lib/libc/gdtoa/_hldtoa.c

   1 /*-
   2  * Copyright (c) 2004-2008 David Schultz <das@FreeBSD.ORG>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  *
  26  * $FreeBSD: src/lib/libc/gdtoa/_hldtoa.c,v 1.2 2008/04/12 14:53:52 das Exp $
  27  */
  28
  29 #include <float.h>
  30 #include <limits.h>
  31 #include <math.h>
  32 #include <stdint.h>
  33
  34 #include "../stdio/floatio.h"
  35 #include "fpmath.h"
  36 #include "gdtoaimp.h"
  37
  38 #if (LDBL_MANT_DIG > DBL_MANT_DIG)
  39
  40 /* Strings values used by dtoa() */
  41 #define INFSTR  "Infinity"
  42 #define NANSTR  "NaN"
  43
  44 #ifdef LDBL_IMPLICIT_NBIT
  45 #define MANH_SIZE       LDBL_MANH_SIZE
  46 #else
  47 #define MANH_SIZE       (LDBL_MANH_SIZE - 1)
  48 #endif
  49
  50 #if MANH_SIZE > 32
  51 typedef uint64_t manh_t;
  52 #else
  53 typedef uint32_t manh_t;
  54 #endif
  55
  56 #if LDBL_MANL_SIZE > 32
  57 typedef uint64_t manl_t;
  58 #else
  59 typedef uint32_t manl_t;
  60 #endif
  61
  62 #define LDBL_ADJ        (LDBL_MAX_EXP - 2)
  63 #define SIGFIGS         ((LDBL_MANT_DIG + 3) / 4 + 1)
  64
  65 static const float one[] = { 1.0f, -1.0f };
  66
  67 /*
  68  * This is the long double version of __hdtoa().
  69  */
  70 char *
  71 __hldtoa(long double e, const char *xdigs, int ndigits, int *decpt, int *sign,
  72     char **rve)
  73 {
  74         union IEEEl2bits u;
  75         char *s, *s0;
  76         manh_t manh;
  77         manl_t manl;
  78         int bufsize;
  79
  80         u.e = e;
  81         *sign = u.bits.sign;
  82
  83         switch (fpclassify(e)) {
  84         case FP_NORMAL:
  85                 *decpt = u.bits.exp - LDBL_ADJ;
  86                 break;
  87         case FP_ZERO:
  88                 *decpt = 1;
  89                 return (nrv_alloc("0", rve, 1));
  90         case FP_SUBNORMAL:
  91                 u.e *= 0x1p514L;
  92                 *decpt = u.bits.exp - (514 + LDBL_ADJ);
  93                 break;
  94         case FP_INFINITE:
  95                 *decpt = INT_MAX;
  96                 return (nrv_alloc(INFSTR, rve, sizeof(INFSTR) - 1));
  97         default:        /* FP_NAN or unrecognized */
  98                 *decpt = INT_MAX;
  99                 return (nrv_alloc(NANSTR, rve, sizeof(NANSTR) - 1));
 100         }
 101
 102         /* FP_NORMAL or FP_SUBNORMAL */
 103
 104         if (ndigits == 0)               /* dtoa() compatibility */
 105                 ndigits = 1;
 106
 107         /*
 108          * If ndigits < 0, we are expected to auto-size, so we allocate
 109          * enough space for all the digits.
 110          */
 111         bufsize = (ndigits > 0) ? ndigits : SIGFIGS;
 112         s0 = rv_alloc(bufsize);
 113
 114         /* Round to the desired number of digits. */
 115         if (SIGFIGS > ndigits && ndigits > 0) {
 116                 float redux = one[u.bits.sign];
 117                 int offset = 4 * ndigits + LDBL_MAX_EXP - 4 - LDBL_MANT_DIG;
 118                 u.bits.exp = offset;
 119                 u.e += redux;
 120                 u.e -= redux;
 121                 *decpt += u.bits.exp - offset;
 122         }
 123
 124         mask_nbit_l(u);
 125         manh = u.bits.manh;
 126         manl = u.bits.manl;
 127         *s0 = '1';
 128         for (s = s0 + 1; s < s0 + bufsize; s++) {
 129                 *s = xdigs[(manh >> (MANH_SIZE - 4)) & 0xf];
 130                 manh = (manh << 4) | (manl >> (LDBL_MANL_SIZE - 4));
 131                 manl <<= 4;
 132         }
 133
 134         /* If ndigits < 0, we are expected to auto-size the precision. */
 135         if (ndigits < 0) {
 136                 for (ndigits = SIGFIGS; s0[ndigits - 1] == '0'; ndigits--)
 137                         ;
 138         }
 139
 140         s = s0 + ndigits;
 141         *s = '\0';
 142         if (rve != NULL)
 143                 *rve = s;
 144         return (s0);
 145 }
 146
 147 #else   /* (LDBL_MANT_DIG == DBL_MANT_DIG) */
 148
 149 char *
 150 __hldtoa(long double e, const char *xdigs, int ndigits, int *decpt, int *sign,
 151     char **rve)
 152 {
 153
 154         return (__hdtoa((double)e, xdigs, ndigits, decpt, sign, rve));
 155 }
 156
 157 #endif  /* (LDBL_MANT_DIG == DBL_MANT_DIG) */