xref: /frameworks/base/core/java/android/database/DatabaseUtils.java

/*
 * Copyright (C) 2006 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 android.database;

import org.apache.commons.codec.binary.Hex;

import android.content.ContentValues;
import android.content.Context;
import android.content.OperationApplicationException;
import android.database.sqlite.SQLiteAbortException;
import android.database.sqlite.SQLiteConstraintException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabaseCorruptException;
import android.database.sqlite.SQLiteDiskIOException;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteFullException;
import android.database.sqlite.SQLiteProgram;
import android.database.sqlite.SQLiteStatement;
import android.os.Parcel;
import android.os.ParcelFileDescriptor;
import android.text.TextUtils;
import android.util.Log;

import java.io.FileNotFoundException;
import java.io.PrintStream;
import java.text.Collator;
import java.util.HashMap;
import java.util.Map;

/**
 * Static utility methods for dealing with databases and {@link Cursor}s.
 */
public class DatabaseUtils {
    private static final String TAG = "DatabaseUtils";

    private static final boolean DEBUG = false;
    private static final boolean LOCAL_LOGV = false;

    private static final String[] countProjection = new String[]{"count(*)"};

    /** One of the values returned by {@link #getSqlStatementType(String)}. */
    public static final int STATEMENT_SELECT = 1;
    /** One of the values returned by {@link #getSqlStatementType(String)}. */
    public static final int STATEMENT_UPDATE = 2;
    /** One of the values returned by {@link #getSqlStatementType(String)}. */
    public static final int STATEMENT_ATTACH = 3;
    /** One of the values returned by {@link #getSqlStatementType(String)}. */
    public static final int STATEMENT_BEGIN = 4;
    /** One of the values returned by {@link #getSqlStatementType(String)}. */
    public static final int STATEMENT_COMMIT = 5;
    /** One of the values returned by {@link #getSqlStatementType(String)}. */
    public static final int STATEMENT_ABORT = 6;
    /** One of the values returned by {@link #getSqlStatementType(String)}. */
    public static final int STATEMENT_PRAGMA = 7;
    /** One of the values returned by {@link #getSqlStatementType(String)}. */
    public static final int STATEMENT_DDL = 8;
    /** One of the values returned by {@link #getSqlStatementType(String)}. */
    public static final int STATEMENT_UNPREPARED = 9;
    /** One of the values returned by {@link #getSqlStatementType(String)}. */
    public static final int STATEMENT_OTHER = 99;

    /**
     * Special function for writing an exception result at the header of
     * a parcel, to be used when returning an exception from a transaction.
     * exception will be re-thrown by the function in another process
     * @param reply Parcel to write to
     * @param e The Exception to be written.
     * @see Parcel#writeNoException
     * @see Parcel#writeException
     */
    public static final void writeExceptionToParcel(Parcel reply, Exception e) {
        int code = 0;
        boolean logException = true;
        if (e instanceof FileNotFoundException) {
            code = 1;
            logException = false;
        } else if (e instanceof IllegalArgumentException) {
            code = 2;
        } else if (e instanceof UnsupportedOperationException) {
            code = 3;
        } else if (e instanceof SQLiteAbortException) {
            code = 4;
        } else if (e instanceof SQLiteConstraintException) {
            code = 5;
        } else if (e instanceof SQLiteDatabaseCorruptException) {
            code = 6;
        } else if (e instanceof SQLiteFullException) {
            code = 7;
        } else if (e instanceof SQLiteDiskIOException) {
            code = 8;
        } else if (e instanceof SQLiteException) {
            code = 9;
        } else if (e instanceof OperationApplicationException) {
            code = 10;
        } else {
            reply.writeException(e);
            Log.e(TAG, "Writing exception to parcel", e);
            return;
        }
        reply.writeInt(code);
        reply.writeString(e.getMessage());

        if (logException) {
            Log.e(TAG, "Writing exception to parcel", e);
        }
    }

    /**
     * Special function for reading an exception result from the header of
     * a parcel, to be used after receiving the result of a transaction.  This
     * will throw the exception for you if it had been written to the Parcel,
     * otherwise return and let you read the normal result data from the Parcel.
     * @param reply Parcel to read from
     * @see Parcel#writeNoException
     * @see Parcel#readException
     */
    public static final void readExceptionFromParcel(Parcel reply) {
        int code = reply.readExceptionCode();
        if (code == 0) return;
        String msg = reply.readString();
        DatabaseUtils.readExceptionFromParcel(reply, msg, code);
    }

    public static void readExceptionWithFileNotFoundExceptionFromParcel(
            Parcel reply) throws FileNotFoundException {
        int code = reply.readExceptionCode();
        if (code == 0) return;
        String msg = reply.readString();
        if (code == 1) {
            throw new FileNotFoundException(msg);
        } else {
            DatabaseUtils.readExceptionFromParcel(reply, msg, code);
        }
    }

    public static void readExceptionWithOperationApplicationExceptionFromParcel(
            Parcel reply) throws OperationApplicationException {
        int code = reply.readExceptionCode();
        if (code == 0) return;
        String msg = reply.readString();
        if (code == 10) {
            throw new OperationApplicationException(msg);
        } else {
            DatabaseUtils.readExceptionFromParcel(reply, msg, code);
        }
    }

    private static final void readExceptionFromParcel(Parcel reply, String msg, int code) {
        switch (code) {
            case 2:
                throw new IllegalArgumentException(msg);
            case 3:
                throw new UnsupportedOperationException(msg);
            case 4:
                throw new SQLiteAbortException(msg);
            case 5:
                throw new SQLiteConstraintException(msg);
            case 6:
                throw new SQLiteDatabaseCorruptException(msg);
            case 7:
                throw new SQLiteFullException(msg);
            case 8:
                throw new SQLiteDiskIOException(msg);
            case 9:
                throw new SQLiteException(msg);
            default:
                reply.readException(code, msg);
        }
    }

