1 /*
   2  * Copyright (c) 2003, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.internal.math;
  27 
  28 /**
  29  * This class contains additional constants documenting limits of the
  30  * {@code double} type.
  31  *
  32  * @author Joseph D. Darcy
  33  */
  34 
  35 public class DoubleConsts {
  36     /**
  37      * Don't let anyone instantiate this class.
  38      */
  39     private DoubleConsts() {}
  40 
  41     /**
  42      * The number of logical bits in the significand of a
  43      * {@code double} number, including the implicit bit.
  44      */
  45     public static final int SIGNIFICAND_WIDTH   = 53;
  46 
  47     /**
  48      * The exponent the smallest positive {@code double}
  49      * subnormal value would have if it could be normalized..
  50      */
  51     public static final int     MIN_SUB_EXPONENT = Double.MIN_EXPONENT -
  52                                                    (SIGNIFICAND_WIDTH - 1);
  53 
  54     /**
  55      * Bias used in representing a {@code double} exponent.
  56      */
  57     public static final int     EXP_BIAS        = 1023;
  58 
  59     /**
  60      * Bit mask to isolate the sign bit of a {@code double}.
  61      */
  62     public static final long    SIGN_BIT_MASK   = 0x8000000000000000L;
  63 
  64     /**
  65      * Bit mask to isolate the exponent field of a
  66      * {@code double}.
  67      */
  68     public static final long    EXP_BIT_MASK    = 0x7FF0000000000000L;
  69 
  70     /**
  71      * Bit mask to isolate the significand field of a
  72      * {@code double}.
  73      */
  74     public static final long    SIGNIF_BIT_MASK = 0x000FFFFFFFFFFFFFL;
  75 
  76     static {
  77         // verify bit masks cover all bit positions and that the bit
  78         // masks are non-overlapping
  79         assert(((SIGN_BIT_MASK | EXP_BIT_MASK | SIGNIF_BIT_MASK) == ~0L) &&
  80                (((SIGN_BIT_MASK & EXP_BIT_MASK) == 0L) &&
  81                 ((SIGN_BIT_MASK & SIGNIF_BIT_MASK) == 0L) &&
  82                 ((EXP_BIT_MASK & SIGNIF_BIT_MASK) == 0L)));
  83     }
  84 }