UnsignedLongs.java
/*
* 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 static com.google.common.base.Preconditions.checkPositionIndexes;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.math.BigInteger;
import java.util.Arrays;
import java.util.Comparator;
/**
* Static utility methods pertaining to {@code long} primitives that interpret values as
* <i>unsigned</i> (that is, any negative value {@code x} is treated as the positive value {@code
* 2^64 + x}). The methods for which signedness is not an issue are in {@link Longs}, as well as
* signed versions of methods for which signedness is an issue.
*
* <p>In addition, this class provides several static methods for converting a {@code long} to a
* {@code String} and a {@code String} to a {@code long} that treat the {@code long} as an unsigned
* number.
*
* <p>Users of these utilities must be <i>extremely careful</i> not to mix up signed and unsigned
* {@code long} values. When possible, it is recommended that the {@link UnsignedLong} 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="https://github.com/google/guava/wiki/PrimitivesExplained#unsigned-support">unsigned
* primitive utilities</a>.
*
* @author Louis Wasserman
* @author Brian Milch
* @author Colin Evans
* @since 10.0
*/
@Beta
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class UnsignedLongs {
private UnsignedLongs() {}
public static final long MAX_VALUE = -1L; // Equivalent to 2^64 - 1
/**
* A (self-inverse) bijection which converts the ordering on unsigned longs to the ordering on
* longs, that is, {@code a <= b} as unsigned longs if and only if {@code flip(a) <= flip(b)} as
* signed longs.
*/
private static long flip(long a) {
return a ^ Long.MIN_VALUE;
}
/**
* Compares the two specified {@code long} values, treating them as unsigned values between {@code
* 0} and {@code 2^64 - 1} inclusive.
*
* <p><b>Java 8 users:</b> use {@link Long#compareUnsigned(long, long)} instead.
*
* @param a the first unsigned {@code long} to compare
* @param b the second unsigned {@code long} 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(long a, long b) {
return Longs.compare(flip(a), flip(b));
}
/**
* Returns the least value present in {@code array}, treating values as unsigned.
*
* @param array a <i>nonempty</i> array of unsigned {@code long} 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 long min(long... array) {
checkArgument(array.length > 0);
long min = flip(array[0]);
for (int i = 1; i < array.length; i++) {
long 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 long} 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 long max(long... array) {
checkArgument(array.length > 0);
long max = flip(array[0]);
for (int i = 1; i < array.length; i++) {
long next = flip(array[i]);
if (next > max) {
max = next;
}
}
return flip(max);
}
/**
* Returns a string containing the supplied unsigned {@code long} 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 long} values, possibly empty
*/
public static String join(String separator, long... 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 long} values <a
* href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
* compares, using {@link #compare(long, long)}), 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 [] < [1L] < [1L, 2L] < [2L] < [1L << 63]}.
*
* <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(long[],
* long[])}.
*/
public static Comparator<long[]> lexicographicalComparator() {
return LexicographicalComparator.INSTANCE;
}
enum LexicographicalComparator implements Comparator<long[]> {
INSTANCE;
@Override
public int compare(long[] left, long[] right) {
int minLength = Math.min(left.length, right.length);
for (int i = 0; i < minLength; i++) {
if (left[i] != right[i]) {
return UnsignedLongs.compare(left[i], right[i]);
}
}
return left.length - right.length;
}
@Override
public String toString() {
return "UnsignedLongs.lexicographicalComparator()";
}
}
/**
* Sorts the array, treating its elements as unsigned 64-bit integers.
*
* @since 23.1
*/
public static void sort(long[] array) {
checkNotNull(array);
sort(array, 0, array.length);
}
/**
* Sorts the array between {@code fromIndex} inclusive and {@code toIndex} exclusive, treating its
* elements as unsigned 64-bit integers.
*
* @since 23.1
*/
public static void sort(long[] 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 64-bit
* integers.
*
* @since 23.1
*/
public static void sortDescending(long[] 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 64-bit integers.
