src/com/android/mtp/MtpDatabase.java - platform/packages/services/Mtp - Git at Google

 /*
  * Copyright (C) 2015 The Android Open Source Project
  *
  * 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.android.mtp;

 import static com.android.mtp.MtpDatabaseConstants.*;

 import android.content.ContentValues;
 import android.content.Context;
 import android.content.res.Resources;
 import android.database.Cursor;
 import android.mtp.MtpObjectInfo;
 import android.provider.DocumentsContract;
 import android.provider.DocumentsContract.Document;
 import android.provider.DocumentsContract.Root;

 import com.android.internal.annotations.VisibleForTesting;

 import java.util.HashMap;
 import java.util.Map;

 /**
  * Database for MTP objects.
  * The object handle which is identifier for object in MTP protocol is not stable over sessions.
  * When we resume the process, we need to remap our document ID with MTP's object handle.
  *
  * If the remote MTP device is backed by typical file system, the file name
  * is unique among files in a directory. However, MTP protocol itself does
  * not guarantee the uniqueness of name so we cannot use fullpath as ID.
  *
  * Instead of fullpath, we use artificial ID generated by MtpDatabase itself. The database object
  * remembers the map of document ID and object handle, and remaps new object handle with document ID
  * by comparing the directory structure and object name.
  *
  * To start putting documents into the database, the client needs to call
  * {@link #startAddingChildDocuments(String)} with the parent document ID. Also it needs to call
  * {@link #stopAddingChildDocuments(String)} after putting all child documents to the database.
  * (All explanations are same for root documents)
  *
  * database.startAddingChildDocuments();
  * database.putChildDocuments();
  * database.stopAddingChildDocuments();
  *
  * To update the existing documents, the client code can repeat to call the three methods again.
  * The newly added rows update corresponding existing rows that have same MTP identifier like
  * objectHandle.
  *
  * The client can call putChildDocuments multiple times to add documents by chunk, but it needs to
  * put all documents under the parent before calling stopAddingChildDocuments. Otherwise missing
  * documents are regarded as deleted, and will be removed from the database.
  *
  * If the client calls clearMtpIdentifier(), it clears MTP identifier in the database. In this case,
  * the database tries to find corresponding rows by using document's name instead of MTP identifier
  * at the next update cycle.
  *
  * TODO: Remove @VisibleForTesting annotation when we start to use this class.
  * TODO: Improve performance by SQL optimization.
  */
 @VisibleForTesting
 class MtpDatabase {
     private final MtpDatabaseInternal mDatabase;

     /**
      * Mapping mode for roots/documents where we start adding child documents.
      * Methods operate the state needs to be synchronized.
      */
     private final Map<String, Integer> mMappingMode = new HashMap<>();

     @VisibleForTesting
     MtpDatabase(Context context, int flags) {
         mDatabase = new MtpDatabaseInternal(context, flags);
     }

     /**
      * Closes the database.
      */
     @VisibleForTesting
     void close() {
         mDatabase.close();
     }

     /**
      * {@link MtpDatabaseInternal#queryRoots}
      */
     Cursor queryRoots(String[] columnNames) {
         return mDatabase.queryRoots(columnNames);
     }

     /**
      * {@link MtpDatabaseInternal#queryRootDocuments}
      */
     @VisibleForTesting
     Cursor queryRootDocuments(String[] columnNames) {
         return mDatabase.queryRootDocuments(columnNames);
     }

     /**
      * {@link MtpDatabaseInternal#queryChildDocuments}
      */
     @VisibleForTesting
     Cursor queryChildDocuments(String[] columnNames, String parentDocumentId) {
         return queryChildDocuments(columnNames, parentDocumentId, false);
     }

     @VisibleForTesting
     Cursor queryChildDocuments(String[] columnNames, String parentDocumentId, boolean useOldId) {
         final String[] newColumnNames = new String[columnNames.length];

