297 lines
9.9 KiB
Java
297 lines
9.9 KiB
Java
/*
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* Copyright (C) 2011 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
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* in compliance with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under the
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* License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
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* express or implied. See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.primitives;
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import static com.google.common.base.Preconditions.checkArgument;
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import static com.google.common.base.Preconditions.checkNotNull;
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import java.util.Arrays;
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import java.util.Comparator;
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import com.google.common.annotations.Beta;
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import com.google.common.annotations.GwtCompatible;
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/**
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* Static utility methods pertaining to {@code int} primitives that interpret
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* values as <i>unsigned</i> (that is, any negative value {@code x} is treated
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* as the positive value {@code 2^32 + x}). The methods for which signedness is
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* not an issue are in {@link Ints}, as well as signed versions of methods for
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* which signedness is an issue.
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*
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* <p>
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* In addition, this class provides several static methods for converting an
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* {@code int} to a {@code String} and a {@code String} to an {@code int} that
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* treat the {@code int} as an unsigned number.
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*
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* <p>
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* Users of these utilities must be <i>extremely careful</i> not to mix up
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* signed and unsigned {@code int} values. When possible, it is recommended that
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* the {@link UnsignedInteger} wrapper class be used, at a small efficiency
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* penalty, to enforce the distinction in the type system.
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*
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* <p>
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* See the Guava User Guide article on <a href=
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* "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained#Unsigned_support">
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* unsigned primitive utilities</a>.
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*
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* @author Louis Wasserman
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* @since 11.0
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*/
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@Beta
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@GwtCompatible
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public final class UnsignedInts {
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static final long INT_MASK = 0xffffffffL;
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private UnsignedInts() {
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}
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static int flip(int value) {
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return value ^ Integer.MIN_VALUE;
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}
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/**
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* Compares the two specified {@code int} values, treating them as unsigned
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* values between {@code 0} and {@code 2^32 - 1} inclusive.
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*
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* @param a the first unsigned {@code int} to compare
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* @param b the second unsigned {@code int} to compare
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* @return a negative value if {@code a} is less than {@code b}; a positive
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* value if {@code a} is greater than {@code b}; or zero if they are
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* equal
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*/
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public static int compare(int a, int b) {
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return Ints.compare(flip(a), flip(b));
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}
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/**
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* Returns the value of the given {@code int} as a {@code long}, when treated as
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* unsigned.
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*/
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public static long toLong(int value) {
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return value & INT_MASK;
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}
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/**
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* Returns the least value present in {@code array}, treating values as
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* unsigned.
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*
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* @param array a <i>nonempty</i> array of unsigned {@code int} values
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* @return the value present in {@code array} that is less than or equal to
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* every other value in the array according to {@link #compare}
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* @throws IllegalArgumentException if {@code array} is empty
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*/
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public static int min(int... array) {
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checkArgument(array.length > 0);
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int min = flip(array[0]);
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for (int i = 1; i < array.length; i++) {
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int next = flip(array[i]);
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if (next < min) {
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min = next;
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}
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}
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return flip(min);
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}
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/**
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* Returns the greatest value present in {@code array}, treating values as
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* unsigned.
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*
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* @param array a <i>nonempty</i> array of unsigned {@code int} values
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* @return the value present in {@code array} that is greater than or equal to
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* every other value in the array according to {@link #compare}
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* @throws IllegalArgumentException if {@code array} is empty
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*/
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public static int max(int... array) {
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checkArgument(array.length > 0);
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int max = flip(array[0]);
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for (int i = 1; i < array.length; i++) {
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int next = flip(array[i]);
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if (next > max) {
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max = next;
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}
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}
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return flip(max);
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}
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/**
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* Returns a string containing the supplied unsigned {@code int} values
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* separated by {@code separator}. For example, {@code join("-", 1, 2, 3)}
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* returns the string {@code "1-2-3"}.
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*
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* @param separator the text that should appear between consecutive values in
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* the resulting string (but not at the start or end)
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* @param array an array of unsigned {@code int} values, possibly empty
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*/
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public static String join(String separator, int... array) {
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checkNotNull(separator);
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if (array.length == 0) {
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return "";
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}
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// For pre-sizing a builder, just get the right order of magnitude
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StringBuilder builder = new StringBuilder(array.length * 5);
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builder.append(toString(array[0]));
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for (int i = 1; i < array.length; i++) {
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builder.append(separator).append(toString(array[i]));
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}
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return builder.toString();
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}
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/**
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* Returns a comparator that compares two arrays of unsigned {@code int} values
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* lexicographically. That is, it compares, using {@link #compare(int, int)}),
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* the first pair of values that follow any common prefix, or when one array is
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* a prefix of the other, treats the shorter array as the lesser. For example,
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* {@code [] < [1] < [1, 2] < [2] < [1 << 31]}.