    /**
     * Binds the given Object to the given SQLiteProgram using the proper
     * typing. For example, bind numbers as longs/doubles, and everything else
     * as a string by call toString() on it.
     *
     * @param prog the program to bind the object to
     * @param index the 1-based index to bind at
     * @param value the value to bind
     */
    public static void bindObjectToProgram(SQLiteProgram prog, int index,
            Object value) {
        if (value == null) {
            prog.bindNull(index);
        } else if (value instanceof Double || value instanceof Float) {
            prog.bindDouble(index, ((Number)value).doubleValue());
        } else if (value instanceof Number) {
            prog.bindLong(index, ((Number)value).longValue());
        } else if (value instanceof Boolean) {
            Boolean bool = (Boolean)value;
            if (bool) {
                prog.bindLong(index, 1);
            } else {
                prog.bindLong(index, 0);
            }
        } else if (value instanceof byte[]){
            prog.bindBlob(index, (byte[]) value);
        } else {
            prog.bindString(index, value.toString());
        }
    }

    /**
     * Returns data type of the given object's value.
     *<p>
     * Returned values are
     * <ul>
     *   <li>{@link Cursor#FIELD_TYPE_NULL}</li>
     *   <li>{@link Cursor#FIELD_TYPE_INTEGER}</li>
     *   <li>{@link Cursor#FIELD_TYPE_FLOAT}</li>
     *   <li>{@link Cursor#FIELD_TYPE_STRING}</li>
     *   <li>{@link Cursor#FIELD_TYPE_BLOB}</li>
     *</ul>
     *</p>
     *
     * @param obj the object whose value type is to be returned
     * @return object value type
     * @hide
     */
    public static int getTypeOfObject(Object obj) {
        if (obj == null) {
            return Cursor.FIELD_TYPE_NULL;
        } else if (obj instanceof byte[]) {
            return Cursor.FIELD_TYPE_BLOB;
        } else if (obj instanceof Float || obj instanceof Double) {
            return Cursor.FIELD_TYPE_FLOAT;
        } else if (obj instanceof Long || obj instanceof Integer
                || obj instanceof Short || obj instanceof Byte) {
            return Cursor.FIELD_TYPE_INTEGER;
        } else {
            return Cursor.FIELD_TYPE_STRING;
        }
    }

    /**
     * Fills the specified cursor window by iterating over the contents of the cursor.
     * The window is filled until the cursor is exhausted or the window runs out
     * of space.
     *
     * The original position of the cursor is left unchanged by this operation.
     *
     * @param cursor The cursor that contains the data to put in the window.
     * @param position The start position for filling the window.
     * @param window The window to fill.
     * @hide
     */
    public static void cursorFillWindow(final Cursor cursor,
            int position, final CursorWindow window) {
        if (position < 0 || position >= cursor.getCount()) {
            return;
        }
        window.acquireReference();
        try {
            final int oldPos = cursor.getPosition();
            final int numColumns = cursor.getColumnCount();
            window.clear();
            window.setStartPosition(position);
            window.setNumColumns(numColumns);
            if (cursor.moveToPosition(position)) {
                do {
                    if (!window.allocRow()) {
                        break;
                    }
                    for (int i = 0; i < numColumns; i++) {
                        final int type = cursor.getType(i);
                        final boolean success;
                        switch (type) {
                            case Cursor.FIELD_TYPE_NULL:
                                success = window.putNull(position, i);
                                break;

                            case Cursor.FIELD_TYPE_INTEGER:
                                success = window.putLong(cursor.getLong(i), position, i);
                                break;

                            case Cursor.FIELD_TYPE_FLOAT:
                                success = window.putDouble(cursor.getDouble(i), position, i);
                                break;

                            case Cursor.FIELD_TYPE_BLOB: {
                                final byte[] value = cursor.getBlob(i);
                                success = value != null ? window.putBlob(value, position, i)
                                        : window.putNull(position, i);
                                break;
                            }

                            default: // assume value is convertible to String
                            case Cursor.FIELD_TYPE_STRING: {
                                final String value = cursor.getString(i);
                                success = value != null ? window.putString(value, position, i)
                                        : window.putNull(position, i);
                                break;
                            }
                        }
                        if (!success) {
                            window.freeLastRow();
                            break;
                        }
                    }
                    position += 1;
                } while (cursor.moveToNext());
            }
            cursor.moveToPosition(oldPos);
        } catch (IllegalStateException e){
            // simply ignore it
        } finally {
            window.releaseReference();
        }
    }

    /**
     * Appends an SQL string to the given StringBuilder, including the opening
     * and closing single quotes. Any single quotes internal to sqlString will
     * be escaped.
     *
     * This method is deprecated because we want to encourage everyone
     * to use the "?" binding form.  However, when implementing a
     * ContentProvider, one may want to add WHERE clauses that were
     * not provided by the caller.  Since "?" is a positional form,
     * using it in this case could break the caller because the
     * indexes would be shifted to accomodate the ContentProvider's
     * internal bindings.  In that case, it may be necessary to
     * construct a WHERE clause manually.  This method is useful for
     * those cases.
     *
     * @param sb the StringBuilder that the SQL string will be appended to
     * @param sqlString the raw string to be appended, which may contain single
     *                  quotes
     */
    public static void appendEscapedSQLString(StringBuilder sb, String sqlString) {
        sb.append('\'');
        if (sqlString.indexOf('\'') != -1) {
            int length = sqlString.length();
            for (int i = 0; i < length; i++) {
                char c = sqlString.charAt(i);
                if (c == '\'') {
                    sb.append('\'');
                }
                sb.append(c);
            }
        } else
            sb.append(sqlString);
        sb.append('\'');
    }

