/*
* Copyright (C) 2011 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 com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import java.util.Arrays;
import java.util.Comparator;
/**
* Static utility methods pertaining to {@code int} primitives that interpret values as
* <i>unsigned</i> (that is, any negative value {@code x} is treated as the positive value
* {@code 2^32 + x}). The methods for which signedness is not an issue are in {@link Ints}, as well
* as signed versions of methods for which signedness is an issue.
*
* <p>In addition, this class provides several static methods for converting an {@code int} to a
* {@code String} and a {@code String} to an {@code int} that treat the {@code int} as an unsigned
* number.
*
* <p>Users of these utilities must be <i>extremely careful</i> not to mix up signed and unsigned
* {@code int} values. When possible, it is recommended that the {@link UnsignedInteger} wrapper
* class be used, at a small efficiency penalty, to enforce the distinction in the type system.
*
* <p>See the Guava User Guide article on <a href=
* "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained#Unsigned_support">
* unsigned primitive utilities</a>.
*
* @author Louis Wasserman
* @since 11.0
*/
@Beta
@GwtCompatible
public final class UnsignedInts {
static final long INT_MASK = 0xffffffffL;
private UnsignedInts() {}
static int flip(int value) {
return value ^ Integer.MIN_VALUE;
}
/**
* Compares the two specified {@code int} values, treating them as unsigned values between
* {@code 0} and {@code 2^32 - 1} inclusive.
*
* @param a the first unsigned {@code int} to compare
* @param b the second unsigned {@code int} 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(int a, int b) {
return Ints.compare(flip(a), flip(b));
}
/**
* Returns the value of the given {@code int} as a {@code long}, when treated as unsigned.
*/
public static long toLong(int value) {
return value & INT_MASK;
}
/**
* Returns the least value present in {@code array}, treating values as unsigned.
*
* @param array a <i>nonempty</i> array of unsigned {@code int} values
* @return the value present in {@code array} that is less than or equal to every other value in
* the array according to {@link #compare}
* @throws IllegalArgumentException if {@code array} is empty
*/
public static int min(int... array) {
checkArgument(array.length > 0);
int min = flip(array[0]);
for (int i = 1; i < array.length; i++) {
int next = flip(array[i]);
if (next < min) {
min = next;
}
}
return flip(min);
}
/**
* Returns the greatest value present in {@code array}, treating values as unsigned.
*
* @param array a <i>nonempty</i> array of unsigned {@code int} values
* @return the value present in {@code array} that is greater than or equal to every other value
* in the array according to {@link #compare}
* @throws IllegalArgumentException if {@code array} is empty
*/
public static int max(int... array) {
checkArgument(array.length > 0);
int max = flip(array[0]);
for (int i = 1; i < array.length; i++) {
int next = flip(array[i]);
if (next > max) {
max = next;
}
}
return flip(max);
}
/**
* Returns a string containing the supplied unsigned {@code int} values separated by
* {@code separator}. For example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}.
*
* @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 unsigned {@code int} values, possibly empty
*/
public static String join(String separator, int... 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 * 5);
builder.append(toString(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 arrays of unsigned {@code int} values lexicographically.
* That is, it compares, using {@link #compare(int, int)}), 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 [] < [1] < [1, 2] < [2] < [1 << 31]}.
*
* <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
* support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}.
*
* @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order"> Lexicographical order
* article at Wikipedia</a>
*/
public static Comparator<int[]> lexicographicalComparator() {
return LexicographicalComparator.INSTANCE;
}
enum LexicographicalComparator implements Comparator<int[]> {
INSTANCE;
@Override
public int compare(int[] left, int[] right) {
int minLength = Math.min(left.length, right.length);
for (int i = 0; i < minLength; i++) {
if (left[i] != right[i]) {
return UnsignedInts.compare(left[i], right[i]);
}
}
return left.length - right.length;
}
}
/**
* Returns dividend / divisor, where the dividend and divisor are treated as unsigned 32-bit
* quantities.
*
* @param dividend the dividend (numerator)
* @param divisor the divisor (denominator)
* @throws ArithmeticException if divisor is 0
*/
public static int divide(int dividend, int divisor) {
return (int) (toLong(dividend) / toLong(divisor));
}
/**
* Returns dividend % divisor, where the dividend and divisor are treated as unsigned 32-bit
* quantities.
*
* @param dividend the dividend (numerator)
* @param divisor the divisor (denominator)
* @throws ArithmeticException if divisor is 0
*/
public static int remainder(int dividend, int divisor) {
return (int) (toLong(dividend) % toLong(divisor));
}
/**
* Returns the unsigned {@code int} value represented by the given string.
*
* Accepts a decimal, hexadecimal, or octal number given by specifying the following prefix:
*
* <ul>
* <li>{@code 0x}<i>HexDigits</i>
* <li>{@code 0X}<i>HexDigits</i>
* <li>{@code #}<i>HexDigits</i>
* <li>{@code 0}<i>OctalDigits</i>
* </ul>
*
* @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
* @since 13.0
*/
public static int decode(String stringValue) {
ParseRequest request = ParseRequest.fromString(stringValue);
try {
return parseUnsignedInt(request.rawValue, request.radix);
} catch (NumberFormatException e) {
NumberFormatException decodeException =
new NumberFormatException("Error parsing value: " + stringValue);
decodeException.initCause(e);
throw decodeException;
}
}
/**
* Returns the unsigned {@code int} value represented by the given decimal string.
*
* @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
* @throws NullPointerException if {@code s} is null
* (in contrast to {@link Integer#parseInt(String)})
*/
public static int parseUnsignedInt(String s) {
return parseUnsignedInt(s, 10);
}
/**
* Returns the unsigned {@code int} value represented by a string with the given radix.
*
* @param string the string containing the unsigned integer representation to be parsed.
* @param radix the radix to use while parsing {@code s}; must be between
* {@link Character#MIN_RADIX} and {@link Character#MAX_RADIX}.
* @throws NumberFormatException if the string does not contain a valid unsigned {@code int}, or
* if supplied radix is invalid.
* @throws NullPointerException if {@code s} is null
* (in contrast to {@link Integer#parseInt(String)})
*/
public static int parseUnsignedInt(String string, int radix) {
checkNotNull(string);
long result = Long.parseLong(string, radix);
if ((result & INT_MASK) != result) {
throw new NumberFormatException("Input " + string + " in base " + radix
+ " is not in the range of an unsigned integer");
}
return (int) result;
}
/**
* Returns a string representation of x, where x is treated as unsigned.
*/
public static String toString(int 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}.
*/
public static String toString(int x, int radix) {
long asLong = x & INT_MASK;
return Long.toString(asLong, radix);
}
}