Commit 143e0376a16462198a3412243e776ff9b69742d5
2019-10-29T20:02:32
simplifications: basic arithmetic functions
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diff --git a/mp_add_d.c b/mp_add_d.c
index 4508cc8..43d50e8 100644
--- a/mp_add_d.c
+++ b/mp_add_d.c
@@ -6,9 +6,7 @@
/* single digit addition */
mp_err mp_add_d(const mp_int *a, mp_digit b, mp_int *c)
{
- mp_err err;
- int ix, oldused;
- mp_digit *tmpa, *tmpc;
+ int oldused;
/* fast path for a == c */
if (a == c) {
@@ -27,6 +25,7 @@ mp_err mp_add_d(const mp_int *a, mp_digit b, mp_int *c)
/* grow c as required */
if (c->alloc < (a->used + 1)) {
+ mp_err err;
if ((err = mp_grow(c, a->used + 1)) != MP_OKAY) {
return err;
}
@@ -34,6 +33,7 @@ mp_err mp_add_d(const mp_int *a, mp_digit b, mp_int *c)
/* if a is negative and |a| >= b, call c = |a| - b */
if ((a->sign == MP_NEG) && ((a->used > 1) || (a->dp[0] >= b))) {
+ mp_err err;
mp_int a_ = *a;
/* temporarily fix sign of a */
a_.sign = MP_ZPOS;
@@ -53,49 +53,34 @@ mp_err mp_add_d(const mp_int *a, mp_digit b, mp_int *c)
/* old number of used digits in c */
oldused = c->used;
- /* source alias */
- tmpa = a->dp;
-
- /* destination alias */
- tmpc = c->dp;
-
/* if a is positive */
if (a->sign == MP_ZPOS) {
/* add digits, mu is carry */
+ int i;
mp_digit mu = b;
- for (ix = 0; ix < a->used; ix++) {
- *tmpc = *tmpa++ + mu;
- mu = *tmpc >> MP_DIGIT_BIT;
- *tmpc++ &= MP_MASK;
+ for (i = 0; i < a->used; i++) {
+ c->dp[i] = a->dp[i] + mu;
+ mu = c->dp[i] >> MP_DIGIT_BIT;
+ c->dp[i] &= MP_MASK;
}
/* set final carry */
- ix++;
- *tmpc++ = mu;
+ c->dp[i] = mu;
/* setup size */
c->used = a->used + 1;
} else {
/* a was negative and |a| < b */
- c->used = 1;
+ c->used = 1;
/* the result is a single digit */
- if (a->used == 1) {
- *tmpc++ = b - a->dp[0];
- } else {
- *tmpc++ = b;
- }
-
- /* setup count so the clearing of oldused
- * can fall through correctly
- */
- ix = 1;
+ c->dp[0] = (a->used == 1) ? b - a->dp[0] : b;
}
/* sign always positive */
c->sign = MP_ZPOS;
/* now zero to oldused */
- MP_ZERO_DIGITS(tmpc, oldused - ix);
+ MP_ZERO_DIGITS(c->dp + c->used, oldused - c->used);
mp_clamp(c);
return MP_OKAY;
diff --git a/mp_div_2.c b/mp_div_2.c
index 60bd63d..573570d 100644
--- a/mp_div_2.c
+++ b/mp_div_2.c
@@ -6,12 +6,11 @@
/* b = a/2 */
mp_err mp_div_2(const mp_int *a, mp_int *b)
{
- int x, oldused;
- mp_digit r, rr, *tmpa, *tmpb;
- mp_err err;
+ int x, oldused;
+ mp_digit r;
- /* copy */
if (b->alloc < a->used) {
+ mp_err err;
if ((err = mp_grow(b, a->used)) != MP_OKAY) {
return err;
}
@@ -20,20 +19,14 @@ mp_err mp_div_2(const mp_int *a, mp_int *b)
oldused = b->used;