         // TODO: Temporary replace document ID with old format.
         for (int i = 0; i < columnNames.length; i++) {
             if (useOldId && DocumentsContract.Document.COLUMN_DOCUMENT_ID.equals(columnNames[i])) {
                 newColumnNames[i] = COLUMN_DEVICE_ID + " || '_' || " + COLUMN_STORAGE_ID +
                         " || '_' || IFNULL(" + COLUMN_OBJECT_HANDLE + ",0) AS " +
                         DocumentsContract.Document.COLUMN_DOCUMENT_ID;
             } else {
                 newColumnNames[i] = columnNames[i];
             }
         }

         return mDatabase.queryChildDocuments(newColumnNames, parentDocumentId);
     }

     Identifier createIdentifier(String parentDocumentId) {
         return mDatabase.createIdentifier(parentDocumentId);
     }

     /**
      * {@link MtpDatabaseInternal#removeDeviceRows}
      */
     void removeDeviceRows(int deviceId) {
         mDatabase.removeDeviceRows(deviceId);
     }

     /**
      * Invokes {@link MtpDatabaseInternal#startAddingDocuments} for root documents.
      * @param deviceId Device ID.
      */
     synchronized void startAddingRootDocuments(int deviceId) {
         final String mappingStateKey = getRootDocumentsMappingStateKey(deviceId);
         if (mMappingMode.containsKey(mappingStateKey)) {
             throw new Error("Mapping for the root has already started.");
         }
         mMappingMode.put(
                 mappingStateKey,
                 mDatabase.startAddingDocuments(
                         SELECTION_ROOT_DOCUMENTS, Integer.toString(deviceId)));
     }

     /**
      * Invokes {@link MtpDatabaseInternal#startAddingDocuments} for child of specific documents.
      * @param parentDocumentId Document ID for parent document.
      */
     @VisibleForTesting
     synchronized void startAddingChildDocuments(String parentDocumentId) {
         final String mappingStateKey = getChildDocumentsMappingStateKey(parentDocumentId);
         if (mMappingMode.containsKey(mappingStateKey)) {
             throw new Error("Mapping for the root has already started.");
         }
         mMappingMode.put(
                 mappingStateKey,
                 mDatabase.startAddingDocuments(SELECTION_CHILD_DOCUMENTS, parentDocumentId));
     }

     /**
      * Puts root information to database.
      * @param deviceId Device ID
      * @param resources Resources required to localize root name.
      * @param roots List of root information.
      * @return If roots are added or removed from the database.
      */
     synchronized boolean putRootDocuments(int deviceId, Resources resources, MtpRoot[] roots) {
         mDatabase.beginTransaction();
         try {
             final boolean heuristic;
             final String mapColumn;
             switch (mMappingMode.get(getRootDocumentsMappingStateKey(deviceId))) {
                 case MAP_BY_MTP_IDENTIFIER:
                     heuristic = false;
                     mapColumn = COLUMN_STORAGE_ID;
                     break;
                 case MAP_BY_NAME:
                     heuristic = true;
                     mapColumn = Document.COLUMN_DISPLAY_NAME;
                     break;
                 default:
                     throw new Error("Unexpected map mode.");
             }
             final ContentValues[] valuesList = new ContentValues[roots.length];
             for (int i = 0; i < roots.length; i++) {
                 if (roots[i].mDeviceId != deviceId) {
                     throw new IllegalArgumentException();
                 }
                 valuesList[i] = new ContentValues();
                 getRootDocumentValues(valuesList[i], resources, roots[i]);
             }
             final boolean changed = mDatabase.putDocuments(
                     valuesList,
                     SELECTION_ROOT_DOCUMENTS,
                     Integer.toString(deviceId),
                     heuristic,
                     mapColumn);
             final ContentValues values = new ContentValues();
             int i = 0;
             for (final MtpRoot root : roots) {
                 // Use the same value for the root ID and the corresponding document ID.
                 final String documentId = valuesList[i++].getAsString(Document.COLUMN_DOCUMENT_ID);
                 // If it fails to insert/update documents, the document ID will be set with -1.
                 // In this case we don't insert/update root extra information neither.
                 if (documentId == null) {
                     continue;
                 }
                 values.put(Root.COLUMN_ROOT_ID, documentId);
                 values.put(
                         Root.COLUMN_FLAGS,
                         Root.FLAG_SUPPORTS_IS_CHILD | Root.FLAG_SUPPORTS_CREATE);
                 values.put(Root.COLUMN_AVAILABLE_BYTES, root.mFreeSpace);
                 values.put(Root.COLUMN_CAPACITY_BYTES, root.mMaxCapacity);
                 values.put(Root.COLUMN_MIME_TYPES, "");
                 mDatabase.putRootExtra(values);
             }
             mDatabase.setTransactionSuccessful();
             return changed;
         } finally {
             mDatabase.endTransaction();
         }
     }

