jimfs/src/main/java/com/google/common/jimfs/AttributeService.java - platform/external/jimfs - Git at Google

 /*
  * Copyright 2013 Google Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package com.google.common.jimfs;

 import static com.google.common.base.Preconditions.checkNotNull;

 import com.google.common.base.Splitter;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import java.nio.file.FileStore;
 import java.nio.file.FileSystem;
 import java.nio.file.Files;
 import java.nio.file.LinkOption;
 import java.nio.file.Path;
 import java.nio.file.attribute.BasicFileAttributes;
 import java.nio.file.attribute.FileAttribute;
 import java.nio.file.attribute.FileAttributeView;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import org.checkerframework.checker.nullness.compatqual.NullableDecl;

 /**
  * Service providing all attribute related operations for a file store. One piece of the file store
  * implementation.
  *
  * @author Colin Decker
  */
 final class AttributeService {

   private static final String ALL_ATTRIBUTES = "*";

   private final ImmutableMap<String, AttributeProvider> providersByName;
   private final ImmutableMap<Class<?>, AttributeProvider> providersByViewType;
   private final ImmutableMap<Class<?>, AttributeProvider> providersByAttributesType;

   private final ImmutableList<FileAttribute<?>> defaultValues;

   /** Creates a new attribute service using the given configuration. */
   public AttributeService(Configuration configuration) {
     this(getProviders(configuration), configuration.defaultAttributeValues);
   }

   /**
    * Creates a new attribute service using the given providers and user provided default attribute
    * values.
    */
   public AttributeService(
       Iterable<? extends AttributeProvider> providers, Map<String, ?> userProvidedDefaults) {
     ImmutableMap.Builder<String, AttributeProvider> byViewNameBuilder = ImmutableMap.builder();
     ImmutableMap.Builder<Class<?>, AttributeProvider> byViewTypeBuilder = ImmutableMap.builder();
     ImmutableMap.Builder<Class<?>, AttributeProvider> byAttributesTypeBuilder =
         ImmutableMap.builder();

     ImmutableList.Builder<FileAttribute<?>> defaultAttributesBuilder = ImmutableList.builder();

     for (AttributeProvider provider : providers) {
       byViewNameBuilder.put(provider.name(), provider);
       byViewTypeBuilder.put(provider.viewType(), provider);
       if (provider.attributesType() != null) {
         byAttributesTypeBuilder.put(provider.attributesType(), provider);
       }

       for (Map.Entry<String, ?> entry : provider.defaultValues(userProvidedDefaults).entrySet()) {
         defaultAttributesBuilder.add(new SimpleFileAttribute<>(entry.getKey(), entry.getValue()));
       }
     }

     this.providersByName = byViewNameBuilder.build();
     this.providersByViewType = byViewTypeBuilder.build();
     this.providersByAttributesType = byAttributesTypeBuilder.build();
     this.defaultValues = defaultAttributesBuilder.build();
   }

   private static Iterable<AttributeProvider> getProviders(Configuration configuration) {
     Map<String, AttributeProvider> result = new HashMap<>();

     for (AttributeProvider provider : configuration.attributeProviders) {
       result.put(provider.name(), provider);
     }

     for (String view : configuration.attributeViews) {
       addStandardProvider(result, view);
     }

     addMissingProviders(result);

     return Collections.unmodifiableCollection(result.values());
   }

   private static void addMissingProviders(Map<String, AttributeProvider> providers) {
     Set<String> missingViews = new HashSet<>();
     for (AttributeProvider provider : providers.values()) {
       for (String inheritedView : provider.inherits()) {
         if (!providers.containsKey(inheritedView)) {
           missingViews.add(inheritedView);
         }
       }
     }

     if (missingViews.isEmpty()) {
       return;
     }

     // add any inherited views that were not listed directly
     for (String view : missingViews) {
       addStandardProvider(providers, view);
     }

     // in case any of the providers that were added themselves have missing views they inherit
     addMissingProviders(providers);
   }

   private static void addStandardProvider(Map<String, AttributeProvider> result, String view) {
     AttributeProvider provider = StandardAttributeProviders.get(view);

     if (provider == null) {
       if (!result.containsKey(view)) {
         throw new IllegalStateException("no provider found for attribute view '" + view + "'");
       }
     } else {
       result.put(provider.name(), provider);
     }
   }

   /** Implements {@link FileSystem#supportedFileAttributeViews()}. */
   public ImmutableSet<String> supportedFileAttributeViews() {
     return providersByName.keySet();
   }

