Initial commit

pywii/ecmodule/_ecmodule.c

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+// Copyright 2007,2008  Segher Boessenkool  <segher@kernel.crashing.org>
+// Copyright 2008  Hector Martin  <marcan@marcansoft.com>
+// Licensed under the terms of the GNU GPL, version 2
+// http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt
+#include "Python.h"
+#include <stdint.h>
+
+typedef uint8_t u8;
+typedef uint32_t u32;
+
+/* ----------------------------------------------------- */
+
+static void elt_copy(u8 *d, const u8 *a)
+{
+	memcpy(d, a, 30);
+}
+
+static void elt_zero(u8 *d)
+{
+	memset(d, 0, 30);
+}
+
+static int elt_is_zero(const u8 *d)
+{
+	u32 i;
+
+	for (i = 0; i < 30; i++)
+		if (d[i] != 0)
+			return 0;
+
+	return 1;
+}
+
+static void elt_add(u8 *d, const u8 *a, const u8 *b)
+{
+	u32 i;
+
+	for (i = 0; i < 30; i++)
+		d[i] = a[i] ^ b[i];
+}
+
+static void elt_mul_x(u8 *d, const u8 *a)
+{
+	u8 carry, x, y;
+	u32 i;
+
+	carry = a[0] & 1;
+
+	x = 0;
+	for (i = 0; i < 29; i++) {
+		y = a[i + 1];
+		d[i] = x ^ (y >> 7);
+		x = y << 1;
+	}
+	d[29] = x ^ carry;
+
+	d[20] ^= carry << 2;
+}
+
+static void elt_mul(u8 *d, const u8 *a, const u8 *b)
+{
+	u32 i, n;
+	u8 mask;
+
+	elt_zero(d);
+
+	i = 0;
+	mask = 1;
+	for (n = 0; n < 233; n++) {
+		elt_mul_x(d, d);
+
+		if ((a[i] & mask) != 0)
+			elt_add(d, d, b);
+
+		mask >>= 1;
+		if (mask == 0) {
+			mask = 0x80;
+			i++;
+		}
+	}
+}
+
+static const u8 square[16] =
+		"\x00\x01\x04\x05\x10\x11\x14\x15\x40\x41\x44\x45\x50\x51\x54\x55";
+
+static void elt_square_to_wide(u8 *d, const u8 *a)
+{
+	u32 i;
+
+	for (i = 0; i < 30; i++) {
+		d[2*i] = square[a[i] >> 4];
+		d[2*i + 1] = square[a[i] & 15];
+	}
+}
+
+static void wide_reduce(u8 *d)
+{
+	u32 i;
+	u8 x;
+
+	for (i = 0; i < 30; i++) {
+		x = d[i];
+
+		d[i + 19] ^= x >> 7;
+		d[i + 20] ^= x << 1;
+
+		d[i + 29] ^= x >> 1;
+		d[i + 30] ^= x << 7;
+	}
+
+	x = d[30] & ~1;
+
+	d[49] ^= x >> 7;
+	d[50] ^= x << 1;
+
+	d[59] ^= x >> 1;
+
+	d[30] &= 1;
+}
+
+static void elt_square(u8 *d, const u8 *a)
+{
+	u8 wide[60];
+
+	elt_square_to_wide(wide, a);
+	wide_reduce(wide);
+
+	elt_copy(d, wide + 30);
+}
+
+static void itoh_tsujii(u8 *d, const u8 *a, const u8 *b, u32 j)
+{
+	u8 t[30];
+
+	elt_copy(t, a);
+	while (j--) {
+		elt_square(d, t);
+		elt_copy(t, d);
+	}
+
+	elt_mul(d, t, b);
+}
+
+static void elt_inv(u8 *d, const u8 *a)
+{
+	u8 t[30];
+	u8 s[30];
+
+	itoh_tsujii(t, a, a, 1);
+	itoh_tsujii(s, t, a, 1);
+	itoh_tsujii(t, s, s, 3);
+	itoh_tsujii(s, t, a, 1);
+	itoh_tsujii(t, s, s, 7);
+	itoh_tsujii(s, t, t, 14);
+	itoh_tsujii(t, s, a, 1);
+	itoh_tsujii(s, t, t, 29);
+	itoh_tsujii(t, s, s, 58);
+	itoh_tsujii(s, t, t, 116);
+	elt_square(d, s);
+}
+
+/* ----------------------------------------------------- */
+
+static PyObject *
+_ec_elt_mul(PyObject *self /* Not used */, PyObject *args)
+{
+	const char *a, *b;
+	char d[30];
+	int la, lb;
+	if (!PyArg_ParseTuple(args, "s#s#", &a, &la, &b, &lb))
+		return NULL;
+	
+	if(la != 30 || lb != 30) {
+		PyErr_SetString(PyExc_ValueError, "ELT lengths must be 30");
+		return NULL;
+	}
+	elt_mul(d,a,b);
+	return Py_BuildValue("s#", d, 30);
+}
+
+static PyObject *
+_ec_elt_inv(PyObject *self /* Not used */, PyObject *args)
+{
+	const char *a;
+	char d[30];
+	int la;
+
+	if (!PyArg_ParseTuple(args, "s#", &a, &la))
+		return NULL;
+	
+	if(la != 30) {
+		PyErr_SetString(PyExc_ValueError, "ELT length must be 30");
+		return NULL;
+	}
+	elt_inv(d,a);
+	return Py_BuildValue("s#", d, 30);
+}
+
+static PyObject *
+_ec_elt_square(PyObject *self /* Not used */, PyObject *args)
+{
+	const char *a;
+	char d[30];
+	int la;
+
+	if (!PyArg_ParseTuple(args, "s#", &a, &la))
+		return NULL;
+	
+	if(la != 30) {
+		PyErr_SetString(PyExc_ValueError, "ELT length must be 30");
+		return NULL;
+	}
+	elt_square(d,a);
+	return Py_BuildValue("s#", d, 30);
+}
+
+/* List of methods defined in the module */
+
+static struct PyMethodDef _ec_methods[] = {
+	{"elt_mul",	(PyCFunction)_ec_elt_mul,	METH_VARARGS,	"Multiply two ELTs"},
+	{"elt_inv",	(PyCFunction)_ec_elt_inv,	METH_VARARGS,	"Take the inverse of an ELT"},
+	{"elt_square",	(PyCFunction)_ec_elt_square,	METH_VARARGS,	"Efficiently square an ELT"},
+ 
+	{NULL,	 (PyCFunction)NULL, 0, NULL}		/* sentinel */
+};
+
+
+/* Initialization function for the module (*must* be called init_ec) */
+
+static char _ec_module_documentation[] = 
+"Faster C versions of some ELT functions"
+;
+
+void
+init_ec()
+{
+	PyObject *m, *d;
+
+	/* Create the module and add the functions */
+	m = Py_InitModule4("_ec", _ec_methods,
+		_ec_module_documentation,
+		(PyObject*)NULL,PYTHON_API_VERSION);
+
+	/* Check for errors */
+	if (PyErr_Occurred())
+		Py_FatalError("can't initialize module _ec");
+}
+