    /**
     * SQL-escape a string.
     */
    public static String sqlEscapeString(String value) {
        StringBuilder escaper = new StringBuilder();

        DatabaseUtils.appendEscapedSQLString(escaper, value);

        return escaper.toString();
    }

    /**
     * Appends an Object to an SQL string with the proper escaping, etc.
     */
    public static final void appendValueToSql(StringBuilder sql, Object value) {
        if (value == null) {
            sql.append("NULL");
        } else if (value instanceof Boolean) {
            Boolean bool = (Boolean)value;
            if (bool) {
                sql.append('1');
            } else {
                sql.append('0');
            }
        } else {
            appendEscapedSQLString(sql, value.toString());
        }
    }

    /**
     * Concatenates two SQL WHERE clauses, handling empty or null values.
     */
    public static String concatenateWhere(String a, String b) {
        if (TextUtils.isEmpty(a)) {
            return b;
        }
        if (TextUtils.isEmpty(b)) {
            return a;
        }

        return "(" + a + ") AND (" + b + ")";
    }

    /**
     * return the collation key
     * @param name
     * @return the collation key
     */
    public static String getCollationKey(String name) {
        byte [] arr = getCollationKeyInBytes(name);
        try {
            return new String(arr, 0, getKeyLen(arr), "ISO8859_1");
        } catch (Exception ex) {
            return "";
        }
    }

    /**
     * return the collation key in hex format
     * @param name
     * @return the collation key in hex format
     */
    public static String getHexCollationKey(String name) {
        byte [] arr = getCollationKeyInBytes(name);
        char[] keys = Hex.encodeHex(arr);
        return new String(keys, 0, getKeyLen(arr) * 2);
    }

    private static int getKeyLen(byte[] arr) {
        if (arr[arr.length - 1] != 0) {
            return arr.length;
        } else {
            // remove zero "termination"
            return arr.length-1;
        }
    }

    private static byte[] getCollationKeyInBytes(String name) {
        if (mColl == null) {
            mColl = Collator.getInstance();
            mColl.setStrength(Collator.PRIMARY);
        }
        return mColl.getCollationKey(name).toByteArray();
    }

    private static Collator mColl = null;
    /**
     * Prints the contents of a Cursor to System.out. The position is restored
     * after printing.
     *
     * @param cursor the cursor to print
     */
    public static void dumpCursor(Cursor cursor) {
        dumpCursor(cursor, System.out);
    }

    /**
     * Prints the contents of a Cursor to a PrintSteam. The position is restored
     * after printing.
     *
     * @param cursor the cursor to print
     * @param stream the stream to print to
     */
    public static void dumpCursor(Cursor cursor, PrintStream stream) {
        stream.println(">>>>> Dumping cursor " + cursor);
        if (cursor != null) {
            int startPos = cursor.getPosition();

            cursor.moveToPosition(-1);
            while (cursor.moveToNext()) {
                dumpCurrentRow(cursor, stream);
            }
            cursor.moveToPosition(startPos);
        }
        stream.println("<<<<<");
    }

    /**
     * Prints the contents of a Cursor to a StringBuilder. The position
     * is restored after printing.
     *
     * @param cursor the cursor to print
     * @param sb the StringBuilder to print to
     */
    public static void dumpCursor(Cursor cursor, StringBuilder sb) {
        sb.append(">>>>> Dumping cursor " + cursor + "\n");
        if (cursor != null) {
            int startPos = cursor.getPosition();

            cursor.moveToPosition(-1);
            while (cursor.moveToNext()) {
                dumpCurrentRow(cursor, sb);
            }
            cursor.moveToPosition(startPos);
        }
        sb.append("<<<<<\n");
    }

    /**
     * Prints the contents of a Cursor to a String. The position is restored
     * after printing.
     *
     * @param cursor the cursor to print
     * @return a String that contains the dumped cursor
     */
    public static String dumpCursorToString(Cursor cursor) {
        StringBuilder sb = new StringBuilder();
        dumpCursor(cursor, sb);
        return sb.toString();
    }

    /**
     * Prints the contents of a Cursor's current row to System.out.
     *
     * @param cursor the cursor to print from
     */
    public static void dumpCurrentRow(Cursor cursor) {
        dumpCurrentRow(cursor, System.out);
    }

    /**
     * Prints the contents of a Cursor's current row to a PrintSteam.
     *
     * @param cursor the cursor to print
     * @param stream the stream to print to
     */
    public static void dumpCurrentRow(Cursor cursor, PrintStream stream) {
        String[] cols = cursor.getColumnNames();
        stream.println("" + cursor.getPosition() + " {");
        int length = cols.length;
        for (int i = 0; i< length; i++) {
            String value;
            try {
                value = cursor.getString(i);
            } catch (SQLiteException e) {
                // assume that if the getString threw this exception then the column is not
                // representable by a string, e.g. it is a BLOB.
                value = "<unprintable>";
            }
            stream.println("   " + cols[i] + '=' + value);
        }
        stream.println("}");
    }