   /** Implements {@link FileStore#supportsFileAttributeView(Class)}. */
   public boolean supportsFileAttributeView(Class<? extends FileAttributeView> type) {
     return providersByViewType.containsKey(type);
   }

   /** Sets all initial attributes for the given file, including the given attributes if possible. */
   public void setInitialAttributes(File file, FileAttribute<?>... attrs) {
     // default values should already be sanitized by their providers
     for (int i = 0; i < defaultValues.size(); i++) {
       FileAttribute<?> attribute = defaultValues.get(i);

       int separatorIndex = attribute.name().indexOf(':');
       String view = attribute.name().substring(0, separatorIndex);
       String attr = attribute.name().substring(separatorIndex + 1);
       file.setAttribute(view, attr, attribute.value());
     }

     for (FileAttribute<?> attr : attrs) {
       setAttribute(file, attr.name(), attr.value(), true);
     }
   }

   /** Copies the attributes of the given file to the given copy file. */
   public void copyAttributes(File file, File copy, AttributeCopyOption copyOption) {
     switch (copyOption) {
       case ALL:
         file.copyAttributes(copy);
         break;
       case BASIC:
         file.copyBasicAttributes(copy);
         break;
       default:
         // don't copy
     }
   }

   /**
    * Gets the value of the given attribute for the given file. {@code attribute} must be of the form
    * "view:attribute" or "attribute".
    */
   public Object getAttribute(File file, String attribute) {
     String view = getViewName(attribute);
     String attr = getSingleAttribute(attribute);
     return getAttribute(file, view, attr);
   }

   /**
    * Gets the value of the given attribute for the given view and file. Neither view nor attribute
    * may have a ':' character.
    */
   public Object getAttribute(File file, String view, String attribute) {
     Object value = getAttributeInternal(file, view, attribute);
     if (value == null) {
       throw new IllegalArgumentException("invalid attribute for view '" + view + "': " + attribute);
     }
     return value;
   }

   @NullableDecl
   private Object getAttributeInternal(File file, String view, String attribute) {
     AttributeProvider provider = providersByName.get(view);
     if (provider == null) {
       return null;
     }

     Object value = provider.get(file, attribute);
     if (value == null) {
       for (String inheritedView : provider.inherits()) {
         value = getAttributeInternal(file, inheritedView, attribute);
         if (value != null) {
           break;
         }
       }
     }

     return value;
   }

   /** Sets the value of the given attribute to the given value for the given file. */
   public void setAttribute(File file, String attribute, Object value, boolean create) {
     String view = getViewName(attribute);
     String attr = getSingleAttribute(attribute);
     setAttributeInternal(file, view, attr, value, create);
   }

   private void setAttributeInternal(
       File file, String view, String attribute, Object value, boolean create) {
     AttributeProvider provider = providersByName.get(view);

     if (provider != null) {
       if (provider.supports(attribute)) {
         provider.set(file, view, attribute, value, create);
         return;
       }

       for (String inheritedView : provider.inherits()) {
         AttributeProvider inheritedProvider = providersByName.get(inheritedView);
         if (inheritedProvider.supports(attribute)) {
           inheritedProvider.set(file, view, attribute, value, create);
           return;
         }
       }
     }

     throw new UnsupportedOperationException(
         "cannot set attribute '" + view + ":" + attribute + "'");
   }

   /**
    * Returns an attribute view of the given type for the given file lookup callback, or {@code null}
    * if the view type is not supported.
    */
   @SuppressWarnings("unchecked")
   @NullableDecl
   public <V extends FileAttributeView> V getFileAttributeView(FileLookup lookup, Class<V> type) {
     AttributeProvider provider = providersByViewType.get(type);

     if (provider != null) {
       return (V) provider.view(lookup, createInheritedViews(lookup, provider));
     }

     return null;
   }

   private FileAttributeView getFileAttributeView(
       FileLookup lookup,
       Class<? extends FileAttributeView> viewType,
       Map<String, FileAttributeView> inheritedViews) {
     AttributeProvider provider = providersByViewType.get(viewType);
     createInheritedViews(lookup, provider, inheritedViews);
     return provider.view(lookup, ImmutableMap.copyOf(inheritedViews));
   }

   private ImmutableMap<String, FileAttributeView> createInheritedViews(
       FileLookup lookup, AttributeProvider provider) {
     if (provider.inherits().isEmpty()) {
       return ImmutableMap.of();
     }

