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Reduce nesting, improve readability

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This commit is contained in:
Frank Denis 2017-11-06 21:55:20 +01:00
parent 1621448f6c
commit f8de352e6d
1 changed files with 23 additions and 22 deletions
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45
src/libsodium/crypto_core/curve25519/ref10/curve25519_ref10.c
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@ -192,29 +192,30 @@ slide_vartime(signed char *r, const unsigned char *a)
r[i] = 1 & (a[i >> 3] >> (i & 7));
}
for (i = 0; i < 256; ++i) {
if (r[i]) {
for (b = 1; b <= 6 && i + b < 256; ++b) {
if (r[i + b]) {
ribs = r[i + b] << b;
cmp = r[i] + ribs;
if (cmp <= 15) {
r[i] = cmp;
r[i + b] = 0;
} else {
cmp = r[i] - ribs;
if (cmp >= -15) {
r[i] = cmp;
for (k = i + b; k < 256; ++k) {
if (!r[k]) {
r[k] = 1;
break;
}
r[k] = 0;
}
} else {
break;
}
if (! r[i]) {
continue;
}
for (b = 1; b <= 6 && i + b < 256; ++b) {
if (! r[i + b]) {
continue;
}
ribs = r[i + b] << b;
cmp = r[i] + ribs;
if (cmp <= 15) {
r[i] = cmp;
r[i + b] = 0;
} else {
cmp = r[i] - ribs;
if (cmp < -15) {
break;
}
r[i] = cmp;
for (k = i + b; k < 256; ++k) {
if (! r[k]) {
r[k] = 1;
break;
}
r[k] = 0;
}
}
}