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src/java.base/share/classes/java/lang/module/Resolver.java

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   1 /*
   2  * Copyright (c) 2013, 2016, 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


  32 import java.util.ArrayDeque;
  33 import java.util.ArrayList;
  34 import java.util.Arrays;
  35 import java.util.Collection;
  36 import java.util.Deque;
  37 import java.util.HashMap;
  38 import java.util.HashSet;
  39 import java.util.LinkedHashSet;
  40 import java.util.List;
  41 import java.util.Map;
  42 import java.util.Objects;
  43 import java.util.Optional;
  44 import java.util.Set;
  45 import java.util.StringJoiner;
  46 import java.util.stream.Collectors;
  47 
  48 import jdk.internal.module.ModuleHashes;
  49 import jdk.internal.module.ModuleReferenceImpl;
  50 
  51 /**
  52  * The resolver used by {@link Configuration#resolveRequires} and
  53  * {@link Configuration#resolveRequiresAndUses}.
  54  *
  55  * @implNote The resolver is used at VM startup and so deliberately avoids
  56  * using lambda and stream usages in code paths used during startup.
  57  */
  58 
  59 final class Resolver {
  60 
  61     private final ModuleFinder beforeFinder;
  62     private final List<Configuration> parents;
  63     private final ModuleFinder afterFinder;
  64     private final PrintStream traceOutput;
  65 
  66     // maps module name to module reference
  67     private final Map<String, ModuleReference> nameToReference = new HashMap<>();
  68 








  69 




  70     Resolver(ModuleFinder beforeFinder,
  71              List<Configuration> parents,
  72              ModuleFinder afterFinder,
  73              PrintStream traceOutput) {
  74         this.beforeFinder = beforeFinder;
  75         this.parents = parents;
  76         this.afterFinder = afterFinder;
  77         this.traceOutput = traceOutput;


































  78     }
  79 





  80 
  81     /**
  82      * Resolves the given named modules.
  83      *
  84      * @throws ResolutionException
  85      */
  86     Resolver resolveRequires(Collection<String> roots) {
  87 
  88         // create the visit stack to get us started
  89         Deque<ModuleDescriptor> q = new ArrayDeque<>();
  90         for (String root : roots) {
  91 
  92             // find root module
  93             ModuleReference mref = findWithBeforeFinder(root);
  94             if (mref == null) {
  95 
  96                 if (findInParent(root) != null) {
  97                     // in parent, nothing to do
  98                     continue;
  99                 }
 100 
 101                 mref = findWithAfterFinder(root);
 102                 if (mref == null) {
 103                     fail("Module %s not found", root);
 104                 }
 105             }
 106 
 107             if (isTracing()) {
 108                 trace("Root module %s located", root);
 109                 mref.location().ifPresent(uri -> trace("  (%s)", uri));
 110             }
 111 
 112             assert mref.descriptor().name().equals(root);
 113             nameToReference.put(root, mref);
 114             q.push(mref.descriptor());
 115         }
 116 
 117         resolve(q);
 118 
 119         return this;
 120     }
 121 
 122     /**
 123      * Resolve all modules in the given queue. On completion the queue will be
 124      * empty and any resolved modules will be added to {@code nameToReference}.
 125      *
 126      * @return The set of module resolved by this invocation of resolve
 127      */
 128     private Set<ModuleDescriptor> resolve(Deque<ModuleDescriptor> q) {
 129         Set<ModuleDescriptor> resolved = new HashSet<>();
 130 
 131         while (!q.isEmpty()) {
 132             ModuleDescriptor descriptor = q.poll();
 133             assert nameToReference.containsKey(descriptor.name());


 135             // process dependences
 136             for (ModuleDescriptor.Requires requires : descriptor.requires()) {
 137 
 138                 // only required at compile-time
 139                 if (requires.modifiers().contains(Modifier.STATIC))
 140                     continue;
 141 
 142                 String dn = requires.name();
 143 
 144                 // find dependence
 145                 ModuleReference mref = findWithBeforeFinder(dn);
 146                 if (mref == null) {
 147 
 148                     if (findInParent(dn) != null) {
 149                         // dependence is in parent
 150                         continue;
 151                     }
 152 
 153                     mref = findWithAfterFinder(dn);
 154                     if (mref == null) {
 155                         fail("Module %s not found, required by %s",
 156                                 dn, descriptor.name());
 157                     }
 158                 }
 159 
 160                 if (!nameToReference.containsKey(dn)) {
 161                     nameToReference.put(dn, mref);
 162                     q.offer(mref.descriptor());
 163                     resolved.add(mref.descriptor());
 164 
 165                     if (isTracing()) {
 166                         trace("Module %s located, required by %s",
 167                                 dn, descriptor.name());
 168                         mref.location().ifPresent(uri -> trace("  (%s)", uri));
 169                     }
 170                 }
 171 
 172             }
 173 
 174             resolved.add(descriptor);
 175         }
 176 
 177         return resolved;
 178     }
 179 
 180     /**
 181      * Augments the set of resolved modules with modules induced by the
 182      * service-use relation.
 183      */
 184     Resolver resolveUses() {
 185 
 186         // Scan the finders for all available service provider modules. As
 187         // java.base uses services then then module finders will be scanned
 188         // anyway.
 189         Map<String, Set<ModuleReference>> availableProviders = new HashMap<>();
 190         for (ModuleReference mref : findAll()) {
 191             ModuleDescriptor descriptor = mref.descriptor();
 192             if (!descriptor.provides().isEmpty()) {
 193 
 194                 for (Provides provides :  descriptor.provides()) {
 195                     String sn = provides.service();
 196 
 197                     // computeIfAbsent
 198                     Set<ModuleReference> providers = availableProviders.get(sn);
 199                     if (providers == null) {
 200                         providers = new HashSet<>();
 201                         availableProviders.put(sn, providers);
 202                     }
 203                     providers.add(mref);
 204                 }


