Implement fast increment / decrement functions.

include/cryb/mpi.h

@@ -49,6 +49,8 @@ const char *cryb_mpi_version(void);
 #define mpi_cmp_u32		cryb_mpi_cmp_u32
 #define mpi_cmp_u64		cryb_mpi_cmp_u64
 #define mpi_copy		cryb_mpi_copy
+#define mpi_dec			cryb_mpi_dec
+#define mpi_dec_abs		cryb_mpi_dec_abs
 #define mpi_destroy		cryb_mpi_destroy
 #define mpi_eq			cryb_mpi_eq
 #define mpi_eq_abs		cryb_mpi_eq_abs
@@ -60,6 +62,8 @@ const char *cryb_mpi_version(void);
 #define mpi_eq_u64		cryb_mpi_eq_u64
 #define mpi_gcd_abs		cryb_mpi_gcd_abs
 #define mpi_grow		cryb_mpi_grow
+#define mpi_inc			cryb_mpi_inc
+#define mpi_inc_abs		cryb_mpi_inc_abs
 #define mpi_init		cryb_mpi_init
 #define mpi_load		cryb_mpi_load
 #define mpi_lsb			cryb_mpi_lsb
@@ -99,6 +103,8 @@ int mpi_cmp_i64(const cryb_mpi *, int64_t);
 int mpi_cmp_u32(const cryb_mpi *, uint32_t);
 int mpi_cmp_u64(const cryb_mpi *, uint64_t);
 int mpi_copy(cryb_mpi *, const cryb_mpi *);
+int mpi_dec(cryb_mpi *);
+int mpi_dec_abs(cryb_mpi *);
 void mpi_destroy(cryb_mpi *);
 int mpi_eq(const cryb_mpi *, const cryb_mpi *);
 int mpi_eq_abs(const cryb_mpi *, const cryb_mpi *);
@@ -110,6 +116,8 @@ int mpi_eq_u32(const cryb_mpi *, uint32_t);
 int mpi_eq_u64(const cryb_mpi *, uint64_t);
 int mpi_gcd_abs(cryb_mpi *, const cryb_mpi *, const cryb_mpi *);
 int mpi_grow(cryb_mpi *, unsigned int);
+int mpi_inc(cryb_mpi *);
+int mpi_inc_abs(cryb_mpi *);
 void mpi_init(cryb_mpi *);
 int mpi_load(cryb_mpi *, const uint8_t *, size_t);
 unsigned int mpi_lsb(const cryb_mpi *);

lib/mpi/Makefile.am

@@ -10,6 +10,8 @@ libcryb_mpi_la_SOURCES = \
 	cryb_mpi_cmp_i32.c \
 	cryb_mpi_cmp_i64.c \
 	cryb_mpi_copy.c \
+	cryb_mpi_dec.c \
+	cryb_mpi_dec_abs.c \
 	cryb_mpi_destroy.c \
 	cryb_mpi_eq.c \
 	cryb_mpi_eq_abs.c \
@@ -17,6 +19,8 @@ libcryb_mpi_la_SOURCES = \
 	cryb_mpi_eq_i64.c \
 	cryb_mpi_gcd_abs.c \
 	cryb_mpi_grow.c \
+	cryb_mpi_inc.c \
+	cryb_mpi_inc_abs.c \
 	cryb_mpi_init.c \
 	cryb_mpi_load.c \
 	cryb_mpi_lsb.c \

lib/mpi/cryb_mpi_dec.c

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2017 Dag-Erling Smørgrav
+ * All rights reserved.
+ *
+ * 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 above 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. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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.
+ */
+
+#include "cryb/impl.h"
+
+#include <stddef.h>
+#include <stdint.h>
+#include <strings.h>
+
+#include <cryb/bitwise.h>
+#include <cryb/mpi.h>
+
+#include "cryb_mpi_impl.h"
+
+/*
+ * Decrement X in place.
+ */
+int
+mpi_dec(cryb_mpi *X)
+{
+
+	if (X->msb == 0) {
+		mpi_set(X, -1);
+	} else if (X->neg) {
+		if (mpi_inc_abs(X) != 0)
+			return (-1);
+	} else {
+		if (mpi_dec_abs(X) != 0)
+			return (-1);
+	}
+	return (0);
+}

lib/mpi/cryb_mpi_dec_abs.c

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2017 Dag-Erling Smørgrav
+ * All rights reserved.
+ *
+ * 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 above 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. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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.
+ */
+
+#include "cryb/impl.h"
+
+#include <errno.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <strings.h>
+
+#include <cryb/bitwise.h>
+#include <cryb/mpi.h>
+
+#include "cryb_mpi_impl.h"
+
+/*
+ * Decrement X in place.
+ */
+int
+mpi_dec_abs(cryb_mpi *X)
+{
+	unsigned int i;
+
+	/* trivial case: zero */
+	if (X->msb == 0) {
+		errno = EINVAL;
+		return (-1);
+	}
+
+	/* decrement least-significant word and propagate */
+	for (i = 0; X->words[i]-- == 0; ++i)
+		/* nothing */;
+	i = X->msb / 32;
+	if (X->words[i] == 0)
+		--i;
+	X->msb = i * 32 + flsl(X->words[i]);
+
+	return (0);
+}

lib/mpi/cryb_mpi_inc.c

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2017 Dag-Erling Smørgrav
+ * All rights reserved.
+ *
+ * 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 above 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. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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.
+ */
+
+#include "cryb/impl.h"
+
+#include <stddef.h>
+#include <stdint.h>
+#include <strings.h>
+
+#include <cryb/bitwise.h>
+#include <cryb/mpi.h>
+
+#include "cryb_mpi_impl.h"
+
+/*
+ * Increment X in place.
+ */
+int
+mpi_inc(cryb_mpi *X)
+{
+
+	if (X->msb == 0) {
+		mpi_set(X, 1);
+	} else if (X->neg) {
+		if (mpi_dec_abs(X) != 0)
+			return (-1);
+	} else {
+		if (mpi_inc_abs(X) != 0)
+			return (-1);
+	}
+	return (0);
+}

lib/mpi/cryb_mpi_inc_abs.c

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2017 Dag-Erling Smørgrav
+ * All rights reserved.
+ *
+ * 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 above 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. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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.
+ */
+
+#include "cryb/impl.h"
+
+#include <stddef.h>
+#include <stdint.h>
+#include <strings.h>
+
+#include <cryb/bitwise.h>
+#include <cryb/mpi.h>
+
+#include "cryb_mpi_impl.h"
+
+/*
+ * Increment X in place.
+ */
+int
+mpi_inc_abs(cryb_mpi *X)
+{
+	unsigned int i;
+
+	/* trivial case: zero */
+	if (X->msb == 0) {
+		X->words[0] = 1;
+		X->msb = 1;
+		return (0);
+	}
+
+	/* may grow by 1 bit */
+	if (mpi_grow(X, X->msb + 1) != 0)
+		return (-1);
+
+	/* increment least-significant word and propagate */
+	for (i = 0; ++X->words[i] == 0; ++i)
+		/* nothing */;
+	i = X->msb / 32;
+	X->msb = i * 32 + flsl(X->words[i]);
+
+	return (0);
+}