| /* |
| * Copyright (C) 2009 The Guava Authors |
| * |
| * 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.google.common.primitives; |
| |
| import static com.google.common.base.Preconditions.checkArgument; |
| import static com.google.common.base.Preconditions.checkNotNull; |
| import static com.google.common.base.Preconditions.checkPositionIndexes; |
| |
| import com.google.common.annotations.Beta; |
| import com.google.common.annotations.GwtIncompatible; |
| import com.google.common.annotations.VisibleForTesting; |
| import com.google.errorprone.annotations.CanIgnoreReturnValue; |
| import java.nio.ByteOrder; |
| import java.util.Arrays; |
| import java.util.Comparator; |
| import sun.misc.Unsafe; |
| |
| /** |
| * Static utility methods pertaining to {@code byte} primitives that interpret values as |
| * <i>unsigned</i> (that is, any negative value {@code b} is treated as the positive value {@code |
| * 256 + b}). The corresponding methods that treat the values as signed are found in {@link |
| * SignedBytes}, and the methods for which signedness is not an issue are in {@link Bytes}. |
| * |
| * <p>See the Guava User Guide article on <a |
| * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>. |
| * |
| * @author Kevin Bourrillion |
| * @author Martin Buchholz |
| * @author Hiroshi Yamauchi |
| * @author Louis Wasserman |
| * @since 1.0 |
| */ |
| @GwtIncompatible |
| public final class UnsignedBytes { |
| private UnsignedBytes() {} |
| |
| /** |
| * The largest power of two that can be represented as an unsigned {@code byte}. |
| * |
| * @since 10.0 |
| */ |
| public static final byte MAX_POWER_OF_TWO = (byte) 0x80; |
| |
| /** |
| * The largest value that fits into an unsigned byte. |
| * |
| * @since 13.0 |
| */ |
| public static final byte MAX_VALUE = (byte) 0xFF; |
| |
| private static final int UNSIGNED_MASK = 0xFF; |
| |
| /** |
| * Returns the value of the given byte as an integer, when treated as unsigned. That is, returns |
| * {@code value + 256} if {@code value} is negative; {@code value} itself otherwise. |
| * |
| * <p><b>Java 8 users:</b> use {@link Byte#toUnsignedInt(byte)} instead. |
| * |
| * @since 6.0 |
| */ |
| public static int toInt(byte value) { |
| return value & UNSIGNED_MASK; |
| } |
| |
| /** |
| * Returns the {@code byte} value that, when treated as unsigned, is equal to {@code value}, if |
| * possible. |
| * |
| * @param value a value between 0 and 255 inclusive |
| * @return the {@code byte} value that, when treated as unsigned, equals {@code value} |
| * @throws IllegalArgumentException if {@code value} is negative or greater than 255 |
| */ |
| @CanIgnoreReturnValue |
| public static byte checkedCast(long value) { |
| checkArgument(value >> Byte.SIZE == 0, "out of range: %s", value); |
| return (byte) value; |
| } |
| |
| /** |
| * Returns the {@code byte} value that, when treated as unsigned, is nearest in value to {@code |
| * value}. |
| * |
| * @param value any {@code long} value |
| * @return {@code (byte) 255} if {@code value >= 255}, {@code (byte) 0} if {@code value <= 0}, and |
| * {@code value} cast to {@code byte} otherwise |
| */ |
| public static byte saturatedCast(long value) { |
| if (value > toInt(MAX_VALUE)) { |
| return MAX_VALUE; // -1 |
| } |
| if (value < 0) { |
| return (byte) 0; |
| } |
| return (byte) value; |
| } |
| |
| /** |
| * Compares the two specified {@code byte} values, treating them as unsigned values between 0 and |
| * 255 inclusive. For example, {@code (byte) -127} is considered greater than {@code (byte) 127} |
| * because it is seen as having the value of positive {@code 129}. |
| * |
| * @param a the first {@code byte} to compare |
| * @param b the second {@code byte} to compare |
| * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is |
| * greater than {@code b}; or zero if they are equal |
| */ |
| public static int compare(byte a, byte b) { |
| return toInt(a) - toInt(b); |
| } |
| |
| /** |
| * Returns the least value present in {@code array}. |
| * |
| * @param array a <i>nonempty</i> array of {@code byte} values |
| * @return the value present in {@code array} that is less than or equal to every other value in |
| * the array |
| * @throws IllegalArgumentException if {@code array} is empty |
| */ |
| public static byte min(byte... array) { |
| checkArgument(array.length > 0); |
