trezor-firmware/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 and/or other
//    materials provided with the distribution.
// 
// 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
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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))