src/resourceshrinker/java/com/android/build/shrinker/r8integration/LegacyResourceShrinker.java - r8 - Git at Google

 // Copyright (c) 2023, the R8 project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 package com.android.build.shrinker.r8integration;

 import static java.nio.charset.StandardCharsets.UTF_16BE;
 import static java.nio.charset.StandardCharsets.UTF_16LE;
 import static java.nio.charset.StandardCharsets.UTF_8;

 import com.android.aapt.Resources.ResourceTable;
 import com.android.aapt.Resources.XmlNode;
 import com.android.build.shrinker.NoDebugReporter;
 import com.android.build.shrinker.ResourceShrinkerImplKt;
 import com.android.build.shrinker.ResourceTableUtilKt;
 import com.android.build.shrinker.graph.ProtoResourcesGraphBuilder;
 import com.android.build.shrinker.graph.ResFolderFileTree;
 import com.android.build.shrinker.obfuscation.ProguardMappingsRecorder;
 import com.android.build.shrinker.r8integration.R8ResourceShrinkerState.R8ResourceShrinkerModel;
 import com.android.build.shrinker.usages.DexFileAnalysisCallback;
 import com.android.build.shrinker.usages.ProtoAndroidManifestUsageRecorderKt;
 import com.android.build.shrinker.usages.R8ResourceShrinker;
 import com.android.build.shrinker.usages.ToolsAttributeUsageRecorderKt;
 import com.android.ide.common.resources.ResourcesUtil;
 import com.android.ide.common.resources.usage.ResourceStore;
 import com.android.ide.common.resources.usage.ResourceUsageModel.Resource;
 import com.android.resources.ResourceType;
 import com.android.tools.r8.FeatureSplit;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
 import com.google.protobuf.InvalidProtocolBufferException;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.Reader;
 import java.io.StringReader;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
 import java.util.stream.Collectors;
 import javax.xml.parsers.ParserConfigurationException;
 import org.xml.sax.SAXException;

 public class LegacyResourceShrinker {
   private final Map<String, byte[]> dexInputs;
   private final List<PathAndBytes> resFolderInputs;
   private final List<PathAndBytes> xmlInputs;
   private List<String> proguardMapStrings;
   private final List<PathAndBytes> manifest;
   private final Map<PathAndBytes, FeatureSplit> resourceTables;

   public static class Builder {

     private final Map<String, byte[]> dexInputs = new HashMap<>();
     private final List<PathAndBytes> resFolderInputs = new ArrayList<>();
     private final List<PathAndBytes> xmlInputs = new ArrayList<>();

     private final List<PathAndBytes> manifests = new ArrayList<>();
     private final Map<PathAndBytes, FeatureSplit> resourceTables = new HashMap<>();
     private List<String> proguardMapStrings;

     private Builder() {}

     public Builder addManifest(Path path, byte[] bytes) {
       manifests.add(new PathAndBytes(bytes, path));
       return this;
     }

     public Builder addResourceTable(Path path, byte[] bytes, FeatureSplit featureSplit) {
       resourceTables.put(new PathAndBytes(bytes, path), featureSplit);
       try {
         ResourceTable resourceTable = ResourceTable.parseFrom(bytes);
         System.currentTimeMillis();
       } catch (InvalidProtocolBufferException e) {
         throw new RuntimeException(e);
       }
       return this;
     }

     public Builder addDexInput(String classesLocation, byte[] bytes) {
       dexInputs.put(classesLocation, bytes);
       return this;
     }

     public Builder addResFolderInput(Path path, byte[] bytes) {
       resFolderInputs.add(new PathAndBytes(bytes, path));
       return this;
     }

     public Builder addXmlInput(Path path, byte[] bytes) {
       xmlInputs.add(new PathAndBytes(bytes, path));
       return this;
     }

