android/database/CursorWindow.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 dalvik.system.CloseGuard;

import android.content.res.Resources;
import android.database.sqlite.SQLiteClosable;
import android.database.sqlite.SQLiteException;
import android.os.Binder;
import android.os.Parcel;
import android.os.Parcelable;
import android.os.Process;
import android.util.Log;
import android.util.SparseIntArray;

/**
 * A buffer containing multiple cursor rows.
 * <p>
 * A {@link CursorWindow} is read-write when initially created and used locally.
 * When sent to a remote process (by writing it to a {@link Parcel}), the remote process
 * receives a read-only view of the cursor window.  Typically the cursor window
 * will be allocated by the producer, filled with data, and then sent to the
 * consumer for reading.
 * </p>
 */
public class CursorWindow extends SQLiteClosable implements Parcelable {
    private static final String STATS_TAG = "CursorWindowStats";

    /** The cursor window size. resource xml file specifies the value in kB.
     * convert it to bytes here by multiplying with 1024.
     */
    private static final int sCursorWindowSize =
        Resources.getSystem().getInteger(
                com.android.internal.R.integer.config_cursorWindowSize) * 1024;

    /**
     * The native CursorWindow object pointer.  (FOR INTERNAL USE ONLY)
     * @hide
     */
    public int mWindowPtr;

    private int mStartPos;

    private final CloseGuard mCloseGuard = CloseGuard.get();

    private static native int nativeCreate(String name, int cursorWindowSize);
    private static native int nativeCreateFromParcel(Parcel parcel);
    private static native void nativeDispose(int windowPtr);
    private static native void nativeWriteToParcel(int windowPtr, Parcel parcel);

    private static native void nativeClear(int windowPtr);

    private static native int nativeGetNumRows(int windowPtr);
    private static native boolean nativeSetNumColumns(int windowPtr, int columnNum);
    private static native boolean nativeAllocRow(int windowPtr);
    private static native void nativeFreeLastRow(int windowPtr);

    private static native int nativeGetType(int windowPtr, int row, int column);
    private static native byte[] nativeGetBlob(int windowPtr, int row, int column);
    private static native String nativeGetString(int windowPtr, int row, int column);
    private static native long nativeGetLong(int windowPtr, int row, int column);
    private static native double nativeGetDouble(int windowPtr, int row, int column);
    private static native void nativeCopyStringToBuffer(int windowPtr, int row, int column,
            CharArrayBuffer buffer);

    private static native boolean nativePutBlob(int windowPtr, byte[] value, int row, int column);
    private static native boolean nativePutString(int windowPtr, String value, int row, int column);
    private static native boolean nativePutLong(int windowPtr, long value, int row, int column);
    private static native boolean nativePutDouble(int windowPtr, double value, int row, int column);
    private static native boolean nativePutNull(int windowPtr, int row, int column);

    /**
     * Creates a new empty cursor window and gives it a name.
     * <p>
     * The cursor initially has no rows or columns.  Call {@link #setNumColumns(int)} to
     * set the number of columns before adding any rows to the cursor.
     * </p>
     *
     * @param name The name of the cursor window, or null if none.
     */
    public CursorWindow(String name) {
        mStartPos = 0;
        mWindowPtr = nativeCreate(name, sCursorWindowSize);
        if (mWindowPtr == 0) {
            throw new CursorWindowAllocationException("Cursor window allocation of " +
                    (sCursorWindowSize / 1024) + " kb failed. " + printStats());
        }
        mCloseGuard.open("close");
        recordNewWindow(Binder.getCallingPid(), mWindowPtr);
    }

    /**
     * Creates a new empty cursor window.
     * <p>
     * The cursor initially has no rows or columns.  Call {@link #setNumColumns(int)} to
     * set the number of columns before adding any rows to the cursor.
     * </p>
     *
     * @param localWindow True if this window will be used in this process only,
     * false if it might be sent to another processes.  This argument is ignored.
     *
     * @deprecated There is no longer a distinction between local and remote
     * cursor windows.  Use the {@link #CursorWindow(String)} constructor instead.
     */
    @Deprecated
    public CursorWindow(boolean localWindow) {
        this((String)null);
    }

    private CursorWindow(Parcel source) {
        mStartPos = source.readInt();
        mWindowPtr = nativeCreateFromParcel(source);
        if (mWindowPtr == 0) {
            throw new CursorWindowAllocationException("Cursor window could not be "
                    + "created from binder.");
        }
        mCloseGuard.open("close");
    }

