OpenTTD Source  20241120-master-g6d3adc6169
bitmath_func.hpp
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1 /*
2  * This file is part of OpenTTD.
3  * OpenTTD 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, version 2.
4  * OpenTTD 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.
5  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
6  */
7 
10 #ifndef BITMATH_FUNC_HPP
11 #define BITMATH_FUNC_HPP
12 
31 template <typename T>
32 debug_inline constexpr static uint GB(const T x, const uint8_t s, const uint8_t n)
33 {
34  return (x >> s) & (((T)1U << n) - 1);
35 }
36 
57 template <typename T, typename U>
58 constexpr T SB(T &x, const uint8_t s, const uint8_t n, const U d)
59 {
60  x &= (T)(~((((T)1U << n) - 1) << s));
61  x |= (T)(d << s);
62  return x;
63 }
64 
82 template <typename T, typename U>
83 constexpr T AB(T &x, const uint8_t s, const uint8_t n, const U i)
84 {
85  const T mask = ((((T)1U << n) - 1) << s);
86  x = (T)((x & ~mask) | ((x + (i << s)) & mask));
87  return x;
88 }
89 
102 template <typename T>
103 debug_inline constexpr bool HasBit(const T x, const uint8_t y)
104 {
105  return (x & ((T)1U << y)) != 0;
106 }
107 
120 template <typename T>
121 constexpr T SetBit(T &x, const uint8_t y)
122 {
123  return x = (T)(x | ((T)1U << y));
124 }
125 
136 #define SETBITS(x, y) ((x) |= (y))
137 
150 template <typename T>
151 constexpr T ClrBit(T &x, const uint8_t y)
152 {
153  return x = (T)(x & ~((T)1U << y));
154 }
155 
166 #define CLRBITS(x, y) ((x) &= ~(y))
167 
180 template <typename T>
181 constexpr T ToggleBit(T &x, const uint8_t y)
182 {
183  return x = (T)(x ^ ((T)1U << y));
184 }
185 
199 template <typename T>
200 constexpr T AssignBit(T &x, const uint8_t y, bool value)
201 {
202  return SB<T>(x, y, 1, value ? 1 : 0);
203 }
204 
212 template <typename T>
213 constexpr uint8_t FindFirstBit(T x)
214 {
215  if (x == 0) return 0;
216 
217  if constexpr (std::is_enum_v<T>) {
218  return std::countr_zero<std::underlying_type_t<T>>(x);
219  } else {
220  return std::countr_zero(x);
221  }
222 }
223 
231 template <typename T>
232 constexpr uint8_t FindLastBit(T x)
233 {
234  if (x == 0) return 0;
235 
236  return std::numeric_limits<T>::digits - std::countl_zero(x) - 1;
237 }
238 
249 template <typename T>
250 constexpr T KillFirstBit(T value)
251 {
252  return value &= (T)(value - 1);
253 }
254 
261 template <typename T>
262 constexpr uint CountBits(T value)
263 {
264  if constexpr (std::is_enum_v<T>) {
265  return std::popcount<std::underlying_type_t<T>>(value);
266  } else {
267  return std::popcount(value);
268  }
269 }
270 
277 template <typename T>
278 constexpr bool HasExactlyOneBit(T value)
279 {
280  return value != 0 && (value & (value - 1)) == 0;
281 }
282 
289 template <typename T>
290 constexpr bool HasAtMostOneBit(T value)
291 {
292  return (value & (value - 1)) == 0;
293 }
294 
300 template <typename Tbitpos = uint, typename Tbitset = uint>
302  struct Iterator {
303  typedef Tbitpos value_type;
304  typedef value_type *pointer;
305  typedef value_type &reference;
306  typedef size_t difference_type;
307  typedef std::forward_iterator_tag iterator_category;
308 
309  explicit Iterator(Tbitset bitset) : bitset(bitset), bitpos(static_cast<Tbitpos>(0))
310  {
311  this->Validate();
312  }
313 
314  bool operator==(const Iterator &other) const
315  {
316  return this->bitset == other.bitset;
317  }
318  bool operator!=(const Iterator &other) const { return !(*this == other); }
319  Tbitpos operator*() const { return this->bitpos; }
320  Iterator & operator++() { this->Next(); this->Validate(); return *this; }
321 
322  private:
323  Tbitset bitset;
324  Tbitpos bitpos;
325  void Validate()
326  {
327  if (this->bitset != 0) {
328  typename std::make_unsigned<Tbitset>::type unsigned_value = this->bitset;
329  this->bitpos = static_cast<Tbitpos>(FindFirstBit(unsigned_value));
330  }
331  }
332  void Next()
333  {
334  this->bitset = KillFirstBit(this->bitset);
335  }
336  };
337 
338  SetBitIterator(Tbitset bitset) : bitset(bitset) {}
339  Iterator begin() { return Iterator(this->bitset); }
340  Iterator end() { return Iterator(static_cast<Tbitset>(0)); }
341  bool empty() { return this->begin() == this->end(); }
342 
343 private:
344  Tbitset bitset;
345 };
346 
347 #if defined(__APPLE__)
348  /* Make endian swapping use Apple's macros to increase speed
349  * (since it will use hardware swapping if available).
