1 /*
2 * Copyright (c) 2017, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24
25 package jdk.internal.vm.compiler.collections;
26
27 import java.util.Iterator;
28 import java.util.Objects;
29 import java.util.function.BiFunction;
30
31 /**
32 * Implementation of a map with a memory-efficient structure that always preserves insertion order
33 * when iterating over keys. Particularly efficient when number of entries is 0 or smaller equal
34 * {@link #INITIAL_CAPACITY} or smaller 256.
35 *
36 * The key/value pairs are kept in an expanding flat object array with keys at even indices and
37 * values at odd indices. If the map has smaller or equal to {@link #HASH_THRESHOLD} entries, there
38 * is no additional hash data structure and comparisons are done via linear checking of the
39 * key/value pairs. For the case where the equality check is particularly cheap (e.g., just an
40 * object identity comparison), this limit below which the map is without an actual hash table is
41 * higher and configured at {@link #HASH_THRESHOLD_IDENTITY_COMPARE}.
42 *
43 * When the hash table needs to be constructed, the field {@link #hashArray} becomes a new hash
44 * array where an entry of 0 means no hit and otherwise denotes the entry number in the
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1 /*
2 * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * The Universal Permissive License (UPL), Version 1.0
6 *
7 * Subject to the condition set forth below, permission is hereby granted to any
8 * person obtaining a copy of this software, associated documentation and/or
9 * data (collectively the "Software"), free of charge and under any and all
10 * copyright rights in the Software, and any and all patent rights owned or
11 * freely licensable by each licensor hereunder covering either (i) the
12 * unmodified Software as contributed to or provided by such licensor, or (ii)
13 * the Larger Works (as defined below), to deal in both
14 *
15 * (a) the Software, and
16 *
17 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
18 * one is included with the Software each a "Larger Work" to which the Software
19 * is contributed by such licensors),
20 *
21 * without restriction, including without limitation the rights to copy, create
22 * derivative works of, display, perform, and distribute the Software and make,
23 * use, sell, offer for sale, import, export, have made, and have sold the
24 * Software and the Larger Work(s), and to sublicense the foregoing rights on
25 * either these or other terms.
26 *
27 * This license is subject to the following condition:
28 *
29 * The above copyright notice and either this complete permission notice or at a
30 * minimum a reference to the UPL must be included in all copies or substantial
31 * portions of the Software.
32 *
33 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
34 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
35 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
36 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
37 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
38 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
39 * SOFTWARE.
40 */
41 package jdk.internal.vm.compiler.collections;
42
43 import java.util.Iterator;
44 import java.util.Objects;
45 import java.util.function.BiFunction;
46
47 /**
48 * Implementation of a map with a memory-efficient structure that always preserves insertion order
49 * when iterating over keys. Particularly efficient when number of entries is 0 or smaller equal
50 * {@link #INITIAL_CAPACITY} or smaller 256.
51 *
52 * The key/value pairs are kept in an expanding flat object array with keys at even indices and
53 * values at odd indices. If the map has smaller or equal to {@link #HASH_THRESHOLD} entries, there
54 * is no additional hash data structure and comparisons are done via linear checking of the
55 * key/value pairs. For the case where the equality check is particularly cheap (e.g., just an
56 * object identity comparison), this limit below which the map is without an actual hash table is
57 * higher and configured at {@link #HASH_THRESHOLD_IDENTITY_COMPARE}.
58 *
59 * When the hash table needs to be constructed, the field {@link #hashArray} becomes a new hash
60 * array where an entry of 0 means no hit and otherwise denotes the entry number in the
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