    /**
     * Prints the contents of a Cursor's current row to a StringBuilder.
     *
     * @param cursor the cursor to print
     * @param sb the StringBuilder to print to
     */
    public static void dumpCurrentRow(Cursor cursor, StringBuilder sb) {
        String[] cols = cursor.getColumnNames();
        sb.append("" + cursor.getPosition() + " {\n");
        int length = cols.length;
        for (int i = 0; i < length; i++) {
            String value;
            try {
                value = cursor.getString(i);
            } catch (SQLiteException e) {
                // assume that if the getString threw this exception then the column is not
                // representable by a string, e.g. it is a BLOB.
                value = "<unprintable>";
            }
            sb.append("   " + cols[i] + '=' + value + "\n");
        }
        sb.append("}\n");
    }

    /**
     * Dump the contents of a Cursor's current row to a String.
     *
     * @param cursor the cursor to print
     * @return a String that contains the dumped cursor row
     */
    public static String dumpCurrentRowToString(Cursor cursor) {
        StringBuilder sb = new StringBuilder();
        dumpCurrentRow(cursor, sb);
        return sb.toString();
    }

    /**
     * Reads a String out of a field in a Cursor and writes it to a Map.
     *
     * @param cursor The cursor to read from
     * @param field The TEXT field to read
     * @param values The {@link ContentValues} to put the value into, with the field as the key
     */
    public static void cursorStringToContentValues(Cursor cursor, String field,
            ContentValues values) {
        cursorStringToContentValues(cursor, field, values, field);
    }

    /**
     * Reads a String out of a field in a Cursor and writes it to an InsertHelper.
     *
     * @param cursor The cursor to read from
     * @param field The TEXT field to read
     * @param inserter The InsertHelper to bind into
     * @param index the index of the bind entry in the InsertHelper
     */
    public static void cursorStringToInsertHelper(Cursor cursor, String field,
            InsertHelper inserter, int index) {
        inserter.bind(index, cursor.getString(cursor.getColumnIndexOrThrow(field)));
    }

    /**
     * Reads a String out of a field in a Cursor and writes it to a Map.
     *
     * @param cursor The cursor to read from
     * @param field The TEXT field to read
     * @param values The {@link ContentValues} to put the value into, with the field as the key
     * @param key The key to store the value with in the map
     */
    public static void cursorStringToContentValues(Cursor cursor, String field,
            ContentValues values, String key) {
        values.put(key, cursor.getString(cursor.getColumnIndexOrThrow(field)));
    }

    /**
     * Reads an Integer out of a field in a Cursor and writes it to a Map.
     *
     * @param cursor The cursor to read from
     * @param field The INTEGER field to read
     * @param values The {@link ContentValues} to put the value into, with the field as the key
     */
    public static void cursorIntToContentValues(Cursor cursor, String field, ContentValues values) {
        cursorIntToContentValues(cursor, field, values, field);
    }

    /**
     * Reads a Integer out of a field in a Cursor and writes it to a Map.
     *
     * @param cursor The cursor to read from
     * @param field The INTEGER field to read
     * @param values The {@link ContentValues} to put the value into, with the field as the key
     * @param key The key to store the value with in the map
     */
    public static void cursorIntToContentValues(Cursor cursor, String field, ContentValues values,
            String key) {
        int colIndex = cursor.getColumnIndex(field);
        if (!cursor.isNull(colIndex)) {
            values.put(key, cursor.getInt(colIndex));
        } else {
            values.put(key, (Integer) null);
        }
    }

    /**
     * Reads a Long out of a field in a Cursor and writes it to a Map.
     *
     * @param cursor The cursor to read from
     * @param field The INTEGER field to read
     * @param values The {@link ContentValues} to put the value into, with the field as the key
     */
    public static void cursorLongToContentValues(Cursor cursor, String field, ContentValues values)
    {
        cursorLongToContentValues(cursor, field, values, field);
    }

    /**
     * Reads a Long out of a field in a Cursor and writes it to a Map.
     *
     * @param cursor The cursor to read from
     * @param field The INTEGER field to read
     * @param values The {@link ContentValues} to put the value into
     * @param key The key to store the value with in the map
     */
    public static void cursorLongToContentValues(Cursor cursor, String field, ContentValues values,
            String key) {
        int colIndex = cursor.getColumnIndex(field);
        if (!cursor.isNull(colIndex)) {
            Long value = Long.valueOf(cursor.getLong(colIndex));
            values.put(key, value);
        } else {
            values.put(key, (Long) null);
        }
    }

    /**
     * Reads a Double out of a field in a Cursor and writes it to a Map.
     *
     * @param cursor The cursor to read from
     * @param field The REAL field to read
     * @param values The {@link ContentValues} to put the value into
     */
    public static void cursorDoubleToCursorValues(Cursor cursor, String field, ContentValues values)
    {
        cursorDoubleToContentValues(cursor, field, values, field);
    }

    /**
     * Reads a Double out of a field in a Cursor and writes it to a Map.
     *
     * @param cursor The cursor to read from
     * @param field The REAL field to read
     * @param values The {@link ContentValues} to put the value into
     * @param key The key to store the value with in the map
     */
    public static void cursorDoubleToContentValues(Cursor cursor, String field,
            ContentValues values, String key) {
        int colIndex = cursor.getColumnIndex(field);
        if (!cursor.isNull(colIndex)) {
            values.put(key, cursor.getDouble(colIndex));
        } else {
            values.put(key, (Double) null);
        }
    }

    /**
     * Read the entire contents of a cursor row and store them in a ContentValues.
     *
     * @param cursor the cursor to read from.
     * @param values the {@link ContentValues} to put the row into.
     */
    public static void cursorRowToContentValues(Cursor cursor, ContentValues values) {
        AbstractWindowedCursor awc =
                (cursor instanceof AbstractWindowedCursor) ? (AbstractWindowedCursor) cursor : null;

