erjang.EPair.java Source code

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Here is the source code for erjang.EPair.java

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/**
 * This file is part of Erjang - A JVM-based Erlang VM
 *
 * Copyright (c) 2009 by Trifork
 *
 * Licensed 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 erjang;

import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;

public class EPair extends ECons {
    public final EObject head;
    public final EObject tail;

    public EPair(EObject h, EObject t) {

        assert (h != null);
        assert (t != null);

        this.head = h;
        this.tail = t;
    }

    public ECons testNonEmptyList() {
        return this;
    }

    public EObject head() {
        return head;
    }

    public EObject tail() {
        return tail;
    }

    @Override
    public String toString() {
        StringBuffer sb = new StringBuffer("[");

        EObject val = this;
        while (val instanceof ECons && val != ERT.NIL) {
            ECons ep = (ECons) val;
            if (val != this) {
                sb.append(",");
            }
            sb.append(ep.head());
            val = ep.tail();
        }

        if (val != ERT.NIL) {
            sb.append('|');
            sb.append(val);
        }

        sb.append("]");
        return sb.toString();
    }

    static Type EPAIR_TYPE = Type.getType(EPair.class);
    static Type ETERM_TYPE = Type.getType(EObject.class);
    static String CONSTRUCTOR_DESC = "(" + ETERM_TYPE.getDescriptor() + ETERM_TYPE.getDescriptor() + ")V";

    @Override
    public Type emit_const(MethodVisitor fa) {
        Type type = EPAIR_TYPE;

        fa.visitTypeInsn(Opcodes.NEW, type.getInternalName());
        fa.visitInsn(Opcodes.DUP);

        ((EObject) head).emit_const(fa);
        ((EObject) tail).emit_const(fa);

        fa.visitMethodInsn(Opcodes.INVOKESPECIAL, type.getInternalName(), "<init>", CONSTRUCTOR_DESC);

        return type;
    }

    @Override
    public void encode(EOutputStream eos) {
        eos.write_list_head(1);
        eos.write_any(head);
        eos.write_any(tail);
    }

    @Override
    public int hashCode() {
        //TODO: use phash() rather than this brittle nonsense:
        return 31 * head.hashCode() + tail.hashCode();
    }
}