     /**
      * Puts document information to database.
      * @param deviceId Device ID
      * @param parentId Parent document ID.
      * @param documents List of document information.
      */
     @VisibleForTesting
     synchronized void putChildDocuments(int deviceId, String parentId, MtpObjectInfo[] documents) {
         final boolean heuristic;
         final String mapColumn;
         switch (mMappingMode.get(getChildDocumentsMappingStateKey(parentId))) {
             case MAP_BY_MTP_IDENTIFIER:
                 heuristic = false;
                 mapColumn = COLUMN_OBJECT_HANDLE;
                 break;
             case MAP_BY_NAME:
                 heuristic = true;
                 mapColumn = Document.COLUMN_DISPLAY_NAME;
                 break;
             default:
                 throw new Error("Unexpected map mode.");
         }
         final ContentValues[] valuesList = new ContentValues[documents.length];
         for (int i = 0; i < documents.length; i++) {
             valuesList[i] = new ContentValues();
             getChildDocumentValues(valuesList[i], deviceId, parentId, documents[i]);
         }
         mDatabase.putDocuments(
                 valuesList, SELECTION_CHILD_DOCUMENTS, parentId, heuristic, mapColumn);
     }

     /**
      * Clears mapping between MTP identifier and document/root ID.
      */
     @VisibleForTesting
     synchronized void clearMapping() {
         mDatabase.clearMapping();
         mMappingMode.clear();
     }

     /**
      * Stops adding root documents.
      * @param deviceId Device ID.
      * @return True if new rows are added/removed.
      */
     synchronized boolean stopAddingRootDocuments(int deviceId) {
         final String mappingModeKey = getRootDocumentsMappingStateKey(deviceId);
         switch (mMappingMode.get(mappingModeKey)) {
             case MAP_BY_MTP_IDENTIFIER:
                 mMappingMode.remove(mappingModeKey);
                 return mDatabase.stopAddingDocuments(
                         SELECTION_ROOT_DOCUMENTS,
                         Integer.toString(deviceId),
                         COLUMN_STORAGE_ID);
             case MAP_BY_NAME:
                 mMappingMode.remove(mappingModeKey);
                 return mDatabase.stopAddingDocuments(
                         SELECTION_ROOT_DOCUMENTS,
                         Integer.toString(deviceId),
                         Document.COLUMN_DISPLAY_NAME);
             default:
                 throw new Error("Unexpected mapping state.");
         }
     }

     /**
      * Stops adding documents under the parent.
      * @param parentId Document ID of the parent.
      */
     @VisibleForTesting
     synchronized void stopAddingChildDocuments(String parentId) {
         final String mappingModeKey = getChildDocumentsMappingStateKey(parentId);
         switch (mMappingMode.get(mappingModeKey)) {
             case MAP_BY_MTP_IDENTIFIER:
                 mDatabase.stopAddingDocuments(
                         SELECTION_CHILD_DOCUMENTS,
                         parentId,
                         COLUMN_OBJECT_HANDLE);
                 break;
             case MAP_BY_NAME:
                 mDatabase.stopAddingDocuments(
                         SELECTION_CHILD_DOCUMENTS,
                         parentId,
                         Document.COLUMN_DISPLAY_NAME);
                 break;
             default:
                 throw new Error("Unexpected mapping state.");
         }
         mMappingMode.remove(mappingModeKey);
     }

