Removed DoubleMath from geometry package and inlined the one function that was

actually ever being invoked into S2.java.
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=24952377

4 files changed, 49 insertions, 155 deletions

diff --git a/src/com/google/common/geometry/DoubleMath.java b/src/com/google/common/geometry/DoubleMath.java
deleted file mode 100644
index 8d64b06..0000000
--- a/src/com/google/common/geometry/DoubleMath.java
+++ /dev/null
@@ -1,78 +0,0 @@
-/*
- * Copyright 2005 Google Inc.
- *
- * 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.geometry;
-
-/**
- * Defines the Java equivalent of a couple of advanced floating point functions
- * that are available in C.
- *
- */
-strictfp class DoubleMath {
-  /** Number of significant digits in a double */
-  private static final int DIGITS = 52;
-
-  /** A class that represents a double and a magnitude */
-  public static class MantissaExponent implements Comparable<MantissaExponent> {
-    public double mantissa;
-    public int exp;
-
-    /** No instantiation allowed */
-    private MantissaExponent() {
-    }
-
-    @Override
-    public int compareTo(MantissaExponent dm) {
-      return Math.signum(mantissa) * exp < Math.signum(dm.mantissa) * dm.exp ? -1 :
-          Math.signum(mantissa) * exp > Math.signum(dm.mantissa) * dm.exp ? 1 : mantissa
-          < dm.mantissa ? -1 : mantissa > dm.mantissa ? 1 : 0;
-    }
-  }
-
-  /**
-   * If v is non-zero return an integer exp, so that (0.5 <= |v|*2^(-exp) < 1).
-   * this is analogous to the integer part of the return value frexp If v is
-   * zero return 0.
-   */
-  public static int getExp(double v) {
-    if (v == 0) {
-      return 0;
-    }
-    return (int) ((0x7ff0000000000000L & Double.doubleToLongBits(v)) >> DIGITS) - 1022;
-  }
-
-
-  /**
-   * As in C++'s <code>double frexp ( double x , int * exp )</code> from math.h,
-   * this function separates the mantissa and exponent of a floating-point
-   * value.
-   *
-   *  This code certainly does not handle java's non-numerical values (NaN and
-   * the like).
-   */
-  public static MantissaExponent frexp(double v) {
-    MantissaExponent dm = new MantissaExponent();
-    if (v == 0) {
-      dm.mantissa = 0;
-      dm.exp = 0;
-      return dm;
-    }
-    long bits = Double.doubleToLongBits(v);
-    dm.mantissa = Double.longBitsToDouble((0x800fffffffffffffL & bits) | 0x3fe0000000000000L);
-    dm.exp = (int) ((0x7ff0000000000000L & bits) >> DIGITS) - 1022;
-    return dm;
-  }
-
-}
diff --git a/src/com/google/common/geometry/S2.java b/src/com/google/common/geometry/S2.java
index 80a994e..9fc876a 100644
--- a/src/com/google/common/geometry/S2.java
+++ b/src/com/google/common/geometry/S2.java
@@ -15,10 +15,12 @@
  */
 package com.google.common.geometry;
 
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
 
-public strictfp class S2 {
-  // declare some frequently use constants
+public final strictfp class S2 {
+
+  // Declare some frequently used constants
   public static final double M_PI = Math.PI;
   public static final double M_1_PI = 1.0 / Math.PI;
   public static final double M_PI_2 = Math.PI / 2.0;
@@ -35,6 +37,30 @@ public strictfp class S2 {
   public static final int SWAP_MASK = 0x01;
   public static final int INVERT_MASK = 0x02;
 
+  // Number of bits in the mantissa of a double.
+  private static final int EXPONENT_SHIFT = 52;
+  // Mask to extract the exponent from a double.
+  private static final long EXPONENT_MASK = 0x7ff0000000000000L;
+
+  /**
+   * If v is non-zero, return an integer {@code exp} such that
+   * {@code (0.5 <= |v|*2^(-exp) < 1)}. If v is zero, return 0.
+   *
+   * <p>Note that this arguably a bad definition of exponent because it makes
+   * {@code exp(9) == 4}. In decimal this would be like saying that the exponent
+   * of 1234 is 4, when in scientific 'exponent' notation 1234 is
+   * {@code 1.234 x 10^3}.
+   *
+   * TODO(dbeaumont): Replace this with "DoubleUtils.getExponent(v) - 1" ?
+   */
+  @VisibleForTesting
+  static int exp(double v) {
+    if (v == 0) {
+      return 0;
+    }
+    long bits = Double.doubleToLongBits(v);
+    return (int) ((EXPONENT_MASK & bits) >> EXPONENT_SHIFT) - 1022;
+  }
 