    @Override
    protected void finalize() throws Throwable {
        try {
            if (mCloseGuard != null) {
                mCloseGuard.warnIfOpen();
            }
            dispose();
        } finally {
            super.finalize();
        }
    }

    private void dispose() {
        if (mCloseGuard != null) {
            mCloseGuard.close();
        }
        if (mWindowPtr != 0) {
            recordClosingOfWindow(mWindowPtr);
            nativeDispose(mWindowPtr);
            mWindowPtr = 0;
        }
    }

    /**
     * Closes the cursor window and frees its underlying resources when all other
     * remaining references have been released.
     */
    public void close() {
        releaseReference();
    }

    /**
     * Clears out the existing contents of the window, making it safe to reuse
     * for new data.
     * <p>
     * The start position ({@link #getStartPosition()}), number of rows ({@link #getNumRows()}),
     * and number of columns in the cursor are all reset to zero.
     * </p>
     */
    public void clear() {
        acquireReference();
        try {
            mStartPos = 0;
            nativeClear(mWindowPtr);
        } finally {
            releaseReference();
        }
    }

    /**
     * Gets the start position of this cursor window.
     * <p>
     * The start position is the zero-based index of the first row that this window contains
     * relative to the entire result set of the {@link Cursor}.
     * </p>
     *
     * @return The zero-based start position.
     */
    public int getStartPosition() {
        return mStartPos;
    }

    /**
     * Sets the start position of this cursor window.
     * <p>
     * The start position is the zero-based index of the first row that this window contains
     * relative to the entire result set of the {@link Cursor}.
     * </p>
     *
     * @param pos The new zero-based start position.
     */
    public void setStartPosition(int pos) {
        mStartPos = pos;
    }

    /**
     * Gets the number of rows in this window.
     *
     * @return The number of rows in this cursor window.
     */
    public int getNumRows() {
        acquireReference();
        try {
            return nativeGetNumRows(mWindowPtr);
        } finally {
            releaseReference();
        }
    }

    /**
     * Sets the number of columns in this window.
     * <p>
     * This method must be called before any rows are added to the window, otherwise
     * it will fail to set the number of columns if it differs from the current number
     * of columns.
     * </p>
     *
     * @param columnNum The new number of columns.
     * @return True if successful.
     */
    public boolean setNumColumns(int columnNum) {
        acquireReference();
        try {
            return nativeSetNumColumns(mWindowPtr, columnNum);
        } finally {
            releaseReference();
        }
    }

    /**
     * Allocates a new row at the end of this cursor window.
     *
     * @return True if successful, false if the cursor window is out of memory.
     */
    public boolean allocRow(){
        acquireReference();
        try {
            return nativeAllocRow(mWindowPtr);
        } finally {
            releaseReference();
        }
    }

    /**
     * Frees the last row in this cursor window.
     */
    public void freeLastRow(){
        acquireReference();
        try {
            nativeFreeLastRow(mWindowPtr);
        } finally {
            releaseReference();
        }
    }

    /**
     * Returns true if the field at the specified row and column index
     * has type {@link Cursor#FIELD_TYPE_NULL}.
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return True if the field has type {@link Cursor#FIELD_TYPE_NULL}.
     * @deprecated Use {@link #getType(int, int)} instead.
     */
    @Deprecated
    public boolean isNull(int row, int column) {
        return getType(row, column) == Cursor.FIELD_TYPE_NULL;
    }

    /**
     * Returns true if the field at the specified row and column index
     * has type {@link Cursor#FIELD_TYPE_BLOB} or {@link Cursor#FIELD_TYPE_NULL}.
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return True if the field has type {@link Cursor#FIELD_TYPE_BLOB} or
     * {@link Cursor#FIELD_TYPE_NULL}.
     * @deprecated Use {@link #getType(int, int)} instead.
     */
    @Deprecated
    public boolean isBlob(int row, int column) {
        int type = getType(row, column);
        return type == Cursor.FIELD_TYPE_BLOB || type == Cursor.FIELD_TYPE_NULL;
    }