 229         Set<ModuleDescriptor> candidateConsumers = initialConsumers;
 230         do {
 231             for (ModuleDescriptor descriptor : candidateConsumers) {
 232                 if (!descriptor.uses().isEmpty()) {
 233                     for (String service : descriptor.uses()) {
 234                         Set<ModuleReference> mrefs = availableProviders.get(service);
 235                         if (mrefs != null) {
 236                             for (ModuleReference mref : mrefs) {
 237                                 ModuleDescriptor provider = mref.descriptor();
 238                                 if (!provider.equals(descriptor)) {
 239 
 240                                     trace("Module %s provides %s, used by %s",
 241                                             provider.name(), service, descriptor.name());
 242 
 243                                     String pn = provider.name();
 244                                     if (!nameToReference.containsKey(pn)) {
 245                                         if (isTracing()) {
 246                                             mref.location()
 247                                                 .ifPresent(uri -> trace("  (%s)", uri));
 248                                         }
 249                                         nameToReference.put(pn, mref);
 250                                         q.push(provider);
 251                                     }
 252                                 }
 253                             }
 254                         }
 255                     }
 256                 }
 257             }
 258 
 259             candidateConsumers = resolve(q);
 260         } while (!candidateConsumers.isEmpty());
 261 
 262         return this;
 263     }
 264 
 265 
 266     /**











































































 267      * Execute post-resolution checks and returns the module graph of resolved
 268      * modules as {@code Map}. The resolved modules will be in the given
 269      * configuration.
 270      *
 271      * @param check {@true} to execute the post resolution checks
 272      */
 273     Map<ResolvedModule, Set<ResolvedModule>> finish(Configuration cf,
 274                                                     boolean check)
 275     {
 276         if (isTracing()) {
 277             trace("Result:");
 278             Set<String> names = nameToReference.keySet();
 279             names.stream().sorted().forEach(name -> trace("  %s", name));
 280         }
 281 
 282         if (check) {
 283             detectCycles();
 284             checkPlatformConstraints();
 285             checkHashes();
 286         }
 287 
 288         Map<ResolvedModule, Set<ResolvedModule>> graph = makeGraph(cf);
 289 
 290         if (check) {
 291             checkExportSuppliers(graph);
 292         }
 293 
 294         return graph;
 295     }
 296 
 297     /**
 298      * Checks the given module graph for cycles.
 299      *
 300      * For now the implementation is a simple depth first search on the
 301      * dependency graph. We'll replace this later, maybe with Tarjan.
 302      */
 303     private void detectCycles() {
 304         visited = new HashSet<>();
 305         visitPath = new LinkedHashSet<>(); // preserve insertion order
 306         for (ModuleReference mref : nameToReference.values()) {
 307             visit(mref.descriptor());
 308         }
 309         visited.clear();
 310     }
 311 
 312     // the modules that were visited
 313     private Set<ModuleDescriptor> visited;
 314 
 315     // the modules in the current visit path
 316     private Set<ModuleDescriptor> visitPath;
 317 
 318     private void visit(ModuleDescriptor descriptor) {
 319         if (!visited.contains(descriptor)) {
 320             boolean added = visitPath.add(descriptor);
 321             if (!added) {
 322                 throw new ResolutionException("Cycle detected: " +
 323                         cycleAsString(descriptor));
 324             }
 325             for (ModuleDescriptor.Requires requires : descriptor.requires()) {
 326                 String dn = requires.name();
 327 
 328                 ModuleReference mref = nameToReference.get(dn);
 329                 if (mref != null) {
 330                     ModuleDescriptor other = mref.descriptor();
 331                     if (other != descriptor) {
 332                         // dependency is in this configuration
 333                         visit(other);
 334                     }
 335                 }
 336             }
 337             visitPath.remove(descriptor);
 338             visited.add(descriptor);
 339         }
 340     }
 341 
 342     /**
 343      * Returns a String with a list of the modules in a detected cycle.
 344      */
 345     private String cycleAsString(ModuleDescriptor descriptor) {
 346         List<ModuleDescriptor> list = new ArrayList<>(visitPath);
 347         list.add(descriptor);
 348         int index = list.indexOf(descriptor);
 349         return list.stream()
 350                 .skip(index)
 351                 .map(ModuleDescriptor::name)
 352                 .collect(Collectors.joining(" -> "));
 353     }
 354 
 355 
 356     /**
 357      * If there are platform specific modules then check that the OS name,
 358      * architecture and version match.
 359      *
 360      * @apiNote This method does not currently check if the OS matches
 361      *          platform specific modules in parent configurations.
 362      */
 363     private void checkPlatformConstraints() {
 364 
 365         // first module encountered that is platform specific
 366         String savedModuleName = null;
 367         String savedOsName = null;
 368         String savedOsArch = null;
 369         String savedOsVersion = null;
 370 
 371         for (ModuleReference mref : nameToReference.values()) {
 372             ModuleDescriptor descriptor = mref.descriptor();
 373 
 374             String osName = descriptor.osName().orElse(null);
 375             String osArch = descriptor.osArch().orElse(null);
 376             String osVersion = descriptor.osVersion().orElse(null);
 377 
 378             if (osName != null || osArch != null || osVersion != null) {
 379 
 380                 if (savedModuleName == null) {
 381 
 382                     savedModuleName = descriptor.name();
 383                     savedOsName = osName;
 384                     savedOsArch = osArch;
 385                     savedOsVersion = osVersion;
 386 
 387                 } else {
 388 
 389                     boolean matches = platformMatches(osName, savedOsName)
 390                             && platformMatches(osArch, savedOsArch)
 391                             && platformMatches(osVersion, savedOsVersion);
 392 
 393                     if (!matches) {
 394                         String s1 = platformAsString(savedOsName,
 395                                                      savedOsArch,
 396                                                      savedOsVersion);
 397 
 398                         String s2 = platformAsString(osName, osArch, osVersion);
 399                         fail("Mismatching constraints on target platform: "
 400                                 + savedModuleName + ": " + s1
 401                                 + ", " + descriptor.name() + ": " + s2);
 402                     }
 403 
 404                 }
 405 
 406             }
 407         }
 408 
 409     }
 410 
 411     /**
 412      * Returns true if the s1 and s2 are equal or one of them is null.
 413      */
 414     private boolean platformMatches(String s1, String s2) {
 415         if (s1 == null || s2 == null)
 416             return true;
 417         else
 418             return Objects.equals(s1, s2);
 419     }
 420 
 421     /**
 422      * Return a string that encodes the OS name/arch/version.
 423      */
 424     private String platformAsString(String osName,
 425                                     String osArch,
 426                                     String osVersion) {
 427 
 428         return new StringJoiner("-")
 429                 .add(Objects.toString(osName, "*"))
 430                 .add(Objects.toString(osArch, "*"))
 431                 .add(Objects.toString(osVersion, "*"))
 432                 .toString();
 433 
 434     }
 435 
 436     /**
 437      * Checks the hashes in the module descriptor to ensure that they match
 438      * any recorded hashes.
 439      */
 440     private void checkHashes() {
 441         for (ModuleReference mref : nameToReference.values()) {
 442 
 443             // get the recorded hashes, if any
 444             if (!(mref instanceof ModuleReferenceImpl))
 445                 continue;
 446             ModuleHashes hashes = ((ModuleReferenceImpl)mref).recordedHashes();
 447             if (hashes == null)
 448                 continue;
 449 
 450             ModuleDescriptor descriptor = mref.descriptor();
 451             String algorithm = hashes.algorithm();
 452             for (String dn : hashes.names()) {
 453                 ModuleReference mref2 = nameToReference.get(dn);
 454                 if (mref2 == null) {
 455                     ResolvedModule resolvedModule = findInParent(dn);
 456                     if (resolvedModule != null)
 457                         mref2 = resolvedModule.reference();
 458                 }
 459                 if (mref2 == null)
 460                     continue;
 461 
 462                 if (!(mref2 instanceof ModuleReferenceImpl)) {
 463                     fail("Unable to compute the hash of module %s", dn);
 464                 }
 465 
 466                 // skip checking the hash if the module has been patched
 467                 ModuleReferenceImpl other = (ModuleReferenceImpl)mref2;
 468                 if (other != null && !other.isPatched()) {
 469                     byte[] recordedHash = hashes.hashFor(dn);
 470                     byte[] actualHash = other.computeHash(algorithm);
 471                     if (actualHash == null)
 472                         fail("Unable to compute the hash of module %s", dn);
 473                     if (!Arrays.equals(recordedHash, actualHash)) {
 474                         fail("Hash of %s (%s) differs to expected hash (%s)" +
 475                              " recorded in %s", dn, toHexString(actualHash),
 476                              toHexString(recordedHash), descriptor.name());
 477                     }
 478                 }
 479             }
 480 
 481         }
 482     }
 483 
 484     private static String toHexString(byte[] ba) {
 485         StringBuilder sb = new StringBuilder(ba.length * 2);
 486         for (byte b: ba) {
 487             sb.append(String.format("%02x", b & 0xff));
 488         }
 489         return sb.toString();
 490     }
 491 
 492 
 493     /**
 494      * Computes the readability graph for the modules in the given Configuration.