| int min = toInt(array[0]); |
| for (int i = 1; i < array.length; i++) { |
| int next = toInt(array[i]); |
| if (next < min) { |
| min = next; |
| } |
| } |
| return (byte) min; |
| } |
| |
| /** |
| * Returns the greatest value present in {@code array}. |
| * |
| * @param array a <i>nonempty</i> array of {@code byte} values |
| * @return the value present in {@code array} that is greater than or equal to every other value |
| * in the array |
| * @throws IllegalArgumentException if {@code array} is empty |
| */ |
| public static byte max(byte... array) { |
| checkArgument(array.length > 0); |
| int max = toInt(array[0]); |
| for (int i = 1; i < array.length; i++) { |
| int next = toInt(array[i]); |
| if (next > max) { |
| max = next; |
| } |
| } |
| return (byte) max; |
| } |
| |
| /** |
| * Returns a string representation of x, where x is treated as unsigned. |
| * |
| * @since 13.0 |
| */ |
| @Beta |
| public static String toString(byte x) { |
| return toString(x, 10); |
| } |
| |
| /** |
| * Returns a string representation of {@code x} for the given radix, where {@code x} is treated as |
| * unsigned. |
| * |
| * @param x the value to convert to a string. |
| * @param radix the radix to use while working with {@code x} |
| * @throws IllegalArgumentException if {@code radix} is not between {@link Character#MIN_RADIX} |
| * and {@link Character#MAX_RADIX}. |
| * @since 13.0 |
| */ |
| @Beta |
| public static String toString(byte x, int radix) { |
| checkArgument( |
| radix >= Character.MIN_RADIX && radix <= Character.MAX_RADIX, |
| "radix (%s) must be between Character.MIN_RADIX and Character.MAX_RADIX", |
| radix); |
| // Benchmarks indicate this is probably not worth optimizing. |
| return Integer.toString(toInt(x), radix); |
| } |
| |
| /** |
| * Returns the unsigned {@code byte} value represented by the given decimal string. |
| * |
| * @throws NumberFormatException if the string does not contain a valid unsigned {@code byte} |
| * value |
| * @throws NullPointerException if {@code string} is null (in contrast to {@link |
| * Byte#parseByte(String)}) |
| * @since 13.0 |
| */ |
| @Beta |
| @CanIgnoreReturnValue |
| public static byte parseUnsignedByte(String string) { |
| return parseUnsignedByte(string, 10); |
| } |
| |
| /** |
| * Returns the unsigned {@code byte} value represented by a string with the given radix. |
| * |
| * @param string the string containing the unsigned {@code byte} representation to be parsed. |
| * @param radix the radix to use while parsing {@code string} |
| * @throws NumberFormatException if the string does not contain a valid unsigned {@code byte} with |
| * the given radix, or if {@code radix} is not between {@link Character#MIN_RADIX} and {@link |
| * Character#MAX_RADIX}. |
| * @throws NullPointerException if {@code string} is null (in contrast to {@link |
| * Byte#parseByte(String)}) |
| * @since 13.0 |
| */ |
| @Beta |
| @CanIgnoreReturnValue |
| public static byte parseUnsignedByte(String string, int radix) { |
| int parse = Integer.parseInt(checkNotNull(string), radix); |
| // We need to throw a NumberFormatException, so we have to duplicate checkedCast. =( |
| if (parse >> Byte.SIZE == 0) { |
| return (byte) parse; |
| } else { |
| throw new NumberFormatException("out of range: " + parse); |
| } |
| } |
| |
| /** |
| * Returns a string containing the supplied {@code byte} values separated by {@code separator}. |
| * For example, {@code join(":", (byte) 1, (byte) 2, (byte) 255)} returns the string {@code |
| * "1:2:255"}. |
| * |
| * @param separator the text that should appear between consecutive values in the resulting string |
| * (but not at the start or end) |
| * @param array an array of {@code byte} values, possibly empty |
| */ |
| public static String join(String separator, byte... array) { |
| checkNotNull(separator); |
| if (array.length == 0) { |
| return ""; |
| } |
| |
| // For pre-sizing a builder, just get the right order of magnitude |
| StringBuilder builder = new StringBuilder(array.length * (3 + separator.length())); |
| builder.append(toInt(array[0])); |
| for (int i = 1; i < array.length; i++) { |
| builder.append(separator).append(toString(array[i])); |
| } |
| return builder.toString(); |
| } |
| |
| /** |
| * Returns a comparator that compares two {@code byte} arrays <a |
| * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it |
| * compares, using {@link #compare(byte, byte)}), the first pair of values that follow any common |
| * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For |
| * example, {@code [] < [0x01] < [0x01, 0x7F] < [0x01, 0x80] < [0x02]}. Values are treated as |
| * unsigned. |
| * |
| * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays |
| * support only identity equality), but it is consistent with {@link |
| * java.util.Arrays#equals(byte[], byte[])}. |
| * |
| * @since 2.0 |
| */ |
| public static Comparator<byte[]> lexicographicalComparator() { |
| return LexicographicalComparatorHolder.BEST_COMPARATOR; |
| } |
| |
| @VisibleForTesting |
| static Comparator<byte[]> lexicographicalComparatorJavaImpl() { |
| return LexicographicalComparatorHolder.PureJavaComparator.INSTANCE; |
| } |
| |
| /** |
| * Provides a lexicographical comparator implementation; either a Java implementation or a faster |
| * implementation based on {@link Unsafe}. |
| * |
| * <p>Uses reflection to gracefully fall back to the Java implementation if {@code Unsafe} isn't |
| * available. |
| */ |
| @VisibleForTesting |
| static class LexicographicalComparatorHolder { |
| static final String UNSAFE_COMPARATOR_NAME = |
| LexicographicalComparatorHolder.class.getName() + "$UnsafeComparator"; |
| |
| static final Comparator<byte[]> BEST_COMPARATOR = getBestComparator(); |
| |
| @VisibleForTesting |
| enum UnsafeComparator implements Comparator<byte[]> { |
| INSTANCE; |
| |
| static final boolean BIG_ENDIAN = ByteOrder.nativeOrder().equals(ByteOrder.BIG_ENDIAN); |
| |
| /* |
| * The following static final fields exist for performance reasons. |
| * |
| * In UnsignedBytesBenchmark, accessing the following objects via static final fields is the |
| * fastest (more than twice as fast as the Java implementation, vs ~1.5x with non-final static |
| * fields, on x86_32) under the Hotspot server compiler. The reason is obviously that the |
| * non-final fields need to be reloaded inside the loop. |
| * |
| * And, no, defining (final or not) local variables out of the loop still isn't as good |
| * because the null check on the theUnsafe object remains inside the loop and |
| * BYTE_ARRAY_BASE_OFFSET doesn't get constant-folded. |
| * |
| * The compiler can treat static final fields as compile-time constants and can constant-fold |
| * them while (final or not) local variables are run time values. |
| */ |
| |
| static final Unsafe theUnsafe = getUnsafe(); |
| |
| /** The offset to the first element in a byte array. */ |
| static final int BYTE_ARRAY_BASE_OFFSET = theUnsafe.arrayBaseOffset(byte[].class); |
| |
| static { |
| // fall back to the safer pure java implementation unless we're in |
| // a 64-bit JVM with an 8-byte aligned field offset. |
| if (!("64".equals(System.getProperty("sun.arch.data.model")) |
| && (BYTE_ARRAY_BASE_OFFSET % 8) == 0 |
| // sanity check - this should never fail |
| && theUnsafe.arrayIndexScale(byte[].class) == 1)) { |
| throw new Error(); // force fallback to PureJavaComparator |
| } |
| } |
| |
| /** |
| * Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. Replace with a simple |
| * call to Unsafe.getUnsafe when integrating into a jdk. |
| * |
| * @return a sun.misc.Unsafe |
| */ |
| private static sun.misc.Unsafe getUnsafe() { |
| try { |
| return sun.misc.Unsafe.getUnsafe(); |
| } catch (SecurityException e) { |
| // that's okay; try reflection instead |
| } |
| try { |
| return java.security.AccessController.doPrivileged( |
| new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
| @Override |
| public sun.misc.Unsafe run() throws Exception { |
| Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class; |
| for (java.lang.reflect.Field f : k.getDeclaredFields()) { |
| f.setAccessible(true); |
| Object x = f.get(null); |
| if (k.isInstance(x)) { |
| return k.cast(x); |
| } |
| } |
| throw new NoSuchFieldError("the Unsafe"); |
| } |
| }); |
| } catch (java.security.PrivilegedActionException e) { |
| throw new RuntimeException("Could not initialize intrinsics", e.getCause()); |
| } |
| } |
| |
| @Override |
| public int compare(byte[] left, byte[] right) { |
| final int stride = 8; |
| int minLength = Math.min(left.length, right.length); |
| int strideLimit = minLength & ~(stride - 1); |
