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Commit e564b19e authored by Tammo Spalink's avatar Tammo Spalink
Browse files

replaced integer * and % with shift operations, for performance

parent 967f7c16

core/java/com/android/internal/util/BitwiseInputStream.java

+6 −6
Original line number Original line Diff line number Diff line
@@ -51,7 +51,7 @@ public class BitwiseInputStream { 
     */

     */

    public BitwiseInputStream(byte buf[]) {

    public BitwiseInputStream(byte buf[]) {

        mBuf = buf;

        mBuf = buf;

        mEnd = buf.length * 8;

        mEnd = buf.length << 3;

        mPos = 0;

        mPos = 0;

    }

    }
@@ -70,13 +70,13 @@ public class BitwiseInputStream { 
     * @return byte of read data (possibly partially filled, from lsb)

     * @return byte of read data (possibly partially filled, from lsb)

     */

     */

    public byte read(int bits) throws AccessException {

    public byte read(int bits) throws AccessException {

        int index = mPos / 8;

        int index = mPos >>> 3;

        int offset = 16 - (mPos % 8) - bits;

        int offset = 16 - (mPos & 0x07) - bits;  // &7==%8

        if ((bits < 0) || (bits > 8) || ((mPos + bits) > mEnd)) {

        if ((bits < 0) || (bits > 8) || ((mPos + bits) > mEnd)) {

            throw new AccessException("illegal read " +

            throw new AccessException("illegal read " +

                "(pos " + mPos + ", end " + mEnd + ", bits " + bits + ")");

                "(pos " + mPos + ", end " + mEnd + ", bits " + bits + ")");

        }

        }

        int data = (mBuf[index] & 0xFF) << 8;

        int data = (mBuf[index] & 0x00FF) << 8;

        if (offset < 8) data |= (mBuf[index + 1] & 0xFF);

        if (offset < 8) data |= (mBuf[index + 1] & 0xFF);

        data >>>= offset;

        data >>>= offset;

        data &= (-1 >>> (32 - bits));

        data &= (-1 >>> (32 - bits));
@@ -92,10 +92,10 @@ public class BitwiseInputStream { 
     * @return newly allocated byte array of read data

     * @return newly allocated byte array of read data

     */

     */

    public byte[] readByteArray(int bits) throws AccessException {

    public byte[] readByteArray(int bits) throws AccessException {

        int bytes = (bits / 8) + ((bits % 8) > 0 ? 1 : 0);

        int bytes = (bits >>> 3) + ((bits & 0x07) > 0 ? 1 : 0);  // &7==%8

        byte[] arr = new byte[bytes];

        byte[] arr = new byte[bytes];

        for (int i = 0; i < bytes; i++) {

        for (int i = 0; i < bytes; i++) {

            int increment = Math.min(8, bits - (i * 8));

            int increment = Math.min(8, bits - (i << 3));

            arr[i] = (byte)(read(increment) << (8 - increment));

            arr[i] = (byte)(read(increment) << (8 - increment));

        }

        }

        return arr;

        return arr;

core/java/com/android/internal/util/BitwiseOutputStream.java

+8 −8
Original line number Original line Diff line number Diff line
@@ -51,7 +51,7 @@ public class BitwiseOutputStream { 
     */

     */

    public BitwiseOutputStream(int startingLength) {

    public BitwiseOutputStream(int startingLength) {

        mBuf = new byte[startingLength];

        mBuf = new byte[startingLength];

        mEnd = startingLength * 8;

        mEnd = startingLength << 3;

        mPos = 0;

        mPos = 0;

    }

    }
@@ -61,7 +61,7 @@ public class BitwiseOutputStream { 
     * @return newly allocated byte array

     * @return newly allocated byte array

     */

     */

    public byte[] toByteArray() {

    public byte[] toByteArray() {

        int len = (mPos / 8) + ((mPos % 8) > 0 ? 1 : 0);

        int len = (mPos >>> 3) + ((mPos & 0x07) > 0 ? 1 : 0);  // &7==%8

        byte[] newBuf = new byte[len];

        byte[] newBuf = new byte[len];

        System.arraycopy(mBuf, 0, newBuf, 0, len);

