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Diffstat (limited to 'lib/ccan/ilog/ilog.h')
| -rw-r--r-- | lib/ccan/ilog/ilog.h | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/lib/ccan/ilog/ilog.h b/lib/ccan/ilog/ilog.h new file mode 100644 index 0000000000..55dd009885 --- /dev/null +++ b/lib/ccan/ilog/ilog.h @@ -0,0 +1,150 @@ +#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 */ |