416 lines
14 KiB
Java
416 lines
14 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.math.BigInteger;
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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 long} 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 2^64 + x}). The methods for which signedness is
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* not an issue are in {@link Longs}, 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 a
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* {@code long} to a {@code String} and a {@code String} to a {@code long} that
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* treat the {@code long} 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 long} values. When possible, it is recommended
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* that the {@link UnsignedLong} 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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* @author Brian Milch
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* @author Colin Evans
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* @since 10.0
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*/
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@Beta
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@GwtCompatible
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public final class UnsignedLongs {
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private UnsignedLongs() {
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}
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public static final long MAX_VALUE = -1L; // Equivalent to 2^64 - 1
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/**
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* A (self-inverse) bijection which converts the ordering on unsigned longs to
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* the ordering on longs, that is, {@code a <= b} as unsigned longs if and only
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* if {@code flip(a) <= flip(b)} as signed longs.
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*/
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private static long flip(long a) {
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return a ^ Long.MIN_VALUE;
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}
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/**
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* Compares the two specified {@code long} values, treating them as unsigned
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* values between {@code 0} and {@code 2^64 - 1} inclusive.
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*
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* @param a the first unsigned {@code long} to compare
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* @param b the second unsigned {@code long} 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(long a, long b) {
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return Longs.compare(flip(a), flip(b));
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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 long} 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 long min(long... array) {
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checkArgument(array.length > 0);
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long min = flip(array[0]);
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for (int i = 1; i < array.length; i++) {
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long 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 long} 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 long max(long... array) {
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checkArgument(array.length > 0);
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long max = flip(array[0]);
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for (int i = 1; i < array.length; i++) {
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long 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 long} 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 long} values, possibly empty
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*/
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public static String join(String separator, long... 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 long} values
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* lexicographically. That is, it compares, using {@link #compare(long, long)}),
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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 [] < [1L] < [1L, 2L] < [2L] < [1L << 63]}.
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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(long[], long[])}.
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*
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* @see <a href=
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* "http://en.wikipedia.org/wiki/Lexicographical_order">Lexicographical
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* order article at Wikipedia</a>
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*/
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public static Comparator<long[]> lexicographicalComparator() {
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return LexicographicalComparator.INSTANCE;
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}
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enum LexicographicalComparator implements Comparator<long[]> {
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INSTANCE;
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@Override
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public int compare(long[] left, long[] 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 UnsignedLongs.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 64-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 long divide(long dividend, long divisor) {
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if (divisor < 0) { // i.e., divisor >= 2^63:
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if (compare(dividend, divisor) < 0) {
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return 0; // dividend < divisor
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} else {
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return 1; // dividend >= divisor
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}
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}
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// Optimization - use signed division if dividend < 2^63
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if (dividend >= 0) {
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return dividend / divisor;
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}
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/*
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* Otherwise, approximate the quotient, check, and correct if necessary. Our
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* approximation is guaranteed to be either exact or one less than the correct
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* value. This follows from fact that floor(floor(x)/i) == floor(x/i) for any
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* real x and integer i != 0. The proof is not quite trivial.
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*/
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long quotient = ((dividend >>> 1) / divisor) << 1;
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long rem = dividend - quotient * divisor;
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return quotient + (compare(rem, divisor) >= 0 ? 1 : 0);
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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 64-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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* @since 11.0
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*/
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public static long remainder(long dividend, long divisor) {
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if (divisor < 0) { // i.e., divisor >= 2^63:
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if (compare(dividend, divisor) < 0) {
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return dividend; // dividend < divisor
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} else {
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return dividend - divisor; // dividend >= divisor
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}
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}
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// Optimization - use signed modulus if dividend < 2^63
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if (dividend >= 0) {
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return dividend % divisor;
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}
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/*
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* Otherwise, approximate the quotient, check, and correct if necessary. Our
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* approximation is guaranteed to be either exact or one less than the correct
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* value. This follows from fact that floor(floor(x)/i) == floor(x/i) for any
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* real x and integer i != 0. The proof is not quite trivial.
