bitmath_func.hpp

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00001 /* $Id: bitmath_func.hpp 17248 2009-08-21 20:21:05Z rubidium $ */
00002 
00003 /*
00004  * This file is part of OpenTTD.
00005  * 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.
00006  * 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.
00007  * 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/>.
00008  */
00009 
00012 #ifndef BITMATH_FUNC_HPP
00013 #define BITMATH_FUNC_HPP
00014 
00031 template <typename T>
00032 static FORCEINLINE uint GB(const T x, const uint8 s, const uint8 n)
00033 {
00034   return (x >> s) & ((1U << n) - 1);
00035 }
00036 
00054 template <typename T, typename U>
00055 static FORCEINLINE T SB(T &x, const uint8 s, const uint8 n, const U d)
00056 {
00057   x &= (T)(~(((1U << n) - 1) << s));
00058   x |= (T)(d << s);
00059   return x;
00060 }
00061 
00076 template <typename T, typename U>
00077 static FORCEINLINE T AB(T &x, const uint8 s, const uint8 n, const U i)
00078 {
00079   const T mask = (T)(((1U << n) - 1) << s);
00080   x = (T)((x & ~mask) | ((x + (i << s)) & mask));
00081   return x;
00082 }
00083 
00095 template <typename T>
00096 static FORCEINLINE bool HasBit(const T x, const uint8 y)
00097 {
00098   return (x & ((T)1U << y)) != 0;
00099 }
00100 
00112 template <typename T>
00113 static FORCEINLINE T SetBit(T &x, const uint8 y)
00114 {
00115   return x = (T)(x | (T)(1U << y));
00116 }
00117 
00128 #define SETBITS(x, y) ((x) |= (y))
00129 
00141 template <typename T>
00142 static FORCEINLINE T ClrBit(T &x, const uint8 y)
00143 {
00144   return x = (T)(x & ~((T)1U << y));
00145 }
00146 
00157 #define CLRBITS(x, y) ((x) &= ~(y))
00158 
00170 template <typename T>
00171 static FORCEINLINE T ToggleBit(T &x, const uint8 y)
00172 {
00173   return x = (T)(x ^ (T)(1U << y));
00174 }
00175 
00176 
00178 extern const uint8 _ffb_64[64];
00179 
00190 #define FIND_FIRST_BIT(x) _ffb_64[(x)]
00191 
00206 static FORCEINLINE uint8 FindFirstBit2x64(const int value)
00207 {
00208   if ((value & 0xFF) == 0) {
00209     return FIND_FIRST_BIT((value >> 8) & 0x3F) + 8;
00210   } else {
00211     return FIND_FIRST_BIT(value & 0x3F);
00212   }
00213 }
00214 
00215 uint8 FindFirstBit(uint32 x);
00216 uint8 FindLastBit(uint64 x);
00217 
00228 template <typename T>
00229 static FORCEINLINE T KillFirstBit(T value)
00230 {
00231   return value &= (T)(value - 1);
00232 }
00233 
00240 template <typename T>
00241 static inline uint CountBits(T value)
00242 {
00243   uint num;
00244 
00245   /* This loop is only called once for every bit set by clearing the lowest
00246    * bit in each loop. The number of bits is therefore equal to the number of
00247    * times the loop was called. It was found at the following website:
00248    * http://graphics.stanford.edu/~seander/bithacks.html */
00249 
00250   for (num = 0; value != 0; num++) {
00251     value &= (T)(value - 1);
00252   }
00253 
00254   return num;
00255 }
00256 
00265 template <typename T>
00266 static FORCEINLINE T ROL(const T x, const uint8 n)
00267 {
00268   return (T)(x << n | x >> (sizeof(x) * 8 - n));
00269 }
00270 
00279 template <typename T>
00280 static FORCEINLINE T ROR(const T x, const uint8 n)
00281 {
00282   return (T)(x >> n | x << (sizeof(x) * 8 - n));
00283 }
00284 
00296 #define FOR_EACH_SET_BIT(i, b)      \
00297   for (i = 0; b != 0; i++, b >>= 1) \
00298     if (b & 1)
00299 
00300 
00301 #if defined(__APPLE__)
00302   /* Make endian swapping use Apple's macros to increase speed
00303    * (since it will use hardware swapping if available).
00304    * Even though they should return uint16 and uint32, we get
00305    * warnings if we don't cast those (why?) */
00306   #define BSWAP32(x) ((uint32)Endian32_Swap(x))
00307   #define BSWAP16(x) ((uint16)Endian16_Swap(x))
00308 #else
00309 
00314   static FORCEINLINE uint32 BSWAP32(uint32 x)
00315   {
00316 #if !defined(__ICC) && defined(__GNUC__) && ((__GNUC__ > 4) || ((__GNUC__ == 4)  && __GNUC_MINOR__ >= 3))
00317     /* GCC >= 4.3 provides a builtin, resulting in faster code */
00318     return (uint32)__builtin_bswap32((int32)x);
00319 #else
00320     return ((x >> 24) & 0xFF) | ((x >> 8) & 0xFF00) | ((x << 8) & 0xFF0000) | ((x << 24) & 0xFF000000);
00321 #endif /* defined(__GNUC__) */
00322   }
00323 
00329   static FORCEINLINE uint16 BSWAP16(uint16 x)
00330   {
00331     return (x >> 8) | (x << 8);
00332   }
00333 #endif /* __APPLE__ */
00334 
00335 #endif /* BITMATH_FUNC_HPP */

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