b->used = a->used;
- /* source alias */
- tmpa = a->dp + b->used - 1;
-
- /* dest alias */
- tmpb = b->dp + b->used - 1;
-
/* carry */
r = 0;
- for (x = b->used - 1; x >= 0; x--) {
+ for (x = b->used; x --> 0;) {
/* get the carry for the next iteration */
- rr = *tmpa & 1u;
+ mp_digit rr = a->dp[x] & 1u;
/* shift the current digit, add in carry and store */
- *tmpb-- = (*tmpa-- >> 1) | (r << (MP_DIGIT_BIT - 1));
+ b->dp[x] = (a->dp[x] >> 1) | (r << (MP_DIGIT_BIT - 1));
/* forward carry to next iteration */
r = rr;
diff --git a/mp_div_2d.c b/mp_div_2d.c
index 9b396ac..e523465 100644
--- a/mp_div_2d.c
+++ b/mp_div_2d.c
@@ -6,23 +6,16 @@
/* shift right by a certain bit count (store quotient in c, optional remainder in d) */
mp_err mp_div_2d(const mp_int *a, int b, mp_int *c, mp_int *d)
{
- mp_digit D, r, rr;
- int x;
mp_err err;
- /* if the shift count is <= 0 then we do no work */
- if (b <= 0) {
- err = mp_copy(a, c);
- if (d != NULL) {
- mp_zero(d);
- }
- return err;
+ if (b < 0) {
+ return MP_VAL;
}
- /* copy */
if ((err = mp_copy(a, c)) != MP_OKAY) {
return err;
}
+
/* 'a' should not be used after here - it might be the same as d */
/* get the remainder */
@@ -38,28 +31,25 @@ mp_err mp_div_2d(const mp_int *a, int b, mp_int *c, mp_int *d)
}
/* shift any bit count < MP_DIGIT_BIT */
- D = (mp_digit)(b % MP_DIGIT_BIT);
- if (D != 0u) {
- mp_digit *tmpc, mask, shift;
+ b %= MP_DIGIT_BIT;
+ if (b != 0u) {
+ int x;
+ mp_digit r, mask, shift;
/* mask */
- mask = ((mp_digit)1 << D) - 1uL;
+ mask = ((mp_digit)1 << b) - 1uL;
/* shift for lsb */
- shift = (mp_digit)MP_DIGIT_BIT - D;
-
- /* alias */
- tmpc = c->dp + (c->used - 1);
+ shift = (mp_digit)(MP_DIGIT_BIT - b);
/* carry */
r = 0;
- for (x = c->used - 1; x >= 0; x--) {
+ for (x = c->used; x --> 0;) {
/* get the lower bits of this word in a temp */
- rr = *tmpc & mask;
+ mp_digit rr = c->dp[x] & mask;
/* shift the current word and mix in the carry bits from the previous word */
- *tmpc = (*tmpc >> D) | (r << shift);
- --tmpc;
+ c->dp[x] = (c->dp[x] >> b) | (r << shift);
/* set the carry to the carry bits of the current word found above */
r = rr;
diff --git a/mp_div_d.c b/mp_div_d.c
index 98b6b24..472ab27 100644
--- a/mp_div_d.c
+++ b/mp_div_d.c
@@ -8,7 +8,6 @@ mp_err mp_div_d(const mp_int *a, mp_digit b, mp_int *c, mp_digit *d)
{
mp_int q;
mp_word w;
- mp_digit t;
mp_err err;
int ix;
@@ -56,14 +55,12 @@ mp_err mp_div_d(const mp_int *a, mp_digit b, mp_int *c, mp_digit *d)
q.used = a->used;
q.sign = a->sign;
w = 0;
- for (ix = a->used - 1; ix >= 0; ix--) {
+ for (ix = a->used; ix --> 0;) {
+ mp_digit t = 0;
w = (w << (mp_word)MP_DIGIT_BIT) | (mp_word)a->dp[ix];