     Map<String, FileAttributeView> inheritedViews = new HashMap<>();
     createInheritedViews(lookup, provider, inheritedViews);
     return ImmutableMap.copyOf(inheritedViews);
   }

   private void createInheritedViews(
       FileLookup lookup,
       AttributeProvider provider,
       Map<String, FileAttributeView> inheritedViews) {

     for (String inherited : provider.inherits()) {
       if (!inheritedViews.containsKey(inherited)) {
         AttributeProvider inheritedProvider = providersByName.get(inherited);
         FileAttributeView inheritedView =
             getFileAttributeView(lookup, inheritedProvider.viewType(), inheritedViews);

         inheritedViews.put(inherited, inheritedView);
       }
     }
   }

   /** Implements {@link Files#readAttributes(Path, String, LinkOption...)}. */
   public ImmutableMap<String, Object> readAttributes(File file, String attributes) {
     String view = getViewName(attributes);
     List<String> attrs = getAttributeNames(attributes);

     if (attrs.size() > 1 && attrs.contains(ALL_ATTRIBUTES)) {
       // attrs contains * and other attributes
       throw new IllegalArgumentException("invalid attributes: " + attributes);
     }

     Map<String, Object> result = new HashMap<>();
     if (attrs.size() == 1 && attrs.contains(ALL_ATTRIBUTES)) {
       // for 'view:*' format, get all keys for all providers for the view
       AttributeProvider provider = providersByName.get(view);
       readAll(file, provider, result);

       for (String inheritedView : provider.inherits()) {
         AttributeProvider inheritedProvider = providersByName.get(inheritedView);
         readAll(file, inheritedProvider, result);
       }
     } else {
       // for 'view:attr1,attr2,etc'
       for (String attr : attrs) {
         result.put(attr, getAttribute(file, view, attr));
       }
     }

     return ImmutableMap.copyOf(result);
   }

   /**
    * Returns attributes of the given file as an object of the given type.
    *
    * @throws UnsupportedOperationException if the given attributes type is not supported
    */
   @SuppressWarnings("unchecked")
   public <A extends BasicFileAttributes> A readAttributes(File file, Class<A> type) {
     AttributeProvider provider = providersByAttributesType.get(type);
     if (provider != null) {
       return (A) provider.readAttributes(file);
     }

     throw new UnsupportedOperationException("unsupported attributes type: " + type);
   }

   private static void readAll(File file, AttributeProvider provider, Map<String, Object> map) {
     for (String attribute : provider.attributes(file)) {
       Object value = provider.get(file, attribute);

       // check for null to protect against race condition when an attribute present when
       // attributes(file) was called is deleted before get() is called for that attribute
       if (value != null) {
         map.put(attribute, value);
       }
     }
   }

   private static String getViewName(String attribute) {
     int separatorIndex = attribute.indexOf(':');

     if (separatorIndex == -1) {
       return "basic";
     }

     // separator must not be at the start or end of the string or appear more than once
     if (separatorIndex == 0
         || separatorIndex == attribute.length() - 1
         || attribute.indexOf(':', separatorIndex + 1) != -1) {
       throw new IllegalArgumentException("illegal attribute format: " + attribute);
     }

     return attribute.substring(0, separatorIndex);
   }

   private static final Splitter ATTRIBUTE_SPLITTER = Splitter.on(',');

   private static ImmutableList<String> getAttributeNames(String attributes) {
     int separatorIndex = attributes.indexOf(':');
     String attributesPart = attributes.substring(separatorIndex + 1);

     return ImmutableList.copyOf(ATTRIBUTE_SPLITTER.split(attributesPart));
   }

   private static String getSingleAttribute(String attribute) {
     ImmutableList<String> attributeNames = getAttributeNames(attribute);

     if (attributeNames.size() != 1 || ALL_ATTRIBUTES.equals(attributeNames.get(0))) {
       throw new IllegalArgumentException("must specify a single attribute: " + attribute);
     }

     return attributeNames.get(0);
   }

   /** Simple implementation of {@link FileAttribute}. */
   private static final class SimpleFileAttribute<T> implements FileAttribute<T> {

     private final String name;
     private final T value;

     SimpleFileAttribute(String name, T value) {
       this.name = checkNotNull(name);
       this.value = checkNotNull(value);
     }

