1 /*
2 * Copyright (c) 2019, 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 package jdk.internal.foreign;
27
28 import jdk.internal.vm.annotation.ForceInline;
29
30 import java.lang.foreign.AddressLayout;
31 import java.lang.foreign.GroupLayout;
32 import java.lang.foreign.MemoryLayout;
33 import java.lang.foreign.MemorySegment;
34 import java.lang.foreign.SequenceLayout;
35 import java.lang.foreign.StructLayout;
36 import java.lang.foreign.ValueLayout;
37 import java.lang.invoke.MethodHandle;
38 import java.lang.invoke.MethodHandles;
39 import java.lang.invoke.MethodType;
40 import java.lang.invoke.VarHandle;
41 import java.util.Arrays;
42 import java.util.Objects;
43 import java.util.function.UnaryOperator;
44
45 /**
46 * This class provide support for constructing layout paths; that is, starting from a root path (see {@link #rootPath(MemoryLayout)},
47 * a path can be constructed by selecting layout elements using the selector methods provided by this class
48 * (see {@link #sequenceElement()}, {@link #sequenceElement(long)}, {@link #sequenceElement(long, long)}, {@link #groupElement(String)}).
49 * Once a path has been fully constructed, clients can ask for the offset associated with the layout element selected
50 * by the path (see {@link #offset}), or obtain var handle to access the selected layout element
51 * given an address pointing to a segment associated with the root layout (see {@link #dereferenceHandle()}).
52 */
53 public class LayoutPath {
54
55 private static final long[] EMPTY_STRIDES = new long[0];
56 private static final long[] EMPTY_BOUNDS = new long[0];
57 private static final MethodHandle[] EMPTY_DEREF_HANDLES = new MethodHandle[0];
58
59 private static final MethodHandle MH_ADD_SCALED_OFFSET;
60 private static final MethodHandle MH_SLICE;
61 private static final MethodHandle MH_SLICE_LAYOUT;
62 private static final MethodHandle MH_CHECK_ALIGN;
63 private static final MethodHandle MH_SEGMENT_RESIZE;
64
65 static {
66 try {
67 MethodHandles.Lookup lookup = MethodHandles.lookup();
68 MH_ADD_SCALED_OFFSET = lookup.findStatic(LayoutPath.class, "addScaledOffset",
69 MethodType.methodType(long.class, long.class, long.class, long.class, long.class));
70 MH_SLICE = lookup.findVirtual(MemorySegment.class, "asSlice",
71 MethodType.methodType(MemorySegment.class, long.class, long.class));
72 MH_SLICE_LAYOUT = lookup.findVirtual(MemorySegment.class, "asSlice",
73 MethodType.methodType(MemorySegment.class, long.class, MemoryLayout.class));
74 MH_CHECK_ALIGN = lookup.findStatic(LayoutPath.class, "checkAlign",
75 MethodType.methodType(MemorySegment.class, MemorySegment.class, MemoryLayout.class));
76 MH_SEGMENT_RESIZE = lookup.findStatic(LayoutPath.class, "resizeSegment",
77 MethodType.methodType(MemorySegment.class, MemorySegment.class, MemoryLayout.class));
78 } catch (Throwable ex) {
79 throw new ExceptionInInitializerError(ex);
80 }
81 }
82
83 private final MemoryLayout layout;
84 private final long offset;
85 private final LayoutPath enclosing;
86 private final long[] strides;
87
88 private final long[] bounds;
89 private final MethodHandle[] derefAdapters;
90
91 private LayoutPath(MemoryLayout layout, long offset, long[] strides, long[] bounds, MethodHandle[] derefAdapters, LayoutPath enclosing) {
92 this.layout = layout;
93 this.offset = offset;
94 this.strides = strides;
95 this.bounds = bounds;
96 this.derefAdapters = derefAdapters;
97 this.enclosing = enclosing;
98 }
99
100 // Layout path selector methods
101
102 public LayoutPath sequenceElement() {
103 check(SequenceLayout.class, "attempting to select a sequence element from a non-sequence layout");
104 SequenceLayout seq = (SequenceLayout)layout;
105 MemoryLayout elem = seq.elementLayout();
106 return LayoutPath.nestedPath(elem, offset, addStride(elem.byteSize()), addBound(seq.elementCount()), derefAdapters, this);
107 }
108
109 public LayoutPath sequenceElement(long start, long step) {
110 check(SequenceLayout.class, "attempting to select a sequence element from a non-sequence layout");
111 SequenceLayout seq = (SequenceLayout)layout;
112 checkSequenceBounds(seq, start);
113 MemoryLayout elem = seq.elementLayout();
114 long elemSize = elem.byteSize();
115 long nelems = step > 0 ?