-
if (w >= b) {
t = (mp_digit)(w / b);
w -= (mp_word)t * (mp_word)b;
- } else {
- t = 0;
}
q.dp[ix] = t;
}
@@ -78,7 +75,7 @@ mp_err mp_div_d(const mp_int *a, mp_digit b, mp_int *c, mp_digit *d)
}
mp_clear(&q);
- return err;
+ return MP_OKAY;
}
#endif
diff --git a/mp_mul.c b/mp_mul.c
index 9c8f8ae..1a7091c 100644
--- a/mp_mul.c
+++ b/mp_mul.c
@@ -7,8 +7,8 @@
mp_err mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
{
mp_err err;
- int min_len = MP_MIN(a->used, b->used),
- max_len = MP_MAX(a->used, b->used),
+ int min = MP_MIN(a->used, b->used),
+ max = MP_MAX(a->used, b->used),
digs = a->used + b->used + 1;
mp_sign neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
@@ -20,16 +20,16 @@ mp_err mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
* Using it to cut the input into slices small enough for s_mp_mul_digs_fast
* was actually slower on the author's machine, but YMMV.
*/
- (min_len >= MP_KARATSUBA_MUL_CUTOFF) &&
- ((max_len / 2) >= MP_KARATSUBA_MUL_CUTOFF) &&
+ (min >= MP_KARATSUBA_MUL_CUTOFF) &&
+ ((max / 2) >= MP_KARATSUBA_MUL_CUTOFF) &&
/* Not much effect was observed below a ratio of 1:2, but again: YMMV. */
- (max_len >= (2 * min_len))) {
+ (max >= (2 * min))) {
err = s_mp_balance_mul(a,b,c);
} else if (MP_HAS(S_MP_TOOM_MUL) &&
- (min_len >= MP_TOOM_MUL_CUTOFF)) {
+ (min >= MP_TOOM_MUL_CUTOFF)) {
err = s_mp_toom_mul(a, b, c);
} else if (MP_HAS(S_MP_KARATSUBA_MUL) &&
- (min_len >= MP_KARATSUBA_MUL_CUTOFF)) {
+ (min >= MP_KARATSUBA_MUL_CUTOFF)) {
err = s_mp_karatsuba_mul(a, b, c);
} else if (MP_HAS(S_MP_MUL_DIGS_FAST) &&
/* can we use the fast multiplier?
@@ -39,7 +39,7 @@ mp_err mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
* digits won't affect carry propagation
*/
(digs < MP_WARRAY) &&
- (min_len <= MP_MAXFAST)) {
+ (min <= MP_MAXFAST)) {
err = s_mp_mul_digs_fast(a, b, c, digs);
} else if (MP_HAS(S_MP_MUL_DIGS)) {
err = s_mp_mul_digs(a, b, c, digs);
diff --git a/mp_mul_2.c b/mp_mul_2.c
index cd5589d..45b6f1c 100644
--- a/mp_mul_2.c
+++ b/mp_mul_2.c
@@ -6,11 +6,12 @@
/* b = a*2 */
mp_err mp_mul_2(const mp_int *a, mp_int *b)
{
- int x, oldused;
- mp_err err;
+ int x, oldused;
+ mp_digit r;
/* grow to accomodate result */
if (b->alloc < (a->used + 1)) {
+ mp_err err;
if ((err = mp_grow(b, a->used + 1)) != MP_OKAY) {
return err;
}
@@ -19,45 +20,35 @@ mp_err mp_mul_2(const mp_int *a, mp_int *b)
oldused = b->used;
b->used = a->used;
- {
- mp_digit r, rr, *tmpa, *tmpb;
+ /* carry */
+ r = 0;
+ for (x = 0; x < a->used; x++) {
- /* alias for source */
- tmpa = a->dp;
-
- /* alias for dest */
- tmpb = b->dp;
-
- /* carry */
- r = 0;