 677      */
 678     private void checkExportSuppliers(Map<ResolvedModule, Set<ResolvedModule>> graph) {
 679 
 680         for (Map.Entry<ResolvedModule, Set<ResolvedModule>> e : graph.entrySet()) {
 681             ModuleDescriptor descriptor1 = e.getKey().descriptor();
 682 
 683             // the map of packages that are local or exported to descriptor1
 684             Map<String, ModuleDescriptor> packageToExporter = new HashMap<>();
 685 
 686             // local packages
 687             Set<String> packages = descriptor1.packages();
 688             for (String pn : packages) {
 689                 packageToExporter.put(pn, descriptor1);
 690             }
 691 
 692             // descriptor1 reads descriptor2
 693             Set<ResolvedModule> reads = e.getValue();
 694             for (ResolvedModule endpoint : reads) {
 695                 ModuleDescriptor descriptor2 = endpoint.descriptor();
 696 
 697                 for (ModuleDescriptor.Exports export : descriptor2.exports()) {





 698 









 699                     if (export.isQualified()) {
 700                         if (!export.targets().contains(descriptor1.name()))
 701                             continue;
 702                     }
 703 
 704                     // source is exported to descriptor2
 705                     String source = export.source();
 706                     ModuleDescriptor other
 707                         = packageToExporter.putIfAbsent(source, descriptor2);
 708 
 709                     if (other != null && other != descriptor2) {
 710                         // package might be local to descriptor1
 711                         if (other == descriptor1) {
 712                             fail("Module %s contains package %s"
 713                                  + ", module %s exports package %s to %s",
 714                                     descriptor1.name(),
 715                                     source,
 716                                     descriptor2.name(),
 717                                     source,
 718                                     descriptor1.name());
 719                         } else {
 720                             fail("Modules %s and %s export package %s to module %s",
 721                                     descriptor2.name(),
 722                                     other.name(),
 723                                     source,
 724                                     descriptor1.name());
 725                         }
 726 
 727                     }

