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ecmult_gen_impl: eliminate scratch memory used when generating context

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This commit is contained in:
Andrew Poelstra
2018-09-20 22:24:57 +00:00
parent 314a61d724
commit 7f7a2ed3a8
5 changed files with 31 additions and 16 deletions
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39
src/group_impl.h
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@@ -126,30 +126,45 @@ static void secp256k1_ge_set_gej_var(secp256k1_ge *r, secp256k1_gej *a) {
r->y = a->y;
}
static void secp256k1_ge_set_all_gej_var(secp256k1_ge *r, const secp256k1_gej *a, size_t len, const secp256k1_callback *cb) {
secp256k1_fe *az;
secp256k1_fe *azi;
static void secp256k1_ge_set_all_gej_var(secp256k1_ge *r, const secp256k1_gej *a, size_t len) {
secp256k1_fe u;
size_t i;
size_t count = 0;
az = (secp256k1_fe *)checked_malloc(cb, sizeof(secp256k1_fe) * len);
size_t last_i = SIZE_MAX;
for (i = 0; i < len; i++) {
if (!a[i].infinity) {
az[count++] = a[i].z;
/* Use destination's x coordinates as scratch space */
if (last_i == SIZE_MAX) {
r[i].x = a[i].z;
} else {
secp256k1_fe_mul(&r[i].x, &r[last_i].x, &a[i].z);
}
last_i = i;
}
}
if (last_i == SIZE_MAX) {
return;
}
secp256k1_fe_inv_var(&u, &r[last_i].x);
azi = (secp256k1_fe *)checked_malloc(cb, sizeof(secp256k1_fe) * count);
secp256k1_fe_inv_all_var(azi, az, count);
free(az);
i = last_i;
while (i > 0) {
i--;
if (!a[i].infinity) {
secp256k1_fe_mul(&r[last_i].x, &r[i].x, &u);
secp256k1_fe_mul(&u, &u, &a[last_i].z);
last_i = i;
}
}
VERIFY_CHECK(!a[last_i].infinity);
r[last_i].x = u;
count = 0;
for (i = 0; i < len; i++) {
r[i].infinity = a[i].infinity;
if (!a[i].infinity) {
secp256k1_ge_set_gej_zinv(&r[i], &a[i], &azi[count++]);
secp256k1_ge_set_gej_zinv(&r[i], &a[i], &r[i].x);
}
}
free(azi);
}
static void secp256k1_ge_set_table_gej_var(secp256k1_ge *r, const secp256k1_gej *a, const secp256k1_fe *zr, size_t len) {