     public LegacyResourceShrinker build() {
       assert manifests != null && resourceTables != null;
       return new LegacyResourceShrinker(
           dexInputs, resFolderInputs, manifests, resourceTables, xmlInputs, proguardMapStrings);
     }

     public void setProguardMapStrings(List<String> proguardMapStrings) {
       this.proguardMapStrings = proguardMapStrings;
     }
   }

   private LegacyResourceShrinker(
       Map<String, byte[]> dexInputs,
       List<PathAndBytes> resFolderInputs,
       List<PathAndBytes> manifests,
       Map<PathAndBytes, FeatureSplit> resourceTables,
       List<PathAndBytes> xmlInputs,
       List<String> proguardMapStrings) {
     this.dexInputs = dexInputs;
     this.resFolderInputs = resFolderInputs;
     this.manifest = manifests;
     this.resourceTables = resourceTables;
     this.xmlInputs = xmlInputs;
     this.proguardMapStrings = proguardMapStrings;
   }

   public static Builder builder() {
     return new Builder();
   }

   public ShrinkerResult run() throws IOException, ParserConfigurationException, SAXException {
     R8ResourceShrinkerModel model = new R8ResourceShrinkerModel(NoDebugReporter.INSTANCE, true);
     for (PathAndBytes pathAndBytes : resourceTables.keySet()) {
       ResourceTable loadedResourceTable = ResourceTable.parseFrom(pathAndBytes.bytes);
       model.instantiateFromResourceTable(loadedResourceTable, false);
     }
     return shrinkModel(model, false);
   }

   public ShrinkerResult shrinkModel(
       R8ResourceShrinkerModel model, boolean exactMatchingOfStyleablesAndAttr) throws IOException {
     if (proguardMapStrings != null) {
       new ProguardMappingsRecorder(proguardMapStrings).recordObfuscationMappings(model);
       proguardMapStrings = null;
     }
     for (Entry<String, byte[]> entry : dexInputs.entrySet()) {
       // The analysis needs an origin for the dex files, synthesize an easy recognizable one.
       Path inMemoryR8 = Paths.get("in_memory_r8_" + entry.getKey() + ".dex");
       R8ResourceShrinker.runResourceShrinkerAnalysis(
           entry.getValue(), inMemoryR8, new DexFileAnalysisCallback(inMemoryR8, model));
     }
     for (PathAndBytes pathAndBytes : manifest) {
       ProtoAndroidManifestUsageRecorderKt.recordUsagesFromNode(
           XmlNode.parseFrom(pathAndBytes.bytes), model);
     }
     for (PathAndBytes xmlInput : xmlInputs) {
       if (xmlInput.path.startsWith("res/raw")) {
         ToolsAttributeUsageRecorderKt.processRawXml(getUtfReader(xmlInput.getBytes()), model);
       }
     }

