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Optimize scalar 8-bit RAID parity generation and recovery in int.c

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Andrea Mazzoleni 2026-08-27 19:19:31 +02:00
parent 69a1ed1125
commit e0c0ea3dcc
7 changed files with 777 additions and 228 deletions
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60
raid/raid.c
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@ -413,63 +413,3 @@ void raid_rec1of1(int *id, int nd, size_t size, void **v)
v[id[0]] = pa;
v[nd] = p;
}
/**
* Recover failure of two data blocks for PAR2.
*
* Starting from the equations:
*
* Pd = Dx + Dy
* Qd = g^id[0] * Dx + g^id[1] * Dy
*
* and solving we get:
*
* 1 g^(-id[0])
* Dy = ------------------- * Pd + ------------------- * Qd
* g^(id[1]-id[0]) + 1 g^(id[1]-id[0]) + 1
*
* Dx = Dy + Pd
*
* with conditions:
*
* g^id[0] != 0
* g^(id[1]-id[0]) + 1 != 0
*
* That are always satisfied for any 0<=id[0]<id[1]<255.
*/
void raid_rec2of2_int8(int *id, int *ip, int nd, size_t size, void **vv)
{
uint8_t **v = (uint8_t **)vv;
size_t i;
uint8_t *p;
uint8_t *pa;
uint8_t *q;
uint8_t *qa;
const uint8_t *T[2];
/* get multiplication tables */
T[0] = table(inv(powgen(id[1] - id[0]) ^ 1));
T[1] = table(inv(powgen(id[0]) ^ powgen(id[1])));
/* compute delta parity */
raid_delta_gen(2, id, ip, nd, size, vv);
p = v[nd];
q = v[nd + 1];
pa = v[id[0]];
qa = v[id[1]];
for (i = 0; i < size; ++i) {
/* delta */
uint8_t Pd = p[i] ^ pa[i];
uint8_t Qd = q[i] ^ qa[i];
/* reconstruct */
uint8_t Dy = T[0][Pd] ^ T[1][Qd];
uint8_t Dx = Pd ^ Dy;
/* set */
pa[i] = Dx;
qa[i] = Dy;
}
}