1  /* Round to integer type.  ldbl-96 version.
       2     Copyright (C) 2016-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <errno.h>
      20  #include <fenv.h>
      21  #include <math.h>
      22  #include <math_private.h>
      23  #include <libm-alias-ldouble.h>
      24  #include <stdbool.h>
      25  #include <stdint.h>
      26  
      27  #define BIAS 0x3fff
      28  #define MANT_DIG 64
      29  
      30  #if UNSIGNED
      31  # define RET_TYPE uintmax_t
      32  #else
      33  # define RET_TYPE intmax_t
      34  #endif
      35  
      36  #include <fromfp.h>
      37  
      38  RET_TYPE
      39  FUNC (long double x, int round, unsigned int width)
      40  {
      41    if (width > INTMAX_WIDTH)
      42      width = INTMAX_WIDTH;
      43    uint16_t se;
      44    uint32_t hx, lx;
      45    GET_LDOUBLE_WORDS (se, hx, lx, x);
      46    bool negative = (se & 0x8000) != 0;
      47    if (width == 0)
      48      return fromfp_domain_error (negative, width);
      49    if ((hx | lx) == 0)
      50      return 0;
      51    int exponent = se & 0x7fff;
      52    exponent -= BIAS;
      53    int max_exponent = fromfp_max_exponent (negative, width);
      54    if (exponent > max_exponent)
      55      return fromfp_domain_error (negative, width);
      56  
      57    uint64_t ix = (((uint64_t) hx) << 32) | lx;
      58    uintmax_t uret;
      59    bool half_bit, more_bits;
      60    if (exponent >= MANT_DIG - 1)
      61      {
      62        uret = ix;
      63        /* Exponent 63; no shifting required.  */
      64        half_bit = false;
      65        more_bits = false;
      66      }
      67    else if (exponent >= -1)
      68      {
      69        uint64_t h = 1ULL << (MANT_DIG - 2 - exponent);
      70        half_bit = (ix & h) != 0;
      71        more_bits = (ix & (h - 1)) != 0;
      72        if (exponent == -1)
      73  	uret = 0;
      74        else
      75  	uret = ix >> (MANT_DIG - 1 - exponent);
      76      }
      77    else
      78      {
      79        uret = 0;
      80        half_bit = false;
      81        more_bits = true;
      82      }
      83    return fromfp_round_and_return (negative, uret, half_bit, more_bits, round,
      84  				  exponent, max_exponent, width);
      85  }