   /**
    * kPosToOrientation[pos] -> orientation_modifier
@@ -114,10 +140,10 @@ public strictfp class S2 {
       }
 
       // This code is equivalent to computing a floating-point "level"
-      // value and rounding up. frexp() returns a fraction in the
-      // range [0.5,1) and the corresponding exponent.
-      int level = DoubleMath.frexp(value / ((1 << dim) * deriv)).exp;
-      level = Math.max(0, Math.min(S2CellId.MAX_LEVEL, -((level - 1) >> (dim - 1))));
+      // value and rounding up.
+      int exponent = exp(value / ((1 << dim) * deriv));
+      int level = Math.max(0,
+          Math.min(S2CellId.MAX_LEVEL, -((exponent - 1) >> (dim - 1))));
       // assert (level == S2CellId.MAX_LEVEL || getValue(level) <= value);
       // assert (level == 0 || getValue(level - 1) > value);
       return level;
@@ -137,8 +163,9 @@ public strictfp class S2 {
 
       // This code is equivalent to computing a floating-point "level"
       // value and rounding down.
-      int level = DoubleMath.frexp((1 << dim) * deriv / value).exp;
-      level = Math.max(0, Math.min(S2CellId.MAX_LEVEL, (level - 1) >> (dim - 1)));
+      int exponent = exp((1 << dim) * deriv / value);
+      int level = Math.max(0,
+          Math.min(S2CellId.MAX_LEVEL, ((exponent - 1) >> (dim - 1))));
       // assert (level == 0 || getValue(level) >= value);
       // assert (level == S2CellId.MAX_LEVEL || getValue(level + 1) < value);
       return level;
diff --git a/tests/com/google/common/geometry/DoubleMathTest.java b/tests/com/google/common/geometry/DoubleMathTest.java
deleted file mode 100644
index 0443426..0000000
--- a/tests/com/google/common/geometry/DoubleMathTest.java
+++ /dev/null
@@ -1,69 +0,0 @@
-/*
- * Copyright 2005 Google Inc.
- *
- * 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.geometry;
-
-import com.google.common.geometry.DoubleMath.MantissaExponent;
-
-import junit.framework.TestCase;
-
-import java.util.Random;
-
-/**
- * Tests the advanced floating point operations defined in DoubleMath.java.
- *
- */
-public class DoubleMathTest extends TestCase {
-
-  Random rnd = new Random(12345);
-
-  public void testFrexp() {
-    for (int i = 0; i < 10; ++i) {
-      MantissaExponent me = DoubleMath.frexp(Math.pow(2, i));
-      assertEquals(0.5, me.mantissa);
-      assertEquals(i + 1, me.exp);
-    }
-
-    for (int i = 0; i < 10; ++i) {
-      MantissaExponent me = DoubleMath.frexp(-Math.pow(2, i));
-      assertEquals(-0.5, me.mantissa);
-      assertEquals(i + 1, me.exp);
-    }
-
-    MantissaExponent me = DoubleMath.frexp(0);
-    assertEquals(0.0, me.mantissa);
-    assertEquals(0, me.exp);
-
-    me = DoubleMath.frexp(3);
-    assertEquals(0.75, me.mantissa);
-    assertEquals(2, me.exp);
-
-    me = DoubleMath.frexp(5);
-    assertEquals(0.625, me.mantissa);
-    assertEquals(3, me.exp);
-  }
-
-  public void testCompareTo() {
-    for (int i = 0; i < 100; ++i) {
-      double x = rnd.nextDouble() * 100 - 50;
-      double y = rnd.nextDouble() * 100 - 50;
-      MantissaExponent m1 = DoubleMath.frexp(x);
-      MantissaExponent m2 = DoubleMath.frexp(y);
-
-      assertEquals(new Double(x).compareTo(y), m1.compareTo(m2));
-    }
-  }
-}
diff --git a/tests/com/google/common/geometry/S2Test.java b/tests/com/google/common/geometry/S2Test.java
index f94f594..6b90661 100644
--- a/tests/com/google/common/geometry/S2Test.java
+++ b/tests/com/google/common/geometry/S2Test.java
@@ -302,4 +302,18 @@ public strictfp class S2Test extends GeometryTestCase {
       assertEquals(S2Projections.MIN_AREA.getClosestLevel(0.8 * area1), expectedLevel);
     }
   }
+
+  public void testExp() {
+    for (int i = 0; i < 10; ++i) {
+      assertEquals(i + 1, S2.exp(Math.pow(2, i)));
+    }
+
+    for (int i = 0; i < 10; ++i) {
+      assertEquals(i + 1, S2.exp(-Math.pow(2, i)));
+    }
+
+    assertEquals(0, S2.exp(0));
+    assertEquals(2, S2.exp(3));
+    assertEquals(3, S2.exp(5));
+  }
 }