1 /*
 2  * Copyright (c) 2021, 2023, 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.  Oracle designates this
 8  * particular file as subject to the "Classpath" exception as provided
 9  * by Oracle in the LICENSE file that accompanied this code.
10  *
11  * This code is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
16  *
17  * You should have received a copy of the GNU General Public License version
18  * 2 along with this work; if not, write to the Free Software Foundation,
19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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24  */
25 
26 package jdk.internal.foreign;
27 
28 import java.lang.foreign.MemorySegment;
29 import java.lang.foreign.SegmentAllocator;
30 
31 public final class SlicingAllocator implements SegmentAllocator {
32 
33     private final MemorySegment segment;
34     private final long maxAlign;
35 
36     private long sp = 0L;
37 
38     public SlicingAllocator(MemorySegment segment) {
39         this.segment = segment;
40         this.maxAlign = ((AbstractMemorySegmentImpl)segment).maxAlignMask();
41     }
42 
43     MemorySegment trySlice(long byteSize, long byteAlignment) {
44         long min = segment.address();
45         long start = Utils.alignUp(min + sp, byteAlignment) - min;
46         MemorySegment slice = segment.asSlice(start, byteSize, byteAlignment);
47         sp = start + byteSize;
48         return slice;
49     }
50 
51     @Override
52     public MemorySegment allocate(long byteSize, long byteAlignment) {
53         Utils.checkAllocationSizeAndAlign(byteSize, byteAlignment);
54         // try to slice from current segment first...
55         return trySlice(byteSize, byteAlignment);
56     }
57 }