- for (x = 0; x < a->used; x++) {
+ /* get what will be the *next* carry bit from the
+ * MSB of the current digit
+ */
+ mp_digit rr = a->dp[x] >> (mp_digit)(MP_DIGIT_BIT - 1);
- /* get what will be the *next* carry bit from the
- * MSB of the current digit
- */
- rr = *tmpa >> (mp_digit)(MP_DIGIT_BIT - 1);
+ /* now shift up this digit, add in the carry [from the previous] */
+ b->dp[x] = ((a->dp[x] << 1uL) | r) & MP_MASK;
- /* now shift up this digit, add in the carry [from the previous] */
- *tmpb++ = ((*tmpa++ << 1uL) | r) & MP_MASK;
+ /* copy the carry that would be from the source
+ * digit into the next iteration
+ */
+ r = rr;
+ }
- /* copy the carry that would be from the source
- * digit into the next iteration
- */
- r = rr;
- }
+ /* new leading digit? */
+ if (r != 0u) {
+ /* add a MSB which is always 1 at this point */
+ b->dp[b->used++] = 1;
+ }
- /* new leading digit? */
- if (r != 0u) {
- /* add a MSB which is always 1 at this point */
- *tmpb = 1;
- ++(b->used);
- }
+ /* now zero any excess digits on the destination
+ * that we didn't write to
+ */
+ MP_ZERO_DIGITS(b->dp + b->used, oldused - b->used);
- /* now zero any excess digits on the destination
- * that we didn't write to
- */
- MP_ZERO_DIGITS(b->dp + b->used, oldused - b->used);
- }
b->sign = a->sign;
return MP_OKAY;
}
diff --git a/mp_mul_2d.c b/mp_mul_2d.c
index 1ba53a0..f1016ea 100644
--- a/mp_mul_2d.c
+++ b/mp_mul_2d.c
@@ -6,17 +6,19 @@
/* shift left by a certain bit count */
mp_err mp_mul_2d(const mp_int *a, int b, mp_int *c)
{
- mp_digit d;
- mp_err err;
+ if (b < 0) {
+ return MP_VAL;
+ }
- /* copy */
if (a != c) {
+ mp_err err;
if ((err = mp_copy(a, c)) != MP_OKAY) {
return err;
}
}
if (c->alloc < (c->used + (b / MP_DIGIT_BIT) + 1)) {
+ mp_err err;
if ((err = mp_grow(c, c->used + (b / MP_DIGIT_BIT) + 1)) != MP_OKAY) {
return err;
}
@@ -24,35 +26,32 @@ mp_err mp_mul_2d(const mp_int *a, int b, mp_int *c)
/* shift by as many digits in the bit count */
if (b >= MP_DIGIT_BIT) {
+ mp_err err;
if ((err = mp_lshd(c, b / MP_DIGIT_BIT)) != MP_OKAY) {
return err;
}
}
/* shift any bit count < MP_DIGIT_BIT */
- d = (mp_digit)(b % MP_DIGIT_BIT);
- if (d != 0u) {
- mp_digit *tmpc, shift, mask, r, rr;
+ b %= MP_DIGIT_BIT;
+ if (b != 0u) {
+ mp_digit shift, mask, r;
int x;
/* bitmask for carries */
- mask = ((mp_digit)1 << d) - (mp_digit)1;
+ mask = ((mp_digit)1 << b) - (mp_digit)1;
/* shift for msbs */
- shift = (mp_digit)MP_DIGIT_BIT - d;
-
- /* alias */
- tmpc = c->dp;
+ shift = (mp_digit)(MP_DIGIT_BIT - b);
/* carry */
r = 0;
for (x = 0; x < c->used; x++) {
/* get the higher bits of the current word */