116 seq.elementCount() - start :
117 start + 1;
118 long maxIndex = Math.ceilDiv(nelems, Math.abs(step));
119 return LayoutPath.nestedPath(elem, offset + (start * elemSize),
120 addStride(elemSize * step), addBound(maxIndex), derefAdapters, this);
121 }
122
123 public LayoutPath sequenceElement(long index) {
124 check(SequenceLayout.class, "attempting to select a sequence element from a non-sequence layout");
125 SequenceLayout seq = (SequenceLayout)layout;
126 checkSequenceBounds(seq, index);
127 long elemSize = seq.elementLayout().byteSize();
128 long elemOffset = elemSize * index;
129 return LayoutPath.nestedPath(seq.elementLayout(), offset + elemOffset, strides, bounds, derefAdapters,this);
130 }
131
132 public LayoutPath groupElement(String name) {
133 check(GroupLayout.class, "attempting to select a group element from a non-group layout");
134 GroupLayout g = (GroupLayout)layout;
135 long offset = 0;
136 MemoryLayout elem = null;
137 for (int i = 0; i < g.memberLayouts().size(); i++) {
138 MemoryLayout l = g.memberLayouts().get(i);
139 if (l.name().isPresent() &&
140 l.name().get().equals(name)) {
141 elem = l;
142 break;
143 } else if (g instanceof StructLayout) {
144 offset += l.byteSize();
145 }
146 }
147 if (elem == null) {
148 throw badLayoutPath("cannot resolve '" + name + "' in layout " + layout);
149 }
150 return LayoutPath.nestedPath(elem, this.offset + offset, strides, bounds, derefAdapters, this);
151 }
152
153 public LayoutPath groupElement(long index) {
154 check(GroupLayout.class, "attempting to select a group element from a non-group layout");
155 GroupLayout g = (GroupLayout)layout;
156 long elemSize = g.memberLayouts().size();
157 long offset = 0;
158 MemoryLayout elem = null;
159 for (int i = 0; i <= index; i++) {
160 if (i == elemSize) {
161 throw badLayoutPath("cannot resolve element " + index + " in layout " + layout);
162 }
163 elem = g.memberLayouts().get(i);
164 if (g instanceof StructLayout && i < index) {
165 offset += elem.byteSize();
166 }
167 }
168 return LayoutPath.nestedPath(elem, this.offset + offset, strides, bounds, derefAdapters, this);
169 }
170
171 public LayoutPath derefElement() {
172 if (!(layout instanceof AddressLayout addressLayout) ||
173 addressLayout.targetLayout().isEmpty()) {
174 throw badLayoutPath("Cannot dereference layout: " + layout);
175 }
176 MemoryLayout derefLayout = addressLayout.targetLayout().get();
177 MethodHandle handle = dereferenceHandle(false).toMethodHandle(VarHandle.AccessMode.GET);
178 handle = MethodHandles.filterReturnValue(handle,
179 MethodHandles.insertArguments(MH_SEGMENT_RESIZE, 1, derefLayout));
180 return derefPath(derefLayout, handle, this);
181 }
182
183 private static MemorySegment resizeSegment(MemorySegment segment, MemoryLayout layout) {
184 return Utils.longToAddress(segment.address(), layout.byteSize(), layout.byteAlignment());
185 }
186
187 // Layout path projections
188
189 public long offset() {
190 return offset;
191 }
192
193 public VarHandle dereferenceHandle() {
194 return dereferenceHandle(true);
195 }
196
197 public VarHandle dereferenceHandle(boolean adapt) {
198 if (!(layout instanceof ValueLayout valueLayout)) {
199 throw new IllegalArgumentException("Path does not select a value layout");
200 }
201
202 // If we have an enclosing layout, drop the alignment check for the accessed element,
203 // we check the root layout instead
204 ValueLayout accessedLayout = enclosing != null ? valueLayout.withByteAlignment(1) : valueLayout;
205 VarHandle handle = Utils.makeSegmentViewVarHandle(accessedLayout);
206 handle = MethodHandles.collectCoordinates(handle, 1, offsetHandle());
207
208 // we only have to check the alignment of the root layout for the first dereference we do,
209 // as each dereference checks the alignment of the target address when constructing its segment
210 // (see Utils::longToAddress)
211 if (derefAdapters.length == 0 && enclosing != null) {
212 MethodHandle checkHandle = MethodHandles.insertArguments(MH_CHECK_ALIGN, 1, rootLayout());
213 handle = MethodHandles.filterCoordinates(handle, 0, checkHandle);
214 }
215
216 if (adapt) {
217 for (int i = derefAdapters.length; i > 0; i--) {
218 handle = MethodHandles.collectCoordinates(handle, 0, derefAdapters[i - 1]);
219 }
220 }
221 return handle;
222 }
223
224 @ForceInline
225 private static long addScaledOffset(long base, long index, long stride, long bound) {
226 Objects.checkIndex(index, bound);
227 return base + (stride * index);
228 }
229
230 public MethodHandle offsetHandle() {
231 MethodHandle mh = MethodHandles.identity(long.class);
232 for (int i = strides.length - 1; i >=0; i--) {