350  * Even though they should return uint16_t and uint32_t, we get
351  * warnings if we don't cast those (why?) */
352 # define BSWAP32(x) (static_cast<uint32_t>(CFSwapInt32(x)))
353 # define BSWAP16(x) (static_cast<uint16_t>(CFSwapInt16(x)))
354 #elif defined(_MSC_VER)
355  /* MSVC has intrinsics for swapping, resulting in faster code */
356 # define BSWAP32(x) (_byteswap_ulong(x))
357 # define BSWAP16(x) (_byteswap_ushort(x))
358 #else
364  static inline uint32_t BSWAP32(uint32_t x)
365  {
366 #if !defined(__ICC) && defined(__GNUC__) && ((__GNUC__ > 4) || ((__GNUC__ == 4) && __GNUC_MINOR__ >= 3))
367  /* GCC >= 4.3 provides a builtin, resulting in faster code */
368  return static_cast<uint32_t>(__builtin_bswap32(static_cast<int32_t>(x)));
369 #else
370  return ((x >> 24) & 0xFF) | ((x >> 8) & 0xFF00) | ((x << 8) & 0xFF0000) | ((x << 24) & 0xFF000000);
371 #endif /* defined(__GNUC__) */
372  }
373 
379  static inline uint16_t BSWAP16(uint16_t x)
380  {
381  return (x >> 8) | (x << 8);
382  }
383 #endif /* __APPLE__ */
384 
385 #endif /* BITMATH_FUNC_HPP */
constexpr bool HasExactlyOneBit(T value)
Test whether value has exactly 1 bit set.
constexpr debug_inline bool HasBit(const T x, const uint8_t y)
Checks if a bit in a value is set.
constexpr T AssignBit(T &x, const uint8_t y, bool value)
Assigns a bit in a variable.
constexpr T SB(T &x, const uint8_t s, const uint8_t n, const U d)
Set n bits in x starting at bit s to d.
constexpr uint8_t FindLastBit(T x)
Search the last set bit in a value.
constexpr T SetBit(T &x, const uint8_t y)
Set a bit in a variable.
static uint32_t BSWAP32(uint32_t x)
Perform a 32 bits endianness bitswap on x.
constexpr uint8_t FindFirstBit(T x)
Search the first set bit in a value.
constexpr uint CountBits(T value)
Counts the number of set bits in a variable.
constexpr static debug_inline uint GB(const T x, const uint8_t s, const uint8_t n)
Fetch n bits from x, started at bit s.
constexpr bool HasAtMostOneBit(T value)
Test whether value has at most 1 bit set.
constexpr T AB(T &x, const uint8_t s, const uint8_t n, const U i)
Add i to n bits of x starting at bit s.
static uint16_t BSWAP16(uint16_t x)
Perform a 16 bits endianness bitswap on x.
constexpr T ToggleBit(T &x, const uint8_t y)
Toggles a bit in a variable.
constexpr T KillFirstBit(T value)
Clear the first bit in an integer.
constexpr T ClrBit(T &x, const uint8_t y)
Clears a bit in a variable.
Iterable ensemble of each set bit in a value.