diff options
Diffstat (limited to 'src/nbits_ulong.c')
| -rw-r--r-- | src/nbits_ulong.c | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/src/nbits_ulong.c b/src/nbits_ulong.c index 13bf11cd3..4f6d35110 100644 --- a/src/nbits_ulong.c +++ b/src/nbits_ulong.c @@ -1,4 +1,5 @@ /* mpfr_nbits_ulong -- number of significant bits in an unsigned long + mpfr_nbits_uj -- number of significant bits in an uintmax_t Copyright 2018-2021 Free Software Foundation, Inc. Contributed by the AriC and Caramba projects, INRIA. @@ -21,6 +22,7 @@ https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ #define MPFR_NEED_LONGLONG_H /* for count_leading_zeros */ +#define MPFR_NEED_INTMAX_H #include "mpfr-impl.h" /* count the number of significant bits of n, i.e., @@ -81,3 +83,55 @@ mpfr_nbits_ulong (unsigned long n) MPFR_ASSERTD (cnt >= 0); return cnt; } + +#ifdef _MPFR_H_HAVE_INTMAX_T +/* count the number of significant bits of n, i.e., + nbits(uintmax_t) - count_leading_zeros (n) */ +int +mpfr_nbits_uj (uintmax_t n) +{ + int cnt; + + MPFR_ASSERTD (n > 0); + + cnt = 0; + + while (n >= 0x10000) + { + n >>= 16; + cnt += 16; + } + + MPFR_ASSERTD (n <= 0xffff); + + if (n >= 0x100) + { + n >>= 8; + cnt += 8; + } + + MPFR_ASSERTD (n <= 0xff); + + if (n >= 0x10) + { + n >>= 4; + cnt += 4; + } + + MPFR_ASSERTD (n <= 0xf); + + if (n >= 4) + { + n >>= 2; + cnt += 2; + } + + MPFR_ASSERTD (n <= 3); + + /* now n = 1, 2, or 3 */ + cnt += 1 + (n >= 2); + + MPFR_ASSERTD (cnt >= 0); + return cnt; +} +#endif |