        String[] columns = cursor.getColumnNames();
        int length = columns.length;
        for (int i = 0; i < length; i++) {
            if (awc != null && awc.isBlob(i)) {
                values.put(columns[i], cursor.getBlob(i));
            } else {
                values.put(columns[i], cursor.getString(i));
            }
        }
    }

    /**
     * Picks a start position for {@link Cursor#fillWindow} such that the
     * window will contain the requested row and a useful range of rows
     * around it.
     *
     * When the data set is too large to fit in a cursor window, seeking the
     * cursor can become a very expensive operation since we have to run the
     * query again when we move outside the bounds of the current window.
     *
     * We try to choose a start position for the cursor window such that
     * 1/3 of the window's capacity is used to hold rows before the requested
     * position and 2/3 of the window's capacity is used to hold rows after the
     * requested position.
     *
     * @param cursorPosition The row index of the row we want to get.
     * @param cursorWindowCapacity The estimated number of rows that can fit in
     * a cursor window, or 0 if unknown.
     * @return The recommended start position, always less than or equal to
     * the requested row.
     * @hide
     */
    public static int cursorPickFillWindowStartPosition(
            int cursorPosition, int cursorWindowCapacity) {
        return Math.max(cursorPosition - cursorWindowCapacity / 3, 0);
    }

    /**
     * Query the table for the number of rows in the table.
     * @param db the database the table is in
     * @param table the name of the table to query
     * @return the number of rows in the table
     */
    public static long queryNumEntries(SQLiteDatabase db, String table) {
        return queryNumEntries(db, table, null, null);
    }

    /**
     * Query the table for the number of rows in the table.
     * @param db the database the table is in
     * @param table the name of the table to query
     * @param selection A filter declaring which rows to return,
     *              formatted as an SQL WHERE clause (excluding the WHERE itself).
     *              Passing null will count all rows for the given table
     * @return the number of rows in the table filtered by the selection
     */
    public static long queryNumEntries(SQLiteDatabase db, String table, String selection) {
        return queryNumEntries(db, table, selection, null);
    }

    /**
     * Query the table for the number of rows in the table.
     * @param db the database the table is in
     * @param table the name of the table to query
     * @param selection A filter declaring which rows to return,
     *              formatted as an SQL WHERE clause (excluding the WHERE itself).
     *              Passing null will count all rows for the given table
     * @param selectionArgs You may include ?s in selection,
     *              which will be replaced by the values from selectionArgs,
     *              in order that they appear in the selection.
     *              The values will be bound as Strings.
     * @return the number of rows in the table filtered by the selection
     */
    public static long queryNumEntries(SQLiteDatabase db, String table, String selection,
            String[] selectionArgs) {
        String s = (!TextUtils.isEmpty(selection)) ? " where " + selection : "";
        return longForQuery(db, "select count(*) from " + table + s,
                    selectionArgs);
    }

    /**
     * Utility method to run the query on the db and return the value in the
     * first column of the first row.
     */
    public static long longForQuery(SQLiteDatabase db, String query, String[] selectionArgs) {
        SQLiteStatement prog = db.compileStatement(query);
        try {
            return longForQuery(prog, selectionArgs);
        } finally {
            prog.close();
        }
    }

    /**
     * Utility method to run the pre-compiled query and return the value in the
     * first column of the first row.
     */
    public static long longForQuery(SQLiteStatement prog, String[] selectionArgs) {
        prog.bindAllArgsAsStrings(selectionArgs);
        return prog.simpleQueryForLong();
    }

    /**
     * Utility method to run the query on the db and return the value in the
     * first column of the first row.
     */
    public static String stringForQuery(SQLiteDatabase db, String query, String[] selectionArgs) {
        SQLiteStatement prog = db.compileStatement(query);
        try {
            return stringForQuery(prog, selectionArgs);
        } finally {
            prog.close();
        }
    }

    /**
     * Utility method to run the pre-compiled query and return the value in the
     * first column of the first row.
     */
    public static String stringForQuery(SQLiteStatement prog, String[] selectionArgs) {
        prog.bindAllArgsAsStrings(selectionArgs);
        return prog.simpleQueryForString();
    }

    /**
     * Utility method to run the query on the db and return the blob value in the
     * first column of the first row.
     *
     * @return A read-only file descriptor for a copy of the blob value.
     */
    public static ParcelFileDescriptor blobFileDescriptorForQuery(SQLiteDatabase db,
            String query, String[] selectionArgs) {
        SQLiteStatement prog = db.compileStatement(query);
        try {
            return blobFileDescriptorForQuery(prog, selectionArgs);
        } finally {
            prog.close();
        }
    }

    /**
     * Utility method to run the pre-compiled query and return the blob value in the
     * first column of the first row.
     *
     * @return A read-only file descriptor for a copy of the blob value.
     */
    public static ParcelFileDescriptor blobFileDescriptorForQuery(SQLiteStatement prog,
            String[] selectionArgs) {
        prog.bindAllArgsAsStrings(selectionArgs);
        return prog.simpleQueryForBlobFileDescriptor();
    }

    /**
     * Reads a String out of a column in a Cursor and writes it to a ContentValues.
     * Adds nothing to the ContentValues if the column isn't present or if its value is null.
     *
     * @param cursor The cursor to read from
     * @param column The column to read
     * @param values The {@link ContentValues} to put the value into
     */
    public static void cursorStringToContentValuesIfPresent(Cursor cursor, ContentValues values,
            String column) {
        final int index = cursor.getColumnIndex(column);
        if (index != -1 && !cursor.isNull(index)) {
            values.put(column, cursor.getString(index));
        }
    }

