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+/* -*-c-*-
+ *
+ * Simple scalar fields
+ *
+ * (c) 2017 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of secnet.
+ * See README for full list of copyright holders.
+ *
+ * secnet is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version d of the License, or
+ * (at your option) any later version.
+ *
+ * secnet 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 3 along with secnet; if not, see
+ * https://www.gnu.org/licenses/gpl.html.
+ *
+ * This file was originally part of Catacomb, but has been automatically
+ * modified for incorporation into secnet: see `import-catacomb-crypto'
+ * for details.
+ *
+ * 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_SCAF_H
+#define CATACOMB_SCAF_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "fake-mLib-bits.h"
+
+/*----- Type selection ----------------------------------------------------*/
+
+  typedef uint32 scaf_piece;
+  typedef uint64 scaf_dblpiece;
+
+#define SCAF_NPIECE(bits, piecewd) (((bits) + piecewd - 1)/piecewd)
+
+/*----- Functions provided -----------------------------------------------*/
+
+/* --- @scaf_load@ --- *
+ *
+ * Arguments:	@scaf_piece *z@ = where to write the result
+ *		@const octet *b@ = source buffer to read
+ *		@size_t sz@ = size of the source buffer
+ *		@size_t npiece@ = number of pieces to read
+ *		@unsigned piecewd@ = nominal width of pieces in bits
+ *
+ * Returns:	---
+ *
+ * Use:		Loads a little-endian encoded scalar into a vector @z@ of
+ *		single-precision pieces.
+ */
+
+extern void scaf_load(scaf_piece */*z*/, const octet */*b*/, size_t /*sz*/,
+		      size_t /*npiece*/, unsigned /*piecewd*/);
+
+/* --- @scaf_loaddbl@ --- *
+ *
+ * Arguments:	@scaf_dblpiece *z@ = where to write the result
+ *		@const octet *b@ = source buffer to read
+ *		@size_t sz@ = size of the source buffer
+ *		@size_t npiece@ = number of pieces to read
+ *		@unsigned piecewd@ = nominal width of pieces in bits
+ *
+ * Returns:	---
+ *
+ * Use:		Loads a little-endian encoded scalar into a vector @z@ of
+ *		double-precision pieces.
+ */
+
+extern void scaf_loaddbl(scaf_dblpiece */*z*/, const octet */*b*/,
+			 size_t /*sz*/, size_t /*npiece*/,
+			 unsigned /*piecewd*/);
+
+/* --- @scaf_store@ --- *
+ *
+ * Arguments:	@octet *b@ = buffer to fill in
+ *		@size_t sz@ = size of the buffer
+ *		@const scaf_piece *x@ = scalar to store
+ *		@size_t npiece@ = number of pieces in @x@
+ *		@unsigned piecewd@ = nominal width of pieces in bits
+ *
+ * Returns:	---
+ *
+ * Use:		Stores a scalar in a vector of single-precison pieces as a
+ *		little-endian vector of bytes.
+ */
+
+extern void scaf_store(octet */*b*/, size_t /*sz*/, const scaf_piece */*x*/,
+		       size_t /*npiece*/, unsigned /*piecewd*/);
+
+/* --- @scaf_mul@ --- *
+ *
+ * Arguments:	@scaf_dblpiece *z@ = where to put the answer
+ *		@const scaf_piece *x, *y@ = the operands
+ *		@size_t npiece@ = the length of the operands
+ *
+ * Returns:	---
+ *
+ * Use:		Multiply two scalars.  The destination must have space for
+ *		@2*npiece@ pieces (though the last one will always be zero).
+ *		The result is not reduced.
+ */
+
+extern void scaf_mul(scaf_dblpiece */*z*/, const scaf_piece */*x*/,
+		     const scaf_piece */*y*/, size_t /*npiece*/);
+
+/* --- @scaf_reduce@ --- *
+ *
+ * Arguments:	@scaf_piece *z@ = where to write the result
+ *		@const scaf_dblpiece *x@ = the operand to reduce
+ *		@const scaf_piece *l@ = the modulus, in internal format
+ *		@const scaf_piece *mu@ = scaled approximation to @1/l@
+ *		@size_t npiece@ = number of pieces in @l@
+ *		@unsigned piecewd@ = nominal width of a piece in bits
+ *		@scaf_piece *scratch@ = @3*npiece@ scratch pieces
+ *
+ * Returns:	---
+ *
+ * Use:		Reduce @x@ (a vector of @2*npiece@ double-precision pieces)
+ *		modulo @l@ (a vector of @npiece@ single-precision pieces),
+ *		writing the result to @z@.
+ *
+ *		Write @n = npiece@, @w = piecewd@, and %$B = 2^w$%.  The
+ *		operand @mu@ must contain %$\lfloor B^{2n}/l \rfloor$%, in
+ *		@npiece + 1@ pieces.  Furthermore, we must have
+ *		%$3 l < B^n$%.  (Fiddle with %$w$% if necessary.)
+ */
+
+extern void scaf_reduce(scaf_piece */*z*/, const scaf_dblpiece */*x*/,
+			const scaf_piece */*l*/, const scaf_piece */*mu*/,
+			size_t /*npiece*/, unsigned /*piecewd*/,
+			scaf_piece */*scratch*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif