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/*
 * Copyright (c) 2020, 2023, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * The Universal Permissive License (UPL), Version 1.0
 *
 * Subject to the condition set forth below, permission is hereby granted to any
 * person obtaining a copy of this software, associated documentation and/or
 * data (collectively the "Software"), free of charge and under any and all
 * copyright rights in the Software, and any and all patent rights owned or
 * freely licensable by each licensor hereunder covering either (i) the
 * unmodified Software as contributed to or provided by such licensor, or (ii)
 * the Larger Works (as defined below), to deal in both
 *
 * (a) the Software, and
 *
 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
 * is contributed by such licensors),
 *
 * without restriction, including without limitation the rights to copy, create
 * derivative works of, display, perform, and distribute the Software and make,
 * use, sell, offer for sale, import, export, have made, and have sold the
 * Software and the Larger Work(s), and to sublicense the foregoing rights on
 * either these or other terms.
 *
 * This license is subject to the following condition:
 *
 * The above copyright notice and either this complete permission notice or at a
 * minimum a reference to the UPL must 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,
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 * SOFTWARE.
 */
package com.oracle.graal.python.nodes.util;

import com.oracle.graal.python.builtins.objects.ints.PInt;
import com.oracle.graal.python.util.OverflowException;
import com.oracle.truffle.api.dsl.GenerateCached;
import com.oracle.truffle.api.dsl.GenerateInline;
import com.oracle.truffle.api.dsl.GenerateUncached;
import com.oracle.truffle.api.dsl.Specialization;

/**
 * Do not use for a regular cast "to long". This is only meant for the use with hash functions where
 * the sign bit does not really matter but just the bits. Also in case of a BigInteger
 * overflow the PInt args hash value is returned.
 *
 * Casts a Python integer to a Java long without coercion. The difference to
 * {@link CastToJavaLongExactNode} is that if a {@link PInt} is larger than
 * {@link Integer#MAX_VALUE} but still just requires 64-bits, we will still to the cast resulting in
 * a negative Java long.
 *
 * ATTENTION: If the cast isn't possible, the node will throw a {@link CannotCastException}.
 */
@GenerateUncached
@GenerateInline
@GenerateCached(false)
public abstract class CastUnsignedToJavaLongHashNode extends CastToJavaLongNode {

    @Specialization(rewriteOn = OverflowException.class, insertBefore = "doNativeObject")
    static long toLongNoOverflow(PInt x) throws OverflowException {
        return x.longValueExact();
    }

    @Specialization(replaces = "toLongNoOverflow", insertBefore = "doNativeObject")
    static long toLong(PInt x) {
        try {
            return x.longValueExact();
        } catch (OverflowException e) {
            if (x.isZeroOrPositive() && x.bitLength() <= 64) {
                return x.longValue();
            }
            // see slot_tp_hash()
            // res was not within range, so we're free to use any sufficiently bit-mixing
            // transformation; long.__hash__ will do nicely
            return x.hash();
        }
    }
}