     /**
      * Gets {@link ContentValues} for the given root.
      * @param values {@link ContentValues} that receives values.
      * @param resources Resources used to get localized root name.
      * @param root Root to be converted {@link ContentValues}.
      */
     private static void getRootDocumentValues(
             ContentValues values, Resources resources, MtpRoot root) {
         values.clear();
         values.put(COLUMN_DEVICE_ID, root.mDeviceId);
         values.put(COLUMN_STORAGE_ID, root.mStorageId);
         values.putNull(COLUMN_OBJECT_HANDLE);
         values.putNull(COLUMN_PARENT_DOCUMENT_ID);
         values.put(COLUMN_ROW_STATE, ROW_STATE_VALID);
         values.put(Document.COLUMN_MIME_TYPE, Document.MIME_TYPE_DIR);
         values.put(Document.COLUMN_DISPLAY_NAME, root.getRootName(resources));
         values.putNull(Document.COLUMN_SUMMARY);
         values.putNull(Document.COLUMN_LAST_MODIFIED);
         values.putNull(Document.COLUMN_ICON);
         values.put(Document.COLUMN_FLAGS, 0);
         values.put(Document.COLUMN_SIZE,
                 (int) Math.min(root.mMaxCapacity - root.mFreeSpace, Integer.MAX_VALUE));
     }

     /**
      * Gets {@link ContentValues} for the given MTP object.
      * @param values {@link ContentValues} that receives values.
      * @param deviceId Device ID of the object.
      * @param parentId Parent document ID of the object.
      * @param info MTP object info.
      */
     private void getChildDocumentValues(
             ContentValues values, int deviceId, String parentId, MtpObjectInfo info) {
         values.clear();
         final String mimeType = CursorHelper.formatTypeToMimeType(info.getFormat());
         int flag = 0;
         if (info.getProtectionStatus() == 0) {
             flag |= Document.FLAG_SUPPORTS_DELETE |
                     Document.FLAG_SUPPORTS_WRITE;
             if (mimeType == Document.MIME_TYPE_DIR) {
                 flag |= Document.FLAG_DIR_SUPPORTS_CREATE;
             }
         }
         if (info.getThumbCompressedSize() > 0) {
             flag |= Document.FLAG_SUPPORTS_THUMBNAIL;
         }
         values.put(COLUMN_DEVICE_ID, deviceId);
         values.put(COLUMN_STORAGE_ID, info.getStorageId());
         values.put(COLUMN_OBJECT_HANDLE, info.getObjectHandle());
         values.put(COLUMN_PARENT_DOCUMENT_ID, parentId);
         values.put(COLUMN_ROW_STATE, ROW_STATE_VALID);
         values.put(Document.COLUMN_MIME_TYPE, mimeType);
         values.put(Document.COLUMN_DISPLAY_NAME, info.getName());
         values.putNull(Document.COLUMN_SUMMARY);
         values.put(
                 Document.COLUMN_LAST_MODIFIED,
                 info.getDateModified() != 0 ? info.getDateModified() : null);
         values.putNull(Document.COLUMN_ICON);
         values.put(Document.COLUMN_FLAGS, flag);
         values.put(Document.COLUMN_SIZE, info.getCompressedSize());
     }

     /**
      * @param deviceId Device ID.
      * @return Key for {@link #mMappingMode}.
      */
     private static String getRootDocumentsMappingStateKey(int deviceId) {
         return "RootDocuments/" + deviceId;
     }