| int i; |
| |
| /* |
| * Compare 8 bytes at a time. Benchmarking on x86 shows a stride of 8 bytes is no slower |
| * than 4 bytes even on 32-bit. On the other hand, it is substantially faster on 64-bit. |
| */ |
| for (i = 0; i < strideLimit; i += stride) { |
| long lw = theUnsafe.getLong(left, BYTE_ARRAY_BASE_OFFSET + (long) i); |
| long rw = theUnsafe.getLong(right, BYTE_ARRAY_BASE_OFFSET + (long) i); |
| if (lw != rw) { |
| if (BIG_ENDIAN) { |
| return UnsignedLongs.compare(lw, rw); |
| } |
| |
| /* |
| * We want to compare only the first index where left[index] != right[index]. This |
| * corresponds to the least significant nonzero byte in lw ^ rw, since lw and rw are |
| * little-endian. Long.numberOfTrailingZeros(diff) tells us the least significant |
| * nonzero bit, and zeroing out the first three bits of L.nTZ gives us the shift to get |
| * that least significant nonzero byte. |
| */ |
| int n = Long.numberOfTrailingZeros(lw ^ rw) & ~0x7; |
| return ((int) ((lw >>> n) & UNSIGNED_MASK)) - ((int) ((rw >>> n) & UNSIGNED_MASK)); |
| } |
| } |
| |
| // The epilogue to cover the last (minLength % stride) elements. |
| for (; i < minLength; i++) { |
| int result = UnsignedBytes.compare(left[i], right[i]); |
| if (result != 0) { |
| return result; |
| } |
| } |
| return left.length - right.length; |
| } |
| |
| @Override |
| public String toString() { |
| return "UnsignedBytes.lexicographicalComparator() (sun.misc.Unsafe version)"; |
| } |
| } |
| |
| enum PureJavaComparator implements Comparator<byte[]> { |
| INSTANCE; |
| |
| @Override |
| public int compare(byte[] left, byte[] right) { |
| int minLength = Math.min(left.length, right.length); |
| for (int i = 0; i < minLength; i++) { |
| int result = UnsignedBytes.compare(left[i], right[i]); |
| if (result != 0) { |
| return result; |
| } |
| } |
| return left.length - right.length; |
| } |
| |
| @Override |
| public String toString() { |
| return "UnsignedBytes.lexicographicalComparator() (pure Java version)"; |
| } |
| } |
| |
| /** |
| * Returns the Unsafe-using Comparator, or falls back to the pure-Java implementation if unable |
| * to do so. |
| */ |
| static Comparator<byte[]> getBestComparator() { |
| try { |
| Class<?> theClass = Class.forName(UNSAFE_COMPARATOR_NAME); |
| |
| // yes, UnsafeComparator does implement Comparator<byte[]> |
| @SuppressWarnings("unchecked") |
| Comparator<byte[]> comparator = (Comparator<byte[]>) theClass.getEnumConstants()[0]; |
| return comparator; |
| } catch (Throwable t) { // ensure we really catch *everything* |
| return lexicographicalComparatorJavaImpl(); |
| } |
| } |
| } |
| |
| private static byte flip(byte b) { |
| return (byte) (b ^ 0x80); |
| } |
| |
| /** |
| * Sorts the array, treating its elements as unsigned bytes. |
| * |
| * @since 23.1 |
| */ |
| public static void sort(byte[] array) { |
| checkNotNull(array); |
| sort(array, 0, array.length); |
| } |
| |
| /** |
| * Sorts the array between {@code fromIndex} inclusive and {@code toIndex} exclusive, treating its |
| * elements as unsigned bytes. |
| * |
| * @since 23.1 |
| */ |
| public static void sort(byte[] array, int fromIndex, int toIndex) { |
| checkNotNull(array); |
| checkPositionIndexes(fromIndex, toIndex, array.length); |
| for (int i = fromIndex; i < toIndex; i++) { |
| array[i] = flip(array[i]); |
| } |
| Arrays.sort(array, fromIndex, toIndex); |
| for (int i = fromIndex; i < toIndex; i++) { |
| array[i] = flip(array[i]); |
| } |
| } |
| |
| /** |
| * Sorts the elements of {@code array} in descending order, interpreting them as unsigned 8-bit |
| * integers. |
| * |
| * @since 23.1 |
| */ |
| public static void sortDescending(byte[] array) { |
| checkNotNull(array); |
| sortDescending(array, 0, array.length); |
| } |
| |
| /** |
| * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} |
| * exclusive in descending order, interpreting them as unsigned 8-bit integers. |
| * |
| * @since 23.1 |
| */ |
| public static void sortDescending(byte[] array, int fromIndex, int toIndex) { |
| checkNotNull(array); |
| checkPositionIndexes(fromIndex, toIndex, array.length); |
| for (int i = fromIndex; i < toIndex; i++) { |
| array[i] ^= Byte.MAX_VALUE; |
| } |
| Arrays.sort(array, fromIndex, toIndex); |
| for (int i = fromIndex; i < toIndex; i++) { |
| array[i] ^= Byte.MAX_VALUE; |
| } |
| } |
| } |