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*/
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long quotient = ((dividend >>> 1) / divisor) << 1;
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long rem = dividend - quotient * divisor;
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return rem - (compare(rem, divisor) >= 0 ? divisor : 0);
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}
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/**
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* Returns the unsigned {@code long} 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 long} value
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* @throws NullPointerException if {@code s} is null (in contrast to
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* {@link Long#parseLong(String)})
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*/
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public static long parseUnsignedLong(String s) {
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return parseUnsignedLong(s, 10);
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}
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/**
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* Returns the unsigned {@code long} 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 long} value
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* @since 13.0
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*/
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public static long decode(String stringValue) {
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ParseRequest request = ParseRequest.fromString(stringValue);
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try {
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return parseUnsignedLong(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 long} value represented by a string with the
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* given radix.
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*
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* @param s the string containing the unsigned {@code long} representation
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* to be parsed.
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* @param radix the radix to use while parsing {@code s}
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* @throws NumberFormatException if the string does not contain a valid unsigned
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* {@code long} with the given radix, or if
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* {@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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* @throws NullPointerException if {@code s} is null (in contrast to
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* {@link Long#parseLong(String)})
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*/
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public static long parseUnsignedLong(String s, int radix) {
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checkNotNull(s);
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if (s.length() == 0) {
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throw new NumberFormatException("empty string");
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}
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if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) {
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throw new NumberFormatException("illegal radix: " + radix);
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}
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int max_safe_pos = maxSafeDigits[radix] - 1;
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long value = 0;
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for (int pos = 0; pos < s.length(); pos++) {
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int digit = Character.digit(s.charAt(pos), radix);
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if (digit == -1) {
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throw new NumberFormatException(s);
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}
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if (pos > max_safe_pos && overflowInParse(value, digit, radix)) {
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throw new NumberFormatException("Too large for unsigned long: " + s);
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}
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value = (value * radix) + digit;
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}
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return value;
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}
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/**
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* Returns true if (current * radix) + digit is a number too large to be
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* represented by an unsigned long. This is useful for detecting overflow while
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* parsing a string representation of a number. Does not verify whether supplied
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* radix is valid, passing an invalid radix will give undefined results or an
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* ArrayIndexOutOfBoundsException.
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*/
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private static boolean overflowInParse(long current, int digit, int radix) {
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if (current >= 0) {
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if (current < maxValueDivs[radix]) {
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return false;
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}
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if (current > maxValueDivs[radix]) {
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return true;
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}
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// current == maxValueDivs[radix]
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return (digit > maxValueMods[radix]);
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}
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// current < 0: high bit is set
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return true;
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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(long 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(long x, int radix) {
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checkArgument(radix >= Character.MIN_RADIX && radix <= Character.MAX_RADIX,
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"radix (%s) must be between Character.MIN_RADIX and Character.MAX_RADIX", radix);
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if (x == 0) {
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// Simply return "0"
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return "0";
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} else {
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char[] buf = new char[64];
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int i = buf.length;
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if (x < 0) {
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// Separate off the last digit using unsigned division. That will leave
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// a number that is nonnegative as a signed integer.
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long quotient = divide(x, radix);
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long rem = x - quotient * radix;
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buf[--i] = Character.forDigit((int) rem, radix);
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x = quotient;
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}
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// Simple modulo/division approach
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while (x > 0) {
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buf[--i] = Character.forDigit((int) (x % radix), radix);
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x /= radix;
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}
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// Generate string
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return new String(buf, i, buf.length - i);
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}
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}
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// calculated as 0xffffffffffffffff / radix
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private static final long[] maxValueDivs = new long[Character.MAX_RADIX + 1];
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private static final int[] maxValueMods = new int[Character.MAX_RADIX + 1];
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private static final int[] maxSafeDigits = new int[Character.MAX_RADIX + 1];
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static {
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BigInteger overflow = new BigInteger("10000000000000000", 16);
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for (int i = Character.MIN_RADIX; i <= Character.MAX_RADIX; i++) {
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maxValueDivs[i] = divide(MAX_VALUE, i);
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maxValueMods[i] = (int) remainder(MAX_VALUE, i);
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maxSafeDigits[i] = overflow.toString(i).length() - 1;
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}
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}
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}
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