 728                 }
 729             }
 730 
 731             // uses/provides checks not applicable to automatic modules
 732             if (!descriptor1.isAutomatic()) {
 733 
 734                 // uses S
 735                 for (String service : descriptor1.uses()) {
 736                     String pn = packageName(service);
 737                     if (!packageToExporter.containsKey(pn)) {
 738                         fail("Module %s does not read a module that exports %s",
 739                              descriptor1.name(), pn);
 740                     }
 741                 }
 742 
 743                 // provides S
 744                 for (ModuleDescriptor.Provides provides : descriptor1.provides()) {
 745                     String pn = packageName(provides.service());
 746                     if (!packageToExporter.containsKey(pn)) {
 747                         fail("Module %s does not read a module that exports %s",
 748                              descriptor1.name(), pn);
 749                     }

 750 
 751                     for (String provider : provides.providers()) {
 752                         if (!packages.contains(packageName(provider))) {
 753                             fail("Provider %s not in module %s",
 754                                  provider, descriptor1.name());
 755                         }

 756                     }

 757                 }
 758 















 759             }
 760 














 761         }
 762 
 763     }
 764 

 765     /**
 766      * Find a module of the given name in the parent configurations
 767      */
 768     private ResolvedModule findInParent(String mn) {
 769         for (Configuration parent : parents) {
 770             Optional<ResolvedModule> om = parent.findModule(mn);
 771             if (om.isPresent())
 772                 return om.get();
 773         }
 774         return null;
 775     }
 776 
 777 
 778     /**
 779      * Invokes the beforeFinder to find method to find the given module.
 780      */
 781     private ModuleReference findWithBeforeFinder(String mn) {
 782         try {
 783             return beforeFinder.find(mn).orElse(null);
 784         } catch (FindException e) {
 785             // unwrap
 786             throw new ResolutionException(e.getMessage(), e.getCause());
 787         }
 788     }
 789 
 790     /**
 791      * Invokes the afterFinder to find method to find the given module.
 792      */
 793     private ModuleReference findWithAfterFinder(String mn) {
 794         try {
 795             return afterFinder.find(mn).orElse(null);
 796         } catch (FindException e) {
 797             // unwrap
 798             throw new ResolutionException(e.getMessage(), e.getCause());
 799         }
 800     }
 801 
 802     /**
 803      * Returns the set of all modules that are observable with the before
 804      * and after ModuleFinders.
 805      */
 806     private Set<ModuleReference> findAll() {
 807         try {
 808 
 809             Set<ModuleReference> beforeModules = beforeFinder.findAll();
 810             Set<ModuleReference> afterModules = afterFinder.findAll();
 811 
 812             if (afterModules.isEmpty())
 813                 return beforeModules;
 814 
 815             if (beforeModules.isEmpty()
 816                     && parents.size() == 1
 817                     && parents.get(0) == Configuration.empty())
 818                 return afterModules;
 819 
 820             Set<ModuleReference> result = new HashSet<>(beforeModules);
 821             for (ModuleReference mref : afterModules) {
 822                 String name = mref.descriptor().name();
 823                 if (!beforeFinder.find(name).isPresent()
 824                         && findInParent(name) == null) {
 825                     result.add(mref);
 826                 }
 827             }
 828 
 829             return result;
 830 
 831         } catch (FindException e) {
 832             // unwrap
 833             throw new ResolutionException(e.getMessage(), e.getCause());
 834         }
 835     }
 836 
 837     /**
 838      * Returns the package name
 839      */
 840     private static String packageName(String cn) {
 841         int index = cn.lastIndexOf(".");
 842         return (index == -1) ? "" : cn.substring(0, index);
 843     }
 844 
 845     /**








 846      * Throw ResolutionException with the given format string and arguments
 847      */
 848     private static void fail(String fmt, Object ... args) {
 849         String msg = String.format(fmt, args);
 850         throw new ResolutionException(msg);
 851     }
 852 
 853     /**
 854      * Tracing support
 855      */
 856 
 857     private boolean isTracing() {
 858         return traceOutput != null;
 859     }
 860 
 861     private void trace(String fmt, Object ... args) {
 862         if (traceOutput != null) {
 863             traceOutput.format("[Resolver] " + fmt, args);
 864             traceOutput.println();
 865         }
 866     }
 867 
 868 }
   1 /*
   2  * Copyright (c) 2013, 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.  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