        System.arraycopy(mBuf, 0, newBuf, 0, len);

        return newBuf;

        return newBuf;
@@ -74,8 +74,8 @@ public class BitwiseOutputStream { 
     */

     */

    private void possExpand(int bits) {

    private void possExpand(int bits) {

        if ((mPos + bits) < mEnd) return;

        if ((mPos + bits) < mEnd) return;

        byte[] newBuf = new byte[((mPos + bits) * 2) / 8];

        byte[] newBuf = new byte[(mPos + bits) >>> 2];

        System.arraycopy(mBuf, 0, newBuf, 0, mEnd / 8);

        System.arraycopy(mBuf, 0, newBuf, 0, mEnd >>> 3);

        mBuf = newBuf;

        mBuf = newBuf;

    }

    }
@@ -91,12 +91,12 @@ public class BitwiseOutputStream { 
        }

        }

        possExpand(bits);

        possExpand(bits);

        data &= (-1 >>> (32 - bits));

        data &= (-1 >>> (32 - bits));

        int index = mPos / 8;

        int index = mPos >>> 3;

        int offset = 16 - (mPos % 8) - bits;

        int offset = 16 - (mPos & 0x07) - bits;  // &7==%8

        data <<= offset;

        data <<= offset;

        mPos += bits;

        mPos += bits;

        mBuf[index] |= (data >>> 8);

        mBuf[index] |= (data >>> 8);

        if (offset < 8) mBuf[index + 1] |= (data & 0xFF);

        if (offset < 8) mBuf[index + 1] |= (data & 0x00FF);

    }

    }





    /**

    /**
@@ -107,7 +107,7 @@ public class BitwiseOutputStream { 
     */

     */

    public void writeByteArray(int bits, byte[] arr) throws AccessException {

    public void writeByteArray(int bits, byte[] arr) throws AccessException {

        for (int i = 0; i < arr.length; i++) {

        for (int i = 0; i < arr.length; i++) {

            int increment = Math.min(8, bits - (i * 8));

            int increment = Math.min(8, bits - (i << 3));

            if (increment > 0) {

            if (increment > 0) {

                write(increment, (byte)(arr[i] >>> (8 - increment)));

                write(increment, (byte)(arr[i] >>> (8 - increment)));

            }

            }

tests/AndroidTests/src/com/android/unit_tests/BitwiseStreamsTest.java

+25 −0
Original line number Original line Diff line number Diff line
@@ -23,6 +23,8 @@ import com.android.internal.util.HexDump; 
import android.test.AndroidTestCase;

import android.test.AndroidTestCase;

import android.test.suitebuilder.annotation.SmallTest;

import android.test.suitebuilder.annotation.SmallTest;





import android.util.Log;



public class BitwiseStreamsTest extends AndroidTestCase {

public class BitwiseStreamsTest extends AndroidTestCase {

    private final static String LOG_TAG = "BitwiseStreamsTest";

    private final static String LOG_TAG = "BitwiseStreamsTest";
@@ -85,4 +87,27 @@ public class BitwiseStreamsTest extends AndroidTestCase { 
        for (int i = 0; i < inBufDup.length; i++) inBufDup[i] = inStream.read(8);

        for (int i = 0; i < inBufDup.length; i++) inBufDup[i] = inStream.read(8);

        assertEquals(HexDump.toHexString(inBuf), HexDump.toHexString(inBufDup));

        assertEquals(HexDump.toHexString(inBuf), HexDump.toHexString(inBufDup));

    }

    }



    @SmallTest

    public void testFive() throws Exception {

        int num_runs = 10;

        long start = android.os.SystemClock.elapsedRealtime();

        for (int run = 0; run < num_runs; run++) {

            int offset = run % 8;

            byte[] inBuf = HexDump.hexStringToByteArray("00031040900112488ea794e0");

            BitwiseOutputStream outStream = new BitwiseOutputStream(30);

            outStream.skip(offset);

            for (int i = 0; i < inBuf.length; i++) {

                outStream.write(5, inBuf[i] >>> 3);

                outStream.write(3, inBuf[i] & 0x07);

            }

            BitwiseInputStream inStream = new BitwiseInputStream(outStream.toByteArray());

            inStream.skip(offset);

            byte[] inBufDup = new byte[inBuf.length];

            for (int i = 0; i < inBufDup.length; i++) inBufDup[i] = inStream.read(8);

            assertEquals(HexDump.toHexString(inBuf), HexDump.toHexString(inBufDup));

        }

        long end = android.os.SystemClock.elapsedRealtime();

        Log.d(LOG_TAG, "repeated encode-decode took " + (end - start) + " ms");

    }

}
 
}