OpenTTD Source: src/core/bitmath_func.hpp Source File

OpenTTD Source 1.11.0-RC1

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 static inline uint GB(const T x, const uint8 s, const uint8 n)
33 {
34 return (x >> s) & (((T)1U << n) - 1);
35 }
36
57 template <typename T, typename U>
58 static inline T SB(T &x, const uint8 s, const uint8 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 static inline T AB(T &x, const uint8 s, const uint8 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 static inline bool HasBit(const T x, const uint8 y)
104 {
105 return (x & ((T)1U << y)) != 0;
106 }
107
120 template <typename T>
121 static inline T SetBit(T &x, const uint8 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 static inline T ClrBit(T &x, const uint8 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 static inline T ToggleBit(T &x, const uint8 y)
182 {
183 return x = (T)(x ^ ((T)1U << y));
184 }
185
186
188 extern const uint8 _ffb_64[64];
189
200 #define FIND_FIRST_BIT(x) _ffb_64[(x)]
201
216 static inline uint8 FindFirstBit2x64(const int value)
217 {
218 if ((value & 0xFF) == 0) {
219 return FIND_FIRST_BIT((value >> 8) & 0x3F) + 8;
220 } else {
221 return FIND_FIRST_BIT(value & 0x3F);
222 }
223 }
224
225 uint8 FindFirstBit(uint32 x);
226 uint8 FindLastBit(uint64 x);
227
238 template <typename T>
239 static inline T KillFirstBit(T value)
240 {
241 return value &= (T)(value - 1);
242 }
243
250 template <typename T>
251 static inline uint CountBits(T value)
252 {
253 uint num;
254
255 /* This loop is only called once for every bit set by clearing the lowest
256 * bit in each loop. The number of bits is therefore equal to the number of
257 * times the loop was called. It was found at the following website:
258 * http://graphics.stanford.edu/~seander/bithacks.html */
259
260 for (num = 0; value != 0; num++) {
261 value &= (T)(value - 1);
262 }
263
264 return num;
265 }
266
273 template <typename T>
274 static inline bool HasExactlyOneBit(T value)
275 {
276 return value != 0 && (value & (value - 1)) == 0;
277 }
278
285 template <typename T>
286 static inline bool HasAtMostOneBit(T value)
287 {
288 return (value & (value - 1)) == 0;
289 }
290
300 template <typename T>
301 static inline T ROL(const T x, const uint8 n)
302 {
303 if (n == 0) return x;
304 return (T)(x << n | x >> (sizeof(x) * 8 - n));
305 }
306
316 template <typename T>
317 static inline T ROR(const T x, const uint8 n)
318 {
319 if (n == 0) return x;
320 return (T)(x >> n | x << (sizeof(x) * 8 - n));
321 }
322
340 #define FOR_EACH_SET_BIT_EX(Tbitpos_type, bitpos_var, Tbitset_type, bitset_value) \
341 for ( \
342 Tbitset_type ___FESBE_bits = (bitpos_var = (Tbitpos_type)0, bitset_value); \
343 ___FESBE_bits != (Tbitset_type)0; \
344 ___FESBE_bits = (Tbitset_type)(___FESBE_bits >> 1), bitpos_var++ \
345 ) \
346 if ((___FESBE_bits & 1) != 0)
347
361 #define FOR_EACH_SET_BIT(bitpos_var, bitset_value) FOR_EACH_SET_BIT_EX(uint, bitpos_var, uint, bitset_value)
362
363 #if defined(__APPLE__)
364 /* Make endian swapping use Apple's macros to increase speed
365 * (since it will use hardware swapping if available).