- rr = (*tmpc >> shift) & mask;
+ mp_digit rr = (c->dp[x] >> shift) & mask;
/* shift the current word and OR in the carry */
- *tmpc = ((*tmpc << d) | r) & MP_MASK;
- ++tmpc;
+ c->dp[x] = ((c->dp[x] << b) | r) & MP_MASK;
/* set the carry to the carry bits of the current word */
r = rr;
diff --git a/mp_mul_d.c b/mp_mul_d.c
index 399dc7b..3e5335f 100644
--- a/mp_mul_d.c
+++ b/mp_mul_d.c
@@ -6,10 +6,9 @@
/* multiply by a digit */
mp_err mp_mul_d(const mp_int *a, mp_digit b, mp_int *c)
{
- mp_digit u, *tmpa, *tmpc;
- mp_word r;
+ mp_digit u;
mp_err err;
- int ix, olduse;
+ int ix, oldused;
/* make sure c is big enough to hold a*b */
if (c->alloc < (a->used + 1)) {
@@ -19,41 +18,35 @@ mp_err mp_mul_d(const mp_int *a, mp_digit b, mp_int *c)
}
/* get the original destinations used count */
- olduse = c->used;
+ oldused = c->used;
/* set the sign */
c->sign = a->sign;
- /* alias for a->dp [source] */
- tmpa = a->dp;
-
- /* alias for c->dp [dest] */
- tmpc = c->dp;
-
/* zero carry */
u = 0;
/* compute columns */
for (ix = 0; ix < a->used; ix++) {
/* compute product and carry sum for this term */
- r = (mp_word)u + ((mp_word)*tmpa++ * (mp_word)b);
+ mp_word r = (mp_word)u + ((mp_word)a->dp[ix] * (mp_word)b);
/* mask off higher bits to get a single digit */
- *tmpc++ = (mp_digit)(r & (mp_word)MP_MASK);
+ c->dp[ix] = (mp_digit)(r & (mp_word)MP_MASK);
/* send carry into next iteration */
u = (mp_digit)(r >> (mp_word)MP_DIGIT_BIT);
}
/* store final carry [if any] and increment ix offset */
- *tmpc++ = u;
- ++ix;
-
- /* now zero digits above the top */
- MP_ZERO_DIGITS(tmpc, olduse - ix);
+ c->dp[ix] = u;
/* set used count */
c->used = a->used + 1;
+
+ /* now zero digits above the top */
+ MP_ZERO_DIGITS(c->dp + c->used, oldused - c->used);
+
mp_clamp(c);
return MP_OKAY;
diff --git a/mp_sub_d.c b/mp_sub_d.c
index 96a747c..c5cf726 100644
--- a/mp_sub_d.c
+++ b/mp_sub_d.c
@@ -6,9 +6,7 @@
/* single digit subtraction */
mp_err mp_sub_d(const mp_int *a, mp_digit b, mp_int *c)
{
- mp_digit *tmpa, *tmpc;
- mp_err err;
- int ix, oldused;
+ int oldused;
/* fast path for a == c */
if (a == c) {
@@ -26,6 +24,7 @@ mp_err mp_sub_d(const mp_int *a, mp_digit b, mp_int *c)
/* grow c as required */
if (c->alloc < (a->used + 1)) {
+ mp_err err;
if ((err = mp_grow(c, a->used + 1)) != MP_OKAY) {
return err;
}
@@ -35,6 +34,7 @@ mp_err mp_sub_d(const mp_int *a, mp_digit b, mp_int *c)
* addition [with fudged signs]
*/
if (a->sign == MP_NEG) {
+ mp_err err;
mp_int a_ = *a;
a_.sign = MP_ZPOS;
err = mp_add_d(&a_, b, c);
@@ -46,24 +46,17 @@ mp_err mp_sub_d(const mp_int *a, mp_digit b, mp_int *c)
return err;
}
