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/**
* @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 isnan = require( './../../../../base/assert/is-nan' );
var toWords = require( '@stdlib/number/float64/base/to-words' );
var fromWords = require( '@stdlib/number/float64/base/from-words' );
var PINF = require( '@stdlib/constants/float64/pinf' );
var FLOAT64_EXPONENT_BIAS = require( '@stdlib/constants/float64/exponent-bias' );
var FLOAT64_HIGH_WORD_EXPONENT_MASK = require( '@stdlib/constants/float64/high-word-exponent-mask' ); // eslint-disable-line id-length
var FLOAT64_HIGH_WORD_SIGNIFICAND_MASK = require( '@stdlib/constants/float64/high-word-significand-mask' ); // eslint-disable-line id-length
// VARIABLES //
// 4294967295 => 0xffffffff => 11111111111111111111111111111111
var ALL_ONES = 4294967295>>>0; // asm type annotation
// High/low words workspace:
var WORDS = [ 0|0, 0|0 ]; // WARNING: not thread safe
// MAIN //
/**
* Decomposes a double-precision floating-point number into integral and fractional parts, each having the same type and sign as the input value.
*
* @private
* @param {(Array|TypedArray|Object)} out - output array
* @param {number} x - input value
* @returns {(Array|TypedArray|Object)} output array
*
* @example
* var parts = modf( [ 0.0, 0.0 ], 3.14 );
* // returns [ 3.0, 0.14000000000000012 ]
*/
function modf( out, x ) {
var high;
var low;
var exp;
var i;
// Special cases...
if ( x < 1.0 ) {
if ( x < 0.0 ) {
modf( out, -x );
out[ 0 ] *= -1.0;
out[ 1 ] *= -1.0;
return out;
}
if ( x === 0.0 ) { // [ +-0, +-0 ]
out[ 0 ] = x;
out[ 1 ] = x;
return out;
}
out[ 0 ] = 0.0;
out[ 1 ] = x;
return out;
}
if ( isnan( x ) ) {
out[ 0 ] = NaN;
out[ 1 ] = NaN;
return out;
}
if ( x === PINF ) {
out[ 0 ] = PINF;
out[ 1 ] = 0.0;
return out;
}
// Decompose |x|...
// Extract the high and low words:
toWords( WORDS, x );
high = WORDS[ 0 ];
low = WORDS[ 1 ];
// Extract the unbiased exponent from the high word:
exp = ((high & FLOAT64_HIGH_WORD_EXPONENT_MASK) >> 20)|0; // asm type annotation
exp -= FLOAT64_EXPONENT_BIAS|0; // asm type annotation
// Handle smaller values (x < 2**20 = 1048576)...
if ( exp < 20 ) {
i = (FLOAT64_HIGH_WORD_SIGNIFICAND_MASK >> exp)|0; // asm type annotation
// Determine if `x` is integral by checking for significand bits which cannot be exponentiated away...
if ( ((high&i)|low) === 0 ) {
out[ 0 ] = x;
out[ 1 ] = 0.0;
return out;
}
// Turn off all the bits which cannot be exponentiated away:
high &= (~i);
// Generate the integral part:
i = fromWords( high, 0 );
// The fractional part is whatever is leftover:
out[ 0 ] = i;
out[ 1 ] = x - i;
return out;
}
// Check if `x` can even have a fractional part...
if ( exp > 51 ) {
// `x` is integral:
out[ 0 ] = x;
out[ 1 ] = 0.0;
return out;
}
i = ALL_ONES >>> (exp-20);
// Determine if `x` is integral by checking for less significant significand bits which cannot be exponentiated away...
if ( (low&i) === 0 ) {
out[ 0 ] = x;
out[ 1 ] = 0.0;
return out;
}
// Turn off all the bits which cannot be exponentiated away:
low &= (~i);
// Generate the integral part:
i = fromWords( high, low );
// The fractional part is whatever is leftover:
out[ 0 ] = i;
out[ 1 ] = x - i;
return out;
}
// EXPORTS //
module.exports = modf;
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