366 * Even though they should return uint16 and uint32, we get
367 * warnings if we don't cast those (why?) */
368 # define BSWAP32(x) (static_cast<uint32>(CFSwapInt32(x)))
369 # define BSWAP16(x) (static_cast<uint16>(CFSwapInt16(x)))
370 #elif defined(_MSC_VER)
371 /* MSVC has intrinsics for swapping, resulting in faster code */
372 # define BSWAP32(x) (_byteswap_ulong(x))
373 # define BSWAP16(x) (_byteswap_ushort(x))
374 #else
375
380 static inline uint32 BSWAP32(uint32 x)
381 {
382 #if !defined(__ICC) && defined(__GNUC__) && ((__GNUC__ > 4) || ((__GNUC__ == 4) && __GNUC_MINOR__ >= 3))
383 /* GCC >= 4.3 provides a builtin, resulting in faster code */
384 return static_cast<uint32>(__builtin_bswap32(static_cast<int32>(x)));
385 #else
386 return ((x >> 24) & 0xFF) | ((x >> 8) & 0xFF00) | ((x << 8) & 0xFF0000) | ((x << 24) & 0xFF000000);
387 #endif /* defined(__GNUC__) */
388 }
389
395 static inline uint16 BSWAP16(uint16 x)
396 {
397 return (x >> 8) | (x << 8);
398 }
399 #endif /* __APPLE__ */
400
401 #endif /* BITMATH_FUNC_HPP */
HasAtMostOneBit
static bool HasAtMostOneBit(T value)
Test whether value has at most 1 bit set.
Definition: bitmath_func.hpp:286
GB
static uint GB(const T x, const uint8 s, const uint8 n)
Fetch n bits from x, started at bit s.
Definition: bitmath_func.hpp:32
KillFirstBit
static T KillFirstBit(T value)
Clear the first bit in an integer.
Definition: bitmath_func.hpp:239
HasBit
static bool HasBit(const T x, const uint8 y)
Checks if a bit in a value is set.
Definition: bitmath_func.hpp:103
ClrBit
static T ClrBit(T &x, const uint8 y)
Clears a bit in a variable.
Definition: bitmath_func.hpp:151
AB
static T AB(T &x, const uint8 s, const uint8 n, const U i)
Add i to n bits of x starting at bit s.
Definition: bitmath_func.hpp:83
CountBits
static uint CountBits(T value)
Counts the number of set bits in a variable.
Definition: bitmath_func.hpp:251
BSWAP16
static uint16 BSWAP16(uint16 x)
Perform a 16 bits endianness bitswap on x.
Definition: bitmath_func.hpp:395
HasExactlyOneBit
static bool HasExactlyOneBit(T value)
Test whether value has exactly 1 bit set.
Definition: bitmath_func.hpp:274
SB
static T SB(T &x, const uint8 s, const uint8 n, const U d)
Set n bits in x starting at bit s to d.
Definition: bitmath_func.hpp:58
FindFirstBit2x64
static uint8 FindFirstBit2x64(const int value)
Finds the position of the first non-zero bit in an integer.
Definition: bitmath_func.hpp:216
FindFirstBit
uint8 FindFirstBit(uint32 x)
Search the first set bit in a 32 bit variable.
Definition: bitmath_func.cpp:37
ROL
static T ROL(const T x, const uint8 n)
ROtate x Left by n.
Definition: bitmath_func.hpp:301
BSWAP32
static uint32 BSWAP32(uint32 x)
Perform a 32 bits endianness bitswap on x.
Definition: bitmath_func.hpp:380
FindLastBit
uint8 FindLastBit(uint64 x)
Search the last set bit in a 64 bit variable.
Definition: bitmath_func.cpp:65
_ffb_64
const uint8 _ffb_64[64]
Lookup table to check which bit is set in a 6 bit variable.
Definition: bitmath_func.cpp:15
ToggleBit
static T ToggleBit(T &x, const uint8 y)
Toggles a bit in a variable.
Definition: bitmath_func.hpp:181
SetBit
static T SetBit(T &x, const uint8 y)
Set a bit in a variable.
Definition: bitmath_func.hpp:121
ROR
static T ROR(const T x, const uint8 n)
ROtate x Right by n.
Definition: bitmath_func.hpp:317
FIND_FIRST_BIT
#define FIND_FIRST_BIT(x)
Returns the first non-zero bit in a 6-bit value (from right).
Definition: bitmath_func.hpp:200