     ImmutableMap<String, PathAndBytes> resFolderMappings =
         new ImmutableMap.Builder<String, PathAndBytes>()
             .putAll(
                 xmlInputs.stream()
                     .collect(Collectors.toMap(PathAndBytes::getPathWithoutRes, a -> a)))
             .putAll(
                 resFolderInputs.stream()
                     .collect(Collectors.toMap(PathAndBytes::getPathWithoutRes, a -> a)))
             .build();
     for (PathAndBytes pathAndBytes : resourceTables.keySet()) {
       ResourceTable resourceTable = ResourceTable.parseFrom(pathAndBytes.bytes);
       new ProtoResourcesGraphBuilder(
               new ResFolderFileTree() {
                 @Override
                 public byte[] getEntryByName(String pathInRes) {
                   return resFolderMappings.get(pathInRes).getBytes();
                 }
               },
               unused -> resourceTable)
           .buildGraph(model);
     }
     ResourceStore resourceStore = model.getResourceStore();
     resourceStore.processToolsAttributes();
     model.keepPossiblyReferencedResources();
     // Transitively mark the reachable resources in the model.
     // Finds unused resources in provided resources collection.
     // Marks all used resources as 'reachable' in original collection.
     List<Resource> unusedResources =
         ResourcesUtil.findUnusedResources(model.getResourceStore().getResources(), x -> {});
     ImmutableSet.Builder<String> resEntriesToKeep = new ImmutableSet.Builder<>();
     for (PathAndBytes xmlInput : Iterables.concat(xmlInputs, resFolderInputs)) {
       if (ResourceShrinkerImplKt.isJarPathReachable(resourceStore, xmlInput.path.toString())) {
         resEntriesToKeep.add(xmlInput.path.toString());
       }
     }
     List<Integer> resourceIdsToRemove =
         getResourceIdsToRemove(unusedResources, model, exactMatchingOfStyleablesAndAttr);
     Map<FeatureSplit, ResourceTable> shrunkenTables = new HashMap<>();
     for (Entry<PathAndBytes, FeatureSplit> entry : resourceTables.entrySet()) {
       ResourceTable shrunkenResourceTable =
           ResourceTableUtilKt.nullOutEntriesWithIds(
               ResourceTable.parseFrom(entry.getKey().bytes), resourceIdsToRemove);
       shrunkenTables.put(entry.getValue(), shrunkenResourceTable);
     }
     return new ShrinkerResult(resEntriesToKeep.build(), shrunkenTables);
   }

   private static List<Integer> getResourceIdsToRemove(
       List<Resource> unusedResources,
       R8ResourceShrinkerModel model,
       boolean exactMatchingOfStyleablesAndAttr) {
     if (!exactMatchingOfStyleablesAndAttr) {
       return unusedResources.stream()
           .filter(s -> s.type != ResourceType.ID)
           .map(resource -> resource.value)
           .collect(Collectors.toList());
     }
     return model.getResourceStore().getResources().stream()
         .filter(r -> !r.isReachable())
         .filter(r -> r.type != ResourceType.ID)
         .map(r -> r.value)
         .collect(Collectors.toList());
   }

   // Lifted from com/android/utils/XmlUtils.java which we can't easily update internal dependency
   // for.
   /**
    * Returns a character reader for the given bytes, which must be a UTF encoded file.
    *
    * <p>The reader does not need to be closed by the caller (because the file is read in full in one
    * shot and the resulting array is then wrapped in a byte array input stream, which does not need
    * to be closed.)
    */
   public static Reader getUtfReader(byte[] bytes) throws IOException {
     int length = bytes.length;
     if (length == 0) {
       return new StringReader("");
     }

     switch (bytes[0]) {
       case (byte) 0xEF:
         {
           if (length >= 3 && bytes[1] == (byte) 0xBB && bytes[2] == (byte) 0xBF) {
             // UTF-8 BOM: EF BB BF: Skip it
             return new InputStreamReader(new ByteArrayInputStream(bytes, 3, length - 3), UTF_8);
           }
           break;
         }
       case (byte) 0xFE:
         {
           if (length >= 2 && bytes[1] == (byte) 0xFF) {
             // UTF-16 Big Endian BOM: FE FF
             return new InputStreamReader(new ByteArrayInputStream(bytes, 2, length - 2), UTF_16BE);
           }
           break;
         }
       case (byte) 0xFF:
         {
           if (length >= 2 && bytes[1] == (byte) 0xFE) {
             if (length >= 4 && bytes[2] == (byte) 0x00 && bytes[3] == (byte) 0x00) {
               // UTF-32 Little Endian BOM: FF FE 00 00
               return new InputStreamReader(
                   new ByteArrayInputStream(bytes, 4, length - 4), "UTF-32LE");
             }

