From ff4f080282d1b0010ff8335b78e303338c7f32a8 Mon Sep 17 00:00:00 2001
From: Andrea Mazzoleni <amadvance@gmail.com>
Date: Sat, 7 Sep 2013 19:43:33 +0200
Subject: [PATCH] Adds table generation for reference.

---
 Makefile.am |   4 ++
 mktables.c  | 122 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 tables.h    |   6 +--
 3 files changed, 128 insertions(+), 4 deletions(-)
 create mode 100644 mktables.c

diff --git a/Makefile.am b/Makefile.am
index 026cda31..da0fab24 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,5 +1,6 @@
 bin_PROGRAMS = snapraid
 check_PROGRAMS = mktest
+EXTRA_PROGRAMS = mktables
 
 snapraid_SOURCES = \
 	snapraid.c \
@@ -26,6 +27,9 @@ snapraid_SOURCES = \
 	mingw.c \
 	unix.c
 
+mktables_SOURCES = \
+	mktables.c
+
 noinst_HEADERS = \
 	portable.h \
 	snapraid.h \
diff --git a/mktables.c b/mktables.c
new file mode 100644
index 00000000..8e4777ff
--- /dev/null
+++ b/mktables.c
@@ -0,0 +1,122 @@
+/*
+ * Copyright (C) 2011 Andrea Mazzoleni
+ *
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+
+unsigned char gfmul(unsigned char a, unsigned char b)
+{
+	unsigned char v;
+
+	v = 0;
+	while (b)  {
+		if ((b & 1) != 0)
+			v ^= a;
+
+		if ((a & 0x80) != 0) {
+			a <<= 1;
+			a ^= 0x1d;
+		} else {
+			a <<= 1;
+		}
+
+		b >>= 1;
+	}
+
+	return v;
+}
+
+int main(void)
+{
+	unsigned char pow2[256];
+	unsigned char log2[256];
+	unsigned char v;
+	int i, j;
+
+	/* a*b */
+	printf("const unsigned char  __attribute__((aligned(256))) gfmul[256][256] =\n");
+	printf("{\n");
+	for(i=0;i<256;++i) {
+		printf("\t{\n");
+		for(j=0;j<256;++j) {
+			if (j % 8 == 0)
+				printf("\t\t");
+			printf("0x%02x,", gfmul(i, j));
+			if (j % 8 == 7)
+				printf("\n");
+			else
+				printf(" ");
+		}
+		printf("\t},\n");
+	}
+	printf("};\n\n");
+
+	/* 2^a */
+	printf("const unsigned char __attribute__((aligned(256))) gfexp2[256] =\n");
+	printf("{\n");
+	v = 1;
+	for(i=0;i<256;++i) {
+		if (i % 8 == 0)
+			printf("\t");
+		pow2[i] = v;
+		log2[pow2[i]] = i;
+		printf("0x%02x,", v);
+		v = gfmul(v, 2);
+		if (i % 8 == 7)
+			printf("\n");
+		else
+			printf(" ");
+	}
+	printf("};\n\n");
+
+	/* 4^a */
+	printf("const unsigned char __attribute__((aligned(256))) gfexp4[256] =\n");
+	printf("{\n");
+	v = 1;
+	for(i=0;i<256;++i) {
+		if (i % 8 == 0)
+			printf("\t");
+		printf("0x%02x,", v);
+		v = gfmul(v, 4);
+		if (i % 8 == 7)
+			printf("\n");
+		else
+			printf(" ");
+	}
+	printf("};\n\n");
+
+	/* 1/a */
+	printf("const unsigned char __attribute__((aligned(256))) gfinv[256] =\n");
+	printf("{\n");
+	printf("\t/* note that the first element is not significative */\n");
+	for(i=0;i<256;++i) {
+		if (i % 8 == 0)
+			printf("\t");
+		if (i == 0)
+			v = 0;
+		else
+			v = pow2[255 - log2[i]];
+		printf("0x%02x,", v);
+		if (i % 8 == 7)
+			printf("\n");
+		else
+			printf(" ");
+	}
+	printf("};\n\n");
+
+	return 0;
+}
+
diff --git a/tables.h b/tables.h
index 55547f58..b710e19b 100644
--- a/tables.h
+++ b/tables.h
@@ -8756,8 +8756,7 @@ const unsigned char __attribute__((aligned(256))) gfexp2[256] =
 	0x12, 0x24, 0x48, 0x90, 0x3d, 0x7a, 0xf4, 0xf5,
 	0xf7, 0xf3, 0xfb, 0xeb, 0xcb, 0x8b, 0x0b, 0x16,
 	0x2c, 0x58, 0xb0, 0x7d, 0xfa, 0xe9, 0xcf, 0x83,
-	0x1b, 0x36, 0x6c, 0xd8, 0xad, 0x47, 0x8e, 0x00,
-	/* note that the last element is not significative */
+	0x1b, 0x36, 0x6c, 0xd8, 0xad, 0x47, 0x8e, 0x01,
 };
 
 const unsigned char __attribute__((aligned(256))) gfexp4[256] =
@@ -8793,8 +8792,7 @@ const unsigned char __attribute__((aligned(256))) gfexp4[256] =
 	0x19, 0x64, 0x8d, 0x0e, 0x38, 0xe0, 0xa7, 0xa6,
 	0xa2, 0xb2, 0xf2, 0xef, 0x9b, 0x56, 0x45, 0x09,
 	0x24, 0x90, 0x7a, 0xf5, 0xf3, 0xeb, 0x8b, 0x16,
-	0x58, 0x7d, 0xe9, 0x83, 0x36, 0xd8, 0x47, 0x00,
-	/* note that the last element is not significative */
+	0x58, 0x7d, 0xe9, 0x83, 0x36, 0xd8, 0x47, 0x01,
 };
 
 const unsigned char __attribute__((aligned(256))) gfinv[256] =