  32 import java.util.ArrayDeque;
  33 import java.util.ArrayList;
  34 import java.util.Arrays;
  35 import java.util.Collection;
  36 import java.util.Deque;
  37 import java.util.HashMap;
  38 import java.util.HashSet;
  39 import java.util.LinkedHashSet;
  40 import java.util.List;
  41 import java.util.Map;
  42 import java.util.Objects;
  43 import java.util.Optional;
  44 import java.util.Set;
  45 import java.util.StringJoiner;
  46 import java.util.stream.Collectors;
  47 
  48 import jdk.internal.module.ModuleHashes;
  49 import jdk.internal.module.ModuleReferenceImpl;
  50 
  51 /**
  52  * The resolver used by {@link Configuration#resolve} and {@link
  53  * Configuration#resolveAndBind}.
  54  *
  55  * @implNote The resolver is used at VM startup and so deliberately avoids
  56  * using lambda and stream usages in code paths used during startup.
  57  */
  58 
  59 final class Resolver {
  60 
  61     private final ModuleFinder beforeFinder;
  62     private final List<Configuration> parents;
  63     private final ModuleFinder afterFinder;
  64     private final PrintStream traceOutput;
  65 
  66     // maps module name to module reference
  67     private final Map<String, ModuleReference> nameToReference = new HashMap<>();
  68 
  69     // module constraints on target platform
  70     private String osName;
  71     private String osArch;
  72     private String osVersion;
  73 
  74     String osName() { return osName; }
  75     String osArch() { return osArch; }
  76     String osVersion() { return osVersion; }
  77 
  78     /**
  79      * @throws IllegalArgumentException if there are more than one parent and
  80      *         the constraints on the target platform conflict
  81      */
  82     Resolver(ModuleFinder beforeFinder,
  83              List<Configuration> parents,
  84              ModuleFinder afterFinder,
  85              PrintStream traceOutput) {
  86         this.beforeFinder = beforeFinder;
  87         this.parents = parents;
  88         this.afterFinder = afterFinder;
  89         this.traceOutput = traceOutput;
  90 
  91         // record constraints on target platform, checking that they don't conflict
  92         for (Configuration parent : parents) {
  93             String value = parent.osName();
  94             if (value != null) {
  95                 if (osName == null) {
  96                     osName = value;
  97                 } else {
  98                     if (!value.equals(osName)) {
  99                         failParentConflict("Operating System", osName, value);
 100                     }
 101                 }
 102             }
 103             value = parent.osArch();
 104             if (value != null) {
 105                 if (osArch == null) {
 106                     osArch = value;
 107                 } else {
 108                     if (!value.equals(osArch)) {
 109                         failParentConflict("OS architecture", osArch, value);
 110                     }
 111                 }
 112             }
 113             value = parent.osVersion();
 114             if (value != null) {
 115                 if (osVersion == null) {
 116                     osVersion  = value;
 117                 } else {
 118                     if (!value.equals(osVersion)) {
 119                         failParentConflict("OS version", osVersion, value);
 120                     }
 121                 }
 122             }
 123         }
 124     }
 125 
 126     private void failParentConflict(String constraint, String s1, String s2) {
 127         String msg = "Parents have conflicting constraints on target "
 128                      + constraint + ": " + s1 + ", " + s2;
 129         throw new IllegalArgumentException(msg);
 130     }
 131 
 132     /**
 133      * Resolves the given named modules.
 134      *
 135      * @throws ResolutionException
 136      */
 137     Resolver resolve(Collection<String> roots) {
 138 
 139         // create the visit stack to get us started
 140         Deque<ModuleDescriptor> q = new ArrayDeque<>();
 141         for (String root : roots) {
 142 
 143             // find root module
 144             ModuleReference mref = findWithBeforeFinder(root);
 145             if (mref == null) {
 146 
 147                 if (findInParent(root) != null) {
 148                     // in parent, nothing to do
 149                     continue;
 150                 }
 151 
 152                 mref = findWithAfterFinder(root);
 153                 if (mref == null) {
 154                     findFail("Module %s not found", root);
 155                 }
 156             }
 157 
 158             if (isTracing()) {
 159                 trace("Root module %s located", root);
 160                 mref.location().ifPresent(uri -> trace("  (%s)", uri));
 161             }
 162 
 163             addFoundModule(mref);

 164             q.push(mref.descriptor());
 165         }
 166 
 167         resolve(q);
 168 
 169         return this;
 170     }
 171 
 172     /**
 173      * Resolve all modules in the given queue. On completion the queue will be
 174      * empty and any resolved modules will be added to {@code nameToReference}.
 175      *
 176      * @return The set of module resolved by this invocation of resolve
 177      */
 178     private Set<ModuleDescriptor> resolve(Deque<ModuleDescriptor> q) {
 179         Set<ModuleDescriptor> resolved = new HashSet<>();
 180 
 181         while (!q.isEmpty()) {
 182             ModuleDescriptor descriptor = q.poll();
 183             assert nameToReference.containsKey(descriptor.name());


 185             // process dependences
 186             for (ModuleDescriptor.Requires requires : descriptor.requires()) {
 187 
 188                 // only required at compile-time
 189                 if (requires.modifiers().contains(Modifier.STATIC))
 190                     continue;
 191 
 192                 String dn = requires.name();
 193 
 194                 // find dependence
 195                 ModuleReference mref = findWithBeforeFinder(dn);
 196                 if (mref == null) {
 197 
 198                     if (findInParent(dn) != null) {
 199                         // dependence is in parent
 200                         continue;
 201                     }
 202 
 203                     mref = findWithAfterFinder(dn);
 204                     if (mref == null) {
 205                         findFail("Module %s not found, required by %s",
 206                                  dn, descriptor.name());
 207                     }
 208                 }
 209 
 210                 if (!nameToReference.containsKey(dn)) {
 211                     addFoundModule(mref);
 212                     q.offer(mref.descriptor());
 213                     resolved.add(mref.descriptor());
 214 
 215                     if (isTracing()) {
 216                         trace("Module %s located, required by %s",
 217                               dn, descriptor.name());
 218                         mref.location().ifPresent(uri -> trace("  (%s)", uri));
 219                     }
 220                 }
 221 
 222             }
 223 
 224             resolved.add(descriptor);
 225         }
 226 
 227         return resolved;
 228     }
 229 
 230     /**
 231      * Augments the set of resolved modules with modules induced by the
 232      * service-use relation.
 233      */
 234     Resolver bind() {
 235 
 236         // Scan the finders for all available service provider modules. As
 237         // java.base uses services then then module finders will be scanned
 238         // anyway.
 239         Map<String, Set<ModuleReference>> availableProviders = new HashMap<>();
 240         for (ModuleReference mref : findAll()) {
 241             ModuleDescriptor descriptor = mref.descriptor();
 242             if (!descriptor.provides().isEmpty()) {
 243 
 244                 for (Provides provides :  descriptor.provides()) {
 245                     String sn = provides.service();
 246 
 247                     // computeIfAbsent
 248                     Set<ModuleReference> providers = availableProviders.get(sn);
 249                     if (providers == null) {
 250                         providers = new HashSet<>();
 251                         availableProviders.put(sn, providers);
 252                     }
 253                     providers.add(mref);
 254                 }


