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Merge pull request #2763 from SparkiDev/sp_int_div_word 

Add support to sp_int.c for platforms that do not divide an sp_int_wo…
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David Garske 2020-01-23 18:37:04 -08:00 committed by GitHub
parent 945d34533c ec877aa91e
commit 126dceee1f
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 49 additions and 8 deletions
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57
wolfcrypt/src/sp_int.c
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@ -669,7 +669,9 @@ static int sp_div(sp_int* a, sp_int* d, sp_int* r, sp_int* rem)
int done = 0;
int i;
int s;
#ifndef WOLFSSL_SP_DIV_32
sp_int_word w = 0;
#endif
sp_int_digit dt;
sp_int_digit t;
#ifdef WOLFSSL_SMALL_STACK
@ -752,15 +754,22 @@ static int sp_div(sp_int* a, sp_int* d, sp_int* r, sp_int* rem)
sp_clear(tr);
tr->used = sa->used - d->used + 1;
dt = d->dp[d->used-1];
for (i = sa->used - 1; i >= d->used; i--) {
w = ((sp_int_word)sa->dp[i] << SP_WORD_SIZE) | sa->dp[i-1];
w /= dt;
if (w > (sp_int_digit)-1) {
#ifndef WOLFSSL_SP_DIV_32
for (i = sa->used - 1; i >= d->used; ) {
if (sa->dp[i] > dt) {
t = (sp_int_digit)-1;
}
else {
t = (sp_int_digit)w;
w = ((sp_int_word)sa->dp[i] << SP_WORD_SIZE) | sa->dp[i-1];
w /= dt;
if (w > (sp_int_digit)-1) {
t = (sp_int_digit)-1;
}
else {
t = (sp_int_digit)w;
}
}
if (t > 0) {
_sp_mul_d(d, t, trial, i - d->used);
while (sp_cmp(trial, sa) == MP_GT) {
@ -771,11 +780,43 @@ static int sp_div(sp_int* a, sp_int* d, sp_int* r, sp_int* rem)
tr->dp[i - d->used] += t;
if (tr->dp[i - d->used] < t)
tr->dp[i + 1 - d->used]++;
if (w > (sp_int_digit)-1) {
i++;
}
}
i = sa->used - 1;
}
#else
{
sp_int_digit div = (dt >> (SP_WORD_SIZE / 2)) + 1;
for (i = sa->used - 1; i >= d->used; ) {
t = sa->dp[i] / div;
if ((t > 0) && (t << (SP_WORD_SIZE / 2) == 0))
t = (sp_int_digit)-1;
t <<= SP_WORD_SIZE / 2;
if (t == 0) {
t = sa->dp[i] << (SP_WORD_SIZE / 2);
t += sa->dp[i-1] >> (SP_WORD_SIZE / 2);
t /= div;
}
if (t > 0) {
_sp_mul_d(d, t, trial, i - d->used);
while (sp_cmp(trial, sa) == MP_GT) {
t--;
_sp_mul_d(d, t, trial, i - d->used);
}
sp_sub(sa, trial, sa);
tr->dp[i - d->used] += t;
if (tr->dp[i - d->used] < t)
tr->dp[i + 1 - d->used]++;
}
i = sa->used - 1;
}
while (sp_cmp(sa, d) != MP_LT) {
sp_sub(sa, d, sa);
sp_add_d(tr, 1, tr);
}
}
#endif
sp_clamp(tr);