     /**
      * @param parentDocumentId Document ID for the parent document.
      * @return Key for {@link #mMappingMode}.
      */
     private static String getChildDocumentsMappingStateKey(String parentDocumentId) {
         return "ChildDocuments/" + parentDocumentId;
     }
 }
	/*
	* Copyright (C) 2015 The Android Open Source Project
	*
	* 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.android.mtp;

	import static com.android.mtp.MtpDatabaseConstants.*;

	import android.content.ContentValues;
	import android.content.Context;
	import android.content.res.Resources;
	import android.database.Cursor;
	import android.mtp.MtpObjectInfo;
	import android.provider.DocumentsContract;
	import android.provider.DocumentsContract.Document;
	import android.provider.DocumentsContract.Root;

	import com.android.internal.annotations.VisibleForTesting;

	import java.util.HashMap;
	import java.util.Map;

	/**
	* Database for MTP objects.
	* The object handle which is identifier for object in MTP protocol is not stable over sessions.
	* When we resume the process, we need to remap our document ID with MTP's object handle.
	*
	* If the remote MTP device is backed by typical file system, the file name
	* is unique among files in a directory. However, MTP protocol itself does
	* not guarantee the uniqueness of name so we cannot use fullpath as ID.
	*
	* Instead of fullpath, we use artificial ID generated by MtpDatabase itself. The database object
	* remembers the map of document ID and object handle, and remaps new object handle with document ID
	* by comparing the directory structure and object name.
	*
	* To start putting documents into the database, the client needs to call
	* {@link #startAddingChildDocuments(String)} with the parent document ID. Also it needs to call
	* {@link #stopAddingChildDocuments(String)} after putting all child documents to the database.
	* (All explanations are same for root documents)
	*
	* database.startAddingChildDocuments();
	* database.putChildDocuments();
	* database.stopAddingChildDocuments();
	*
	* To update the existing documents, the client code can repeat to call the three methods again.
	* The newly added rows update corresponding existing rows that have same MTP identifier like
	* objectHandle.
	*
	* The client can call putChildDocuments multiple times to add documents by chunk, but it needs to
	* put all documents under the parent before calling stopAddingChildDocuments. Otherwise missing
	* documents are regarded as deleted, and will be removed from the database.
	*
	* If the client calls clearMtpIdentifier(), it clears MTP identifier in the database. In this case,
	* the database tries to find corresponding rows by using document's name instead of MTP identifier
	* at the next update cycle.
	*
	* TODO: Remove @VisibleForTesting annotation when we start to use this class.
	* TODO: Improve performance by SQL optimization.
	*/
	@VisibleForTesting
	class MtpDatabase {
	private final MtpDatabaseInternal mDatabase;

	/**
	* Mapping mode for roots/documents where we start adding child documents.
	* Methods operate the state needs to be synchronized.
	*/
	private final Map<String, Integer> mMappingMode = new HashMap<>();

	@VisibleForTesting
	MtpDatabase(Context context, int flags) {
	mDatabase = new MtpDatabaseInternal(context, flags);
	}

	/**
	* Closes the database.
	*/
	@VisibleForTesting
	void close() {
	mDatabase.close();
	}

	/**
	* {@link MtpDatabaseInternal#queryRoots}
	*/
	Cursor queryRoots(String[] columnNames) {
	return mDatabase.queryRoots(columnNames);
	}

	/**
	* {@link MtpDatabaseInternal#queryRootDocuments}
	*/
	@VisibleForTesting
	Cursor queryRootDocuments(String[] columnNames) {
	return mDatabase.queryRootDocuments(columnNames);
	}

	/**
	* {@link MtpDatabaseInternal#queryChildDocuments}
	*/
	@VisibleForTesting
	Cursor queryChildDocuments(String[] columnNames, String parentDocumentId) {
	return queryChildDocuments(columnNames, parentDocumentId, false);
	}

	@VisibleForTesting
	Cursor queryChildDocuments(String[] columnNames, String parentDocumentId, boolean useOldId) {
	final String[] newColumnNames = new String[columnNames.length];

