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* @license Apache-2.0
*
* Copyright (c) 2026 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.
*
*
* ## Notice
*
* The following copyright and license were part of the original implementation available as part of [FreeBSD]{@link https://svnweb.freebsd.org/base/release/12.2.0/lib/msun/src/e_log10f.c}. The implementation follows the original, but has been modified for JavaScript.
*
* ```text
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ```
*/
'use strict';
// MODULES //
var isnanf = require( '@stdlib/math/base/assert/is-nanf' );
var toWordf = require( '@stdlib/number/float32/base/to-word' );
var fromWordf = require( '@stdlib/number/float32/base/from-word' );
var NINF = require( '@stdlib/constants/float32/ninf' );
var ABS_MASK = require( '@stdlib/constants/float32/abs-mask' );
var FLOAT32_EXPONENT_MASK = require( '@stdlib/constants/float32/exponent-mask' );
var FLOAT32_EXPONENT_BIAS = require( '@stdlib/constants/float32/exponent-bias' );
var FLOAT32_SIGNIFICAND_MASK = require( '@stdlib/constants/float32/significand-mask' );
var kernelLog1pf = require( '@stdlib/math/base/special/kernel-log1pf' );
var f32 = require( '@stdlib/number/float64/base/to-float32' );
// VARIABLES //
// 2^25 = 33554432 => 0 10011000 00000000000000000000000 => 0x4c000000 = 1275068416
var TWO25 = f32( 3.3554432000e+07 );
// 1/ln(10) high part = 4.3432617188e-01 => 0 01111101 10111100110000000000000 => 0x3ede6000 = 1054760960
var IVLN10HI = f32( 4.3432617188e-01 );
// 1/ln(10) low part = -3.1689971365e-05 => 1 01110000 00001001110101011011001 => 0xb804ead9 = -1207637287
var IVLN10LO = f32( -3.1689971365e-05 );
// log10(2) high part = 3.0102920532e-01 => 0 01111101 00110100010000010000000 => 0x3e9a2080 = 1050288256
var LOG10_2HI = f32( 3.0102920532e-01 );
// log10(2) low part = 7.9034151668e-07 => 0 01101010 10101000010011111011011 => 0x355427db = 894707675
var LOG10_2LO = f32( 7.9034151668e-07 );
// 2**-126 => 0 00000001 00000000000000000000000 => 0x00800000 = 8388608
var MIN_NORMAL_WORD = 0x00800000|0; // asm type annotation
// 1.0 => 0 01111111 00000000000000000000000 => 0x3f800000 = 1065353216
var ONE_WORD = 0x3f800000|0; // asm type annotation
// Normalization offset:
var NORM_OFFSET = 0x4afb0d|0; // asm type annotation
// High word mask:
var HI_MASK = 0xfffff000|0; // asm type annotation
// MAIN //
/**
* Evaluates the common logarithm (base ten) of a single-precision floating-point number.
*
* @param {number} x - input value
* @returns {number} function value
*
* @example
* var v = log10f( 4.0 );
* // returns ~0.602
*
* @example
* var v = log10f( 8.0 );
* // returns ~0.903
*
* @example
* var v = log10f( 0.0 );
* // returns -Infinity
*
* @example
* var v = log10f( Infinity );
* // returns Infinity
*
* @example
* var v = log10f( NaN );
* // returns NaN
*
* @example
* var v = log10f( -4.0 );
* // returns NaN
*/
function log10f( x ) {
var hfsq;
var hi;
var hx;
var lo;
var f;
var i;
var k;
var r;
var y;
if ( isnanf( x ) || x < 0.0 ) {
return NaN;
}
x = f32( x );
hx = toWordf( x ) |0; // asm type annotation
k = 0;
// x < 2**-126
if ( hx < MIN_NORMAL_WORD ) {
if ( ( hx & ABS_MASK ) === 0 ) {
return NINF;
}
k -= 25;
// Subnormal number, scale up x:
x = f32( x * TWO25 );
hx = toWordf( x ) |0; // asm type annotation
}
if ( hx >= FLOAT32_EXPONENT_MASK ) {
return f32( x + x );
}
if ( hx === ONE_WORD ) {
return 0.0;
}
k += ( ( hx >> 23 ) - FLOAT32_EXPONENT_BIAS );
hx &= FLOAT32_SIGNIFICAND_MASK;
i = ( ( hx + NORM_OFFSET ) & MIN_NORMAL_WORD ) |0; // asm type annotation
// Normalize x or x/2:
x = fromWordf( hx | ( i ^ ONE_WORD ) );
k += ( i >> 23 );
y = f32( k );
f = f32( x - 1.0 );
hfsq = f32( 0.5 * f32( f * f ) );
r = kernelLog1pf( f );
hi = f32( f - hfsq );
hx = toWordf( hi ) |0; // asm type annotation
hi = fromWordf( hx & HI_MASK );
lo = f32( f32( f - hi ) - hfsq + r );
return f32( f32( y * LOG10_2LO ) + f32( f32( f32( lo + hi ) * IVLN10LO ) + f32( f32( lo * IVLN10HI ) + f32( f32( hi * IVLN10HI ) + f32( y * LOG10_2HI ) ) ) ) ); // eslint-disable-line max-len
}
// EXPORTS //
module.exports = log10f;
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