    /**
     * Reads a Long out of a column in a Cursor and writes it to a ContentValues.
     * Adds nothing to the ContentValues if the column isn't present or if its value is null.
     *
     * @param cursor The cursor to read from
     * @param column The column to read
     * @param values The {@link ContentValues} to put the value into
     */
    public static void cursorLongToContentValuesIfPresent(Cursor cursor, ContentValues values,
            String column) {
        final int index = cursor.getColumnIndex(column);
        if (index != -1 && !cursor.isNull(index)) {
            values.put(column, cursor.getLong(index));
        }
    }

    /**
     * Reads a Short out of a column in a Cursor and writes it to a ContentValues.
     * Adds nothing to the ContentValues if the column isn't present or if its value is null.
     *
     * @param cursor The cursor to read from
     * @param column The column to read
     * @param values The {@link ContentValues} to put the value into
     */
    public static void cursorShortToContentValuesIfPresent(Cursor cursor, ContentValues values,
            String column) {
        final int index = cursor.getColumnIndex(column);
        if (index != -1 && !cursor.isNull(index)) {
            values.put(column, cursor.getShort(index));
        }
    }

    /**
     * Reads a Integer out of a column in a Cursor and writes it to a ContentValues.
     * Adds nothing to the ContentValues if the column isn't present or if its value is null.
     *
     * @param cursor The cursor to read from
     * @param column The column to read
     * @param values The {@link ContentValues} to put the value into
     */
    public static void cursorIntToContentValuesIfPresent(Cursor cursor, ContentValues values,
            String column) {
        final int index = cursor.getColumnIndex(column);
        if (index != -1 && !cursor.isNull(index)) {
            values.put(column, cursor.getInt(index));
        }
    }

    /**
     * Reads a Float out of a column in a Cursor and writes it to a ContentValues.
     * Adds nothing to the ContentValues if the column isn't present or if its value is null.
     *
     * @param cursor The cursor to read from
     * @param column The column to read
     * @param values The {@link ContentValues} to put the value into
     */
    public static void cursorFloatToContentValuesIfPresent(Cursor cursor, ContentValues values,
            String column) {
        final int index = cursor.getColumnIndex(column);
        if (index != -1 && !cursor.isNull(index)) {
            values.put(column, cursor.getFloat(index));
        }
    }

    /**
     * Reads a Double out of a column in a Cursor and writes it to a ContentValues.
     * Adds nothing to the ContentValues if the column isn't present or if its value is null.
     *
     * @param cursor The cursor to read from
     * @param column The column to read
     * @param values The {@link ContentValues} to put the value into
     */
    public static void cursorDoubleToContentValuesIfPresent(Cursor cursor, ContentValues values,
            String column) {
        final int index = cursor.getColumnIndex(column);
        if (index != -1 && !cursor.isNull(index)) {
            values.put(column, cursor.getDouble(index));
        }
    }

    /**
     * This class allows users to do multiple inserts into a table but
     * compile the SQL insert statement only once, which may increase
     * performance.
     */
    public static class InsertHelper {
        private final SQLiteDatabase mDb;
        private final String mTableName;
        private HashMap<String, Integer> mColumns;
        private String mInsertSQL = null;
        private SQLiteStatement mInsertStatement = null;
        private SQLiteStatement mReplaceStatement = null;
        private SQLiteStatement mPreparedStatement = null;

        /**
         * {@hide}
         *
         * These are the columns returned by sqlite's "PRAGMA
         * table_info(...)" command that we depend on.
         */
        public static final int TABLE_INFO_PRAGMA_COLUMNNAME_INDEX = 1;
        public static final int TABLE_INFO_PRAGMA_DEFAULT_INDEX = 4;

        /**
         * @param db the SQLiteDatabase to insert into
         * @param tableName the name of the table to insert into
         */
        public InsertHelper(SQLiteDatabase db, String tableName) {
            mDb = db;
            mTableName = tableName;
        }

        private void buildSQL() throws SQLException {
            StringBuilder sb = new StringBuilder(128);
            sb.append("INSERT INTO ");
            sb.append(mTableName);
            sb.append(" (");

            StringBuilder sbv = new StringBuilder(128);
            sbv.append("VALUES (");

            int i = 1;
            Cursor cur = null;
            try {
                cur = mDb.rawQuery("PRAGMA table_info(" + mTableName + ")", null);
                mColumns = new HashMap<String, Integer>(cur.getCount());
                while (cur.moveToNext()) {
                    String columnName = cur.getString(TABLE_INFO_PRAGMA_COLUMNNAME_INDEX);
                    String defaultValue = cur.getString(TABLE_INFO_PRAGMA_DEFAULT_INDEX);

                    mColumns.put(columnName, i);
                    sb.append("'");
                    sb.append(columnName);
                    sb.append("'");

                    if (defaultValue == null) {
                        sbv.append("?");
                    } else {
                        sbv.append("COALESCE(?, ");
                        sbv.append(defaultValue);
                        sbv.append(")");
                    }

                    sb.append(i == cur.getCount() ? ") " : ", ");
                    sbv.append(i == cur.getCount() ? ");" : ", ");
                    ++i;
                }
            } finally {
                if (cur != null) cur.close();
            }

            sb.append(sbv);

            mInsertSQL = sb.toString();
            if (LOCAL_LOGV) Log.v(TAG, "insert statement is " + mInsertSQL);
        }

        private SQLiteStatement getStatement(boolean allowReplace) throws SQLException {
            if (allowReplace) {
                if (mReplaceStatement == null) {
                    if (mInsertSQL == null) buildSQL();
                    // chop "INSERT" off the front and prepend "INSERT OR REPLACE" instead.
                    String replaceSQL = "INSERT OR REPLACE" + mInsertSQL.substring(6);
                    mReplaceStatement = mDb.compileStatement(replaceSQL);
                }
                return mReplaceStatement;
            } else {
                if (mInsertStatement == null) {
                    if (mInsertSQL == null) buildSQL();
                    mInsertStatement = mDb.compileStatement(mInsertSQL);
                }
                return mInsertStatement;
            }
        }