	// TODO: Temporary replace document ID with old format.
	for (int i = 0; i < columnNames.length; i++) {
	if (useOldId && DocumentsContract.Document.COLUMN_DOCUMENT_ID.equals(columnNames[i])) {
	newColumnNames[i] = COLUMN_DEVICE_ID + " \|\| '_' \|\| " + COLUMN_STORAGE_ID +
	" \|\| '_' \|\| IFNULL(" + COLUMN_OBJECT_HANDLE + ",0) AS " +
	DocumentsContract.Document.COLUMN_DOCUMENT_ID;
	} else {
	newColumnNames[i] = columnNames[i];
	}
	}

	return mDatabase.queryChildDocuments(newColumnNames, parentDocumentId);
	}

	Identifier createIdentifier(String parentDocumentId) {
	return mDatabase.createIdentifier(parentDocumentId);
	}

	/**
	* {@link MtpDatabaseInternal#removeDeviceRows}
	*/
	void removeDeviceRows(int deviceId) {
	mDatabase.removeDeviceRows(deviceId);
	}

	/**
	* Invokes {@link MtpDatabaseInternal#startAddingDocuments} for root documents.
	* @param deviceId Device ID.
	*/
	synchronized void startAddingRootDocuments(int deviceId) {
	final String mappingStateKey = getRootDocumentsMappingStateKey(deviceId);
	if (mMappingMode.containsKey(mappingStateKey)) {
	throw new Error("Mapping for the root has already started.");
	}
	mMappingMode.put(
	mappingStateKey,
	mDatabase.startAddingDocuments(
	SELECTION_ROOT_DOCUMENTS, Integer.toString(deviceId)));
	}

	/**
	* Invokes {@link MtpDatabaseInternal#startAddingDocuments} for child of specific documents.
	* @param parentDocumentId Document ID for parent document.
	*/
	@VisibleForTesting
	synchronized void startAddingChildDocuments(String parentDocumentId) {
	final String mappingStateKey = getChildDocumentsMappingStateKey(parentDocumentId);
	if (mMappingMode.containsKey(mappingStateKey)) {
	throw new Error("Mapping for the root has already started.");
	}
	mMappingMode.put(
	mappingStateKey,
	mDatabase.startAddingDocuments(SELECTION_CHILD_DOCUMENTS, parentDocumentId));
	}

	/**
	* Puts root information to database.
	* @param deviceId Device ID
	* @param resources Resources required to localize root name.
	* @param roots List of root information.
	* @return If roots are added or removed from the database.
	*/
	synchronized boolean putRootDocuments(int deviceId, Resources resources, MtpRoot[] roots) {
	mDatabase.beginTransaction();
	try {
	final boolean heuristic;
	final String mapColumn;
	switch (mMappingMode.get(getRootDocumentsMappingStateKey(deviceId))) {
	case MAP_BY_MTP_IDENTIFIER:
	heuristic = false;
	mapColumn = COLUMN_STORAGE_ID;
	break;
	case MAP_BY_NAME:
	heuristic = true;
	mapColumn = Document.COLUMN_DISPLAY_NAME;
	break;
	default:
	throw new Error("Unexpected map mode.");
	}
	final ContentValues[] valuesList = new ContentValues[roots.length];
	for (int i = 0; i < roots.length; i++) {
	if (roots[i].mDeviceId != deviceId) {
	throw new IllegalArgumentException();
	}
	valuesList[i] = new ContentValues();
	getRootDocumentValues(valuesList[i], resources, roots[i]);
	}
	final boolean changed = mDatabase.putDocuments(
	valuesList,
	SELECTION_ROOT_DOCUMENTS,
	Integer.toString(deviceId),
	heuristic,
	mapColumn);
	final ContentValues values = new ContentValues();
	int i = 0;
	for (final MtpRoot root : roots) {
	// Use the same value for the root ID and the corresponding document ID.
	final String documentId = valuesList[i++].getAsString(Document.COLUMN_DOCUMENT_ID);
	// If it fails to insert/update documents, the document ID will be set with -1.
	// In this case we don't insert/update root extra information neither.
	if (documentId == null) {
	continue;
	}
	values.put(Root.COLUMN_ROOT_ID, documentId);
	values.put(
	Root.COLUMN_FLAGS,
	Root.FLAG_SUPPORTS_IS_CHILD \| Root.FLAG_SUPPORTS_CREATE);
	values.put(Root.COLUMN_AVAILABLE_BYTES, root.mFreeSpace);
	values.put(Root.COLUMN_CAPACITY_BYTES, root.mMaxCapacity);
	values.put(Root.COLUMN_MIME_TYPES, "");
	mDatabase.putRootExtra(values);
	}
	mDatabase.setTransactionSuccessful();
	return changed;
	} finally {
	mDatabase.endTransaction();
	}
	}