233 MethodHandle collector = MethodHandles.insertArguments(MH_ADD_SCALED_OFFSET, 2, strides[i], bounds[i]);
234 // (J, ...) -> J to (J, J, ...) -> J
235 // i.e. new coord is prefixed. Last coord will correspond to innermost layout
236 mh = MethodHandles.collectArguments(mh, 0, collector);
237 }
238 mh = MethodHandles.insertArguments(mh, 0, offset);
239 return mh;
240 }
241
242 private MemoryLayout rootLayout() {
243 return enclosing != null ? enclosing.rootLayout() : this.layout;
244 }
245
246 public MethodHandle sliceHandle() {
247 MethodHandle sliceHandle;
248 if (enclosing != null) {
249 // drop the alignment check for the accessed element, we check the root layout instead
250 sliceHandle = MH_SLICE; // (MS, long, long) -> MS
251 sliceHandle = MethodHandles.insertArguments(sliceHandle, 2, layout.byteSize()); // (MS, long) -> MS
252 } else {
253 sliceHandle = MH_SLICE_LAYOUT; // (MS, long, MemoryLayout) -> MS
254 sliceHandle = MethodHandles.insertArguments(sliceHandle, 2, layout); // (MS, long) -> MS
255 }
256 sliceHandle = MethodHandles.collectArguments(sliceHandle, 1, offsetHandle()); // (MS, ...) -> MS
257
258 if (enclosing != null) {
259 MethodHandle checkHandle = MethodHandles.insertArguments(MH_CHECK_ALIGN, 1, rootLayout());
260 sliceHandle = MethodHandles.filterArguments(sliceHandle, 0, checkHandle);
261 }
262
263 return sliceHandle;
264 }
265
266 private static MemorySegment checkAlign(MemorySegment segment, MemoryLayout constraint) {
267 if (!((AbstractMemorySegmentImpl) segment).isAlignedForElement(0, constraint)) {
268 throw new IllegalArgumentException("Target offset incompatible with alignment constraints: " + constraint.byteAlignment());
269 }
270 return segment;
271 }
272
273 public MemoryLayout layout() {
274 return layout;
275 }
276
277 // Layout path construction
278
279 public static LayoutPath rootPath(MemoryLayout layout) {
280 return new LayoutPath(layout, 0L, EMPTY_STRIDES, EMPTY_BOUNDS, EMPTY_DEREF_HANDLES, null);
281 }
282
283 private static LayoutPath nestedPath(MemoryLayout layout, long offset, long[] strides, long[] bounds, MethodHandle[] derefAdapters, LayoutPath encl) {
284 return new LayoutPath(layout, offset, strides, bounds, derefAdapters, encl);
285 }
286
287 private static LayoutPath derefPath(MemoryLayout layout, MethodHandle handle, LayoutPath encl) {
288 MethodHandle[] handles = Arrays.copyOf(encl.derefAdapters, encl.derefAdapters.length + 1);
289 handles[encl.derefAdapters.length] = handle;
290 return new LayoutPath(layout, 0L, EMPTY_STRIDES, EMPTY_BOUNDS, handles, null);
291 }
292
293 // Helper methods
294
295 private void check(Class<?> layoutClass, String msg) {
296 if (!layoutClass.isAssignableFrom(layout.getClass())) {
297 throw badLayoutPath(msg);
298 }
299 }
300
301 private void checkSequenceBounds(SequenceLayout seq, long index) {
302 if (index >= seq.elementCount()) {
303 throw badLayoutPath(String.format("Sequence index out of bound; found: %d, size: %d", index, seq.elementCount()));
304 }
305 }
306
307 private static IllegalArgumentException badLayoutPath(String cause) {
308 return new IllegalArgumentException("Bad layout path: " + cause);
309 }
310
311 private long[] addStride(long stride) {
312 long[] newStrides = Arrays.copyOf(strides, strides.length + 1);
313 newStrides[strides.length] = stride;
314 return newStrides;
315 }
316
317 private long[] addBound(long maxIndex) {
318 long[] newBounds = Arrays.copyOf(bounds, bounds.length + 1);
319 newBounds[bounds.length] = maxIndex;
320 return newBounds;
321 }
322
323 /**
324 * This class provides an immutable implementation for the {@code PathElement} interface. A path element implementation
325 * is simply a pointer to one of the selector methods provided by the {@code LayoutPath} class.
326 */
327 public static final class PathElementImpl implements MemoryLayout.PathElement, UnaryOperator<LayoutPath> {
328
329 public enum PathKind {
330 SEQUENCE_ELEMENT("unbound sequence element"),
331 SEQUENCE_ELEMENT_INDEX("bound sequence element"),
332 SEQUENCE_RANGE("sequence range"),
333 GROUP_ELEMENT("group element"),
334 DEREF_ELEMENT("dereference element");
335
336 final String description;
337
338 PathKind(String description) {
339 this.description = description;
340 }
341
342 public String description() {
343 return description;
344 }
345 }
346
347 final PathKind kind;
348 final UnaryOperator<LayoutPath> pathOp;
349
350 public PathElementImpl(PathKind kind, UnaryOperator<LayoutPath> pathOp) {
351 this.kind = kind;
352 this.pathOp = pathOp;
353 }
354
355 @Override
356 public LayoutPath apply(LayoutPath layoutPath) {
357 return pathOp.apply(layoutPath);
358 }
359
360 public PathKind kind() {
361 return kind;
362 }
363 }
364 }