             // UTF-16 Little Endian BOM: FF FE
             return new InputStreamReader(new ByteArrayInputStream(bytes, 2, length - 2), UTF_16LE);
           }
           break;
         }
       case (byte) 0x00:
         {
           if (length >= 4
               && bytes[0] == (byte) 0x00
               && bytes[1] == (byte) 0x00
               && bytes[2] == (byte) 0xFE
               && bytes[3] == (byte) 0xFF) {
             // UTF-32 Big Endian BOM: 00 00 FE FF
             return new InputStreamReader(
                 new ByteArrayInputStream(bytes, 4, length - 4), "UTF-32BE");
           }
           break;
         }
     }

     // No byte order mark: Assume UTF-8 (where the BOM is optional).
     return new InputStreamReader(new ByteArrayInputStream(bytes), UTF_8);
   }

   public static class ShrinkerResult {
     private final Set<String> resFolderEntriesToKeep;
     private final Map<FeatureSplit, ResourceTable> resourceTableInProtoFormat;

     public ShrinkerResult(
         Set<String> resFolderEntriesToKeep,
         Map<FeatureSplit, ResourceTable> resourceTableInProtoFormat) {
       this.resFolderEntriesToKeep = resFolderEntriesToKeep;
       this.resourceTableInProtoFormat = resourceTableInProtoFormat;
     }

     public byte[] getResourceTableInProtoFormat(FeatureSplit featureSplit) {
       return resourceTableInProtoFormat.get(featureSplit).toByteArray();
     }

     public Set<String> getResFolderEntriesToKeep() {
       return resFolderEntriesToKeep;
     }
   }

   private static class PathAndBytes {
     private final byte[] bytes;
     private final Path path;

     private PathAndBytes(byte[] bytes, Path path) {
       this.bytes = bytes;
       this.path = path;
     }

     public Path getPath() {
       return path;
     }

     public String getPathWithoutRes() {
       assert path.toString().startsWith("res/");
       return path.toString().substring(4);
     }

     public byte[] getBytes() {
       return bytes;
     }
   }
 }
	// Copyright (c) 2023, the R8 project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	package com.android.build.shrinker.r8integration;

	import static java.nio.charset.StandardCharsets.UTF_16BE;
	import static java.nio.charset.StandardCharsets.UTF_16LE;
	import static java.nio.charset.StandardCharsets.UTF_8;

	import com.android.aapt.Resources.ResourceTable;
	import com.android.aapt.Resources.XmlNode;
	import com.android.build.shrinker.NoDebugReporter;
	import com.android.build.shrinker.ResourceShrinkerImplKt;
	import com.android.build.shrinker.ResourceTableUtilKt;
	import com.android.build.shrinker.graph.ProtoResourcesGraphBuilder;
	import com.android.build.shrinker.graph.ResFolderFileTree;
	import com.android.build.shrinker.obfuscation.ProguardMappingsRecorder;
	import com.android.build.shrinker.r8integration.R8ResourceShrinkerState.R8ResourceShrinkerModel;
	import com.android.build.shrinker.usages.DexFileAnalysisCallback;
	import com.android.build.shrinker.usages.ProtoAndroidManifestUsageRecorderKt;
	import com.android.build.shrinker.usages.R8ResourceShrinker;
	import com.android.build.shrinker.usages.ToolsAttributeUsageRecorderKt;
	import com.android.ide.common.resources.ResourcesUtil;
	import com.android.ide.common.resources.usage.ResourceStore;
	import com.android.ide.common.resources.usage.ResourceUsageModel.Resource;
	import com.android.resources.ResourceType;
	import com.android.tools.r8.FeatureSplit;
	import com.google.common.collect.ImmutableMap;
	import com.google.common.collect.ImmutableSet;
	import com.google.common.collect.Iterables;
	import com.google.protobuf.InvalidProtocolBufferException;
	import java.io.ByteArrayInputStream;
	import java.io.IOException;
	import java.io.InputStreamReader;
	import java.io.Reader;
	import java.io.StringReader;
	import java.nio.file.Path;
	import java.nio.file.Paths;
	import java.util.ArrayList;
	import java.util.HashMap;
	import java.util.List;
	import java.util.Map;
	import java.util.Map.Entry;
	import java.util.Set;
	import java.util.stream.Collectors;
	import javax.xml.parsers.ParserConfigurationException;
	import org.xml.sax.SAXException;