*
* @since 23.1
*/
public static void sortDescending(long[] array, int fromIndex, int toIndex) {
checkNotNull(array);
checkPositionIndexes(fromIndex, toIndex, array.length);
for (int i = fromIndex; i < toIndex; i++) {
array[i] ^= Long.MAX_VALUE;
}
Arrays.sort(array, fromIndex, toIndex);
for (int i = fromIndex; i < toIndex; i++) {
array[i] ^= Long.MAX_VALUE;
}
}
/**
* Returns dividend / divisor, where the dividend and divisor are treated as unsigned 64-bit
* quantities.
*
* <p><b>Java 8 users:</b> use {@link Long#divideUnsigned(long, long)} instead.
*
* @param dividend the dividend (numerator)
* @param divisor the divisor (denominator)
* @throws ArithmeticException if divisor is 0
*/
public static long divide(long dividend, long divisor) {
if (divisor < 0) { // i.e., divisor >= 2^63:
if (compare(dividend, divisor) < 0) {
return 0; // dividend < divisor
} else {
return 1; // dividend >= divisor
}
}
// Optimization - use signed division if dividend < 2^63
if (dividend >= 0) {
return dividend / divisor;
}
/*
* Otherwise, approximate the quotient, check, and correct if necessary. Our approximation is
* guaranteed to be either exact or one less than the correct value. This follows from fact that
* floor(floor(x)/i) == floor(x/i) for any real x and integer i != 0. The proof is not quite
* trivial.
*/
long quotient = ((dividend >>> 1) / divisor) << 1;
long rem = dividend - quotient * divisor;
return quotient + (compare(rem, divisor) >= 0 ? 1 : 0);
}
/**
* Returns dividend % divisor, where the dividend and divisor are treated as unsigned 64-bit
* quantities.
*
* <p><b>Java 8 users:</b> use {@link Long#remainderUnsigned(long, long)} instead.
*
* @param dividend the dividend (numerator)
* @param divisor the divisor (denominator)
* @throws ArithmeticException if divisor is 0
* @since 11.0
*/
public static long remainder(long dividend, long divisor) {
if (divisor < 0) { // i.e., divisor >= 2^63:
if (compare(dividend, divisor) < 0) {
return dividend; // dividend < divisor
} else {
return dividend - divisor; // dividend >= divisor
}
}
// Optimization - use signed modulus if dividend < 2^63
if (dividend >= 0) {
return dividend % divisor;
}
/*
* Otherwise, approximate the quotient, check, and correct if necessary. Our approximation is
* guaranteed to be either exact or one less than the correct value. This follows from the fact
* that floor(floor(x)/i) == floor(x/i) for any real x and integer i != 0. The proof is not
* quite trivial.
*/
long quotient = ((dividend >>> 1) / divisor) << 1;
long rem = dividend - quotient * divisor;
return rem - (compare(rem, divisor) >= 0 ? divisor : 0);
}
/**
* Returns the unsigned {@code long} value represented by the given decimal string.
*
* <p><b>Java 8 users:</b> use {@link Long#parseUnsignedLong(String)} instead.
*
* @throws NumberFormatException if the string does not contain a valid unsigned {@code long}
* value
* @throws NullPointerException if {@code string} is null (in contrast to {@link
* Long#parseLong(String)})
*/
@CanIgnoreReturnValue
public static long parseUnsignedLong(String string) {
return parseUnsignedLong(string, 10);
}
/**
* Returns the unsigned {@code long} value represented by a string with the given radix.
*
* <p><b>Java 8 users:</b> use {@link Long#parseUnsignedLong(String, int)} instead.
*
* @param string the string containing the unsigned {@code long} 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 long} 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
* Long#parseLong(String)})
*/
@CanIgnoreReturnValue
public static long parseUnsignedLong(String string, int radix) {
checkNotNull(string);
if (string.length() == 0) {
throw new NumberFormatException("empty string");
}
if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) {
throw new NumberFormatException("illegal radix: " + radix);
}
int maxSafePos = ParseOverflowDetection.maxSafeDigits[radix] - 1;
long value = 0;
for (int pos = 0; pos < string.length(); pos++) {
int digit = Character.digit(string.charAt(pos), radix);
if (digit == -1) {
throw new NumberFormatException(string);
}
if (pos > maxSafePos && ParseOverflowDetection.overflowInParse(value, digit, radix)) {
throw new NumberFormatException("Too large for unsigned long: " + string);
}
value = (value * radix) + digit;
}
return value;
}
/**
* Returns the unsigned {@code long} value represented by the given string.
*
* <p>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 long}
* value
* @since 13.0
*/
@CanIgnoreReturnValue
public static long decode(String stringValue) {
ParseRequest request = ParseRequest.fromString(stringValue);
try {
return parseUnsignedLong(request.rawValue, request.radix);
} catch (NumberFormatException e) {
NumberFormatException decodeException =
new NumberFormatException("Error parsing value: " + stringValue);
decodeException.initCause(e);
throw decodeException;
}
}
/*
* We move the static constants into this class so ProGuard can inline UnsignedLongs entirely
* unless the user is actually calling a parse method.
*/
private static final class ParseOverflowDetection {
private ParseOverflowDetection() {}
// calculated as 0xffffffffffffffff / radix
static final long[] maxValueDivs = new long[Character.MAX_RADIX + 1];
static final int[] maxValueMods = new int[Character.MAX_RADIX + 1];
static final int[] maxSafeDigits = new int[Character.MAX_RADIX + 1];
static {
BigInteger overflow = new BigInteger("10000000000000000", 16);
for (int i = Character.MIN_RADIX; i <= Character.MAX_RADIX; i++) {
maxValueDivs[i] = divide(MAX_VALUE, i);
maxValueMods[i] = (int) remainder(MAX_VALUE, i);
maxSafeDigits[i] = overflow.toString(i).length() - 1;
}
}
/**
* Returns true if (current * radix) + digit is a number too large to be represented by an
* unsigned long. This is useful for detecting overflow while parsing a string representation of
* a number. Does not verify whether supplied radix is valid, passing an invalid radix will give
* undefined results or an ArrayIndexOutOfBoundsException.
*/
static boolean overflowInParse(long current, int digit, int radix) {
if (current >= 0) {
if (current < maxValueDivs[radix]) {
return false;
}
if (current > maxValueDivs[radix]) {
return true;
}
// current == maxValueDivs[radix]
return (digit > maxValueMods[radix]);
}
// current < 0: high bit is set
return true;
}
}
/**
* Returns a string representation of x, where x is treated as unsigned.
*
* <p><b>Java 8 users:</b> use {@link Long#toUnsignedString(long)} instead.
*/
public static String toString(long x) {
return toString(x, 10);
}
/**
* Returns a string representation of {@code x} for the given radix, where {@code x} is treated as
* unsigned.
*
* <p><b>Java 8 users:</b> use {@link Long#toUnsignedString(long, int)} instead.
*
* @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(long 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);
if (x == 0) {
// Simply return "0"
return "0";
} else if (x > 0) {
return Long.toString(x, radix);
} else {
char[] buf = new char[64];
int i = buf.length;
if ((radix & (radix - 1)) == 0) {
// Radix is a power of two so we can avoid division.
int shift = Integer.numberOfTrailingZeros(radix);
int mask = radix - 1;
do {
buf[--i] = Character.forDigit(((int) x) & mask, radix);
x >>>= shift;
} while (x != 0);
} else {
// Separate off the last digit using unsigned division. That will leave
// a number that is nonnegative as a signed integer.
long quotient;
if ((radix & 1) == 0) {
// Fast path for the usual case where the radix is even.
quotient = (x >>> 1) / (radix >>> 1);
} else {
quotient = divide(x, radix);
}
long rem = x - quotient * radix;
buf[--i] = Character.forDigit((int) rem, radix);
x = quotient;
// Simple modulo/division approach
while (x > 0) {
buf[--i] = Character.forDigit((int) (x % radix), radix);
x /= radix;
}
}
// Generate string
return new String(buf, i, buf.length - i);
}
}
}