PlatformMathUtils.java

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 * Copyright (c) 2013, Daniel Murphy
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package org.jbox2d.common;

/**
 * Contains methods from MathUtils that rely on JVM features. These are separated out from
 * MathUtils so that they can be overridden when compiling for GWT.
 */
class PlatformMathUtils {

  private static final float SHIFT23 = 1 << 23;
  private static final float INV_SHIFT23 = 1.0f / SHIFT23;

  public static final float fastPow(float a, float b) {
    float x = Float.floatToRawIntBits(a);
    x *= INV_SHIFT23;
    x -= 127;
    float y = x - (x >= 0 ? (int) x : (int) x - 1);
    b *= x + (y - y * y) * 0.346607f;
    y = b - (b >= 0 ? (int) b : (int) b - 1);
    y = (y - y * y) * 0.33971f;
    return Float.intBitsToFloat((int) ((b + 127 - y) * SHIFT23));
  }
}