Module tools.jackson.core

Package tools.jackson.core.io.schubfach

Class MathUtils

java.lang.Object

tools.jackson.core.io.schubfach.MathUtils

public final class MathUtils
extends Object

This class exposes package private utilities for other classes. Thus, all methods are assumed to be invoked with correct arguments, so these are not checked at all.

Author:

Raffaello Giulietti

Field Summary

Fields

Modifier and Type	Field	Description
static final int	H
static final int	K_MAX
static final int	K_MIN

Method Summary

Modifier and Type	Method	Description
static int	flog10pow2(int e)	Returns the unique integer k such that 10k ≤ 2e < 10k+1.
static int	flog10threeQuartersPow2(int e)	Returns the unique integer k such that 10k ≤ 3/4 · 2e < 10k+1.
static int	flog2pow10(int e)	Returns the unique integer k such that 2k ≤ 10e < 2k+1.
static long	g0(int k)	Returns g0 as described in g1(int).
static long	g1(int k)	Let 10-k = β 2r, for the unique pair of integer r and real β meeting 2125 ≤ β < 2126.
static long	pow10(int e)	Returns 10e.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

K_MIN

public static final int K_MIN

See Also:

• Constant Field Values

K_MAX

public static final int K_MAX

See Also:

• Constant Field Values

H

public static final int H

See Also:

• Constant Field Values

Method Details

pow10

public static long pow10(int e)

Returns 10^e.

Parameters:

e - The exponent which must meet 0 ≤ e ≤ H.

Returns:

10^e.

flog10pow2

public static int flog10pow2(int e)

Returns the unique integer k such that 10^k ≤ 2^e < 10^k+1.

The result is correct when |e| ≤ 5_456_721. Otherwise the result is undefined.

Parameters:

e - The exponent of 2, which should meet |e| ≤ 5_456_721 for safe results.

Returns:

⌊log₁₀2^e⌋.

flog10threeQuartersPow2

public static int flog10threeQuartersPow2(int e)

Returns the unique integer k such that 10^k ≤ 3/4 · 2^e < 10^k+1.

The result is correct when -2_956_395 ≤ e ≤ 2_500_325. Otherwise the result is undefined.

Parameters:

e - The exponent of 2, which should meet -2_956_395 ≤ e ≤ 2_500_325 for safe results.

Returns:

⌊log₁₀(3/4 · 2^e)⌋.

flog2pow10

public static int flog2pow10(int e)

Returns the unique integer k such that 2^k ≤ 10^e < 2^k+1.

The result is correct when |e| ≤ 1_838_394. Otherwise the result is undefined.

Parameters:

e - The exponent of 10, which should meet |e| ≤ 1_838_394 for safe results.

Returns:

⌊log₂10^e⌋.

g1

public static long g1(int k)

Let 10^-k = β 2^r, for the unique pair of integer r and real β meeting 2¹²⁵ ≤ β < 2¹²⁶. Further, let g = ⌊β⌋ + 1. Split g into the higher 63 bits g₁ and the lower 63 bits g₀. Thus, g₁ = ⌊g 2^-63⌋ and g₀ = g - g₁ 2⁶³.

This method returns g₁ while g0(int) returns g₀.

If needed, the exponent r can be computed as r = flog2pow10(-k) - 125 (see flog2pow10(int)).

Parameters:

k - The exponent of 10, which must meet K_MIN ≤ e ≤ K_MAX.

Returns:

g₁ as described above.

g0

public static long g0(int k)

Returns g₀ as described in g1(int).

Parameters:

k - The exponent of 10, which must meet K_MIN ≤ e ≤ K_MAX.

Returns:

g₀ as described in g1(int).