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raid6: Optimize by removing division.

This commit is contained in:
Vladimir Serbinenko 2015-02-26 22:07:22 +01:00
parent f76c98b79e
commit 67a6a9512a
1 changed files with 13 additions and 3 deletions
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16
grub-core/disk/raid6_recover.c
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@ -63,6 +63,16 @@ grub_raid6_init_table (void)
}
}
static unsigned
mod_255 (unsigned x)
{
while (x > 0xff)
x = (x >> 8) + (x & 0xff);
if (x == 0xff)
return 0;
return x;
}
static grub_err_t
grub_raid6_recover (struct grub_diskfilter_segment *array, int disknr, int p,
char *buf, grub_disk_addr_t sector, grub_size_t size)
@ -162,11 +172,11 @@ grub_raid6_recover (struct grub_diskfilter_segment *array, int disknr, int p,
grub_crypto_xor (qbuf, qbuf, buf, size);
c = ((255 ^ bad1)
+ (255 ^ powx_inv[(powx[bad2 + (bad1 ^ 255)] ^ 1)])) % 255;
c = mod_255((255 ^ bad1)
+ (255 ^ powx_inv[(powx[bad2 + (bad1 ^ 255)] ^ 1)]));
grub_raid_block_mulx (c, qbuf, size);
c = ((unsigned) bad2 + c) % 255;
c = mod_255((unsigned) bad2 + c);
grub_raid_block_mulx (c, pbuf, size);
grub_crypto_xor (pbuf, pbuf, qbuf, size);