	public class LegacyResourceShrinker {
	private final Map<String, byte[]> dexInputs;
	private final List<PathAndBytes> resFolderInputs;
	private final List<PathAndBytes> xmlInputs;
	private List<String> proguardMapStrings;
	private final List<PathAndBytes> manifest;
	private final Map<PathAndBytes, FeatureSplit> resourceTables;

	public static class Builder {

	private final Map<String, byte[]> dexInputs = new HashMap<>();
	private final List<PathAndBytes> resFolderInputs = new ArrayList<>();
	private final List<PathAndBytes> xmlInputs = new ArrayList<>();

	private final List<PathAndBytes> manifests = new ArrayList<>();
	private final Map<PathAndBytes, FeatureSplit> resourceTables = new HashMap<>();
	private List<String> proguardMapStrings;

	private Builder() {}

	public Builder addManifest(Path path, byte[] bytes) {
	manifests.add(new PathAndBytes(bytes, path));
	return this;
	}

	public Builder addResourceTable(Path path, byte[] bytes, FeatureSplit featureSplit) {
	resourceTables.put(new PathAndBytes(bytes, path), featureSplit);
	try {
	ResourceTable resourceTable = ResourceTable.parseFrom(bytes);
	System.currentTimeMillis();
	} catch (InvalidProtocolBufferException e) {
	throw new RuntimeException(e);
	}
	return this;
	}

	public Builder addDexInput(String classesLocation, byte[] bytes) {
	dexInputs.put(classesLocation, bytes);
	return this;
	}

	public Builder addResFolderInput(Path path, byte[] bytes) {
	resFolderInputs.add(new PathAndBytes(bytes, path));
	return this;
	}

	public Builder addXmlInput(Path path, byte[] bytes) {
	xmlInputs.add(new PathAndBytes(bytes, path));
	return this;
	}

	public LegacyResourceShrinker build() {
	assert manifests != null && resourceTables != null;
	return new LegacyResourceShrinker(
	dexInputs, resFolderInputs, manifests, resourceTables, xmlInputs, proguardMapStrings);
	}

	public void setProguardMapStrings(List<String> proguardMapStrings) {
	this.proguardMapStrings = proguardMapStrings;
	}
	}

	private LegacyResourceShrinker(
	Map<String, byte[]> dexInputs,
	List<PathAndBytes> resFolderInputs,
	List<PathAndBytes> manifests,
	Map<PathAndBytes, FeatureSplit> resourceTables,
	List<PathAndBytes> xmlInputs,
	List<String> proguardMapStrings) {
	this.dexInputs = dexInputs;
	this.resFolderInputs = resFolderInputs;
	this.manifest = manifests;
	this.resourceTables = resourceTables;
	this.xmlInputs = xmlInputs;
	this.proguardMapStrings = proguardMapStrings;
	}

	public static Builder builder() {
	return new Builder();
	}

	public ShrinkerResult run() throws IOException, ParserConfigurationException, SAXException {
	R8ResourceShrinkerModel model = new R8ResourceShrinkerModel(NoDebugReporter.INSTANCE, true);
	for (PathAndBytes pathAndBytes : resourceTables.keySet()) {
	ResourceTable loadedResourceTable = ResourceTable.parseFrom(pathAndBytes.bytes);
	model.instantiateFromResourceTable(loadedResourceTable, false);
	}
	return shrinkModel(model, false);
	}

