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| 1 | +/* |
| 2 | + * Copyright 2014-2019 Real Logic Ltd. |
| 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 | +package io.rsocket.internal; |
| 17 | + |
| 18 | +import static java.nio.charset.StandardCharsets.UTF_8; |
| 19 | + |
| 20 | +import java.util.concurrent.ThreadLocalRandom; |
| 21 | + |
| 22 | +/** Miscellaneous useful functions for dealing with low level bits and bytes. */ |
| 23 | +public class BitUtil { |
| 24 | + /** Size of a byte in bytes */ |
| 25 | + public static final int SIZE_OF_BYTE = 1; |
| 26 | + |
| 27 | + /** Size of a boolean in bytes */ |
| 28 | + public static final int SIZE_OF_BOOLEAN = 1; |
| 29 | + |
| 30 | + /** Size of a char in bytes */ |
| 31 | + public static final int SIZE_OF_CHAR = 2; |
| 32 | + |
| 33 | + /** Size of a short in bytes */ |
| 34 | + public static final int SIZE_OF_SHORT = 2; |
| 35 | + |
| 36 | + /** Size of an int in bytes */ |
| 37 | + public static final int SIZE_OF_INT = 4; |
| 38 | + |
| 39 | + /** Size of a float in bytes */ |
| 40 | + public static final int SIZE_OF_FLOAT = 4; |
| 41 | + |
| 42 | + /** Size of a long in bytes */ |
| 43 | + public static final int SIZE_OF_LONG = 8; |
| 44 | + |
| 45 | + /** Size of a double in bytes */ |
| 46 | + public static final int SIZE_OF_DOUBLE = 8; |
| 47 | + |
| 48 | + /** Length of the data blocks used by the CPU cache sub-system in bytes. */ |
| 49 | + public static final int CACHE_LINE_LENGTH = 64; |
| 50 | + |
| 51 | + private static final byte[] HEX_DIGIT_TABLE = { |
| 52 | + '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' |
| 53 | + }; |
| 54 | + |
| 55 | + private static final byte[] FROM_HEX_DIGIT_TABLE; |
| 56 | + |
| 57 | + static { |
| 58 | + FROM_HEX_DIGIT_TABLE = new byte[128]; |
| 59 | + |
| 60 | + FROM_HEX_DIGIT_TABLE['0'] = 0x00; |
| 61 | + FROM_HEX_DIGIT_TABLE['1'] = 0x01; |
| 62 | + FROM_HEX_DIGIT_TABLE['2'] = 0x02; |
| 63 | + FROM_HEX_DIGIT_TABLE['3'] = 0x03; |
| 64 | + FROM_HEX_DIGIT_TABLE['4'] = 0x04; |
| 65 | + FROM_HEX_DIGIT_TABLE['5'] = 0x05; |
| 66 | + FROM_HEX_DIGIT_TABLE['6'] = 0x06; |
| 67 | + FROM_HEX_DIGIT_TABLE['7'] = 0x07; |
| 68 | + FROM_HEX_DIGIT_TABLE['8'] = 0x08; |
| 69 | + FROM_HEX_DIGIT_TABLE['9'] = 0x09; |
| 70 | + FROM_HEX_DIGIT_TABLE['a'] = 0x0a; |
| 71 | + FROM_HEX_DIGIT_TABLE['A'] = 0x0a; |
| 72 | + FROM_HEX_DIGIT_TABLE['b'] = 0x0b; |
| 73 | + FROM_HEX_DIGIT_TABLE['B'] = 0x0b; |
| 74 | + FROM_HEX_DIGIT_TABLE['c'] = 0x0c; |
| 75 | + FROM_HEX_DIGIT_TABLE['C'] = 0x0c; |
| 76 | + FROM_HEX_DIGIT_TABLE['d'] = 0x0d; |
| 77 | + FROM_HEX_DIGIT_TABLE['D'] = 0x0d; |
| 78 | + FROM_HEX_DIGIT_TABLE['e'] = 0x0e; |
| 79 | + FROM_HEX_DIGIT_TABLE['E'] = 0x0e; |
| 80 | + FROM_HEX_DIGIT_TABLE['f'] = 0x0f; |
| 81 | + FROM_HEX_DIGIT_TABLE['F'] = 0x0f; |
| 82 | + } |
| 83 | + |
| 84 | + private static final int LAST_DIGIT_MASK = 0b1; |
| 85 | + |
| 86 | + /** |
| 87 | + * Fast method of finding the next power of 2 greater than or equal to the supplied value. |
| 88 | + * |
| 89 | + * <p>If the value is <= 0 then 1 will be returned. |
| 90 | + * |
| 91 | + * <p>This method is not suitable for {@link Integer#MIN_VALUE} or numbers greater than 2^30. |
| 92 | + * |
| 93 | + * @param value from which to search for next power of 2 |
| 94 | + * @return The next power of 2 or the value itself if it is a power of 2 |
| 95 | + */ |
| 96 | + public static int findNextPositivePowerOfTwo(final int value) { |
| 97 | + return 1 << (Integer.SIZE - Integer.numberOfLeadingZeros(value - 1)); |
| 98 | + } |
| 99 | + |
| 100 | + /** |
| 101 | + * Align a value to the next multiple up of alignment. If the value equals an alignment multiple |
| 102 | + * then it is returned unchanged. |
| 103 | + * |
| 104 | + * <p>This method executes without branching. This code is designed to be use in the fast path and |