        /**
         * Performs an insert, adding a new row with the given values.
         *
         * @param values the set of values with which  to populate the
         * new row
         * @param allowReplace if true, the statement does "INSERT OR
         *   REPLACE" instead of "INSERT", silently deleting any
         *   previously existing rows that would cause a conflict
         *
         * @return the row ID of the newly inserted row, or -1 if an
         * error occurred
         */
        private synchronized long insertInternal(ContentValues values, boolean allowReplace) {
            try {
                SQLiteStatement stmt = getStatement(allowReplace);
                stmt.clearBindings();
                if (LOCAL_LOGV) Log.v(TAG, "--- inserting in table " + mTableName);
                for (Map.Entry<String, Object> e: values.valueSet()) {
                    final String key = e.getKey();
                    int i = getColumnIndex(key);
                    DatabaseUtils.bindObjectToProgram(stmt, i, e.getValue());
                    if (LOCAL_LOGV) {
                        Log.v(TAG, "binding " + e.getValue() + " to column " +
                              i + " (" + key + ")");
                    }
                }
                return stmt.executeInsert();
            } catch (SQLException e) {
                Log.e(TAG, "Error inserting " + values + " into table  " + mTableName, e);
                return -1;
            }
        }

        /**
         * Returns the index of the specified column. This is index is suitagble for use
         * in calls to bind().
         * @param key the column name
         * @return the index of the column
         */
        public int getColumnIndex(String key) {
            getStatement(false);
            final Integer index = mColumns.get(key);
            if (index == null) {
                throw new IllegalArgumentException("column '" + key + "' is invalid");
            }
            return index;
        }

        /**
         * Bind the value to an index. A prepareForInsert() or prepareForReplace()
         * without a matching execute() must have already have been called.
         * @param index the index of the slot to which to bind
         * @param value the value to bind
         */
        public void bind(int index, double value) {
            mPreparedStatement.bindDouble(index, value);
        }

        /**
         * Bind the value to an index. A prepareForInsert() or prepareForReplace()
         * without a matching execute() must have already have been called.
         * @param index the index of the slot to which to bind
         * @param value the value to bind
         */
        public void bind(int index, float value) {
            mPreparedStatement.bindDouble(index, value);
        }

        /**
         * Bind the value to an index. A prepareForInsert() or prepareForReplace()
         * without a matching execute() must have already have been called.
         * @param index the index of the slot to which to bind
         * @param value the value to bind
         */
        public void bind(int index, long value) {
            mPreparedStatement.bindLong(index, value);
        }

        /**
         * Bind the value to an index. A prepareForInsert() or prepareForReplace()
         * without a matching execute() must have already have been called.
         * @param index the index of the slot to which to bind
         * @param value the value to bind
         */
        public void bind(int index, int value) {
            mPreparedStatement.bindLong(index, value);
        }

        /**
         * Bind the value to an index. A prepareForInsert() or prepareForReplace()
         * without a matching execute() must have already have been called.
         * @param index the index of the slot to which to bind
         * @param value the value to bind
         */
        public void bind(int index, boolean value) {
            mPreparedStatement.bindLong(index, value ? 1 : 0);
        }

        /**
         * Bind null to an index. A prepareForInsert() or prepareForReplace()
         * without a matching execute() must have already have been called.
         * @param index the index of the slot to which to bind
         */
        public void bindNull(int index) {
            mPreparedStatement.bindNull(index);
        }

        /**
         * Bind the value to an index. A prepareForInsert() or prepareForReplace()
         * without a matching execute() must have already have been called.
         * @param index the index of the slot to which to bind
         * @param value the value to bind
         */
        public void bind(int index, byte[] value) {
            if (value == null) {
                mPreparedStatement.bindNull(index);
            } else {
                mPreparedStatement.bindBlob(index, value);
            }
        }

        /**
         * Bind the value to an index. A prepareForInsert() or prepareForReplace()
         * without a matching execute() must have already have been called.
         * @param index the index of the slot to which to bind
         * @param value the value to bind
         */
        public void bind(int index, String value) {
            if (value == null) {
                mPreparedStatement.bindNull(index);
            } else {
                mPreparedStatement.bindString(index, value);
            }
        }

        /**
         * Performs an insert, adding a new row with the given values.
         * If the table contains conflicting rows, an error is
         * returned.
         *
         * @param values the set of values with which to populate the
         * new row
         *
         * @return the row ID of the newly inserted row, or -1 if an
         * error occurred
         */
        public long insert(ContentValues values) {
            return insertInternal(values, false);
        }

        /**
         * Execute the previously prepared insert or replace using the bound values
         * since the last call to prepareForInsert or prepareForReplace.
         *
         * <p>Note that calling bind() and then execute() is not thread-safe. The only thread-safe
         * way to use this class is to call insert() or replace().
         *
         * @return the row ID of the newly inserted row, or -1 if an
         * error occurred
         */
        public long execute() {
            if (mPreparedStatement == null) {
                throw new IllegalStateException("you must prepare this inserter before calling "
                        + "execute");
            }
            try {
                if (LOCAL_LOGV) Log.v(TAG, "--- doing insert or replace in table " + mTableName);
                return mPreparedStatement.executeInsert();
            } catch (SQLException e) {
                Log.e(TAG, "Error executing InsertHelper with table " + mTableName, e);
                return -1;
            } finally {
                // you can only call this once per prepare
                mPreparedStatement = null;
            }
        }

