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Fold LIBC_BITS into LIBC_INTRIN

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Justine Tunney 2022-08-11 12:13:18 -07:00
parent 625aa365f1
commit 05b8f82371
603 changed files with 1071 additions and 1211 deletions
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76
libc/intrin/hilbert.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/intrin/hilbert.h"
static axdx_t RotateQuadrant(long n, long y, long x, long ry, long rx) {
long t;
if (ry == 0) {
if (rx == 1) {
y = n - 1 - y;
x = n - 1 - x;
}
t = x;
x = y;
y = t;
}
return (axdx_t){y, x};
}
/**
* Generates Hilbert space-filling curve.
*
* @see https://en.wikipedia.org/wiki/Hilbert_curve
* @see unhilbert()
*/
long hilbert(long n, long y, long x) {
axdx_t m;
long d, s, ry, rx;
d = 0;
for (s = n / 2; s > 0; s /= 2) {
ry = (y & s) > 0;
rx = (x & s) > 0;
d += s * s * ((3 * rx) ^ ry);
m = RotateQuadrant(n, y, x, ry, rx);
y = m.ax;
x = m.dx;
}
return d;
}
/**
* Decodes Hilbert space-filling curve.
*
* @see https://en.wikipedia.org/wiki/Hilbert_curve
* @see hilbert()
*/
axdx_t unhilbert(long n, long i) {
axdx_t m;
long s, t, y, x, ry, rx;
t = i;
x = y = 0;
for (s = 1; s < n; s *= 2) {
rx = (t / 2) & 1;
ry = (t ^ rx) & 1;
m = RotateQuadrant(s, y, x, ry, rx);
x = m.dx + s * rx;
y = m.ax + s * ry;
t /= 4;
}
return (axdx_t){y, x};
}