X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/ba6e6b64033b1f9de49feccb5c9cd438354481f7..0f00dc4c8eb47e67bc0f148c2dd109f73a451e0a:/math/gf.h

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+/* -*-c-*-
+ *
+ * Arithmetic on binary polynomials
+ *
+ * (c) 2004 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * Catacomb is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+#ifndef CATACOMB_GF_H
+#define CATACOMB_GF_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#ifndef CATACOMB_MP_H
+#  include "mp.h"
+#endif
+
+#ifndef CATACOMB_GFX_H
+#  include "gfx.h"
+#endif
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @gf_add@ --- *
+ *
+ * Arguments:	@mp *d@ = destination
+ *		@mp *a, *b@ = sources
+ *
+ * Returns:	Result, @a@ added to @b@.
+ */
+
+extern mp *gf_add(mp */*d*/, mp */*a*/, mp */*b*/);
+#define gf_sub gf_add
+
+/* --- @gf_mul@ --- *
+ *
+ * Arguments:	@mp *d@ = destination
+ *		@mp *a, *b@ = sources
+ *
+ * Returns:	Result, @a@ multiplied by @b@.
+ */
+
+extern mp *gf_mul(mp */*d*/, mp */*a*/, mp */*b*/);
+
+/* --- @gf_sqr@ --- *
+ *
+ * Arguments:	@mp *d@ = destination
+ *		@mp *a@ = source
+ *
+ * Returns:	Result, @a@ squared.
+ */
+
+extern mp *gf_sqr(mp */*d*/, mp */*a*/);
+
+/* --- @gf_div@ --- *
+ *
+ * Arguments:	@mp **qq, **rr@ = destination, quotient and remainder
+ *		@mp *a, *b@ = sources
+ *
+ * Use:		Calculates the quotient and remainder when @a@ is divided by
+ *		@b@.  The destinations @*qq@ and @*rr@ must be distinct.
+ *		Either of @qq@ or @rr@ may be null to indicate that the
+ *		result is irrelevant.  (Discarding both results is silly.)
+ *		There is a performance advantage if @a == *rr@.
+ */
+
+extern void gf_div(mp **/*qq*/, mp **/*rr*/, mp */*a*/, mp */*b*/);
+
+/* --- @gf_exp@ --- *
+ *
+ * Arguments:	@mp *d@ = fake destination
+ *		@mp *a@ = base
+ *		@mp *e@ = exponent
+ *
+ * Returns:	Result, %$a^e$%.
+ */
+
+extern mp *gf_exp(mp */*d*/, mp */*a*/, mp */*e*/);
+
+/* --- @gf_irreduciblep@ --- *
+ *
+ * Arguments:	@mp *f@ = a polynomial
+ *
+ * Returns:	Nonzero if the polynomial is irreducible; otherwise zero.
+ */
+
+extern int gf_irreduciblep(mp */*f*/);
+
+/* --- @gf_gcd@ --- *
+ *
+ * Arguments:	@mp **gcd, **xx, **yy@ = where to write the results
+ *		@mp *a, *b@ = sources (must be nonzero)
+ *
+ *
+ * Returns:	---
+ *
+ * Use:		Calculates @gcd(a, b)@, and two numbers @x@ and @y@ such that
+ *		@ax + by = gcd(a, b)@.  This is useful for computing modular
+ *		inverses.
+ */
+
+extern void gf_gcd(mp **/*gcd*/, mp **/*xx*/, mp **/*yy*/,
+		   mp */*a*/, mp */*b*/);
+
+/* -- @gf_modinv@ --- *
+ *
+ * Arguments:	@mp *d@ = destination
+ *		@mp *x@ = argument
+ *		@mp *p@ = modulus
+ *
+ * Returns:	The inverse %$x^{-1} \bmod p$%.
+ *
+ * Use:		Computes a modular inverse, the catch being that the
+ *		arguments and results are binary polynomials.  An assertion
+ *		fails if %$p$% has no inverse.
+ */
+
+extern mp *gf_modinv(mp */*d*/, mp */*x*/, mp */*p*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif