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bn_shift.c: minimize reallocations, which allows BN_FLG_STATIC_DATA to

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be shifted in specific cases.
This commit is contained in:
Andy Polyakov 2011-10-17 17:20:48 +00:00
parent 993adc0531
commit 79ba545c09
1 changed files with 15 additions and 12 deletions
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27
crypto/bn/bn_shift.c
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@ -99,7 +99,7 @@ int BN_lshift1(BIGNUM *r, const BIGNUM *a)
int BN_rshift1(BIGNUM *r, const BIGNUM *a) int BN_rshift1(BIGNUM *r, const BIGNUM *a)
{ {
BN_ULONG *ap,*rp,t,c; BN_ULONG *ap,*rp,t,c;
int i; int i,j;
bn_check_top(r); bn_check_top(r);
bn_check_top(a); bn_check_top(a);
@ -109,22 +109,25 @@ int BN_rshift1(BIGNUM *r, const BIGNUM *a)
BN_zero(r); BN_zero(r);
return(1); return(1);
} }
i = a->top;
ap= a->d;
j = i-(ap[i-1]==1);
if (a != r) if (a != r)
{ {
if (bn_wexpand(r,a->top) == NULL) return(0); if (bn_wexpand(r,j) == NULL) return(0);
r->top=a->top;
r->neg=a->neg; r->neg=a->neg;
} }
ap=a->d;
rp=r->d; rp=r->d;
c=0; t=ap[--i];
for (i=a->top-1; i>=0; i--) c=(t&1)?BN_TBIT:0;
if (t>>=1) rp[i]=t;
while (i>0)
{ {
t=ap[i]; t=ap[--i];
rp[i]=((t>>1)&BN_MASK2)|c; rp[i]=((t>>1)&BN_MASK2)|c;
c=(t&1)?BN_TBIT:0; c=(t&1)?BN_TBIT:0;
} }
bn_correct_top(r); r->top=j;
bn_check_top(r); bn_check_top(r);
return(1); return(1);
} }
@ -182,10 +185,11 @@ int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
BN_zero(r); BN_zero(r);
return(1); return(1);
} }
i = (BN_num_bits(a)-n+(BN_BITS2-1))/BN_BITS2;
if (r != a) if (r != a)
{ {
r->neg=a->neg; r->neg=a->neg;
if (bn_wexpand(r,a->top-nw+1) == NULL) return(0); if (bn_wexpand(r,i) == NULL) return(0);
} }
else else
{ {
@ -196,7 +200,7 @@ int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
f= &(a->d[nw]); f= &(a->d[nw]);
t=r->d; t=r->d;
j=a->top-nw; j=a->top-nw;
r->top=j; r->top=i;
if (rb == 0) if (rb == 0)
{ {
@ -212,9 +216,8 @@ int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
l= *(f++); l= *(f++);
*(t++) =(tmp|(l<<lb))&BN_MASK2; *(t++) =(tmp|(l<<lb))&BN_MASK2;
} }
*(t++) =(l>>rb)&BN_MASK2; if ((l = (l>>rb)&BN_MASK2)) *(t) = l;
} }
bn_correct_top(r);
bn_check_top(r); bn_check_top(r);
return(1); return(1);
} }