/**
* Finds an addition chain for (FB_BITS - 1).
*/
static void find_chain() {
int i, j, k, l;
chain_len = -1;
for (i = 0; i < MAX_CHAIN; i++) {
chain[i] = (i << 8) + i;
}
switch (FB_BITS) {
case 193:
chain[1] = (1 << 8) + 0;
chain_len = 8;
break;
case 233:
chain[1] = (1 << 8) + 0;
chain[3] = (3 << 8) + 0;
chain[6] = (6 << 8) + 0;
chain_len = 10;
break;
case 251:
chain[1] = (1 << 8) + 0;
chain[2] = (2 << 8) + 1;
chain[4] = (4 << 8) + 3;
chain[5] = (5 << 8) + 4;
chain[7] = (7 << 8) + 6;
chain[8] = (8 << 8) + 7;
chain_len = 10;
break;
case 353:
chain[2] = (2 << 8) + 0;
chain[4] = (4 << 8) + 0;
chain_len = 10;
break;
case 1223:
chain[1] = (1 << 8) + 0;
chain[2] = (2 << 8) + 0;
chain[4] = (4 << 8) + 2;
chain[5] = (5 << 8) + 4;
chain[10] = (10 << 8) + 2;
chain[11] = (11 << 8) + 10;
chain_len = 13;
break;
default:
l = 0;
j = (FB_BITS - 1);
for (k = 16; k >= 0; k--) {
if (j & (1 << k)) {
break;
}
}
for (i = 1; i < k; i++) {
if (j & (1 << i)) {
l++;
}
}
i = 0;
chain_len = k + l;
while (j != 1) {
if ((j & 0x01) != 0) {
i++;
chain[chain_len - i] = ((chain_len - i) << 8) + 0;
}
i++;
j = j >> 1;
}
break;
}
#ifdef FB_PRECO
int x, y, u[chain_len + 1];
u[0] = 1;
u[1] = 2;
for (i = 2; i <= chain_len; i++) {
x = chain[i - 1] >> 8;
y = chain[i - 1] - (x << 8);
if (x == y) {
u[i] = 2 * u[i - 1];
} else {
u[i] = u[x] + u[y];
}
}
for (i = 0; i <= chain_len; i++) {
fb_itr_pre(fb_poly_tab_sqr(i), u[i]);
}
#endif
}
/**
* Finds an addition chain for (FB_BITS - 1).
*/
static void find_chain() {
int i, j, k, l;
ctx_t *ctx = core_get();
ctx->chain_len = -1;
for (int i = 0; i < MAX_TERMS; i++) {
ctx->chain[i] = (i << 8) + i;
}
switch (FB_BITS) {
case 127:
ctx->chain[1] = (1 << 8) + 0;
ctx->chain[4] = (4 << 8) + 2;
ctx->chain[7] = (7 << 8) + 2;
ctx->chain_len = 9;
break;
case 193:
ctx->chain[1] = (1 << 8) + 0;
ctx->chain_len = 8;
break;
case 233:
ctx->chain[1] = (1 << 8) + 0;
ctx->chain[3] = (3 << 8) + 0;
ctx->chain[6] = (6 << 8) + 0;
ctx->chain_len = 10;
break;
case 251:
ctx->chain[1] = (1 << 8) + 0;
ctx->chain[2] = (2 << 8) + 1;
ctx->chain[4] = (4 << 8) + 3;
ctx->chain[5] = (5 << 8) + 4;
ctx->chain[7] = (7 << 8) + 6;
ctx->chain[8] = (8 << 8) + 7;
ctx->chain_len = 10;
break;
case 283:
ctx->chain[4] = (4 << 8) + 0;
ctx->chain[6] = (6 << 8) + 0;
ctx->chain[9] = (9 << 8) + 0;
ctx->chain_len = 11;
break;
case 353:
ctx->chain[2] = (2 << 8) + 0;
ctx->chain[4] = (4 << 8) + 0;
ctx->chain_len = 10;
break;
case 367:
ctx->chain[1] = (1 << 8) + 0;
ctx->chain[2] = (2 << 8) + 1;
ctx->chain[6] = (6 << 8) + 3;
ctx->chain[9] = (9 << 8) + 2;
ctx->chain_len = 11;
break;
case 1223:
ctx->chain[1] = (1 << 8) + 0;
ctx->chain[2] = (2 << 8) + 0;
ctx->chain[4] = (4 << 8) + 2;
ctx->chain[5] = (5 << 8) + 4;
ctx->chain[10] = (10 << 8) + 2;
ctx->chain[11] = (11 << 8) + 10;
ctx->chain_len = 13;
break;
default:
l = 0;
j = (FB_BITS - 1);
for (k = 16; k >= 0; k--) {
if (j & (1 << k)) {
break;
}
}
for (i = 1; i < k; i++) {
if (j & (1 << i)) {
l++;
}
}
i = 0;
ctx->chain_len = k + l;
while (j != 1) {
if ((j & 0x01) != 0) {
i++;
ctx->chain[ctx->chain_len - i] = ((ctx->chain_len - i) << 8) + 0;
}
i++;
j = j >> 1;
}
break;
}
int x, y, u[ctx->chain_len + 1];
for (i = 0; i < MAX_TERMS; i++) {
for (j = 0; j < FB_TABLE; j++) {
ctx->fb_tab_ptr[i][j] = &(ctx->fb_tab_sqr[i][j]);
}
}
u[0] = 1;
u[1] = 2;
for (i = 2; i <= ctx->chain_len; i++) {
x = ctx->chain[i - 1] >> 8;
y = ctx->chain[i - 1] - (x << 8);
if (x == y) {
u[i] = 2 * u[i - 1];
} else {
u[i] = u[x] + u[y];
}
}
for (i = 0; i <= ctx->chain_len; i++) {
fb_itr_pre((fb_t *)fb_poly_tab_sqr(i), u[i]);
}
}