	/**
	* Puts document information to database.
	* @param deviceId Device ID
	* @param parentId Parent document ID.
	* @param documents List of document information.
	*/
	@VisibleForTesting
	synchronized void putChildDocuments(int deviceId, String parentId, MtpObjectInfo[] documents) {
	final boolean heuristic;
	final String mapColumn;
	switch (mMappingMode.get(getChildDocumentsMappingStateKey(parentId))) {
	case MAP_BY_MTP_IDENTIFIER:
	heuristic = false;
	mapColumn = COLUMN_OBJECT_HANDLE;
	break;
	case MAP_BY_NAME:
	heuristic = true;
	mapColumn = Document.COLUMN_DISPLAY_NAME;
	break;
	default:
	throw new Error("Unexpected map mode.");
	}
	final ContentValues[] valuesList = new ContentValues[documents.length];
	for (int i = 0; i < documents.length; i++) {
	valuesList[i] = new ContentValues();
	getChildDocumentValues(valuesList[i], deviceId, parentId, documents[i]);
	}
	mDatabase.putDocuments(
	valuesList, SELECTION_CHILD_DOCUMENTS, parentId, heuristic, mapColumn);
	}

	/**
	* Clears mapping between MTP identifier and document/root ID.
	*/
	@VisibleForTesting
	synchronized void clearMapping() {
	mDatabase.clearMapping();
	mMappingMode.clear();
	}

	/**
	* Stops adding root documents.
	* @param deviceId Device ID.
	* @return True if new rows are added/removed.
	*/
	synchronized boolean stopAddingRootDocuments(int deviceId) {
	final String mappingModeKey = getRootDocumentsMappingStateKey(deviceId);
	switch (mMappingMode.get(mappingModeKey)) {
	case MAP_BY_MTP_IDENTIFIER:
	mMappingMode.remove(mappingModeKey);
	return mDatabase.stopAddingDocuments(
	SELECTION_ROOT_DOCUMENTS,
	Integer.toString(deviceId),
	COLUMN_STORAGE_ID);
	case MAP_BY_NAME:
	mMappingMode.remove(mappingModeKey);
	return mDatabase.stopAddingDocuments(
	SELECTION_ROOT_DOCUMENTS,
	Integer.toString(deviceId),
	Document.COLUMN_DISPLAY_NAME);
	default:
	throw new Error("Unexpected mapping state.");
	}
	}

	/**
	* Stops adding documents under the parent.
	* @param parentId Document ID of the parent.
	*/
	@VisibleForTesting
	synchronized void stopAddingChildDocuments(String parentId) {
	final String mappingModeKey = getChildDocumentsMappingStateKey(parentId);
	switch (mMappingMode.get(mappingModeKey)) {
	case MAP_BY_MTP_IDENTIFIER:
	mDatabase.stopAddingDocuments(
	SELECTION_CHILD_DOCUMENTS,
	parentId,
	COLUMN_OBJECT_HANDLE);
	break;
	case MAP_BY_NAME:
	mDatabase.stopAddingDocuments(
	SELECTION_CHILD_DOCUMENTS,
	parentId,
	Document.COLUMN_DISPLAY_NAME);
	break;
	default:
	throw new Error("Unexpected mapping state.");
	}
	mMappingMode.remove(mappingModeKey);
	}

