140 lines
3.5 KiB
C++
140 lines
3.5 KiB
C++
/*
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* Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
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*
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* This file is part of PortaPack.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#include "utility.hpp"
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#include <cstdint>
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#if 0
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uint32_t gcd(const uint32_t u, const uint32_t v) {
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/* From http://en.wikipedia.org/wiki/Binary_GCD_algorithm */
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if( u == v ) {
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return u;
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}
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if( u == 0 ) {
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return v;
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}
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if( v == 0 ) {
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return u;
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}
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if( ~u & 1 ) {
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if( v & 1 ) {
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return gcd(u >> 1, v);
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} else {
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return gcd(u >> 1, v >> 1) << 1;
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}
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}
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if( ~v & 1 ) {
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return gcd(u, v >> 1);
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}
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if( u > v ) {
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return gcd((u - v) >> 1, v);
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}
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return gcd((v - u) >> 1, u);
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}
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#endif
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float fast_log2(const float val) {
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// Thank you Stack Overflow!
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// http://stackoverflow.com/questions/9411823/fast-log2float-x-implementation-c
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union {
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float val;
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int32_t x;
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} u = { val };
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float log_2 = (((u.x >> 23) & 255) - 128);
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u.x &= ~(255 << 23);
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u.x += (127 << 23);
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log_2 += ((-0.34484843f) * u.val + 2.02466578f) * u.val - 0.67487759f;
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return log_2;
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}
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float fast_pow2(const float val) {
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union {
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float f;
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uint32_t n;
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} u;
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u.n = val * 8388608 + (0x3f800000 - 60801 * 8);
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return u.f;
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}
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float mag2_to_dbv_norm(const float mag2) {
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constexpr float mag2_log2_max = 0.0f; //std::log2(1.0f);
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constexpr float log_mag2_mag_factor = 0.5f;
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constexpr float log2_log10_factor = 0.3010299956639812f; //std::log10(2.0f);
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constexpr float log10_dbv_factor = 20.0f;
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constexpr float mag2_to_db_factor = log_mag2_mag_factor * log2_log10_factor * log10_dbv_factor;
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return (fast_log2(mag2) - mag2_log2_max) * mag2_to_db_factor;
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}
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/* GCD implementation derived from recursive implementation at
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* http://en.wikipedia.org/wiki/Binary_GCD_algorithm
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*/
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static constexpr uint32_t gcd_top(const uint32_t u, const uint32_t v);
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static constexpr uint32_t gcd_larger(const uint32_t u, const uint32_t v) {
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return (u > v) ? gcd_top((u - v) >> 1, v) : gcd_top((v - u) >> 1, u);
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}
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static constexpr uint32_t gcd_u_odd_v_even(const uint32_t u, const uint32_t v) {
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return (~v & 1) ? gcd_top(u, v >> 1) : gcd_larger(u, v);
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}
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static constexpr uint32_t gcd_v_odd(const uint32_t u, const uint32_t v) {
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return (v & 1)
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? gcd_top(u >> 1, v)
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: (gcd_top(u >> 1, v >> 1) << 1);
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}
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static constexpr uint32_t gcd_u_even(const uint32_t u, const uint32_t v) {
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return (~u & 1)
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? gcd_v_odd(u, v)
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: gcd_u_odd_v_even(u, v)
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;
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}
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static constexpr uint32_t gcd_v_zero(const uint32_t u, const uint32_t v) {
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return (v == 0) ? u : gcd_u_even(u, v);
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}
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static constexpr uint32_t gcd_u_zero(const uint32_t u, const uint32_t v) {
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return (u == 0) ? v : gcd_v_zero(u, v);
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}
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static constexpr uint32_t gcd_uv_equal(const uint32_t u, const uint32_t v) {
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return (u == v) ? u : gcd_u_zero(u, v);
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}
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static constexpr uint32_t gcd_top(const uint32_t u, const uint32_t v) {
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return gcd_uv_equal(u, v);
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}
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uint32_t gcd(const uint32_t u, const uint32_t v) {
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return gcd_top(u, v);
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}
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