trezor-firmware/crypto/monero/int-util.h

// Copyright (c) 2014-2018, The Monero Project
//
// 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.
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// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
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// 3. Neither the name of the copyright holder nor the names of its contributors
//    may be used to endorse or promote products derived from this software
//    without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote
// developers

#pragma once

#include <assert.h>
#include <stdint.h>

static inline uint64_t hi_dword(uint64_t val) { return val >> 32; }

static inline uint64_t lo_dword(uint64_t val) { return val & 0xFFFFFFFF; }

static inline uint64_t mul128(uint64_t multiplier, uint64_t multiplicand,
                              uint64_t* product_hi) {
  // multiplier   = ab = a * 2^32 + b
  // multiplicand = cd = c * 2^32 + d
  // ab * cd = a * c * 2^64 + (a * d + b * c) * 2^32 + b * d
  uint64_t a = hi_dword(multiplier);
  uint64_t b = lo_dword(multiplier);
  uint64_t c = hi_dword(multiplicand);
  uint64_t d = lo_dword(multiplicand);

  uint64_t ac = a * c;
  uint64_t ad = a * d;
  uint64_t bc = b * c;
  uint64_t bd = b * d;

  uint64_t adbc = ad + bc;
  uint64_t adbc_carry = adbc < ad ? 1 : 0;

  // multiplier * multiplicand = product_hi * 2^64 + product_lo
  uint64_t product_lo = bd + (adbc << 32);
  uint64_t product_lo_carry = product_lo < bd ? 1 : 0;
  *product_hi = ac + (adbc >> 32) + (adbc_carry << 32) + product_lo_carry;
  assert(ac <= *product_hi);

  return product_lo;
}

#define SWAP64(x)                                 \
  ((((uint64_t)(x) & 0x00000000000000ff) << 56) | \
   (((uint64_t)(x) & 0x000000000000ff00) << 40) | \
   (((uint64_t)(x) & 0x0000000000ff0000) << 24) | \
   (((uint64_t)(x) & 0x00000000ff000000) << 8) |  \
   (((uint64_t)(x) & 0x000000ff00000000) >> 8) |  \
   (((uint64_t)(x) & 0x0000ff0000000000) >> 24) | \
   (((uint64_t)(x) & 0x00ff000000000000) >> 40) | \
   (((uint64_t)(x) & 0xff00000000000000) >> 56))