- /* setup regs */
oldused = c->used;
- tmpa = a->dp;
- tmpc = c->dp;
/* if a <= b simply fix the single digit */
if (((a->used == 1) && (a->dp[0] <= b)) || (a->used == 0)) {
- if (a->used == 1) {
- *tmpc++ = b - *tmpa;
- } else {
- *tmpc++ = b;
- }
- ix = 1;
+ c->dp[0] = (a->used == 1) ? b - a->dp[0] : b;
/* negative/1digit */
c->sign = MP_NEG;
c->used = 1;
} else {
+ int i;
mp_digit mu = b;
/* positive/size */
@@ -71,15 +64,15 @@ mp_err mp_sub_d(const mp_int *a, mp_digit b, mp_int *c)
c->used = a->used;
/* subtract digits, mu is carry */
- for (ix = 0; ix < a->used; ix++) {
- *tmpc = *tmpa++ - mu;
- mu = *tmpc >> (MP_SIZEOF_BITS(mp_digit) - 1u);
- *tmpc++ &= MP_MASK;
+ for (i = 0; i < a->used; i++) {
+ c->dp[i] = a->dp[i] - mu;
+ mu = c->dp[i] >> (MP_SIZEOF_BITS(mp_digit) - 1u);
+ c->dp[i] &= MP_MASK;
}
}
/* zero excess digits */
- MP_ZERO_DIGITS(tmpc, oldused - ix);
+ MP_ZERO_DIGITS(c->dp + c->used, oldused - c->used);
mp_clamp(c);
return MP_OKAY;
diff --git a/s_mp_add.c b/s_mp_add.c
index 9220719..1dd09f8 100644
--- a/s_mp_add.c
+++ b/s_mp_add.c
@@ -6,84 +6,65 @@
/* low level addition, based on HAC pp.594, Algorithm 14.7 */
mp_err s_mp_add(const mp_int *a, const mp_int *b, mp_int *c)
{
- const mp_int *x;
- mp_err err;
- int olduse, min, max;
+ int oldused, min, max, i;
+ mp_digit u;
/* find sizes, we let |a| <= |b| which means we have to sort
* them. "x" will point to the input with the most digits
*/
- if (a->used > b->used) {
- min = b->used;
- max = a->used;
- x = a;
- } else {
- min = a->used;
- max = b->used;
- x = b;
+ if (a->used < b->used) {
+ MP_EXCH(const mp_int *, a, b);
}
+ min = b->used;
+ max = a->used;
+
/* init result */
if (c->alloc < (max + 1)) {
+ mp_err err;
if ((err = mp_grow(c, max + 1)) != MP_OKAY) {
return err;
}
}
/* get old used digit count and set new one */
- olduse = c->used;
+ oldused = c->used;
c->used = max + 1;
- {
- mp_digit u, *tmpa, *tmpb, *tmpc;
- int i;
-
- /* alias for digit pointers */
-
- /* first input */
- tmpa = a->dp;
+ /* zero the carry */
+ u = 0;
+ for (i = 0; i < min; i++) {
+ /* Compute the sum at one digit, T[i] = A[i] + B[i] + U */
+ c->dp[i] = a->dp[i] + b->dp[i] + u;
- /* second input */
- tmpb = b->dp;
+ /* U = carry bit of T[i] */
+ u = c->dp[i] >> (mp_digit)MP_DIGIT_BIT;
- /* destination */
- tmpc = c->dp;
+ /* take away carry bit from T[i] */
+ c->dp[i] &= MP_MASK;
+ }
- /* zero the carry */
- u = 0;
- for (i = 0; i < min; i++) {
- /* Compute the sum at one digit, T[i] = A[i] + B[i] + U */
- *tmpc = *tmpa++ + *tmpb++ + u;
+ /* now copy higher words if any, that is in A+B
+ * if A or B has more digits add those in
+ */