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*
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* <p>
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* The returned comparator is inconsistent with {@link Object#equals(Object)}
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* (since arrays support only identity equality), but it is consistent with
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* {@link Arrays#equals(int[], int[])}.
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*
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* @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
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* Lexicographical order article at Wikipedia</a>
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*/
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public static Comparator<int[]> lexicographicalComparator() {
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return LexicographicalComparator.INSTANCE;
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}
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enum LexicographicalComparator implements Comparator<int[]> {
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INSTANCE;
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@Override
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public int compare(int[] left, int[] right) {
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int minLength = Math.min(left.length, right.length);
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for (int i = 0; i < minLength; i++) {
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if (left[i] != right[i]) {
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return UnsignedInts.compare(left[i], right[i]);
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}
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}
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return left.length - right.length;
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}
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}
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/**
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* Returns dividend / divisor, where the dividend and divisor are treated as
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* unsigned 32-bit quantities.
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*
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* @param dividend the dividend (numerator)
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* @param divisor the divisor (denominator)
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* @throws ArithmeticException if divisor is 0
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*/
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public static int divide(int dividend, int divisor) {
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return (int) (toLong(dividend) / toLong(divisor));
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}
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/**
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* Returns dividend % divisor, where the dividend and divisor are treated as
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* unsigned 32-bit quantities.
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*
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* @param dividend the dividend (numerator)
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* @param divisor the divisor (denominator)
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* @throws ArithmeticException if divisor is 0
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*/
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public static int remainder(int dividend, int divisor) {
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return (int) (toLong(dividend) % toLong(divisor));
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}
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/**
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* Returns the unsigned {@code int} value represented by the given string.
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*
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* Accepts a decimal, hexadecimal, or octal number given by specifying the
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* following prefix:
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*
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* <ul>
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* <li>{@code 0x}<i>HexDigits</i>
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* <li>{@code 0X}<i>HexDigits</i>
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* <li>{@code #}<i>HexDigits</i>
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* <li>{@code 0}<i>OctalDigits</i>
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* </ul>
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*
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* @throws NumberFormatException if the string does not contain a valid unsigned
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* {@code int} value
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* @since 13.0
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*/
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public static int decode(String stringValue) {
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ParseRequest request = ParseRequest.fromString(stringValue);
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try {
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return parseUnsignedInt(request.rawValue, request.radix);
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} catch (NumberFormatException e) {
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NumberFormatException decodeException = new NumberFormatException("Error parsing value: " + stringValue);
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decodeException.initCause(e);
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throw decodeException;
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}
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}
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/**
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* Returns the unsigned {@code int} value represented by the given decimal
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* string.
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*
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* @throws NumberFormatException if the string does not contain a valid unsigned
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* {@code int} value
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* @throws NullPointerException if {@code s} is null (in contrast to
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* {@link Integer#parseInt(String)})
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*/
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public static int parseUnsignedInt(String s) {
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return parseUnsignedInt(s, 10);
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}
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/**
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* Returns the unsigned {@code int} value represented by a string with the given
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* radix.
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*
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* @param string the string containing the unsigned integer representation to be
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* parsed.
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* @param radix the radix to use while parsing {@code s}; must be between
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* {@link Character#MIN_RADIX} and {@link Character#MAX_RADIX}.
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* @throws NumberFormatException if the string does not contain a valid unsigned
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* {@code int}, or if supplied radix is invalid.
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* @throws NullPointerException if {@code s} is null (in contrast to
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* {@link Integer#parseInt(String)})
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*/
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public static int parseUnsignedInt(String string, int radix) {
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checkNotNull(string);
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long result = Long.parseLong(string, radix);
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if ((result & INT_MASK) != result) {
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throw new NumberFormatException(
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"Input " + string + " in base " + radix + " is not in the range of an unsigned integer");
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}
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return (int) result;
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}
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/**
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* Returns a string representation of x, where x is treated as unsigned.
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*/
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public static String toString(int x) {
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return toString(x, 10);
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}
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/**
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* Returns a string representation of {@code x} for the given radix, where
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* {@code x} is treated as unsigned.
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*
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* @param x the value to convert to a string.
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* @param radix the radix to use while working with {@code x}
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* @throws IllegalArgumentException if {@code radix} is not between
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* {@link Character#MIN_RADIX} and
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* {@link Character#MAX_RADIX}.
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*/
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public static String toString(int x, int radix) {
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long asLong = x & INT_MASK;
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return Long.toString(asLong, radix);
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}
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}
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