btrfs-progs/raid6.c

/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright 2002-2004 H. Peter Anvin - All Rights Reserved
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
 *   Boston MA 02111-1307, USA; either version 2 of the License, or
 *   (at your option) any later version; incorporated herein by reference.
 *
 * ----------------------------------------------------------------------- */

/*
 * raid6int1.c
 *
 * 1-way unrolled portable integer math RAID-6 instruction set
 *
 * This file was postprocessed using unroll.pl and then ported to userspace
 */
#include <stdint.h>
#include <unistd.h>
#include "kerncompat.h"

/*
 * This is the C data type to use
 */

/* Change this from BITS_PER_LONG if there is something better... */
#if BITS_PER_LONG == 64
# define NBYTES(x) ((x) * 0x0101010101010101UL)
# define NSIZE  8
# define NSHIFT 3
typedef uint64_t unative_t;
#else
# define NBYTES(x) ((x) * 0x01010101U)
# define NSIZE  4
# define NSHIFT 2
typedef uint32_t unative_t;
#endif

/*
 * These sub-operations are separate inlines since they can sometimes be
 * specially optimized using architecture-specific hacks.
 */

/*
 * The SHLBYTE() operation shifts each byte left by 1, *not*
 * rolling over into the next byte
 */
static inline __attribute_const__ unative_t SHLBYTE(unative_t v)
{
	unative_t vv;

	vv = (v << 1) & NBYTES(0xfe);
	return vv;
}

/*
 * The MASK() operation returns 0xFF in any byte for which the high
 * bit is 1, 0x00 for any byte for which the high bit is 0.
 */
static inline __attribute_const__ unative_t MASK(unative_t v)
{
	unative_t vv;

	vv = v & NBYTES(0x80);
	vv = (vv << 1) - (vv >> 7); /* Overflow on the top bit is OK */
	return vv;
}


void raid6_gen_syndrome(int disks, size_t bytes, void **ptrs)
{
	uint8_t **dptr = (uint8_t **)ptrs;
	uint8_t *p, *q;
	int d, z, z0;

	unative_t wd0, wq0, wp0, w10, w20;

	z0 = disks - 3;		/* Highest data disk */
	p = dptr[z0+1];		/* XOR parity */
	q = dptr[z0+2];		/* RS syndrome */

	for ( d = 0 ; d < bytes ; d += NSIZE*1 ) {
		wq0 = wp0 = *(unative_t *)&dptr[z0][d+0*NSIZE];
		for ( z = z0-1 ; z >= 0 ; z-- ) {
			wd0 = *(unative_t *)&dptr[z][d+0*NSIZE];
			wp0 ^= wd0;
			w20 = MASK(wq0);
			w10 = SHLBYTE(wq0);
			w20 &= NBYTES(0x1d);
			w10 ^= w20;
			wq0 = w10 ^ wd0;
		}
		*(unative_t *)&p[d+NSIZE*0] = wp0;
		*(unative_t *)&q[d+NSIZE*0] = wq0;
	}
}