/**
* @license Apache-2.0
*
* Copyright (c) 2018 The Stdlib Authors.
*
* 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.
*/

'use strict';

// MODULES //

var getHighWord = require( './../../../../float64/base/get-high-word' );
var EXP_MASK = require( '@stdlib/constants/float64/high-word-exponent-mask' );
var BIAS = require( '@stdlib/constants/float64/exponent-bias' );


// MAIN //

/**
* Returns an integer corresponding to the unbiased exponent of a double-precision floating-point number.
*
* @param {number} x - input value
* @returns {integer32} unbiased exponent
*
* @example
* var exp = exponent( 3.14e-307 ); // => 2**-1019 ~ 1e-307
* // returns -1019
*
* @example
* var exp = exponent( -3.14 );
* // returns 1
*
* @example
* var exp = exponent( 0.0 );
* // returns -1023
*
* @example
* var exp = exponent( NaN );
* // returns 1024
*/
function exponent( x ) {
	// Extract from the input value a higher order word (unsigned 32-bit integer) which contains the exponent:
	var high = getHighWord( x );

	// Apply a mask to isolate only the exponent bits and then shift off all bits which are part of the fraction:
	high = ( high & EXP_MASK ) >>> 20;

	// Remove the bias and return:
	return (high - BIAS)|0; // asm type annotation
}


// EXPORTS //

module.exports = exponent;
