1 /*
2 * Copyright (c) 2020, 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.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 *
25 */
26
27 package jdk.internal.foreign;
28
29 import java.lang.foreign.MemorySegment;
30 import java.nio.ByteBuffer;
31 import java.util.Optional;
32
33 import jdk.internal.misc.Unsafe;
34 import jdk.internal.misc.VM;
35 import jdk.internal.vm.annotation.ForceInline;
36
37 /**
38 * Implementation for native memory segments. A native memory segment is essentially a wrapper around
39 * a native long address.
40 */
41 public sealed class NativeMemorySegmentImpl extends AbstractMemorySegmentImpl permits MappedMemorySegmentImpl {
42
43 private static final Unsafe UNSAFE = Unsafe.getUnsafe();
44
45 // The maximum alignment supported by malloc - typically 16 bytes on
46 // 64-bit platforms and 8 bytes on 32-bit platforms.
47 private static final long MAX_MALLOC_ALIGN = Unsafe.ADDRESS_SIZE == 4 ? 8 : 16;
48
49 final long min;
50
51 @ForceInline
52 NativeMemorySegmentImpl(long min, long length, boolean readOnly, MemorySessionImpl scope) {
53 super(length, readOnly, scope);
54 this.min = (Unsafe.getUnsafe().addressSize() == 4)
55 // On 32-bit systems, normalize the upper unused 32-bits to zero
56 ? min & 0x0000_0000_FFFF_FFFFL
57 // On 64-bit systems, all the bits are used
58 : min;
59 }
60
61 /**
62 * This constructor should only be used when initializing {@link MemorySegment#NULL}. Note: because of the memory
63 * segment class hierarchy, it is possible to end up in a situation where this constructor is called
64 * when the static fields in this class are not yet initialized.
65 */
66 @ForceInline
67 public NativeMemorySegmentImpl() {
68 super(0L, false, MemorySessionImpl.NATIVE_SESSION);
69 this.min = 0L;
70 }
71
72 @Override
73 public long address() {
74 return min;
75 }
76
77 @Override
78 public Optional<Object> heapBase() {
79 return Optional.empty();
80 }
81
82 @ForceInline
83 @Override
84 NativeMemorySegmentImpl dup(long offset, long size, boolean readOnly, MemorySessionImpl scope) {
85 return new NativeMemorySegmentImpl(min + offset, size, readOnly, scope);
86 }
87
88 @Override
89 ByteBuffer makeByteBuffer() {
90 return NIO_ACCESS.newDirectByteBuffer(min, (int) this.length, null, this);
91 }
92
93 @Override
94 public boolean isNative() {
95 return true;
96 }
97
98 @Override
99 public long unsafeGetOffset() {
100 return min;
101 }
102
103 @Override
104 public Object unsafeGetBase() {
105 return null;
106 }
107
108 @Override
109 public long maxAlignMask() {
110 return 0;
111 }
112
113 // factories
114
115 public static MemorySegment makeNativeSegment(long byteSize, long byteAlignment, MemorySessionImpl sessionImpl,
116 boolean shouldReserve) {
117 sessionImpl.checkValidState();
118 if (VM.isDirectMemoryPageAligned()) {
119 byteAlignment = Math.max(byteAlignment, NIO_ACCESS.pageSize());
120 }
121 long alignedSize = Math.max(1L, byteAlignment > MAX_MALLOC_ALIGN ?
122 byteSize + (byteAlignment - 1) :
123 byteSize);
124
125 if (shouldReserve) {
126 NIO_ACCESS.reserveMemory(alignedSize, byteSize);
127 }
128
129 long buf = allocateMemoryWrapper(alignedSize);
130 long alignedBuf = Utils.alignUp(buf, byteAlignment);
131 AbstractMemorySegmentImpl segment = new NativeMemorySegmentImpl(buf, alignedSize,
132 false, sessionImpl);
133 sessionImpl.addOrCleanupIfFail(new MemorySessionImpl.ResourceList.ResourceCleanup() {
134 @Override
135 public void cleanup() {
136 UNSAFE.freeMemory(buf);
137 if (shouldReserve) {
138 NIO_ACCESS.unreserveMemory(alignedSize, byteSize);
139 }
140 }
141 });
142 if (alignedSize != byteSize) {
143 long delta = alignedBuf - buf;
144 segment = segment.asSlice(delta, byteSize);
145 }
146 return segment;
147 }
148
149 private static long allocateMemoryWrapper(long size) {
150 try {
151 return UNSAFE.allocateMemory(size);
152 } catch (IllegalArgumentException ex) {
153 throw new OutOfMemoryError();
154 }
155 }
156
157 // Unsafe native segment factories. These are used by the implementation code, to skip the sanity checks
158 // associated with MemorySegment::ofAddress.
159
160 @ForceInline
161 public static MemorySegment makeNativeSegmentUnchecked(long min, long byteSize, MemorySessionImpl sessionImpl, Runnable action) {
162 if (action == null) {
163 sessionImpl.checkValidState();
164 } else {
165 sessionImpl.addCloseAction(action);
166 }
167 return new NativeMemorySegmentImpl(min, byteSize, false, sessionImpl);
168 }
169
170 @ForceInline
171 public static MemorySegment makeNativeSegmentUnchecked(long min, long byteSize, MemorySessionImpl sessionImpl) {
172 sessionImpl.checkValidState();
173 return new NativeMemorySegmentImpl(min, byteSize, false, sessionImpl);
174 }
175
176 @ForceInline
177 public static MemorySegment makeNativeSegmentUnchecked(long min, long byteSize) {
178 return new NativeMemorySegmentImpl(min, byteSize, false, MemorySessionImpl.NATIVE_SESSION);
179 }
180 }