Ed25519 signature algorithm

libraries/Crypto/utility/LimbUtil.h

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+/*
+ * Copyright (C) 2015 Southern Storm Software, Pty Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef CRYPTO_LIMBUTIL_H
+#define CRYPTO_LIMBUTIL_H
+
+#include "ProgMemUtil.h"
+
+// Number of limbs in a big number value of various sizes.
+#define NUM_LIMBS_128BIT (16 / sizeof(limb_t))
+#define NUM_LIMBS_256BIT (32 / sizeof(limb_t))
+#define NUM_LIMBS_512BIT (64 / sizeof(limb_t))
+
+// The number of bits in a limb.
+#define LIMB_BITS   (8 * sizeof(limb_t))
+
+// Read a limb-sized quantity from program memory.
+#if BIGNUMBER_LIMB_8BIT
+#define pgm_read_limb(x)    (pgm_read_byte((x)))
+#elif BIGNUMBER_LIMB_16BIT
+#define pgm_read_limb(x)    (pgm_read_word((x)))
+#elif BIGNUMBER_LIMB_32BIT
+#define pgm_read_limb(x)    (pgm_read_dword((x)))
+#endif
+
+// Expand a 32-bit value into a set of limbs depending upon the limb size.
+// This is used when initializing constant big number values in the code.
+#if BIGNUMBER_LIMB_8BIT
+#define LIMB(value)     ((uint8_t)(value)), \
+                        ((uint8_t)((value) >> 8)), \
+                        ((uint8_t)((value) >> 16)), \
+                        ((uint8_t)((value) >> 24))
+#elif BIGNUMBER_LIMB_16BIT
+#define LIMB(value)     ((uint16_t)(value)), \
+                        ((uint16_t)((value) >> 16))
+#elif BIGNUMBER_LIMB_32BIT
+#define LIMB(value)     (value)
+#endif
+
+#endif