(final LocalVariables vars) {
        this(new OperandStack(), vars);
    }

    /**
     * Constructor.
     * @param ostack Operand stack.
     */
    public DecompilerState(final OperandStack ostack) {
        this(ostack, new LocalVariables());
    }

    /**
     * Constructor.
     * @param operands Operand stack.
     * @param vars Method local variables.
     */
    public DecompilerState(final OperandStack operands, final LocalVariables vars) {
        this(new LinkedList<>(), operands, vars);
    }

    /**
     * Constructor.
     * @param opcodes Remaining opcodes.
     * @param stack Operand stack.
     * @param vars Method local variables.
     */
    public DecompilerState(
        final Deque opcodes,
        final OperandStack stack,
        final LocalVariables vars
    ) {
        this.opcodes = opcodes;
        this.ostack = stack;
        this.vars = vars;
    }

    /**
     * Retrieve current bytecode instruction.
     * @return Current bytecode instruction.
     */
    public Opcode current() {
        if (this.opcodes.isEmpty()) {
            throw new IllegalStateException("No instructions left");
        }
        return this.opcodes.peek();
    }

    /**
     * Check if there are any instructions left.
     * @return True if there are instructions left.
     */
    public boolean hasInstructions() {
        return !this.opcodes.isEmpty();
    }

    /**
     * Remove current instruction from the list.
     * This is used when we decompile an instruction.
     */
    public void popInstruction() {
        if (!this.opcodes.isEmpty()) {
            this.opcodes.pop();
        }
    }

    /**
     * Instruction operand.
     * @param index Operand index.
     * @return Instruction operand.
     */
    public Object operand(final int index) {
        return this.current().operand(index);
    }

    /**
     * Retrieve variable by index and type.
     * @param index Variable index.
     * @param type Varaiable type.
     * @return Variable node.
     */
    public AstNode variable(final int index, final Type type) {
        return this.vars.variable(index, type);
    }

    /**
     * Retrieve current stack.
     * @return Operand stack.
     */
    public OperandStack stack() {
        return this.ostack;
    }

    /**
     * Print opcodes in a pretty way.
     * @return Pretty opcodes string
     */
    public String prettyOpcodes() {
        return this.opcodes.stream().map(Opcode::pretty).collect(Collectors.joining(" "));
    }
}