     @Override
     public String name() {
       return name;
     }

     @Override
     public T value() {
       return value;
     }
   }
 }
	/*
	* Copyright 2013 Google Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package com.google.common.jimfs;

	import static com.google.common.base.Preconditions.checkNotNull;

	import com.google.common.base.Splitter;
	import com.google.common.collect.ImmutableList;
	import com.google.common.collect.ImmutableMap;
	import com.google.common.collect.ImmutableSet;
	import java.nio.file.FileStore;
	import java.nio.file.FileSystem;
	import java.nio.file.Files;
	import java.nio.file.LinkOption;
	import java.nio.file.Path;
	import java.nio.file.attribute.BasicFileAttributes;
	import java.nio.file.attribute.FileAttribute;
	import java.nio.file.attribute.FileAttributeView;
	import java.util.Collections;
	import java.util.HashMap;
	import java.util.HashSet;
	import java.util.List;
	import java.util.Map;
	import java.util.Set;
	import org.checkerframework.checker.nullness.compatqual.NullableDecl;

	/**
	* Service providing all attribute related operations for a file store. One piece of the file store
	* implementation.
	*
	* @author Colin Decker
	*/
	final class AttributeService {

	private static final String ALL_ATTRIBUTES = "*";

	private final ImmutableMap<String, AttributeProvider> providersByName;
	private final ImmutableMap<Class<?>, AttributeProvider> providersByViewType;
	private final ImmutableMap<Class<?>, AttributeProvider> providersByAttributesType;

	private final ImmutableList<FileAttribute<?>> defaultValues;

	/** Creates a new attribute service using the given configuration. */
	public AttributeService(Configuration configuration) {
	this(getProviders(configuration), configuration.defaultAttributeValues);
	}

	/**
	* Creates a new attribute service using the given providers and user provided default attribute
	* values.
	*/
	public AttributeService(
	Iterable<? extends AttributeProvider> providers, Map<String, ?> userProvidedDefaults) {
	ImmutableMap.Builder<String, AttributeProvider> byViewNameBuilder = ImmutableMap.builder();
	ImmutableMap.Builder<Class<?>, AttributeProvider> byViewTypeBuilder = ImmutableMap.builder();
	ImmutableMap.Builder<Class<?>, AttributeProvider> byAttributesTypeBuilder =
	ImmutableMap.builder();

	ImmutableList.Builder<FileAttribute<?>> defaultAttributesBuilder = ImmutableList.builder();

	for (AttributeProvider provider : providers) {
	byViewNameBuilder.put(provider.name(), provider);
	byViewTypeBuilder.put(provider.viewType(), provider);
	if (provider.attributesType() != null) {
	byAttributesTypeBuilder.put(provider.attributesType(), provider);
	}

	for (Map.Entry<String, ?> entry : provider.defaultValues(userProvidedDefaults).entrySet()) {
	defaultAttributesBuilder.add(new SimpleFileAttribute<>(entry.getKey(), entry.getValue()));
	}
	}

	this.providersByName = byViewNameBuilder.build();
	this.providersByViewType = byViewTypeBuilder.build();
	this.providersByAttributesType = byAttributesTypeBuilder.build();
	this.defaultValues = defaultAttributesBuilder.build();
	}

	private static Iterable<AttributeProvider> getProviders(Configuration configuration) {
	Map<String, AttributeProvider> result = new HashMap<>();

	for (AttributeProvider provider : configuration.attributeProviders) {
	result.put(provider.name(), provider);
	}

	for (String view : configuration.attributeViews) {
	addStandardProvider(result, view);
	}

	addMissingProviders(result);

	return Collections.unmodifiableCollection(result.values());
	}

	private static void addMissingProviders(Map<String, AttributeProvider> providers) {
	Set<String> missingViews = new HashSet<>();
	for (AttributeProvider provider : providers.values()) {
	for (String inheritedView : provider.inherits()) {
	if (!providers.containsKey(inheritedView)) {
	missingViews.add(inheritedView);
	}
	}
	}

	if (missingViews.isEmpty()) {
	return;
	}

	// add any inherited views that were not listed directly
	for (String view : missingViews) {
	addStandardProvider(providers, view);
	}

	// in case any of the providers that were added themselves have missing views they inherit
	addMissingProviders(providers);
	}

	private static void addStandardProvider(Map<String, AttributeProvider> result, String view) {
	AttributeProvider provider = StandardAttributeProviders.get(view);

	if (provider == null) {
	if (!result.containsKey(view)) {
	throw new IllegalStateException("no provider found for attribute view '" + view + "'");
	}
	} else {
	result.put(provider.name(), provider);
	}
	}