    /**
     * Returns true if the field at the specified row and column index
     * has type {@link Cursor#FIELD_TYPE_INTEGER}.
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return True if the field has type {@link Cursor#FIELD_TYPE_INTEGER}.
     * @deprecated Use {@link #getType(int, int)} instead.
     */
    @Deprecated
    public boolean isLong(int row, int column) {
        return getType(row, column) == Cursor.FIELD_TYPE_INTEGER;
    }

    /**
     * Returns true if the field at the specified row and column index
     * has type {@link Cursor#FIELD_TYPE_FLOAT}.
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return True if the field has type {@link Cursor#FIELD_TYPE_FLOAT}.
     * @deprecated Use {@link #getType(int, int)} instead.
     */
    @Deprecated
    public boolean isFloat(int row, int column) {
        return getType(row, column) == Cursor.FIELD_TYPE_FLOAT;
    }

    /**
     * Returns true if the field at the specified row and column index
     * has type {@link Cursor#FIELD_TYPE_STRING} or {@link Cursor#FIELD_TYPE_NULL}.
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return True if the field has type {@link Cursor#FIELD_TYPE_STRING}
     * or {@link Cursor#FIELD_TYPE_NULL}.
     * @deprecated Use {@link #getType(int, int)} instead.
     */
    @Deprecated
    public boolean isString(int row, int column) {
        int type = getType(row, column);
        return type == Cursor.FIELD_TYPE_STRING || type == Cursor.FIELD_TYPE_NULL;
    }

    /**
     * Returns the type of the field at the specified row and column index.
     * <p>
     * The returned field types 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 row The zero-based row index.
     * @param column The zero-based column index.
     * @return The field type.
     */
    public int getType(int row, int column) {
        acquireReference();
        try {
            return nativeGetType(mWindowPtr, row - mStartPos, column);
        } finally {
            releaseReference();
        }
    }

    /**
     * Gets the value of the field at the specified row and column index as a byte array.
     * <p>
     * The result is determined as follows:
     * <ul>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_NULL}, then the result
     * is <code>null</code>.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_BLOB}, then the result
     * is the blob value.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_STRING}, then the result
     * is the array of bytes that make up the internal representation of the
     * string value.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_INTEGER} or
     * {@link Cursor#FIELD_TYPE_FLOAT}, then a {@link SQLiteException} is thrown.</li>
     * </ul>
     * </p>
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return The value of the field as a byte array.
     */
    public byte[] getBlob(int row, int column) {
        acquireReference();
        try {
            return nativeGetBlob(mWindowPtr, row - mStartPos, column);
        } finally {
            releaseReference();
        }
    }

    /**
     * Gets the value of the field at the specified row and column index as a string.
     * <p>
     * The result is determined as follows:
     * <ul>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_NULL}, then the result
     * is <code>null</code>.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_STRING}, then the result
     * is the string value.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_INTEGER}, then the result
     * is a string representation of the integer in decimal, obtained by formatting the
     * value with the <code>printf</code> family of functions using
     * format specifier <code>%lld</code>.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_FLOAT}, then the result
     * is a string representation of the floating-point value in decimal, obtained by
     * formatting the value with the <code>printf</code> family of functions using
     * format specifier <code>%g</code>.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_BLOB}, then a
     * {@link SQLiteException} is thrown.</li>
     * </ul>
     * </p>
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return The value of the field as a string.
     */
    public String getString(int row, int column) {
        acquireReference();
        try {
            return nativeGetString(mWindowPtr, row - mStartPos, column);
        } finally {
            releaseReference();
        }
    }

