Implement efficient reduction for pleasant-looking primes.

[u/mdw/catacomb] / mpreduce.h

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+/* -*-c-*-
+ *
+ * $Id: mpreduce.h,v 1.1 2004/03/27 00:04:46 mdw Exp $
+ *
+ * Efficient reduction modulo nice primes
+ *
+ * (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.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: mpreduce.h,v $
+ * Revision 1.1  2004/03/27 00:04:46  mdw
+ * Implement efficient reduction for pleasant-looking primes.
+ *
+ */
+
+#ifndef CATACOMB_MPREDUCE_H
+#define CATACOMB_MPREDUCE_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef struct mpreduce_instr {
+  unsigned op;                         /* Instruction opcode */
+  size_t argx, argy;                   /* Immediate arguments */
+} mpreduce_instr;
+
+enum {
+  MPRI_ADD,                            /* Add @p@ offset by @x@ words */
+  MPRI_ADDLSL,                         /* Add @p << y@ offset by @x@ */
+  MPRI_SUB,                            /* Sub @p@ offset by @x@ words */
+  MPRI_SUBLSL,                         /* Sub @p << y@ offset by @x@ */
+  MPRI_MAX
+};
+
+typedef struct mpreduce {
+  size_t lim;                          /* Word containing top bit */
+  unsigned s;                          /* Shift for top word */
+  mp *p;                               /* Copy of the modulus */
+  size_t in;                           /* Number of instruction words */
+  mpreduce_instr *iv;                  /* Vector of instructions */
+} mpreduce;
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @mpreduce_create@ --- *
+ *
+ * Arguments:  @gfreduce *r@ = structure to fill in
+ *             @mp *x@ = an integer
+ *
+ * Returns:    ---
+ *
+ * Use:                Initializes a context structure for reduction.
+ */
+
+extern void mpreduce_create(mpreduce */*r*/, mp */*p*/);
+
+/* --- @mpreduce_destroy@ --- *
+ *
+ * Arguments:  @mpreduce *r@ = structure to free
+ *
+ * Returns:    ---
+ *
+ * Use:                Reclaims the resources from a reduction context.
+ */
+
+extern void mpreduce_destroy(mpreduce */*r*/);
+
+/* --- @mpreduce_dump@ --- *
+ *
+ * Arguments:  @mpreduce *r@ = structure to dump
+ *             @FILE *fp@ = file to dump on
+ *
+ * Returns:    ---
+ *
+ * Use:                Dumps a reduction context.
+ */
+
+extern void mpreduce_dump(mpreduce */*r*/, FILE */*fp*/);
+
+/* --- @mpreduce_do@ --- *
+ *
+ * Arguments:  @mpreduce *r@ = reduction context
+ *             @mp *d@ = destination
+ *             @mp *x@ = source
+ *
+ * Returns:    Destination, @x@ reduced modulo the reduction poly.
+ */
+
+extern mp *mpreduce_do(mpreduce */*r*/, mp */*d*/, mp */*x*/);
+
+/* --- @mpreduce_exp@ --- *
+ *
+ * Arguments:  @mpreduce *mr@ = pointer to reduction context
+ *              @mp *d@ = fake destination
+ *              @mp *a@ = base
+ *              @mp *e@ = exponent
+ *
+ * Returns:     Result, %$a^e \bmod m$%.
+ */
+
+extern mp *mpreduce_exp(mpreduce */*mr*/, mp */*d*/, mp */*a*/, mp */*e*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif