/*
 * Copyright (c) 2003, 2007, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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/*
 * Portions Copyright IBM Corporation, 1997, 2001. All Rights Reserved.
 */

package java.math;
import java.io.*;

/**
 * Immutable objects which encapsulate the context settings which
 * describe certain rules for numerical operators, such as those
 * implemented by the {@link BigDecimal} class.
 *
 * <p>The base-independent settings are:
 * <ol>
 * <li>{@code precision}:
 * the number of digits to be used for an operation; results are
 * rounded to this precision
 *
 * <li>{@code roundingMode}:
 * a {@link RoundingMode} object which specifies the algorithm to be
 * used for rounding.
 * </ol>
 *
 * @see BigDecimal
 * @see RoundingMode
 * @author Mike Cowlishaw
 * @author Joseph D. Darcy
 * @since 1.5
 */

public final class MathContext implements Serializable {

 /* ----- Constants ----- */

 // defaults for constructors
 private static final int DEFAULT_DIGITS = 9;
 private static final RoundingMode DEFAULT_ROUNDINGMODE = RoundingMode.HALF_UP;
 // Smallest values for digits (Maximum is Integer.MAX_VALUE)
 private static final int MIN_DIGITS = 0;

 // Serialization version
 private static final long serialVersionUID = 5579720004786848255L;

 /* ----- Public Properties ----- */
 /**
 * A {@code MathContext} object whose settings have the values
 * required for unlimited precision arithmetic.
 * The values of the settings are:
 * <code>
 * precision=0 roundingMode=HALF_UP
 * </code>
 */
 public static final MathContext UNLIMITED =
 new MathContext(0, RoundingMode.HALF_UP);

 /**
 * A {@code MathContext} object with a precision setting
 * matching the IEEE 754R Decimal32 format, 7 digits, and a
 * rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}, the
 * IEEE 754R default.
 */
 public static final MathContext DECIMAL32 =
 new MathContext(7, RoundingMode.HALF_EVEN);

 /**
 * A {@code MathContext} object with a precision setting
 * matching the IEEE 754R Decimal64 format, 16 digits, and a
 * rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}, the
 * IEEE 754R default.
 */
 public static final MathContext DECIMAL64 =
 new MathContext(16, RoundingMode.HALF_EVEN);

 /**
 * A {@code MathContext} object with a precision setting
 * matching the IEEE 754R Decimal128 format, 34 digits, and a
 * rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}, the
 * IEEE 754R default.
 */
 public static final MathContext DECIMAL128 =
 new MathContext(34, RoundingMode.HALF_EVEN);

 /* ----- Shared Properties ----- */
 /**
 * The number of digits to be used for an operation. A value of 0
 * indicates that unlimited precision (as many digits as are
 * required) will be used. Note that leading zeros (in the
 * coefficient of a number) are never significant.
 *
 * <p>{@code precision} will always be non-negative.
 *
 * @serial
 */
 final int precision;

 /**
 * The rounding algorithm to be used for an operation.
 *
 * @see RoundingMode
 * @serial
 */
 final RoundingMode roundingMode;

 /* ----- Constructors ----- */

 /**
 * Constructs a new {@code MathContext} with the specified
 * precision and the {@link RoundingMode#HALF_UP HALF_UP} rounding
 * mode.
 *
 * @param setPrecision The non-negative {@code int} precision setting.
 * @throws IllegalArgumentException if the {@code setPrecision} parameter is less
 * than zero.
 */
 public MathContext(int setPrecision) {
 this(setPrecision, DEFAULT_ROUNDINGMODE);
 return;
 }

 /**
 * Constructs a new {@code MathContext} with a specified
 * precision and rounding mode.
 *
 * @param setPrecision The non-negative {@code int} precision setting.
 * @param setRoundingMode The rounding mode to use.
 * @throws IllegalArgumentException if the {@code setPrecision} parameter is less
 * than zero.
 * @throws NullPointerException if the rounding mode argument is {@code null}
 */
 public MathContext(int setPrecision,
 RoundingMode setRoundingMode) {
 if (setPrecision < MIN_DIGITS)
 throw new IllegalArgumentException("Digits < 0");
 if (setRoundingMode == null)
 throw new NullPointerException("null RoundingMode");

 precision = setPrecision;
 roundingMode = setRoundingMode;
 return;
 }

 /**
 * Constructs a new {@code MathContext} from a string.
 *
 * The string must be in the same format as that produced by the
 * {@link #toString} method.
 *
 * <p>An {@code IllegalArgumentException} is thrown if the precision
 * section of the string is out of range ({@code < 0}) or the string is
 * not in the format created by the {@link #toString} method.
 *
 * @param val The string to be parsed
 * @throws IllegalArgumentException if the precision section is out of range
 * or of incorrect format
 * @throws NullPointerException if the argument is {@code null}
 */
 public MathContext(String val) {
 boolean bad = false;
 int setPrecision;
 if (val == null)
 throw new NullPointerException("null String");
 try { // any error here is a string format problem
 if (!val.startsWith("precision=")) throw new RuntimeException();
 int fence = val.indexOf(' '); // could be -1
 int off = 10; // where value starts
 setPrecision = Integer.parseInt(val.substring(10, fence));

 if (!val.startsWith("roundingMode=", fence+1))
 throw new RuntimeException();
 off = fence + 1 + 13;
 String str = val.substring(off, val.length());
 roundingMode = RoundingMode.valueOf(str);
 } catch (RuntimeException re) {
 throw new IllegalArgumentException("bad string format");
 }

 if (setPrecision < MIN_DIGITS)
 throw new IllegalArgumentException("Digits < 0");
 // the other parameters cannot be invalid if we got here
 precision = setPrecision;
 }

 /**
 * Returns the {@code precision} setting.
 * This value is always non-negative.
 *
 * @return an {@code int} which is the value of the {@code precision}
 * setting
 */
 public int getPrecision() {
 return precision;
 }

 /**
 * Returns the roundingMode setting.
 * This will be one of
 * {@link RoundingMode#CEILING},
 * {@link RoundingMode#DOWN},
 * {@link RoundingMode#FLOOR},
 * {@link RoundingMode#HALF_DOWN},
 * {@link RoundingMode#HALF_EVEN},
 * {@link RoundingMode#HALF_UP},
 * {@link RoundingMode#UNNECESSARY}, or
 * {@link RoundingMode#UP}.
 *
 * @return a {@code RoundingMode} object which is the value of the
 * {@code roundingMode} setting
 */

 public RoundingMode getRoundingMode() {
 return roundingMode;
 }

 /**
 * Compares this {@code MathContext} with the specified
 * {@code Object} for equality.
 *
 * @param x {@code Object} to which this {@code MathContext} is to
 * be compared.
 * @return {@code true} if and only if the specified {@code Object} is
 * a {@code MathContext} object which has exactly the same
 * settings as this object
 */
 public boolean equals(Object x){
 MathContext mc;
 if (!(x instanceof MathContext))
 return false;
 mc = (MathContext) x;
 return mc.precision == this.precision
 && mc.roundingMode == this.roundingMode; // no need for .equals()
 }

 /**
 * Returns the hash code for this {@code MathContext}.
 *
 * @return hash code for this {@code MathContext}
 */
 public int hashCode() {
 return this.precision + roundingMode.hashCode() * 59;
 }

 /**
 * Returns the string representation of this {@code MathContext}.
 * The {@code String} returned represents the settings of the
 * {@code MathContext} object as two space-delimited words
 * (separated by a single space character, <tt>'&#92;u0020'</tt>,
 * and with no leading or trailing white space), as follows:
 * <ol>
 * <li>
 * The string {@code "precision="}, immediately followed
 * by the value of the precision setting as a numeric string as if
 * generated by the {@link Integer#toString(int) Integer.toString}
 * method.
 *
 * <li>
 * The string {@code "roundingMode="}, immediately
 * followed by the value of the {@code roundingMode} setting as a
 * word. This word will be the same as the name of the
 * corresponding public constant in the {@link RoundingMode}
 * enum.
 * </ol>
 * <p>
 * For example:
 * <pre>
 * precision=9 roundingMode=HALF_UP
 * </pre>
 *
 * Additional words may be appended to the result of
 * {@code toString} in the future if more properties are added to
 * this class.
 *
 * @return a {@code String} representing the context settings
 */
 public java.lang.String toString() {
 return "precision=" + precision + " " +
 "roundingMode=" + roundingMode.toString();
 }

 // Private methods

 /**
 * Reconstitute the {@code MathContext} instance from a stream (that is,
 * deserialize it).
 *
 * @param s the stream being read.
 */
 private void readObject(java.io.ObjectInputStream s)
 throws java.io.IOException, ClassNotFoundException {
 s.defaultReadObject(); // read in all fields
 // validate possibly bad fields
 if (precision < MIN_DIGITS) {
 String message = "MathContext: invalid digits in stream";
 throw new java.io.StreamCorruptedException(message);
 }
 if (roundingMode == null) {
 String message = "MathContext: null roundingMode in stream";
 throw new java.io.StreamCorruptedException(message);
 }
 }

}