+ if (min != max) {
+ for (; i < max; i++) {
+ /* T[i] = A[i] + U */
+ c->dp[i] = a->dp[i] + u;
/* U = carry bit of T[i] */
- u = *tmpc >> (mp_digit)MP_DIGIT_BIT;
+ u = c->dp[i] >> (mp_digit)MP_DIGIT_BIT;
/* take away carry bit from T[i] */
- *tmpc++ &= MP_MASK;
- }
-
- /* now copy higher words if any, that is in A+B
- * if A or B has more digits add those in
- */
- if (min != max) {
- for (; i < max; i++) {
- /* T[i] = X[i] + U */
- *tmpc = x->dp[i] + u;
-
- /* U = carry bit of T[i] */
- u = *tmpc >> (mp_digit)MP_DIGIT_BIT;
-
- /* take away carry bit from T[i] */
- *tmpc++ &= MP_MASK;
- }
+ c->dp[i] &= MP_MASK;
}
+ }
- /* add carry */
- *tmpc++ = u;
+ /* add carry */
+ c->dp[i] = u;
- /* clear digits above oldused */
- MP_ZERO_DIGITS(tmpc, olduse - c->used);
- }
+ /* clear digits above oldused */
+ MP_ZERO_DIGITS(c->dp + c->used, oldused - c->used);
mp_clamp(c);
return MP_OKAY;
diff --git a/s_mp_sqr.c b/s_mp_sqr.c
index 61106ed..4a20306 100644
--- a/s_mp_sqr.c
+++ b/s_mp_sqr.c
@@ -7,10 +7,8 @@
mp_err s_mp_sqr(const mp_int *a, mp_int *b)
{
mp_int t;
- int ix, iy, pa;
+ int ix, pa;
mp_err err;
- mp_word r;
- mp_digit u, tmpx, *tmpt;
pa = a->used;
if ((err = mp_init_size(&t, (2 * pa) + 1)) != MP_OKAY) {
@@ -21,10 +19,13 @@ mp_err s_mp_sqr(const mp_int *a, mp_int *b)
t.used = (2 * pa) + 1;
for (ix = 0; ix < pa; ix++) {
+ mp_digit u;
+ int iy;
+
/* first calculate the digit at 2*ix */
/* calculate double precision result */
- r = (mp_word)t.dp[2*ix] +
- ((mp_word)a->dp[ix] * (mp_word)a->dp[ix]);
+ mp_word r = (mp_word)t.dp[2*ix] +
+ ((mp_word)a->dp[ix] * (mp_word)a->dp[ix]);
/* store lower part in result */
t.dp[ix+ix] = (mp_digit)(r & (mp_word)MP_MASK);
@@ -32,32 +33,27 @@ mp_err s_mp_sqr(const mp_int *a, mp_int *b)
/* get the carry */
u = (mp_digit)(r >> (mp_word)MP_DIGIT_BIT);
- /* left hand side of A[ix] * A[iy] */
- tmpx = a->dp[ix];
-
- /* alias for where to store the results */
- tmpt = t.dp + ((2 * ix) + 1);
-
for (iy = ix + 1; iy < pa; iy++) {
/* first calculate the product */
- r = (mp_word)tmpx * (mp_word)a->dp[iy];
+ r = (mp_word)a->dp[ix] * (mp_word)a->dp[iy];
/* now calculate the double precision result, note we use
* addition instead of *2 since it's easier to optimize
*/
- r = (mp_word)*tmpt + r + r + (mp_word)u;
+ r = (mp_word)t.dp[ix + iy] + r + r + (mp_word)u;
/* store lower part */
- *tmpt++ = (mp_digit)(r & (mp_word)MP_MASK);
+ t.dp[ix + iy] = (mp_digit)(r & (mp_word)MP_MASK);
/* get carry */
u = (mp_digit)(r >> (mp_word)MP_DIGIT_BIT);
}
/* propagate upwards */
while (u != 0uL) {
- r = (mp_word)*tmpt + (mp_word)u;
- *tmpt++ = (mp_digit)(r & (mp_word)MP_MASK);