	public ShrinkerResult shrinkModel(
	R8ResourceShrinkerModel model, boolean exactMatchingOfStyleablesAndAttr) throws IOException {
	if (proguardMapStrings != null) {
	new ProguardMappingsRecorder(proguardMapStrings).recordObfuscationMappings(model);
	proguardMapStrings = null;
	}
	for (Entry<String, byte[]> entry : dexInputs.entrySet()) {
	// The analysis needs an origin for the dex files, synthesize an easy recognizable one.
	Path inMemoryR8 = Paths.get("in_memory_r8_" + entry.getKey() + ".dex");
	R8ResourceShrinker.runResourceShrinkerAnalysis(
	entry.getValue(), inMemoryR8, new DexFileAnalysisCallback(inMemoryR8, model));
	}
	for (PathAndBytes pathAndBytes : manifest) {
	ProtoAndroidManifestUsageRecorderKt.recordUsagesFromNode(
	XmlNode.parseFrom(pathAndBytes.bytes), model);
	}
	for (PathAndBytes xmlInput : xmlInputs) {
	if (xmlInput.path.startsWith("res/raw")) {
	ToolsAttributeUsageRecorderKt.processRawXml(getUtfReader(xmlInput.getBytes()), model);
	}
	}

	ImmutableMap<String, PathAndBytes> resFolderMappings =
	new ImmutableMap.Builder<String, PathAndBytes>()
	.putAll(
	xmlInputs.stream()
	.collect(Collectors.toMap(PathAndBytes::getPathWithoutRes, a -> a)))
	.putAll(
	resFolderInputs.stream()
	.collect(Collectors.toMap(PathAndBytes::getPathWithoutRes, a -> a)))
	.build();
	for (PathAndBytes pathAndBytes : resourceTables.keySet()) {
	ResourceTable resourceTable = ResourceTable.parseFrom(pathAndBytes.bytes);
	new ProtoResourcesGraphBuilder(
	new ResFolderFileTree() {
	@Override
	public byte[] getEntryByName(String pathInRes) {
	return resFolderMappings.get(pathInRes).getBytes();
	}
	},
	unused -> resourceTable)
	.buildGraph(model);
	}
	ResourceStore resourceStore = model.getResourceStore();
	resourceStore.processToolsAttributes();
	model.keepPossiblyReferencedResources();
	// Transitively mark the reachable resources in the model.
	// Finds unused resources in provided resources collection.
	// Marks all used resources as 'reachable' in original collection.
	List<Resource> unusedResources =
	ResourcesUtil.findUnusedResources(model.getResourceStore().getResources(), x -> {});
	ImmutableSet.Builder<String> resEntriesToKeep = new ImmutableSet.Builder<>();
	for (PathAndBytes xmlInput : Iterables.concat(xmlInputs, resFolderInputs)) {
	if (ResourceShrinkerImplKt.isJarPathReachable(resourceStore, xmlInput.path.toString())) {
	resEntriesToKeep.add(xmlInput.path.toString());
	}
	}
	List<Integer> resourceIdsToRemove =
	getResourceIdsToRemove(unusedResources, model, exactMatchingOfStyleablesAndAttr);
	Map<FeatureSplit, ResourceTable> shrunkenTables = new HashMap<>();
	for (Entry<PathAndBytes, FeatureSplit> entry : resourceTables.entrySet()) {
	ResourceTable shrunkenResourceTable =
	ResourceTableUtilKt.nullOutEntriesWithIds(
	ResourceTable.parseFrom(entry.getKey().bytes), resourceIdsToRemove);
	shrunkenTables.put(entry.getValue(), shrunkenResourceTable);
	}
	return new ShrinkerResult(resEntriesToKeep.build(), shrunkenTables);
	}

	private static List<Integer> getResourceIdsToRemove(
	List<Resource> unusedResources,
	R8ResourceShrinkerModel model,
	boolean exactMatchingOfStyleablesAndAttr) {
	if (!exactMatchingOfStyleablesAndAttr) {
	return unusedResources.stream()
	.filter(s -> s.type != ResourceType.ID)
	.map(resource -> resource.value)
	.collect(Collectors.toList());
	}
	return model.getResourceStore().getResources().stream()
	.filter(r -> !r.isReachable())
	.filter(r -> r.type != ResourceType.ID)
	.map(r -> r.value)
	.collect(Collectors.toList());
	}

