diff options
Diffstat (limited to 'crypto/bn/bn_div.c')
| -rw-r--r-- | crypto/bn/bn_div.c | 53 |
1 files changed, 13 insertions, 40 deletions
diff --git a/crypto/bn/bn_div.c b/crypto/bn/bn_div.c index c3772c243b..2e600c7c54 100644 --- a/crypto/bn/bn_div.c +++ b/crypto/bn/bn_div.c @@ -61,6 +61,7 @@ #include "cryptlib.h" #include "bn_lcl.h" + /* The old slow way */ #if 0 int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, @@ -152,6 +153,14 @@ int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, # endif /* __GNUC__ */ #endif /* NO_ASM */ + +/* BN_div computes dv := num / divisor, rounding towards zero, and sets up + * rm such that dv*divisor + rm = num holds. + * Thus: + * dv->neg == num->neg ^ divisor->neg (unless the result is zero) + * rm->neg == num->neg (unless the remainder is zero) + * If 'dv' or 'rm' is NULL, the respective value is not returned. + */ int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor, BN_CTX *ctx) { @@ -180,13 +189,13 @@ int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor, BN_CTX_start(ctx); tmp=BN_CTX_get(ctx); - tmp->neg=0; snum=BN_CTX_get(ctx); sdiv=BN_CTX_get(ctx); if (dv == NULL) res=BN_CTX_get(ctx); else res=dv; - if (res == NULL) goto err; + if (sdiv == NULL || res == NULL) goto err; + tmp->neg=0; /* First we normalise the numbers */ norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2); @@ -331,7 +340,8 @@ int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor, if (rm != NULL) { BN_rshift(rm,snum,norm_shift); - rm->neg=num->neg; + if (!BN_is_zero(rm)) + rm->neg = num->neg; } BN_CTX_end(ctx); return(1); @@ -341,40 +351,3 @@ err: } #endif - -/* rem != m */ -int BN_mod(BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx) - { -#if 0 /* The old slow way */ - int i,nm,nd; - BIGNUM *dv; - - if (BN_ucmp(m,d) < 0) - return((BN_copy(rem,m) == NULL)?0:1); - - BN_CTX_start(ctx); - dv=BN_CTX_get(ctx); - - if (!BN_copy(rem,m)) goto err; - - nm=BN_num_bits(rem); - nd=BN_num_bits(d); - if (!BN_lshift(dv,d,nm-nd)) goto err; - for (i=nm-nd; i>=0; i--) - { - if (BN_cmp(rem,dv) >= 0) - { - if (!BN_sub(rem,rem,dv)) goto err; - } - if (!BN_rshift1(dv,dv)) goto err; - } - BN_CTX_end(ctx); - return(1); - err: - BN_CTX_end(ctx); - return(0); -#else - return(BN_div(NULL,rem,m,d,ctx)); -#endif - } - |