| 105 | + * should not be used with negative numbers. Negative numbers will result in undefined behaviour. |
| 106 | + * |
| 107 | + * @param value to be aligned up. |
| 108 | + * @param alignment to be used. |
| 109 | + * @return the value aligned to the next boundary. |
| 110 | + */ |
| 111 | + public static int align(final int value, final int alignment) { |
| 112 | + return (value + (alignment - 1)) & -alignment; |
| 113 | + } |
| 114 | + |
| 115 | + /** |
| 116 | + * Generate a byte array from the hex representation of the given byte array. |
| 117 | + * |
| 118 | + * @param buffer to convert from a hex representation (in Big Endian). |
| 119 | + * @return new byte array that is decimal representation of the passed array. |
| 120 | + */ |
| 121 | + public static byte[] fromHexByteArray(final byte[] buffer) { |
| 122 | + final byte[] outputBuffer = new byte[buffer.length >> 1]; |
| 123 | + |
| 124 | + for (int i = 0; i < buffer.length; i += 2) { |
| 125 | + final int hi = FROM_HEX_DIGIT_TABLE[buffer[i]] << 4; |
| 126 | + final int lo = FROM_HEX_DIGIT_TABLE[buffer[i + 1]]; // lgtm [java/index-out-of-bounds] |
| 127 | + outputBuffer[i >> 1] = (byte) (hi | lo); |
| 128 | + } |
| 129 | + |
| 130 | + return outputBuffer; |
| 131 | + } |
| 132 | + |
| 133 | + /** |
| 134 | + * Generate a byte array that is a hex representation of a given byte array. |
| 135 | + * |
| 136 | + * @param buffer to convert to a hex representation. |
| 137 | + * @return new byte array that is hex representation (in Big Endian) of the passed array. |
| 138 | + */ |
| 139 | + public static byte[] toHexByteArray(final byte[] buffer) { |
| 140 | + return toHexByteArray(buffer, 0, buffer.length); |
| 141 | + } |
| 142 | + |
| 143 | + /** |
| 144 | + * Generate a byte array that is a hex representation of a given byte array. |
| 145 | + * |
| 146 | + * @param buffer to convert to a hex representation. |
| 147 | + * @param offset the offset into the buffer. |
| 148 | + * @param length the number of bytes to convert. |
| 149 | + * @return new byte array that is hex representation (in Big Endian) of the passed array. |
| 150 | + */ |
| 151 | + public static byte[] toHexByteArray(final byte[] buffer, final int offset, final int length) { |
| 152 | + final byte[] outputBuffer = new byte[length << 1]; |
| 153 | + |
| 154 | + for (int i = 0; i < (length << 1); i += 2) { |
| 155 | + final byte b = buffer[offset + (i >> 1)]; |
| 156 | + |
| 157 | + outputBuffer[i] = HEX_DIGIT_TABLE[(b >> 4) & 0x0F]; |
| 158 | + outputBuffer[i + 1] = HEX_DIGIT_TABLE[b & 0x0F]; |
| 159 | + } |
| 160 | + |
| 161 | + return outputBuffer; |
| 162 | + } |
| 163 | + |
| 164 | + /** |
| 165 | + * Generate a byte array from a string that is the hex representation of the given byte array. |
| 166 | + * |
| 167 | + * @param string to convert from a hex representation (in Big Endian). |
| 168 | + * @return new byte array holding the decimal representation of the passed array. |
| 169 | + */ |
| 170 | + public static byte[] fromHex(final String string) { |
| 171 | + return fromHexByteArray(string.getBytes(UTF_8)); |
| 172 | + } |
| 173 | + |
| 174 | + /** |
| 175 | + * Generate a string that is the hex representation of a given byte array. |
| 176 | + * |
| 177 | + * @param buffer to convert to a hex representation. |
| 178 | + * @param offset the offset into the buffer. |
| 179 | + * @param length the number of bytes to convert. |
| 180 | + * @return new String holding the hex representation (in Big Endian) of the passed array. |
| 181 | + */ |
| 182 | + public static String toHex(final byte[] buffer, final int offset, final int length) { |
| 183 | + return new String(toHexByteArray(buffer, offset, length), UTF_8); |
| 184 | + } |
| 185 | + |
| 186 | + /** |
| 187 | + * Generate a string that is the hex representation of a given byte array. |