 279         Set<ModuleDescriptor> candidateConsumers = initialConsumers;
 280         do {
 281             for (ModuleDescriptor descriptor : candidateConsumers) {
 282                 if (!descriptor.uses().isEmpty()) {
 283                     for (String service : descriptor.uses()) {
 284                         Set<ModuleReference> mrefs = availableProviders.get(service);
 285                         if (mrefs != null) {
 286                             for (ModuleReference mref : mrefs) {
 287                                 ModuleDescriptor provider = mref.descriptor();
 288                                 if (!provider.equals(descriptor)) {
 289 
 290                                     trace("Module %s provides %s, used by %s",
 291                                             provider.name(), service, descriptor.name());
 292 
 293                                     String pn = provider.name();
 294                                     if (!nameToReference.containsKey(pn)) {
 295                                         if (isTracing()) {
 296                                             mref.location()
 297                                                 .ifPresent(uri -> trace("  (%s)", uri));
 298                                         }
 299                                         addFoundModule(mref);
 300                                         q.push(provider);
 301                                     }
 302                                 }
 303                             }
 304                         }
 305                     }
 306                 }
 307             }
 308 
 309             candidateConsumers = resolve(q);
 310         } while (!candidateConsumers.isEmpty());
 311 
 312         return this;
 313     }
 314 
 315 
 316     /**
 317      * Add the module to the nameToReference map. Also check any constraints on
 318      * the target platform with the constraints of other modules.
 319      */
 320     private void addFoundModule(ModuleReference mref) {
 321         ModuleDescriptor descriptor = mref.descriptor();
 322         nameToReference.put(descriptor.name(), mref);
 323 
 324         if (descriptor.osName().isPresent()
 325                 || descriptor.osArch().isPresent()
 326                 || descriptor.osVersion().isPresent())
 327             checkTargetConstraints(descriptor);
 328     }
 329 
 330     /**
 331      * Check that the module's constraints on the target platform do not
 332      * conflict with the constraints of other modules resolved so far or
 333      * modules in parent configurations.
 334      */
 335     private void checkTargetConstraints(ModuleDescriptor descriptor) {
 336         String value = descriptor.osName().orElse(null);
 337         if (value != null) {
 338             if (osName == null) {
 339                 osName = value;
 340             } else {
 341                 if (!value.equals(osName)) {
 342                     failTargetConstraint(descriptor);
 343                 }
 344             }
 345         }
 346         value = descriptor.osArch().orElse(null);
 347         if (value != null) {
 348             if (osArch == null) {
 349                 osArch = value;
 350             } else {
 351                 if (!value.equals(osArch)) {
 352                     failTargetConstraint(descriptor);
 353                 }
 354             }
 355         }
 356         value = descriptor.osVersion().orElse(null);
 357         if (value != null) {
 358             if (osVersion == null) {
 359                 osVersion = value;
 360             } else {
 361                 if (!value.equals(osVersion)) {
 362                     failTargetConstraint(descriptor);
 363                 }
 364             }
 365         }
 366     }
 367 
 368     private void failTargetConstraint(ModuleDescriptor md) {
 369         String s1 = targetAsString(osName, osArch, osVersion);
 370         String s2 = targetAsString(md);
 371         findFail("Module %s has constraints on target platform that conflict" +
 372                  " with other modules: %s, %s", md.name(), s1, s2);
 373     }
 374 
 375     private String targetAsString(ModuleDescriptor descriptor) {
 376         String osName = descriptor.osName().orElse(null);
 377         String osArch = descriptor.osArch().orElse(null);
 378         String osVersion = descriptor.osVersion().orElse(null);
 379         return targetAsString(osName, osArch, osVersion);
 380     }
 381 
 382     private String targetAsString(String osName, String osArch, String osVersion) {
 383         return new StringJoiner("-")
 384                 .add(Objects.toString(osName, "*"))
 385                 .add(Objects.toString(osArch, "*"))
 386                 .add(Objects.toString(osVersion, "*"))
 387                 .toString();
 388     }
 389 
 390 
 391     /**
 392      * Execute post-resolution checks and returns the module graph of resolved
 393      * modules as {@code Map}. The resolved modules will be in the given
 394      * configuration.
 395      *
 396      * @param check {@true} to execute the post resolution checks
 397      */
 398     Map<ResolvedModule, Set<ResolvedModule>> finish(Configuration cf,
 399                                                     boolean check)
 400     {
 401         if (isTracing()) {
 402             trace("Result:");
 403             Set<String> names = nameToReference.keySet();
 404             names.stream().sorted().forEach(name -> trace("  %s", name));
 405         }
 406 
 407         if (check) {
 408             detectCycles();