	// Lifted from com/android/utils/XmlUtils.java which we can't easily update internal dependency
	// for.
	/**
	* Returns a character reader for the given bytes, which must be a UTF encoded file.
	*
	* <p>The reader does not need to be closed by the caller (because the file is read in full in one
	* shot and the resulting array is then wrapped in a byte array input stream, which does not need
	* to be closed.)
	*/
	public static Reader getUtfReader(byte[] bytes) throws IOException {
	int length = bytes.length;
	if (length == 0) {
	return new StringReader("");
	}

	switch (bytes[0]) {
	case (byte) 0xEF:
	{
	if (length >= 3 && bytes[1] == (byte) 0xBB && bytes[2] == (byte) 0xBF) {
	// UTF-8 BOM: EF BB BF: Skip it
	return new InputStreamReader(new ByteArrayInputStream(bytes, 3, length - 3), UTF_8);
	}
	break;
	}
	case (byte) 0xFE:
	{
	if (length >= 2 && bytes[1] == (byte) 0xFF) {
	// UTF-16 Big Endian BOM: FE FF
	return new InputStreamReader(new ByteArrayInputStream(bytes, 2, length - 2), UTF_16BE);
	}
	break;
	}
	case (byte) 0xFF:
	{
	if (length >= 2 && bytes[1] == (byte) 0xFE) {
	if (length >= 4 && bytes[2] == (byte) 0x00 && bytes[3] == (byte) 0x00) {
	// UTF-32 Little Endian BOM: FF FE 00 00
	return new InputStreamReader(
	new ByteArrayInputStream(bytes, 4, length - 4), "UTF-32LE");
	}

	// UTF-16 Little Endian BOM: FF FE
	return new InputStreamReader(new ByteArrayInputStream(bytes, 2, length - 2), UTF_16LE);
	}
	break;
	}
	case (byte) 0x00:
	{
	if (length >= 4
	&& bytes[0] == (byte) 0x00
	&& bytes[1] == (byte) 0x00
	&& bytes[2] == (byte) 0xFE
	&& bytes[3] == (byte) 0xFF) {
	// UTF-32 Big Endian BOM: 00 00 FE FF
	return new InputStreamReader(
	new ByteArrayInputStream(bytes, 4, length - 4), "UTF-32BE");
	}
	break;
	}
	}

	// No byte order mark: Assume UTF-8 (where the BOM is optional).
	return new InputStreamReader(new ByteArrayInputStream(bytes), UTF_8);
	}

	public static class ShrinkerResult {
	private final Set<String> resFolderEntriesToKeep;
	private final Map<FeatureSplit, ResourceTable> resourceTableInProtoFormat;

	public ShrinkerResult(
	Set<String> resFolderEntriesToKeep,
	Map<FeatureSplit, ResourceTable> resourceTableInProtoFormat) {
	this.resFolderEntriesToKeep = resFolderEntriesToKeep;
	this.resourceTableInProtoFormat = resourceTableInProtoFormat;
	}

	public byte[] getResourceTableInProtoFormat(FeatureSplit featureSplit) {
	return resourceTableInProtoFormat.get(featureSplit).toByteArray();
	}

	public Set<String> getResFolderEntriesToKeep() {
	return resFolderEntriesToKeep;
	}
	}

	private static class PathAndBytes {
	private final byte[] bytes;
	private final Path path;

	private PathAndBytes(byte[] bytes, Path path) {
	this.bytes = bytes;
	this.path = path;
	}

	public Path getPath() {
	return path;
	}

	public String getPathWithoutRes() {
	assert path.toString().startsWith("res/");
	return path.toString().substring(4);
	}

	public byte[] getBytes() {
	return bytes;
	}
	}
	}