49 lines
868 B
C
49 lines
868 B
C
// SPDX-License-Identifier: ISC
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#include "y16t_internal.h"
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// rotate/flip a quadrant appropriately
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static void y16t_hilbert_rot(
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uint32_t n,
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uint32_t *x,
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uint32_t *y,
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uint32_t rx,
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uint32_t ry
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) {
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if (ry == 0) {
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if (rx == 1) {
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*x = n-1 - *x;
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*y = n-1 - *y;
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}
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//Swap x and y
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uint32_t t = *x;
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*x = *y;
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*y = t;
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}
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}
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__attribute__((pure))
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uint32_t y16t_hilbert_xy2d(uint32_t n, uint32_t x, uint32_t y) {
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uint32_t rx, ry, s, d=0;
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for (s=n/2; s>0; s/=2) {
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rx = (x & s) > 0;
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ry = (y & s) > 0;
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d += s * s * ((3 * rx) ^ ry);
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y16t_hilbert_rot(n, &x, &y, rx, ry);
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}
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return d;
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}
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void y16t_hilbert_d2xy(uint32_t n, uint32_t d, uint32_t *x, uint32_t *y) {
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uint32_t rx, ry, s, t=d;
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*x = *y = 0;
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for (s=1; s<n; s*=2) {
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rx = 1 & (t/2);
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ry = 1 & (t ^ rx);
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y16t_hilbert_rot(s, x, y, rx, ry);
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*x += s * rx;
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*y += s * ry;
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t /= 4;
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}
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}
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