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Diffstat (limited to 'crypto/bn/bn_sub.c')
| -rw-r--r-- | crypto/bn/bn_sub.c | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/crypto/bn/bn_sub.c b/crypto/bn/bn_sub.c new file mode 100644 index 0000000000..b0febc3421 --- /dev/null +++ b/crypto/bn/bn_sub.c @@ -0,0 +1,176 @@ +/* crypto/bn/bn_sub.c */ +/* Copyright (C) 1995-1997 Eric Young (eay@cryptsoft.com) + * All rights reserved. + * + * This package is an SSL implementation written + * by Eric Young (eay@cryptsoft.com). + * The implementation was written so as to conform with Netscapes SSL. + * + * This library is free for commercial and non-commercial use as long as + * the following conditions are aheared to. The following conditions + * apply to all code found in this distribution, be it the RC4, RSA, + * lhash, DES, etc., code; not just the SSL code. The SSL documentation + * included with this distribution is covered by the same copyright terms + * except that the holder is Tim Hudson (tjh@cryptsoft.com). + * + * Copyright remains Eric Young's, and as such any Copyright notices in + * the code are not to be removed. + * If this package is used in a product, Eric Young should be given attribution + * as the author of the parts of the library used. + * This can be in the form of a textual message at program startup or + * in documentation (online or textual) provided with the package. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * "This product includes cryptographic software written by + * Eric Young (eay@cryptsoft.com)" + * The word 'cryptographic' can be left out if the rouines from the library + * being used are not cryptographic related :-). + * 4. If you include any Windows specific code (or a derivative thereof) from + * the apps directory (application code) you must include an acknowledgement: + * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" + * + * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * The licence and distribution terms for any publically available version or + * derivative of this code cannot be changed. i.e. this code cannot simply be + * copied and put under another distribution licence + * [including the GNU Public Licence.] + */ + +#include <stdio.h> +#include "cryptlib.h" +#include "bn_lcl.h" + +/* unsigned subtraction of b from a, a must be larger than b. */ +void bn_qsub(r, a, b) +BIGNUM *r; +BIGNUM *a; +BIGNUM *b; + { + int max,min; + register BN_ULONG t1,t2,*ap,*bp,*rp; + int i,carry; +#if defined(IRIX_CC_BUG) && !defined(LINT) + int dummy; +#endif + + max=a->top; + min=b->top; + ap=a->d; + bp=b->d; + rp=r->d; + + carry=0; + for (i=0; i<min; i++) + { + t1= *(ap++); + t2= *(bp++); + if (carry) + { + carry=(t1 <= t2); + t1=(t1-t2-1); + } + else + { + carry=(t1 < t2); + t1=(t1-t2); + } +#if defined(IRIX_CC_BUG) && !defined(LINT) + dummy=t1; +#endif + *(rp++)=t1&BN_MASK2; + } + if (carry) /* subtracted */ + { + while (i < max) + { + i++; + t1= *(ap++); + t2=(t1-1)&BN_MASK2; + *(rp++)=t2; + if (t1 > t2) break; + } + } + memcpy(rp,ap,sizeof(*rp)*(max-i)); +/* for (; i<max; i++) + *(rp++)= *(ap++);*/ + + r->top=max; + bn_fix_top(r); + } + +int BN_sub(r, a, b) +BIGNUM *r; +BIGNUM *a; +BIGNUM *b; + { + int max,i; + int add=0,neg=0; + BIGNUM *tmp; + + /* a - b a-b + * a - -b a+b + * -a - b -(a+b) + * -a - -b b-a + */ + if (a->neg) + { + if (b->neg) + { tmp=a; a=b; b=tmp; } + else + { add=1; neg=1; } + } + else + { + if (b->neg) { add=1; neg=0; } + } + + if (add) + { + i=(a->top > b->top); + if (bn_expand(r,(((i)?a->top:b->top)+1)*BN_BITS2) == NULL) + return(0); + if (i) + bn_qadd(r,a,b); + else + bn_qadd(r,b,a); + r->neg=neg; + return(1); + } + + /* We are actually doing a - b :-) */ + + max=(a->top > b->top)?a->top:b->top; + if (bn_expand(r,max*BN_BITS2) == NULL) return(0); + if (BN_ucmp(a,b) < 0) + { + bn_qsub(r,b,a); + r->neg=1; + } + else + { + bn_qsub(r,a,b); + r->neg=0; + } + return(1); + } + |