Sortable floating point to integer

[electrum]

It is often useful to convert a floating point values to integers in a way that preserves ordering. For example, when converting to a sortable binary key for LevelDB, storing in a SQL database that doesn't handle NaN or infinity, etc.

This trick doesn't seem to be well-publicized, but is used by Lucene, etc.

/**
 * Converts a double value to a sortable long. The value is converted by swapping
 * some bits in the IEEE 754 layout to be able to compare the result as a long.
 *
 * @see #sortableLongToDouble(long)
 */
public static long doubleToSortableLong(double value)
{
    long bits = doubleToLongBits(value);
    return bits ^ ((bits >> 63) & Long.MAX_VALUE);
}

/**
 * Converts a sortable long to double.
 *
 * @see #doubleToSortableLong(double)
 */
public static double sortableLongToDouble(long value)
{
    value ^= (value >> 63) & Long.MAX_VALUE;
    return longBitsToDouble(value);
}

/**
 * Converts a float value to a sortable int. The value is converted by swapping
 * some bits in the IEEE 754 layout to be able to compare the result as a int.
 *
 * @see #sortableIntToFloat(int)
 */
public static int floatToSortableInt(float value)
{
    int bits = floatToIntBits(value);
    return bits ^ ((bits >> 31) & Integer.MAX_VALUE);
}

/**
 * Converts a sortable int to float.
 *
 * @see #floatToSortableInt(float)
 */
public static float sortableIntToFloat(int value)
{
    value ^= (value >> 31) & Integer.MAX_VALUE;
    return intBitsToFloat(value);
}