    /**
     * Copies the text of the field at the specified row and column index into
     * a {@link CharArrayBuffer}.
     * <p>
     * The buffer is populated as follows:
     * <ul>
     * <li>If the buffer is too small for the value to be copied, then it is
     * automatically resized.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_NULL}, then the buffer
     * is set to an empty string.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_STRING}, then the buffer
     * is set to the contents of the string.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_INTEGER}, then the buffer
     * is set to a string representation of the integer in decimal, obtained by formatting the
     * value with the <code>printf</code> family of functions using
     * format specifier <code>%lld</code>.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_FLOAT}, then the buffer is
     * set to a string representation of the floating-point value in decimal, obtained by
     * formatting the value with the <code>printf</code> family of functions using
     * format specifier <code>%g</code>.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_BLOB}, then a
     * {@link SQLiteException} is thrown.</li>
     * </ul>
     * </p>
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @param buffer The {@link CharArrayBuffer} to hold the string.  It is automatically
     * resized if the requested string is larger than the buffer's current capacity.
      */
    public void copyStringToBuffer(int row, int column, CharArrayBuffer buffer) {
        if (buffer == null) {
            throw new IllegalArgumentException("CharArrayBuffer should not be null");
        }
        acquireReference();
        try {
            nativeCopyStringToBuffer(mWindowPtr, row - mStartPos, column, buffer);
        } finally {
            releaseReference();
        }
    }

    /**
     * Gets the value of the field at the specified row and column index as a <code>long</code>.
     * <p>
     * The result is determined as follows:
     * <ul>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_NULL}, then the result
     * is <code>0L</code>.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_STRING}, then the result
     * is the value obtained by parsing the string value with <code>strtoll</code>.
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_INTEGER}, then the result
     * is the <code>long</code> value.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_FLOAT}, then the result
     * is the floating-point value converted to a <code>long</code>.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_BLOB}, then a
     * {@link SQLiteException} is thrown.</li>
     * </ul>
     * </p>
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return The value of the field as a <code>long</code>.
     */
    public long getLong(int row, int column) {
        acquireReference();
        try {
            return nativeGetLong(mWindowPtr, row - mStartPos, column);
        } finally {
            releaseReference();
        }
    }

    /**
     * Gets the value of the field at the specified row and column index as a
     * <code>double</code>.
     * <p>
     * The result is determined as follows:
     * <ul>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_NULL}, then the result
     * is <code>0.0</code>.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_STRING}, then the result
     * is the value obtained by parsing the string value with <code>strtod</code>.
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_INTEGER}, then the result
     * is the integer value converted to a <code>double</code>.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_FLOAT}, then the result
     * is the <code>double</code> value.</li>
     * <li>If the field is of type {@link Cursor#FIELD_TYPE_BLOB}, then a
     * {@link SQLiteException} is thrown.</li>
     * </ul>
     * </p>
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return The value of the field as a <code>double</code>.
     */
    public double getDouble(int row, int column) {
        acquireReference();
        try {
            return nativeGetDouble(mWindowPtr, row - mStartPos, column);
        } finally {
            releaseReference();
        }
    }

    /**
     * Gets the value of the field at the specified row and column index as a
     * <code>short</code>.
     * <p>
     * The result is determined by invoking {@link #getLong} and converting the
     * result to <code>short</code>.
     * </p>
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return The value of the field as a <code>short</code>.
     */
    public short getShort(int row, int column) {
        return (short) getLong(row, column);
    }

    /**
     * Gets the value of the field at the specified row and column index as an
     * <code>int</code>.
     * <p>
     * The result is determined by invoking {@link #getLong} and converting the
     * result to <code>int</code>.
     * </p>
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return The value of the field as an <code>int</code>.
     */
    public int getInt(int row, int column) {
        return (int) getLong(row, column);
    }

    /**
     * Gets the value of the field at the specified row and column index as a
     * <code>float</code>.
     * <p>
     * The result is determined by invoking {@link #getDouble} and converting the
     * result to <code>float</code>.
     * </p>
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return The value of the field as an <code>float</code>.
     */
    public float getFloat(int row, int column) {
        return (float) getDouble(row, column);
    }

    /**
     * Copies a byte array into the field at the specified row and column index.
     *
     * @param value The value to store.
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return True if successful.
     */
    public boolean putBlob(byte[] value, int row, int column) {
        acquireReference();
        try {
            return nativePutBlob(mWindowPtr, value, row - mStartPos, column);
        } finally {
            releaseReference();
        }
    }

