#if !defined(_ilog_H) # define _ilog_H (1) # include "config.h" # include <stdint.h> # include <limits.h> # include <ccan/compiler/compiler.h> /** * ilog32 - Integer binary logarithm of a 32-bit value. * @_v: A 32-bit value. * Returns floor(log2(_v))+1, or 0 if _v==0. * This is the number of bits that would be required to represent _v in two's * complement notation with all of the leading zeros stripped. * Note that many uses will resolve to the fast macro version instead. * * See Also: * ilog32_nz(), ilog64() * * Example: * // Rounds up to next power of 2 (if not a power of 2). * static uint32_t round_up32(uint32_t i) * { * assert(i != 0); * return 1U << ilog32(i-1); * } */ int ilog32(uint32_t _v) IDEMPOTENT; /** * ilog32_nz - Integer binary logarithm of a non-zero 32-bit value. * @_v: A 32-bit value. * Returns floor(log2(_v))+1, or undefined if _v==0. * This is the number of bits that would be required to represent _v in two's * complement notation with all of the leading zeros stripped. * Note that many uses will resolve to the fast macro version instead. * See Also: * ilog32(), ilog64_nz() * Example: * // Find Last Set (ie. highest bit set, 0 to 31). * static uint32_t fls32(uint32_t i) * { * assert(i != 0); * return ilog32_nz(i) - 1; * } */ int ilog32_nz(uint32_t _v) IDEMPOTENT; /** * ilog64 - Integer binary logarithm of a 64-bit value. * @_v: A 64-bit value. * Returns floor(log2(_v))+1, or 0 if _v==0. * This is the number of bits that would be required to represent _v in two's * complement notation with all of the leading zeros stripped. * Note that many uses will resolve to the fast macro version instead. * See Also: * ilog64_nz(), ilog32() */ int ilog64(uint64_t _v) IDEMPOTENT; /** * ilog64_nz - Integer binary logarithm of a non-zero 64-bit value. * @_v: A 64-bit value. * Returns floor(log2(_v))+1, or undefined if _v==0. * This is the number of bits that would be required to represent _v in two's * complement notation with all of the leading zeros stripped. * Note that many uses will resolve to the fast macro version instead. * See Also: * ilog64(), ilog32_nz() */ int ilog64_nz(uint64_t _v) IDEMPOTENT; /** * STATIC_ILOG_32 - The integer logarithm of an (unsigned, 32-bit) constant. * @_v: A non-negative 32-bit constant. * Returns floor(log2(_v))+1, or 0 if _v==0. * This is the number of bits that would be required to represent _v in two's * complement notation with all of the leading zeros stripped. * This macro should only be used when you need a compile-time constant, * otherwise ilog32 or ilog32_nz are just as fast and more flexible. * * Example: * #define MY_PAGE_SIZE 4096 * #define MY_PAGE_BITS (STATIC_ILOG_32(PAGE_SIZE) - 1) */ #define STATIC_ILOG_32(_v) (STATIC_ILOG5((uint32_t)(_v))) /** * STATIC_ILOG_64 - The integer logarithm of an (unsigned, 64-bit) constant. * @_v: A non-negative 64-bit constant. * Returns floor(log2(_v))+1, or 0 if _v==0. * This is the number of bits that would be required to represent _v in two's * complement notation with all of the leading zeros stripped. * This macro should only be used when you need a compile-time constant, * otherwise ilog64 or ilog64_nz are just as fast and more flexible. */ #define STATIC_ILOG_64(_v) (STATIC_ILOG6((uint64_t)(_v))) /* Private implementation details */ /*Note the casts to (int) below: this prevents "upgrading" the type of an entire expression to an (unsigned) size_t.*/ #if INT_MAX>=2147483647 && HAVE_BUILTIN_CLZ #define builtin_ilog32_nz(v) \ (((int)sizeof(unsigned)*CHAR_BIT) - __builtin_clz(v)) #elif LONG_MAX>=2147483647L && HAVE_BUILTIN_CLZL #define builtin_ilog32_nz(v) \ (((int)sizeof(unsigned)*CHAR_BIT) - __builtin_clzl(v)) #endif #if INT_MAX>=9223372036854775807LL && HAVE_BUILTIN_CLZ #define builtin_ilog64_nz(v) \ (((int)sizeof(unsigned)*CHAR_BIT) - __builtin_clz(v)) #elif LONG_MAX>=9223372036854775807LL && HAVE_BUILTIN_CLZL #define builtin_ilog64_nz(v) \ (((int)sizeof(unsigned long)*CHAR_BIT) - __builtin_clzl(v)) #elif HAVE_BUILTIN_CLZLL #define builtin_ilog64_nz(v) \ (((int)sizeof(unsigned long long)*CHAR_BIT) - __builtin_clzll(v)) #endif #ifdef builtin_ilog32_nz #define ilog32(_v) (builtin_ilog32_nz(_v)&-!!(_v)) #define ilog32_nz(_v) builtin_ilog32_nz(_v) #else #define ilog32_nz(_v) ilog32(_v) #define ilog32(_v) (IS_COMPILE_CONSTANT(_v) ? STATIC_ILOG_32(_v) : ilog32(_v)) #endif /* builtin_ilog32_nz */ #ifdef builtin_ilog64_nz #define ilog64(_v) (builtin_ilog64_nz(_v)&-!!(_v)) #define ilog64_nz(_v) builtin_ilog64_nz(_v) #else #define ilog64_nz(_v) ilog64(_v) #define ilog64(_v) (IS_COMPILE_CONSTANT(_v) ? STATIC_ILOG_64(_v) : ilog64(_v)) #endif /* builtin_ilog64_nz */ /* Macros for evaluating compile-time constant ilog. */ # define STATIC_ILOG0(_v) (!!(_v)) # define STATIC_ILOG1(_v) (((_v)&0x2)?2:STATIC_ILOG0(_v)) # define STATIC_ILOG2(_v) (((_v)&0xC)?2+STATIC_ILOG1((_v)>>2):STATIC_ILOG1(_v)) # define STATIC_ILOG3(_v) \ (((_v)&0xF0)?4+STATIC_ILOG2((_v)>>4):STATIC_ILOG2(_v)) # define STATIC_ILOG4(_v) \ (((_v)&0xFF00)?8+STATIC_ILOG3((_v)>>8):STATIC_ILOG3(_v)) # define STATIC_ILOG5(_v) \ (((_v)&0xFFFF0000)?16+STATIC_ILOG4((_v)>>16):STATIC_ILOG4(_v)) # define STATIC_ILOG6(_v) \ (((_v)&0xFFFFFFFF00000000ULL)?32+STATIC_ILOG5((_v)>>32):STATIC_ILOG5(_v)) #endif /* _ilog_H */