1/*
2 * Copyright (C) 2017 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17
18package com.android.internal.util;
19
20import android.annotation.Nullable;
21import android.text.TextUtils;
22
23import libcore.util.Objects;
24
25import java.nio.ByteBuffer;
26import java.util.Arrays;
27import java.util.UUID;
28import java.util.function.IntFunction;
29
30/**
31 * A utility class for handling unsigned integers and unsigned arithmetics, as well as syntactic
32 * sugar methods for ByteBuffer. Useful for networking and packet manipulations.
33 * {@hide}
34 */
35public final class BitUtils {
36    private BitUtils() {}
37
38    public static boolean maskedEquals(long a, long b, long mask) {
39        return (a & mask) == (b & mask);
40    }
41
42    public static boolean maskedEquals(byte a, byte b, byte mask) {
43        return (a & mask) == (b & mask);
44    }
45
46    public static boolean maskedEquals(byte[] a, byte[] b, @Nullable byte[] mask) {
47        if (a == null || b == null) return a == b;
48        Preconditions.checkArgument(a.length == b.length, "Inputs must be of same size");
49        if (mask == null) return Arrays.equals(a, b);
50        Preconditions.checkArgument(a.length == mask.length, "Mask must be of same size as inputs");
51        for (int i = 0; i < mask.length; i++) {
52            if (!maskedEquals(a[i], b[i], mask[i])) return false;
53        }
54        return true;
55    }
56
57    public static boolean maskedEquals(UUID a, UUID b, @Nullable UUID mask) {
58        if (mask == null) {
59            return Objects.equal(a, b);
60        }
61        return maskedEquals(a.getLeastSignificantBits(), b.getLeastSignificantBits(),
62                    mask.getLeastSignificantBits())
63                && maskedEquals(a.getMostSignificantBits(), b.getMostSignificantBits(),
64                    mask.getMostSignificantBits());
65    }
66
67    public static int[] unpackBits(long val) {
68        int size = Long.bitCount(val);
69        int[] result = new int[size];
70        int index = 0;
71        int bitPos = 0;
72        while (val > 0) {
73            if ((val & 1) == 1) result[index++] = bitPos;
74            val = val >> 1;
75            bitPos++;
76        }
77        return result;
78    }
79
80    public static long packBits(int[] bits) {
81        long packed = 0;
82        for (int b : bits) {
83            packed |= (1 << b);
84        }
85        return packed;
86    }
87
88    public static int uint8(byte b) {
89        return b & 0xff;
90    }
91
92    public static int uint16(short s) {
93        return s & 0xffff;
94    }
95
96    public static long uint32(int i) {
97        return i & 0xffffffffL;
98    }
99
100    public static int bytesToBEInt(byte[] bytes) {
101        return (uint8(bytes[0]) << 24)
102                + (uint8(bytes[1]) << 16)
103                + (uint8(bytes[2]) << 8)
104                + (uint8(bytes[3]));
105    }
106
107    public static int bytesToLEInt(byte[] bytes) {
108        return Integer.reverseBytes(bytesToBEInt(bytes));
109    }
110
111    public static int getUint8(ByteBuffer buffer, int position) {
112        return uint8(buffer.get(position));
113    }
114
115    public static int getUint16(ByteBuffer buffer, int position) {
116        return uint16(buffer.getShort(position));
117    }
118
119    public static long getUint32(ByteBuffer buffer, int position) {
120        return uint32(buffer.getInt(position));
121    }
122
123    public static void put(ByteBuffer buffer, int position, byte[] bytes) {
124        final int original = buffer.position();
125        buffer.position(position);
126        buffer.put(bytes);
127        buffer.position(original);
128    }
129
130    public static boolean isBitSet(long flags, int bitIndex) {
131        return (flags & bitAt(bitIndex)) != 0;
132    }
133
134    public static long bitAt(int bitIndex) {
135        return 1L << bitIndex;
136    }
137
138    public static String flagsToString(int flags, IntFunction<String> getFlagName) {
139        StringBuilder builder = new StringBuilder();
140        int count = 0;
141        while (flags != 0) {
142            final int flag = 1 << Integer.numberOfTrailingZeros(flags);
143            flags &= ~flag;
144            if (count > 0) builder.append(", ");
145            builder.append(getFlagName.apply(flag));
146            count++;
147        }
148        TextUtils.wrap(builder, "[", "]");
149        return builder.toString();
150    }
151}
152