    /**
     * Copies a string into the field at the specified row and column index.
     *
     * @param value The value to store.
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return True if successful.
     */
    public boolean putString(String value, int row, int column) {
        acquireReference();
        try {
            return nativePutString(mWindowPtr, value, row - mStartPos, column);
        } finally {
            releaseReference();
        }
    }

    /**
     * Puts a long integer into the field at the specified row and column index.
     *
     * @param value The value to store.
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return True if successful.
     */
    public boolean putLong(long value, int row, int column) {
        acquireReference();
        try {
            return nativePutLong(mWindowPtr, value, row - mStartPos, column);
        } finally {
            releaseReference();
        }
    }

    /**
     * Puts a double-precision floating point value into the field at the
     * specified row and column index.
     *
     * @param value The value to store.
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return True if successful.
     */
    public boolean putDouble(double value, int row, int column) {
        acquireReference();
        try {
            return nativePutDouble(mWindowPtr, value, row - mStartPos, column);
        } finally {
            releaseReference();
        }
    }

    /**
     * Puts a null value into the field at the specified row and column index.
     *
     * @param row The zero-based row index.
     * @param column The zero-based column index.
     * @return True if successful.
     */
    public boolean putNull(int row, int column) {
        acquireReference();
        try {
            return nativePutNull(mWindowPtr, row - mStartPos, column);
        } finally {
            releaseReference();
        }
    }

    public static final Parcelable.Creator<CursorWindow> CREATOR
            = new Parcelable.Creator<CursorWindow>() {
        public CursorWindow createFromParcel(Parcel source) {
            return new CursorWindow(source);
        }

        public CursorWindow[] newArray(int size) {
            return new CursorWindow[size];
        }
    };

    public static CursorWindow newFromParcel(Parcel p) {
        return CREATOR.createFromParcel(p);
    }

    public int describeContents() {
        return 0;
    }

    public void writeToParcel(Parcel dest, int flags) {
        dest.writeInt(mStartPos);
        nativeWriteToParcel(mWindowPtr, dest);

        if ((flags & Parcelable.PARCELABLE_WRITE_RETURN_VALUE) != 0) {
            releaseReference();
        }
    }

    @Override
    protected void onAllReferencesReleased() {
        dispose();
    }

    private static final SparseIntArray sWindowToPidMap = new SparseIntArray();

    private void recordNewWindow(int pid, int window) {
        synchronized (sWindowToPidMap) {
            sWindowToPidMap.put(window, pid);
            if (Log.isLoggable(STATS_TAG, Log.VERBOSE)) {
                Log.i(STATS_TAG, "Created a new Cursor. " + printStats());
            }
        }
    }

    private void recordClosingOfWindow(int window) {
        synchronized (sWindowToPidMap) {
            if (sWindowToPidMap.size() == 0) {
                // this means we are not in the ContentProvider.
                return;
            }
            sWindowToPidMap.delete(window);
        }
    }

    private String printStats() {
        StringBuilder buff = new StringBuilder();
        int myPid = Process.myPid();
        int total = 0;
        SparseIntArray pidCounts = new SparseIntArray();
        synchronized (sWindowToPidMap) {
            int size = sWindowToPidMap.size();
            if (size == 0) {
                // this means we are not in the ContentProvider.
                return "";
            }
            for (int indx = 0; indx < size; indx++) {
                int pid = sWindowToPidMap.valueAt(indx);
                int value = pidCounts.get(pid);
                pidCounts.put(pid, ++value);
            }
        }
        int numPids = pidCounts.size();
        for (int i = 0; i < numPids;i++) {
            buff.append(" (# cursors opened by ");
            int pid = pidCounts.keyAt(i);
            if (pid == myPid) {
                buff.append("this proc=");
            } else {
                buff.append("pid " + pid + "=");
            }
            int num = pidCounts.get(pid);
            buff.append(num + ")");
            total += num;
        }
        // limit the returned string size to 1000
        String s = (buff.length() > 980) ? buff.substring(0, 980) : buff.toString();
        return "# Open Cursors=" + total + s;
    }
}