 409             checkHashes();
 410         }
 411 
 412         Map<ResolvedModule, Set<ResolvedModule>> graph = makeGraph(cf);
 413 
 414         if (check) {
 415             checkExportSuppliers(graph);
 416         }
 417 
 418         return graph;
 419     }
 420 
 421     /**
 422      * Checks the given module graph for cycles.
 423      *
 424      * For now the implementation is a simple depth first search on the
 425      * dependency graph. We'll replace this later, maybe with Tarjan.
 426      */
 427     private void detectCycles() {
 428         visited = new HashSet<>();
 429         visitPath = new LinkedHashSet<>(); // preserve insertion order
 430         for (ModuleReference mref : nameToReference.values()) {
 431             visit(mref.descriptor());
 432         }
 433         visited.clear();
 434     }
 435 
 436     // the modules that were visited
 437     private Set<ModuleDescriptor> visited;
 438 
 439     // the modules in the current visit path
 440     private Set<ModuleDescriptor> visitPath;
 441 
 442     private void visit(ModuleDescriptor descriptor) {
 443         if (!visited.contains(descriptor)) {
 444             boolean added = visitPath.add(descriptor);
 445             if (!added) {
 446                 resolveFail("Cycle detected: %s", cycleAsString(descriptor));

 447             }
 448             for (ModuleDescriptor.Requires requires : descriptor.requires()) {
 449                 String dn = requires.name();
 450 
 451                 ModuleReference mref = nameToReference.get(dn);
 452                 if (mref != null) {
 453                     ModuleDescriptor other = mref.descriptor();
 454                     if (other != descriptor) {
 455                         // dependency is in this configuration
 456                         visit(other);
 457                     }
 458                 }
 459             }
 460             visitPath.remove(descriptor);
 461             visited.add(descriptor);
 462         }
 463     }
 464 
 465     /**
 466      * Returns a String with a list of the modules in a detected cycle.
 467      */
 468     private String cycleAsString(ModuleDescriptor descriptor) {
 469         List<ModuleDescriptor> list = new ArrayList<>(visitPath);
 470         list.add(descriptor);
 471         int index = list.indexOf(descriptor);
 472         return list.stream()
 473                 .skip(index)
 474                 .map(ModuleDescriptor::name)
 475                 .collect(Collectors.joining(" -> "));
 476     }
 477 
 478 
 479     /**
















































































 480      * Checks the hashes in the module descriptor to ensure that they match
 481      * any recorded hashes.
 482      */
 483     private void checkHashes() {
 484         for (ModuleReference mref : nameToReference.values()) {
 485 
 486             // get the recorded hashes, if any
 487             if (!(mref instanceof ModuleReferenceImpl))
 488                 continue;
 489             ModuleHashes hashes = ((ModuleReferenceImpl)mref).recordedHashes();
 490             if (hashes == null)
 491                 continue;
 492 
 493             ModuleDescriptor descriptor = mref.descriptor();
 494             String algorithm = hashes.algorithm();
 495             for (String dn : hashes.names()) {
 496                 ModuleReference mref2 = nameToReference.get(dn);
 497                 if (mref2 == null) {
 498                     ResolvedModule resolvedModule = findInParent(dn);
 499                     if (resolvedModule != null)
 500                         mref2 = resolvedModule.reference();
 501                 }
 502                 if (mref2 == null)
 503                     continue;
 504 
 505                 if (!(mref2 instanceof ModuleReferenceImpl)) {
 506                     findFail("Unable to compute the hash of module %s", dn);
 507                 }
 508 
 509                 // skip checking the hash if the module has been patched
 510                 ModuleReferenceImpl other = (ModuleReferenceImpl)mref2;
 511                 if (other != null && !other.isPatched()) {
 512                     byte[] recordedHash = hashes.hashFor(dn);
 513                     byte[] actualHash = other.computeHash(algorithm);
 514                     if (actualHash == null)
 515                         findFail("Unable to compute the hash of module %s", dn);
 516                     if (!Arrays.equals(recordedHash, actualHash)) {
 517                         findFail("Hash of %s (%s) differs to expected hash (%s)" +
 518                                  " recorded in %s", dn, toHexString(actualHash),
 519                                  toHexString(recordedHash), descriptor.name());
 520                     }
 521                 }
 522             }
 523 
 524         }
 525     }
 526 
 527     private static String toHexString(byte[] ba) {
 528         StringBuilder sb = new StringBuilder(ba.length * 2);
 529         for (byte b: ba) {
 530             sb.append(String.format("%02x", b & 0xff));
 531         }
 532         return sb.toString();
 533     }
 534 
 535 
 536     /**
 537      * Computes the readability graph for the modules in the given Configuration.


 720      */
 721     private void checkExportSuppliers(Map<ResolvedModule, Set<ResolvedModule>> graph) {
 722 
 723         for (Map.Entry<ResolvedModule, Set<ResolvedModule>> e : graph.entrySet()) {
 724             ModuleDescriptor descriptor1 = e.getKey().descriptor();
 725 
 726             // the map of packages that are local or exported to descriptor1
 727             Map<String, ModuleDescriptor> packageToExporter = new HashMap<>();
 728 
 729             // local packages
 730             Set<String> packages = descriptor1.packages();
 731             for (String pn : packages) {
 732                 packageToExporter.put(pn, descriptor1);
 733             }
 734 
 735             // descriptor1 reads descriptor2
 736             Set<ResolvedModule> reads = e.getValue();
 737             for (ResolvedModule endpoint : reads) {
 738                 ModuleDescriptor descriptor2 = endpoint.descriptor();
 739 
 740                 if (descriptor2.isAutomatic()) {
 741                     // automatic modules read self and export all packages
 742                     if (descriptor2 != descriptor1){
 743                         for (String source : descriptor2.packages()) {
 744                             ModuleDescriptor supplier
 745                                 = packageToExporter.putIfAbsent(source, descriptor2);
 746 
 747                             // descriptor2 and 'supplier' export source to descriptor1
 748                             if (supplier != null) {
 749                                 failTwoSuppliers(descriptor1, source, descriptor2, supplier);
 750                             }
 751                         }
 752 
 753                     }
 754                 } else {
 755                     for (ModuleDescriptor.Exports export : descriptor2.exports()) {
 756                         if (export.isQualified()) {
 757                             if (!export.targets().contains(descriptor1.name()))
 758                                 continue;
 759                         }
 760 
 761                         // source is exported by descriptor2
 762                         String source = export.source();
 763                         ModuleDescriptor supplier
 764                             = packageToExporter.putIfAbsent(source, descriptor2);
 765 
 766                         // descriptor2 and 'supplier' export source to descriptor1
 767                         if (supplier != null) {
 768                             failTwoSuppliers(descriptor1, source, descriptor2, supplier);