        /**
         * Prepare the InsertHelper for an insert. The pattern for this is:
         * <ul>
         * <li>prepareForInsert()
         * <li>bind(index, value);
         * <li>bind(index, value);
         * <li>...
         * <li>bind(index, value);
         * <li>execute();
         * </ul>
         */
        public void prepareForInsert() {
            mPreparedStatement = getStatement(false);
            mPreparedStatement.clearBindings();
        }

        /**
         * Prepare the InsertHelper for a replace. The pattern for this is:
         * <ul>
         * <li>prepareForReplace()
         * <li>bind(index, value);
         * <li>bind(index, value);
         * <li>...
         * <li>bind(index, value);
         * <li>execute();
         * </ul>
         */
        public void prepareForReplace() {
            mPreparedStatement = getStatement(true);
            mPreparedStatement.clearBindings();
        }

        /**
         * Performs an insert, adding a new row with the given values.
         * If the table contains conflicting rows, they are deleted
         * and replaced with the new row.
         *
         * @param values the set of values with which to populate the
         * new row
         *
         * @return the row ID of the newly inserted row, or -1 if an
         * error occurred
         */
        public long replace(ContentValues values) {
            return insertInternal(values, true);
        }

        /**
         * Close this object and release any resources associated with
         * it.  The behavior of calling <code>insert()</code> after
         * calling this method is undefined.
         */
        public void close() {
            if (mInsertStatement != null) {
                mInsertStatement.close();
                mInsertStatement = null;
            }
            if (mReplaceStatement != null) {
                mReplaceStatement.close();
                mReplaceStatement = null;
            }
            mInsertSQL = null;
            mColumns = null;
        }
    }

    /**
     * Creates a db and populates it with the sql statements in sqlStatements.
     *
     * @param context the context to use to create the db
     * @param dbName the name of the db to create
     * @param dbVersion the version to set on the db
     * @param sqlStatements the statements to use to populate the db. This should be a single string
     *   of the form returned by sqlite3's <tt>.dump</tt> command (statements separated by
     *   semicolons)
     */
    static public void createDbFromSqlStatements(
            Context context, String dbName, int dbVersion, String sqlStatements) {
        SQLiteDatabase db = context.openOrCreateDatabase(dbName, 0, null);
        // TODO: this is not quite safe since it assumes that all semicolons at the end of a line
        // terminate statements. It is possible that a text field contains ;\n. We will have to fix
        // this if that turns out to be a problem.
        String[] statements = TextUtils.split(sqlStatements, ";\n");
        for (String statement : statements) {
            if (TextUtils.isEmpty(statement)) continue;
            db.execSQL(statement);
        }
        db.setVersion(dbVersion);
        db.close();
    }

    /**
     * Returns one of the following which represent the type of the given SQL statement.
     * <ol>
     *   <li>{@link #STATEMENT_SELECT}</li>
     *   <li>{@link #STATEMENT_UPDATE}</li>
     *   <li>{@link #STATEMENT_ATTACH}</li>
     *   <li>{@link #STATEMENT_BEGIN}</li>
     *   <li>{@link #STATEMENT_COMMIT}</li>
     *   <li>{@link #STATEMENT_ABORT}</li>
     *   <li>{@link #STATEMENT_OTHER}</li>
     * </ol>
     * @param sql the SQL statement whose type is returned by this method
     * @return one of the values listed above
     */
    public static int getSqlStatementType(String sql) {
        sql = sql.trim();
        if (sql.length() < 3) {
            return STATEMENT_OTHER;
        }
        String prefixSql = sql.substring(0, 3).toUpperCase();
        if (prefixSql.equals("SEL")) {
            return STATEMENT_SELECT;
        } else if (prefixSql.equals("INS") ||
                prefixSql.equals("UPD") ||
                prefixSql.equals("REP") ||
                prefixSql.equals("DEL")) {
            return STATEMENT_UPDATE;
        } else if (prefixSql.equals("ATT")) {
            return STATEMENT_ATTACH;
        } else if (prefixSql.equals("COM")) {
            return STATEMENT_COMMIT;
        } else if (prefixSql.equals("END")) {
            return STATEMENT_COMMIT;
        } else if (prefixSql.equals("ROL")) {
            return STATEMENT_ABORT;
        } else if (prefixSql.equals("BEG")) {
            return STATEMENT_BEGIN;
        } else if (prefixSql.equals("PRA")) {
            return STATEMENT_PRAGMA;
        } else if (prefixSql.equals("CRE") || prefixSql.equals("DRO") ||
                prefixSql.equals("ALT")) {
            return STATEMENT_DDL;
        } else if (prefixSql.equals("ANA") || prefixSql.equals("DET")) {
            return STATEMENT_UNPREPARED;
        }
        return STATEMENT_OTHER;
    }

    /**
     * Appends one set of selection args to another. This is useful when adding a selection
     * argument to a user provided set.
     */
    public static String[] appendSelectionArgs(String[] originalValues, String[] newValues) {
        if (originalValues == null || originalValues.length == 0) {
            return newValues;
        }
        String[] result = new String[originalValues.length + newValues.length ];
        System.arraycopy(originalValues, 0, result, 0, originalValues.length);
        System.arraycopy(newValues, 0, result, originalValues.length, newValues.length);
        return result;
    }
}