/*
 * Copyright (C) 2017 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.internal.util;

import static com.android.internal.util.BitUtils.bytesToBEInt;
import static com.android.internal.util.BitUtils.bytesToLEInt;
import static com.android.internal.util.BitUtils.getUint16;
import static com.android.internal.util.BitUtils.getUint32;
import static com.android.internal.util.BitUtils.getUint8;
import static com.android.internal.util.BitUtils.packBits;
import static com.android.internal.util.BitUtils.uint16;
import static com.android.internal.util.BitUtils.uint32;
import static com.android.internal.util.BitUtils.uint8;
import static com.android.internal.util.BitUtils.unpackBits;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

import androidx.test.filters.SmallTest;
import androidx.test.runner.AndroidJUnit4;

import org.junit.Test;
import org.junit.runner.RunWith;

import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.Random;

@SmallTest
@RunWith(AndroidJUnit4.class)
public class BitUtilsTest {

    @Test
    public void testUnsignedByteWideningConversions() {
        byte b0 = 0;
        byte b1 = 1;
        byte bm1 = -1;
        assertEquals(0, uint8(b0));
        assertEquals(1, uint8(b1));
        assertEquals(127, uint8(Byte.MAX_VALUE));
        assertEquals(128, uint8(Byte.MIN_VALUE));
        assertEquals(255, uint8(bm1));
        assertEquals(255, uint8((byte)255));
    }

    @Test
    public void testUnsignedShortWideningConversions() {
        short s0 = 0;
        short s1 = 1;
        short sm1 = -1;
        assertEquals(0, uint16(s0));
        assertEquals(1, uint16(s1));
        assertEquals(32767, uint16(Short.MAX_VALUE));
        assertEquals(32768, uint16(Short.MIN_VALUE));
        assertEquals(65535, uint16(sm1));
        assertEquals(65535, uint16((short)65535));
    }

    @Test
    public void testUnsignedShortComposition() {
        byte b0 = 0;
        byte b1 = 1;
        byte b2 = 2;
        byte b10 = 10;
        byte b16 = 16;
        byte b128 = -128;
        byte b224 = -32;
        byte b255 = -1;
        assertEquals(0x0000, uint16(b0, b0));
        assertEquals(0xffff, uint16(b255, b255));
        assertEquals(0x0a01, uint16(b10, b1));
        assertEquals(0x8002, uint16(b128, b2));
        assertEquals(0x01ff, uint16(b1, b255));
        assertEquals(0x80ff, uint16(b128, b255));
        assertEquals(0xe010, uint16(b224, b16));
    }

    @Test
    public void testUnsignedIntWideningConversions() {
        assertEquals(0, uint32(0));
        assertEquals(1, uint32(1));
        assertEquals(2147483647L, uint32(Integer.MAX_VALUE));
        assertEquals(2147483648L, uint32(Integer.MIN_VALUE));
        assertEquals(4294967295L, uint32(-1));
        assertEquals(4294967295L, uint32((int)4294967295L));
    }

    @Test
    public void testBytesToInt() {
        assertEquals(0x00000000, bytesToBEInt(bytes(0, 0, 0, 0)));
        assertEquals(0xffffffff, bytesToBEInt(bytes(255, 255, 255, 255)));
        assertEquals(0x0a000001, bytesToBEInt(bytes(10, 0, 0, 1)));
        assertEquals(0x0a000002, bytesToBEInt(bytes(10, 0, 0, 2)));
        assertEquals(0x0a001fff, bytesToBEInt(bytes(10, 0, 31, 255)));
        assertEquals(0xe0000001, bytesToBEInt(bytes(224, 0, 0, 1)));

        assertEquals(0x00000000, bytesToLEInt(bytes(0, 0, 0, 0)));
        assertEquals(0x01020304, bytesToLEInt(bytes(4, 3, 2, 1)));
        assertEquals(0xffff0000, bytesToLEInt(bytes(0, 0, 255, 255)));
    }

    @Test
    public void testUnsignedGetters() {
        ByteBuffer b = ByteBuffer.allocate(4);
        b.putInt(0xffff);

        assertEquals(0x0, getUint8(b, 0));
        assertEquals(0x0, getUint8(b, 1));
        assertEquals(0xff, getUint8(b, 2));
        assertEquals(0xff, getUint8(b, 3));

        assertEquals(0x0, getUint16(b, 0));
        assertEquals(0xffff, getUint16(b, 2));

        b.rewind();
        b.putInt(0xffffffff);
        assertEquals(0xffffffffL, getUint32(b, 0));
    }

    @Test
    public void testBitsPacking() {
        BitPackingTestCase[] testCases = {
            new BitPackingTestCase(0, ints()),
            new BitPackingTestCase(1, ints(0)),
            new BitPackingTestCase(2, ints(1)),
            new BitPackingTestCase(3, ints(0, 1)),
            new BitPackingTestCase(4, ints(2)),
            new BitPackingTestCase(6, ints(1, 2)),
            new BitPackingTestCase(9, ints(0, 3)),
            new BitPackingTestCase(~Long.MAX_VALUE, ints(63)),
            new BitPackingTestCase(~Long.MAX_VALUE + 1, ints(0, 63)),
            new BitPackingTestCase(~Long.MAX_VALUE + 2, ints(1, 63)),
        };
        for (BitPackingTestCase tc : testCases) {
            int[] got = unpackBits(tc.packedBits);
            assertTrue(
                    "unpackBits("
                            + tc.packedBits
                            + "): expected "
                            + Arrays.toString(tc.bits)
                            + " but got "
                            + Arrays.toString(got),
                    Arrays.equals(tc.bits, got));
        }
        for (BitPackingTestCase tc : testCases) {
            long got = packBits(tc.bits);
            assertEquals(
                    "packBits("
                            + Arrays.toString(tc.bits)
                            + "): expected "
                            + tc.packedBits
                            + " but got "
                            + got,
                    tc.packedBits,
                    got);
        }

        long[] moreTestCases = {
            0, 1, -1, 23895, -908235, Long.MAX_VALUE, Long.MIN_VALUE, new Random().nextLong(),
        };
        for (long l : moreTestCases) {
            assertEquals(l, packBits(unpackBits(l)));
        }
    }

    static byte[] bytes(int b1, int b2, int b3, int b4) {
        return new byte[] {b(b1), b(b2), b(b3), b(b4)};
    }

    static byte b(int i) {
        return (byte) i;
    }

    static int[] ints(int... array) {
        return array;
    }

    static class BitPackingTestCase {
        final int[] bits;
        final long packedBits;

        BitPackingTestCase(long packedBits, int[] bits) {
            this.bits = bits;
            this.packedBits = packedBits;
        }
    }
}