 769                         }

 770                     }
 771 
 772                 }
 773             }
 774 
 775             // uses/provides checks not applicable to automatic modules
 776             if (!descriptor1.isAutomatic()) {
 777 
 778                 // uses S
 779                 for (String service : descriptor1.uses()) {
 780                     String pn = packageName(service);
 781                     if (!packageToExporter.containsKey(pn)) {
 782                         resolveFail("Module %s does not read a module that exports %s",
 783                                     descriptor1.name(), pn);
 784                     }
 785                 }
 786 
 787                 // provides S
 788                 for (ModuleDescriptor.Provides provides : descriptor1.provides()) {
 789                     String pn = packageName(provides.service());
 790                     if (!packageToExporter.containsKey(pn)) {
 791                         resolveFail("Module %s does not read a module that exports %s",
 792                                     descriptor1.name(), pn);
 793                     }
 794                 }
 795 




 796             }
 797 
 798         }
 799 
 800     }
 801 
 802     /**
 803      * Fail because a module in the configuration exports the same package to
 804      * a module that reads both. This includes the case where a module M
 805      * containing a package p reads another module that exports p to at least
 806      * module M.
 807      */
 808     private void failTwoSuppliers(ModuleDescriptor descriptor,
 809                                   String source,
 810                                   ModuleDescriptor supplier1,
 811                                   ModuleDescriptor supplier2) {
 812 
 813         if (supplier2 == descriptor) {
 814             ModuleDescriptor tmp = supplier1;
 815             supplier1 = supplier2;
 816             supplier2 = tmp;
 817         }
 818 
 819         if (supplier1 == descriptor) {
 820             resolveFail("Module %s contains package %s"
 821                          + ", module %s exports package %s to %s",
 822                     descriptor.name(),
 823                     source,
 824                     supplier2.name(),
 825                     source,
 826                     descriptor.name());
 827         } else {
 828             resolveFail("Modules %s and %s export package %s to module %s",
 829                     supplier1.name(),
 830                     supplier2.name(),
 831                     source,
 832                     descriptor.name());
 833         }
 834 
 835     }
 836 
 837 
 838     /**
 839      * Find a module of the given name in the parent configurations
 840      */
 841     private ResolvedModule findInParent(String mn) {
 842         for (Configuration parent : parents) {
 843             Optional<ResolvedModule> om = parent.findModule(mn);
 844             if (om.isPresent())
 845                 return om.get();
 846         }
 847         return null;
 848     }
 849 
 850 
 851     /**
 852      * Invokes the beforeFinder to find method to find the given module.
 853      */
 854     private ModuleReference findWithBeforeFinder(String mn) {
 855 
 856         return beforeFinder.find(mn).orElse(null);
 857 



 858     }
 859 
 860     /**
 861      * Invokes the afterFinder to find method to find the given module.
 862      */
 863     private ModuleReference findWithAfterFinder(String mn) {

 864         return afterFinder.find(mn).orElse(null);




 865     }
 866 
 867     /**
 868      * Returns the set of all modules that are observable with the before
 869      * and after ModuleFinders.
 870      */
 871     private Set<ModuleReference> findAll() {


 872         Set<ModuleReference> beforeModules = beforeFinder.findAll();
 873         Set<ModuleReference> afterModules = afterFinder.findAll();
 874 
 875         if (afterModules.isEmpty())
 876             return beforeModules;
 877 
 878         if (beforeModules.isEmpty()
 879                 && parents.size() == 1
 880                 && parents.get(0) == Configuration.empty())
 881             return afterModules;
 882 
 883         Set<ModuleReference> result = new HashSet<>(beforeModules);
 884         for (ModuleReference mref : afterModules) {
 885             String name = mref.descriptor().name();
 886             if (!beforeFinder.find(name).isPresent()
 887                     && findInParent(name) == null) {
 888                 result.add(mref);
 889             }
 890         }
 891 
 892         return result;





 893     }
 894 
 895     /**
 896      * Returns the package name
 897      */
 898     private static String packageName(String cn) {
 899         int index = cn.lastIndexOf(".");
 900         return (index == -1) ? "" : cn.substring(0, index);
 901     }
 902 
 903     /**
 904      * Throw FindException with the given format string and arguments
 905      */
 906     private static void findFail(String fmt, Object ... args) {
 907         String msg = String.format(fmt, args);
 908         throw new FindException(msg);
 909     }
 910 
 911     /**
 912      * Throw ResolutionException with the given format string and arguments
 913      */
 914     private static void resolveFail(String fmt, Object ... args) {
 915         String msg = String.format(fmt, args);
 916         throw new ResolutionException(msg);
 917     }
 918 
 919     /**
 920      * Tracing support
 921      */
 922 
 923     private boolean isTracing() {
 924         return traceOutput != null;
 925     }
 926 
 927     private void trace(String fmt, Object ... args) {
 928         if (traceOutput != null) {
 929             traceOutput.format("[Resolver] " + fmt, args);
 930             traceOutput.println();
 931         }
 932     }
 933 
 934 }
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