+ r = (mp_word)t.dp[ix + iy] + (mp_word)u;
+ t.dp[ix + iy] = (mp_digit)(r & (mp_word)MP_MASK);
u = (mp_digit)(r >> (mp_word)MP_DIGIT_BIT);
+ ++iy;
}
}
diff --git a/s_mp_sub.c b/s_mp_sub.c
index bef1fce..05386e5 100644
--- a/s_mp_sub.c
+++ b/s_mp_sub.c
@@ -6,64 +6,51 @@
/* low level subtraction (assumes |a| > |b|), HAC pp.595 Algorithm 14.9 */
mp_err s_mp_sub(const mp_int *a, const mp_int *b, mp_int *c)
{
- int olduse, min, max;
- mp_err err;
-
- /* find sizes */
- min = b->used;
- max = a->used;
+ int oldused = c->used, min = b->used, max = a->used, i;
+ mp_digit u;
/* init result */
if (c->alloc < max) {
+ mp_err err;
if ((err = mp_grow(c, max)) != MP_OKAY) {
return err;
}
}
- olduse = c->used;
- c->used = max;
-
- {
- mp_digit u, *tmpa, *tmpb, *tmpc;
- int i;
-
- /* alias for digit pointers */
- tmpa = a->dp;
- tmpb = b->dp;
- tmpc = c->dp;
-
- /* set carry to zero */
- u = 0;
- for (i = 0; i < min; i++) {
- /* T[i] = A[i] - B[i] - U */
- *tmpc = (*tmpa++ - *tmpb++) - u;
-
- /* U = carry bit of T[i]
- * Note this saves performing an AND operation since
- * if a carry does occur it will propagate all the way to the
- * MSB. As a result a single shift is enough to get the carry
- */
- u = *tmpc >> (MP_SIZEOF_BITS(mp_digit) - 1u);
- /* Clear carry from T[i] */
- *tmpc++ &= MP_MASK;
- }
+ c->used = max;
- /* now copy higher words if any, e.g. if A has more digits than B */
- for (; i < max; i++) {
- /* T[i] = A[i] - U */
- *tmpc = *tmpa++ - u;
+ /* set carry to zero */
+ u = 0;
+ for (i = 0; i < min; i++) {
+ /* T[i] = A[i] - B[i] - U */
+ c->dp[i] = (a->dp[i] - b->dp[i]) - u;
+
+ /* U = carry bit of T[i]
+ * Note this saves performing an AND operation since
+ * if a carry does occur it will propagate all the way to the
+ * MSB. As a result a single shift is enough to get the carry
+ */
+ u = c->dp[i] >> (MP_SIZEOF_BITS(mp_digit) - 1u);
+
+ /* Clear carry from T[i] */
+ c->dp[i] &= MP_MASK;
+ }
- /* U = carry bit of T[i] */
- u = *tmpc >> (MP_SIZEOF_BITS(mp_digit) - 1u);
+ /* now copy higher words if any, e.g. if A has more digits than B */
+ for (; i < max; i++) {
+ /* T[i] = A[i] - U */
+ c->dp[i] = a->dp[i] - u;
- /* Clear carry from T[i] */
- *tmpc++ &= MP_MASK;
- }
+ /* U = carry bit of T[i] */
+ u = c->dp[i] >> (MP_SIZEOF_BITS(mp_digit) - 1u);
- /* clear digits above used (since we may not have grown result above) */
- MP_ZERO_DIGITS(tmpc, olduse - c->used);
+ /* Clear carry from T[i] */
+ c->dp[i] &= MP_MASK;
}
+ /* clear digits above used (since we may not have grown result above) */
+ MP_ZERO_DIGITS(c->dp + c->used, oldused - c->used);
+
mp_clamp(c);
return MP_OKAY;
}