monero/src/common/int-util.h

// Copyright (c) 2012-2013 The Cryptonote developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#pragma once

#include <assert.h>
#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include <sys/param.h>

#if defined(_MSC_VER)
#include <stdlib.h>

static inline uint32_t rol32(uint32_t x, int r) {
  static_assert(sizeof(uint32_t) == sizeof(unsigned int), "this code assumes 32-bit integers");
  return _rotl(x, r);
}

static inline uint64_t rol64(uint64_t x, int r) {
  return _rotl64(x, r);
}

#else

static inline uint32_t rol32(uint32_t x, int r) {
  return (x << (r & 31)) | (x >> (-r & 31));
}

static inline uint64_t rol64(uint64_t x, int r) {
  return (x << (r & 63)) | (x >> (-r & 63));
}

#endif

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

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

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;
}

inline uint64_t div_with_reminder(uint64_t dividend, uint32_t divisor, uint32_t* remainder) {
  dividend |= ((uint64_t)*remainder) << 32;
  *remainder = dividend % divisor;
  return dividend / divisor;
}

// Long division with 2^32 base
inline uint32_t div128_32(uint64_t dividend_hi, uint64_t dividend_lo, uint32_t divisor, uint64_t* quotient_hi, uint64_t* quotient_lo) {
  uint64_t dividend_dwords[4];
  uint32_t remainder = 0;

  dividend_dwords[3] = hi_dword(dividend_hi);
  dividend_dwords[2] = lo_dword(dividend_hi);
  dividend_dwords[1] = hi_dword(dividend_lo);
  dividend_dwords[0] = lo_dword(dividend_lo);

  *quotient_hi  = div_with_reminder(dividend_dwords[3], divisor, &remainder) << 32;
  *quotient_hi |= div_with_reminder(dividend_dwords[2], divisor, &remainder);
  *quotient_lo  = div_with_reminder(dividend_dwords[1], divisor, &remainder) << 32;
  *quotient_lo |= div_with_reminder(dividend_dwords[0], divisor, &remainder);

  return remainder;
}

#define IDENT32(x) ((uint32_t) (x))
#define IDENT64(x) ((uint64_t) (x))

#define SWAP32(x) ((((uint32_t) (x) & 0x000000ff) << 24) | \
  (((uint32_t) (x) & 0x0000ff00) <<  8) | \
  (((uint32_t) (x) & 0x00ff0000) >>  8) | \
  (((uint32_t) (x) & 0xff000000) >> 24))
#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))

static inline uint32_t ident32(uint32_t x) { return x; }
static inline uint64_t ident64(uint64_t x) { return x; }

static inline uint32_t swap32(uint32_t x) {
  x = ((x & 0x00ff00ff) << 8) | ((x & 0xff00ff00) >> 8);
  return (x << 16) | (x >> 16);
}
static inline uint64_t swap64(uint64_t x) {
  x = ((x & 0x00ff00ff00ff00ff) <<  8) | ((x & 0xff00ff00ff00ff00) >>  8);
  x = ((x & 0x0000ffff0000ffff) << 16) | ((x & 0xffff0000ffff0000) >> 16);
  return (x << 32) | (x >> 32);
}

#if defined(__GNUC__)
#define UNUSED __attribute__((unused))
#else
#define UNUSED
#endif
static inline void mem_inplace_ident(void *mem UNUSED, size_t n UNUSED) { }
#undef UNUSED

static inline void mem_inplace_swap32(void *mem, size_t n) {
  size_t i;
  for (i = 0; i < n; i++) {
    ((uint32_t *) mem)[i] = swap32(((const uint32_t *) mem)[i]);
  }
}
static inline void mem_inplace_swap64(void *mem, size_t n) {
  size_t i;
  for (i = 0; i < n; i++) {
    ((uint64_t *) mem)[i] = swap64(((const uint64_t *) mem)[i]);
  }
}

static inline void memcpy_ident32(void *dst, const void *src, size_t n) {
  memcpy(dst, src, 4 * n);
}
static inline void memcpy_ident64(void *dst, const void *src, size_t n) {
  memcpy(dst, src, 8 * n);
}

static inline void memcpy_swap32(void *dst, const void *src, size_t n) {
  size_t i;
  for (i = 0; i < n; i++) {
    ((uint32_t *) dst)[i] = swap32(((const uint32_t *) src)[i]);
  }
}
static inline void memcpy_swap64(void *dst, const void *src, size_t n) {
  size_t i;
  for (i = 0; i < n; i++) {
    ((uint64_t *) dst)[i] = swap64(((const uint64_t *) src)[i]);
  }
}

#if !defined(BYTE_ORDER) || !defined(LITTLE_ENDIAN) || !defined(BIG_ENDIAN)
static_assert(false, "BYTE_ORDER is undefined. Perhaps, GNU extensions are not enabled");
#endif

#if BYTE_ORDER == LITTLE_ENDIAN
#define SWAP32LE IDENT32
#define SWAP32BE SWAP32
#define swap32le ident32
#define swap32be swap32
#define mem_inplace_swap32le mem_inplace_ident
#define mem_inplace_swap32be mem_inplace_swap32
#define memcpy_swap32le memcpy_ident32
#define memcpy_swap32be memcpy_swap32
#define SWAP64LE IDENT64
#define SWAP64BE SWAP64
#define swap64le ident64
#define swap64be swap64
#define mem_inplace_swap64le mem_inplace_ident
#define mem_inplace_swap64be mem_inplace_swap64
#define memcpy_swap64le memcpy_ident64
#define memcpy_swap64be memcpy_swap64
#endif

#if BYTE_ORDER == BIG_ENDIAN
#define SWAP32BE IDENT32
#define SWAP32LE SWAP32
#define swap32be ident32
#define swap32le swap32
#define mem_inplace_swap32be mem_inplace_ident
#define mem_inplace_swap32le mem_inplace_swap32
#define memcpy_swap32be memcpy_ident32
#define memcpy_swap32le memcpy_swap32
#define SWAP64BE IDENT64
#define SWAP64LE SWAP64
#define swap64be ident64
#define swap64le swap64
#define mem_inplace_swap64be mem_inplace_ident
#define mem_inplace_swap64le mem_inplace_swap64
#define memcpy_swap64be memcpy_ident64
#define memcpy_swap64le memcpy_swap64
#endif