42 lines
2.5 KiB
C
42 lines
2.5 KiB
C
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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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; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ 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; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/bits/morton.h"
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static unsigned long GetOddBits(unsigned long x) {
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x = (x | x >> 000) & 0x5555555555555555;
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x = (x | x >> 001) & 0x3333333333333333;
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x = (x | x >> 002) & 0x0F0F0F0F0F0F0F0F;
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x = (x | x >> 004) & 0x00FF00FF00FF00FF;
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x = (x | x >> 010) & 0x0000FFFF0000FFFF;
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x = (x | x >> 020) & 0x00000000FFFFFFFF;
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return x;
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}
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/**
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* Deinterleaves bits.
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*
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* @param 𝑖 is interleaved index
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* @return deinterleaved coordinate {ax := 𝑦, dx := 𝑥}
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* @see en.wikipedia.org/wiki/Z-order_curve
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*/
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axdx_t(unmorton)(unsigned long i) {
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return (axdx_t){GetOddBits(i >> 1), GetOddBits(i)};
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}
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