1 files changed, 137 insertions, 0 deletions
diff --git a/c_src/raid/gf.h b/c_src/raid/gf.h
new file mode 100644
index 00000000..1702c287
--- /dev/null
+++ b/c_src/raid/gf.h
@@ -0,0 +1,137 @@
+/*
+ * Copyright (C) 2013 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.
+ */
+
+#ifndef __RAID_GF_H
+#define __RAID_GF_H
+
+/*
+ * Galois field operations.
+ *
+ * Basic range checks are implemented using BUG_ON().
+ */
+
+/*
+ * GF a*b.
+ */
+static __always_inline uint8_t mul(uint8_t a, uint8_t b)
+{
+	return gfmul[a][b];
+}
+
+/*
+ * GF 1/a.
+ * Not defined for a == 0.
+ */
+static __always_inline uint8_t inv(uint8_t v)
+{
+	BUG_ON(v == 0); /* division by zero */
+
+	return gfinv[v];
+}
+
+/*
+ * GF 2^a.
+ */
+static __always_inline uint8_t pow2(int v)
+{
+	BUG_ON(v < 0 || v > 254); /* invalid exponent */
+
+	return gfexp[v];
+}
+
+/*
+ * Gets the multiplication table for a specified value.
+ */
+static __always_inline const uint8_t *table(uint8_t v)
+{
+	return gfmul[v];
+}
+
+/*
+ * Gets the generator matrix coefficient for parity 'p' and disk 'd'.
+ */
+static __always_inline uint8_t A(int p, int d)
+{
+	return gfgen[p][d];
+}
+
+/*
+ * Dereference as uint8_t
+ */
+#define v_8(p) (*(uint8_t *)&(p))
+
+/*
+ * Dereference as uint32_t
+ */
+#define v_32(p) (*(uint32_t *)&(p))
+
+/*
+ * Dereference as uint64_t
+ */
+#define v_64(p) (*(uint64_t *)&(p))
+
+/*
+ * Multiply each byte of a uint32 by 2 in the GF(2^8).
+ */
+static __always_inline uint32_t x2_32(uint32_t v)
+{
+	uint32_t mask = v & 0x80808080U;
+
+	mask = (mask << 1) - (mask >> 7);
+	v = (v << 1) & 0xfefefefeU;
+	v ^= mask & 0x1d1d1d1dU;
+	return v;
+}
+
+/*
+ * Multiply each byte of a uint64 by 2 in the GF(2^8).
+ */
+static __always_inline uint64_t x2_64(uint64_t v)
+{
+	uint64_t mask = v & 0x8080808080808080ULL;
+
+	mask = (mask << 1) - (mask >> 7);
+	v = (v << 1) & 0xfefefefefefefefeULL;
+	v ^= mask & 0x1d1d1d1d1d1d1d1dULL;
+	return v;
+}
+
+/*
+ * Divide each byte of a uint32 by 2 in the GF(2^8).
+ */
+static __always_inline uint32_t d2_32(uint32_t v)
+{
+	uint32_t mask = v & 0x01010101U;
+
+	mask = (mask << 8) - mask;
+	v = (v >> 1) & 0x7f7f7f7fU;
+	v ^= mask & 0x8e8e8e8eU;
+	return v;
+}
+
+/*
+ * Divide each byte of a uint64 by 2 in the GF(2^8).
+ */
+static __always_inline uint64_t d2_64(uint64_t v)
+{
+	uint64_t mask = v & 0x0101010101010101ULL;
+
+	mask = (mask << 8) - mask;
+	v = (v >> 1) & 0x7f7f7f7f7f7f7f7fULL;
+	v ^= mask & 0x8e8e8e8e8e8e8e8eULL;
+	return v;
+}
+
+#endif
+