	/** Implements {@link FileSystem#supportedFileAttributeViews()}. */
	public ImmutableSet<String> supportedFileAttributeViews() {
	return providersByName.keySet();
	}

	/** Implements {@link FileStore#supportsFileAttributeView(Class)}. */
	public boolean supportsFileAttributeView(Class<? extends FileAttributeView> type) {
	return providersByViewType.containsKey(type);
	}

	/** Sets all initial attributes for the given file, including the given attributes if possible. */
	public void setInitialAttributes(File file, FileAttribute<?>... attrs) {
	// default values should already be sanitized by their providers
	for (int i = 0; i < defaultValues.size(); i++) {
	FileAttribute<?> attribute = defaultValues.get(i);

	int separatorIndex = attribute.name().indexOf(':');
	String view = attribute.name().substring(0, separatorIndex);
	String attr = attribute.name().substring(separatorIndex + 1);
	file.setAttribute(view, attr, attribute.value());
	}

	for (FileAttribute<?> attr : attrs) {
	setAttribute(file, attr.name(), attr.value(), true);
	}
	}

	/** Copies the attributes of the given file to the given copy file. */
	public void copyAttributes(File file, File copy, AttributeCopyOption copyOption) {
	switch (copyOption) {
	case ALL:
	file.copyAttributes(copy);
	break;
	case BASIC:
	file.copyBasicAttributes(copy);
	break;
	default:
	// don't copy
	}
	}

	/**
	* Gets the value of the given attribute for the given file. {@code attribute} must be of the form
	* "view:attribute" or "attribute".
	*/
	public Object getAttribute(File file, String attribute) {
	String view = getViewName(attribute);
	String attr = getSingleAttribute(attribute);
	return getAttribute(file, view, attr);
	}

	/**
	* Gets the value of the given attribute for the given view and file. Neither view nor attribute
	* may have a ':' character.
	*/
	public Object getAttribute(File file, String view, String attribute) {
	Object value = getAttributeInternal(file, view, attribute);
	if (value == null) {
	throw new IllegalArgumentException("invalid attribute for view '" + view + "': " + attribute);
	}
	return value;
	}

	@NullableDecl
	private Object getAttributeInternal(File file, String view, String attribute) {
	AttributeProvider provider = providersByName.get(view);
	if (provider == null) {
	return null;
	}

	Object value = provider.get(file, attribute);
	if (value == null) {
	for (String inheritedView : provider.inherits()) {
	value = getAttributeInternal(file, inheritedView, attribute);
	if (value != null) {
	break;
	}
	}
	}

	return value;
	}

	/** Sets the value of the given attribute to the given value for the given file. */
	public void setAttribute(File file, String attribute, Object value, boolean create) {
	String view = getViewName(attribute);
	String attr = getSingleAttribute(attribute);
	setAttributeInternal(file, view, attr, value, create);
	}

	private void setAttributeInternal(
	File file, String view, String attribute, Object value, boolean create) {
	AttributeProvider provider = providersByName.get(view);

	if (provider != null) {
	if (provider.supports(attribute)) {
	provider.set(file, view, attribute, value, create);
	return;
	}

	for (String inheritedView : provider.inherits()) {
	AttributeProvider inheritedProvider = providersByName.get(inheritedView);
	if (inheritedProvider.supports(attribute)) {
	inheritedProvider.set(file, view, attribute, value, create);
	return;
	}
	}
	}

	throw new UnsupportedOperationException(
	"cannot set attribute '" + view + ":" + attribute + "'");
	}

	/**
	* Returns an attribute view of the given type for the given file lookup callback, or {@code null}
	* if the view type is not supported.
	*/
	@SuppressWarnings("unchecked")
	@NullableDecl
	public <V extends FileAttributeView> V getFileAttributeView(FileLookup lookup, Class<V> type) {
	AttributeProvider provider = providersByViewType.get(type);

	if (provider != null) {
	return (V) provider.view(lookup, createInheritedViews(lookup, provider));
	}

	return null;
	}

	private FileAttributeView getFileAttributeView(
	FileLookup lookup,
	Class<? extends FileAttributeView> viewType,
	Map<String, FileAttributeView> inheritedViews) {
	AttributeProvider provider = providersByViewType.get(viewType);
	createInheritedViews(lookup, provider, inheritedViews);
	return provider.view(lookup, ImmutableMap.copyOf(inheritedViews));
	}

	private ImmutableMap<String, FileAttributeView> createInheritedViews(
	FileLookup lookup, AttributeProvider provider) {
	if (provider.inherits().isEmpty()) {
	return ImmutableMap.of();
	}

	Map<String, FileAttributeView> inheritedViews = new HashMap<>();
	createInheritedViews(lookup, provider, inheritedViews);
	return ImmutableMap.copyOf(inheritedViews);
	}

	private void createInheritedViews(
	FileLookup lookup,
	AttributeProvider provider,
	Map<String, FileAttributeView> inheritedViews) {

	for (String inherited : provider.inherits()) {
	if (!inheritedViews.containsKey(inherited)) {
	AttributeProvider inheritedProvider = providersByName.get(inherited);
	FileAttributeView inheritedView =
	getFileAttributeView(lookup, inheritedProvider.viewType(), inheritedViews);

	inheritedViews.put(inherited, inheritedView);
	}
	}
	}

	/** Implements {@link Files#readAttributes(Path, String, LinkOption...)}. */
	public ImmutableMap<String, Object> readAttributes(File file, String attributes) {
	String view = getViewName(attributes);
	List<String> attrs = getAttributeNames(attributes);

	if (attrs.size() > 1 && attrs.contains(ALL_ATTRIBUTES)) {
	// attrs contains * and other attributes
	throw new IllegalArgumentException("invalid attributes: " + attributes);
	}

	Map<String, Object> result = new HashMap<>();
	if (attrs.size() == 1 && attrs.contains(ALL_ATTRIBUTES)) {
	// for 'view:*' format, get all keys for all providers for the view
	AttributeProvider provider = providersByName.get(view);
	readAll(file, provider, result);

	for (String inheritedView : provider.inherits()) {
	AttributeProvider inheritedProvider = providersByName.get(inheritedView);
	readAll(file, inheritedProvider, result);
	}
	} else {
	// for 'view:attr1,attr2,etc'
	for (String attr : attrs) {
	result.put(attr, getAttribute(file, view, attr));
	}
	}

	return ImmutableMap.copyOf(result);
	}

	/**
	* Returns attributes of the given file as an object of the given type.
	*
	* @throws UnsupportedOperationException if the given attributes type is not supported
	*/
	@SuppressWarnings("unchecked")
	public <A extends BasicFileAttributes> A readAttributes(File file, Class<A> type) {
	AttributeProvider provider = providersByAttributesType.get(type);
	if (provider != null) {
	return (A) provider.readAttributes(file);
	}

	throw new UnsupportedOperationException("unsupported attributes type: " + type);
	}

	private static void readAll(File file, AttributeProvider provider, Map<String, Object> map) {
	for (String attribute : provider.attributes(file)) {
	Object value = provider.get(file, attribute);

	// check for null to protect against race condition when an attribute present when
	// attributes(file) was called is deleted before get() is called for that attribute
	if (value != null) {
	map.put(attribute, value);
	}
	}
	}

	private static String getViewName(String attribute) {
	int separatorIndex = attribute.indexOf(':');

	if (separatorIndex == -1) {
	return "basic";
	}

	// separator must not be at the start or end of the string or appear more than once
	if (separatorIndex == 0
	\|\| separatorIndex == attribute.length() - 1
	\|\| attribute.indexOf(':', separatorIndex + 1) != -1) {
	throw new IllegalArgumentException("illegal attribute format: " + attribute);
	}

	return attribute.substring(0, separatorIndex);
	}

	private static final Splitter ATTRIBUTE_SPLITTER = Splitter.on(',');

	private static ImmutableList<String> getAttributeNames(String attributes) {
	int separatorIndex = attributes.indexOf(':');
	String attributesPart = attributes.substring(separatorIndex + 1);

	return ImmutableList.copyOf(ATTRIBUTE_SPLITTER.split(attributesPart));
	}

	private static String getSingleAttribute(String attribute) {
	ImmutableList<String> attributeNames = getAttributeNames(attribute);

	if (attributeNames.size() != 1 \|\| ALL_ATTRIBUTES.equals(attributeNames.get(0))) {
	throw new IllegalArgumentException("must specify a single attribute: " + attribute);
	}

	return attributeNames.get(0);
	}

	/** Simple implementation of {@link FileAttribute}. */
	private static final class SimpleFileAttribute<T> implements FileAttribute<T> {

	private final String name;
	private final T value;

	SimpleFileAttribute(String name, T value) {
	this.name = checkNotNull(name);
	this.value = checkNotNull(value);
	}

	@Override
	public String name() {
	return name;
	}

	@Override
	public T value() {
	return value;
	}
	}
	}