	/**
	* Gets {@link ContentValues} for the given root.
	* @param values {@link ContentValues} that receives values.
	* @param resources Resources used to get localized root name.
	* @param root Root to be converted {@link ContentValues}.
	*/
	private static void getRootDocumentValues(
	ContentValues values, Resources resources, MtpRoot root) {
	values.clear();
	values.put(COLUMN_DEVICE_ID, root.mDeviceId);
	values.put(COLUMN_STORAGE_ID, root.mStorageId);
	values.putNull(COLUMN_OBJECT_HANDLE);
	values.putNull(COLUMN_PARENT_DOCUMENT_ID);
	values.put(COLUMN_ROW_STATE, ROW_STATE_VALID);
	values.put(Document.COLUMN_MIME_TYPE, Document.MIME_TYPE_DIR);
	values.put(Document.COLUMN_DISPLAY_NAME, root.getRootName(resources));
	values.putNull(Document.COLUMN_SUMMARY);
	values.putNull(Document.COLUMN_LAST_MODIFIED);
	values.putNull(Document.COLUMN_ICON);
	values.put(Document.COLUMN_FLAGS, 0);
	values.put(Document.COLUMN_SIZE,
	(int) Math.min(root.mMaxCapacity - root.mFreeSpace, Integer.MAX_VALUE));
	}

	/**
	* Gets {@link ContentValues} for the given MTP object.
	* @param values {@link ContentValues} that receives values.
	* @param deviceId Device ID of the object.
	* @param parentId Parent document ID of the object.
	* @param info MTP object info.
	*/
	private void getChildDocumentValues(
	ContentValues values, int deviceId, String parentId, MtpObjectInfo info) {
	values.clear();
	final String mimeType = CursorHelper.formatTypeToMimeType(info.getFormat());
	int flag = 0;
	if (info.getProtectionStatus() == 0) {
	flag \|= Document.FLAG_SUPPORTS_DELETE \|
	Document.FLAG_SUPPORTS_WRITE;
	if (mimeType == Document.MIME_TYPE_DIR) {
	flag \|= Document.FLAG_DIR_SUPPORTS_CREATE;
	}
	}
	if (info.getThumbCompressedSize() > 0) {
	flag \|= Document.FLAG_SUPPORTS_THUMBNAIL;
	}
	values.put(COLUMN_DEVICE_ID, deviceId);
	values.put(COLUMN_STORAGE_ID, info.getStorageId());
	values.put(COLUMN_OBJECT_HANDLE, info.getObjectHandle());
	values.put(COLUMN_PARENT_DOCUMENT_ID, parentId);
	values.put(COLUMN_ROW_STATE, ROW_STATE_VALID);
	values.put(Document.COLUMN_MIME_TYPE, mimeType);
	values.put(Document.COLUMN_DISPLAY_NAME, info.getName());
	values.putNull(Document.COLUMN_SUMMARY);
	values.put(
	Document.COLUMN_LAST_MODIFIED,
	info.getDateModified() != 0 ? info.getDateModified() : null);
	values.putNull(Document.COLUMN_ICON);
	values.put(Document.COLUMN_FLAGS, flag);
	values.put(Document.COLUMN_SIZE, info.getCompressedSize());
	}

	/**
	* @param deviceId Device ID.
	* @return Key for {@link #mMappingMode}.
	*/
	private static String getRootDocumentsMappingStateKey(int deviceId) {
	return "RootDocuments/" + deviceId;
	}

	/**
	* @param parentDocumentId Document ID for the parent document.
	* @return Key for {@link #mMappingMode}.
	*/
	private static String getChildDocumentsMappingStateKey(String parentDocumentId) {
	return "ChildDocuments/" + parentDocumentId;
	}
	}