| 188 | + * |
| 189 | + * @param buffer to convert to a hex representation. |
| 190 | + * @return new String holding the hex representation (in Big Endian) of the passed array. |
| 191 | + */ |
| 192 | + public static String toHex(final byte[] buffer) { |
| 193 | + return new String(toHexByteArray(buffer), UTF_8); |
| 194 | + } |
| 195 | + |
| 196 | + /** |
| 197 | + * Is a number even. |
| 198 | + * |
| 199 | + * @param value to check. |
| 200 | + * @return true if the number is even otherwise false. |
| 201 | + */ |
| 202 | + public static boolean isEven(final int value) { |
| 203 | + return (value & LAST_DIGIT_MASK) == 0; |
| 204 | + } |
| 205 | + |
| 206 | + /** |
| 207 | + * Is a value a positive power of 2. |
| 208 | + * |
| 209 | + * @param value to be checked. |
| 210 | + * @return true if the number is a positive power of 2, otherwise false. |
| 211 | + */ |
| 212 | + public static boolean isPowerOfTwo(final int value) { |
| 213 | + return value > 0 && ((value & (~value + 1)) == value); |
| 214 | + } |
| 215 | + |
| 216 | + /** |
| 217 | + * Cycles indices of an array one at a time in a forward fashion |
| 218 | + * |
| 219 | + * @param current value to be incremented. |
| 220 | + * @param max value for the cycle. |
| 221 | + * @return the next value, or zero if max is reached. |
| 222 | + */ |
| 223 | + public static int next(final int current, final int max) { |
| 224 | + int next = current + 1; |
| 225 | + if (next == max) { |
| 226 | + next = 0; |
| 227 | + } |
| 228 | + |
| 229 | + return next; |
| 230 | + } |
| 231 | + |
| 232 | + /** |
| 233 | + * Cycles indices of an array one at a time in a backwards fashion |
| 234 | + * |
| 235 | + * @param current value to be decremented. |
| 236 | + * @param max value of the cycle. |
| 237 | + * @return the next value, or max - 1 if current is zero. |
| 238 | + */ |
| 239 | + public static int previous(final int current, final int max) { |
| 240 | + if (0 == current) { |
| 241 | + return max - 1; |
| 242 | + } |
| 243 | + |
| 244 | + return current - 1; |
| 245 | + } |
| 246 | + |
| 247 | + /** |
| 248 | + * Calculate the shift value to scale a number based on how refs are compressed or not. |
| 249 | + * |
| 250 | + * @param scale of the number reported by Unsafe. |
| 251 | + * @return how many times the number needs to be shifted to the left. |
| 252 | + */ |
| 253 | + public static int calculateShiftForScale(final int scale) { |
| 254 | + if (4 == scale) { |
| 255 | + return 2; |
| 256 | + } else if (8 == scale) { |
| 257 | + return 3; |
| 258 | + } |
| 259 | + |
| 260 | + throw new IllegalArgumentException("unknown pointer size for scale=" + scale); |
| 261 | + } |
| 262 | + |
| 263 | + /** |
| 264 | + * Generate a randomised integer over [{@link Integer#MIN_VALUE}, {@link Integer#MAX_VALUE}]. |
| 265 | + * |
| 266 | + * @return randomised integer suitable as an Id. |
| 267 | + */ |
| 268 | + public static int generateRandomisedId() { |
| 269 | + return ThreadLocalRandom.current().nextInt(); |
| 270 | + } |
| 271 | + |
| 272 | + /** |
| 273 | + * Is an address aligned on a boundary. |
| 274 | + * |
| 275 | + * @param address to be tested. |
| 276 | + * @param alignment boundary the address is tested against. |
| 277 | + * @return true if the address is on the aligned boundary otherwise false. |
| 278 | + * @throws IllegalArgumentException if the alignment is not a power of 2. |
| 279 | + */ |
| 280 | + public static boolean isAligned(final long address, final int alignment) { |
| 281 | + if (!BitUtil.isPowerOfTwo(alignment)) { |
| 282 | + throw new IllegalArgumentException("alignment must be a power of 2: alignment=" + alignment); |
| 283 | + } |
| 284 | + |
| 285 | + return (address & (alignment - 1)) == 0; |
| 286 | + } |
| 287 | +} |
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