-rw-r--r-- 1080 libmceliece-20241009/crypto_kem/348864/vec/transpose.h raw
/*
  This file is for matrix transposition
*/

#ifndef TRANSPOSE_H
#define TRANSPOSE_H

#include <stdint.h>

/* input: in, a 64x64 matrix over GF(2) */
/* output: out, transpose of in */
static inline void transpose_64x64(uint64_t * out, uint64_t * in)
{
	int i, j, s, d;

	uint64_t x, y;
	uint64_t masks[6][2] = {
	                        {0x5555555555555555, 0xAAAAAAAAAAAAAAAA},
	                        {0x3333333333333333, 0xCCCCCCCCCCCCCCCC},
	                        {0x0F0F0F0F0F0F0F0F, 0xF0F0F0F0F0F0F0F0},
	                        {0x00FF00FF00FF00FF, 0xFF00FF00FF00FF00},
	                        {0x0000FFFF0000FFFF, 0xFFFF0000FFFF0000},
	                        {0x00000000FFFFFFFF, 0xFFFFFFFF00000000}
	                       };

	for (i = 0; i < 64; i++)
		out[i] = in[i];

	for (d = 5; d >= 0; d--)
	{
		s = 1 << d;

		for (i = 0; i < 64; i += s*2)
		for (j = i; j < i+s; j++)
		{
			x = (out[j] & masks[d][0]) | ((out[j+s] & masks[d][0]) << s);
			y = ((out[j] & masks[d][1]) >> s) | (out[j+s] & masks[d][1]);

			out[j+0] = x;
			out[j+s] = y;
		}
	}
}

#endif