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 #ifdef __i386__
  35 #include <ieeefp.h>
  36 #endif
  37
  38 #include "../stdio/floatio.h"
  39 #include "fpmath.h"
  40 #include "gdtoaimp.h"
  41
  42 #if (LDBL_MANT_DIG > DBL_MANT_DIG)
  43
  44 /* Strings values used by dtoa() */
  45 #define INFSTR  "Infinity"
  46 #define NANSTR  "NaN"
  47
  48 #ifdef LDBL_IMPLICIT_NBIT
  49 #define MANH_SIZE       LDBL_MANH_SIZE
  50 #else
  51 #define MANH_SIZE       (LDBL_MANH_SIZE - 1)
  52 #endif
  53
  54 #if MANH_SIZE > 32
  55 typedef uint64_t manh_t;
  56 #else
  57 typedef uint32_t manh_t;
  58 #endif
  59
  60 #if LDBL_MANL_SIZE > 32
  61 typedef uint64_t manl_t;
  62 #else
  63 typedef uint32_t manl_t;
  64 #endif
  65
  66 #define LDBL_ADJ        (LDBL_MAX_EXP - 2)
  67 #define SIGFIGS         ((LDBL_MANT_DIG + 3) / 4 + 1)
  68
  69 static const float one[] = { 1.0f, -1.0f };
  70
  71 /*
  72  * This is the long double version of __hdtoa().
  73  */
  74 char *
  75 __hldtoa(long double e, const char *xdigs, int ndigits, int *decpt, int *sign,
  76     char **rve)
  77 {
  78         union IEEEl2bits u;
  79         char *s, *s0;
  80         manh_t manh;
  81         manl_t manl;
  82         int bufsize;
  83 #ifdef __i386__
  84         fp_prec_t oldprec;
  85 #endif
  86
  87         u.e = e;
  88         *sign = u.bits.sign;
  89
  90         switch (fpclassify(e)) {
  91         case FP_NORMAL:
  92                 *decpt = u.bits.exp - LDBL_ADJ;
  93                 break;
  94         case FP_ZERO:
  95                 *decpt = 1;
  96                 return (nrv_alloc("0", rve, 1));
  97         case FP_SUBNORMAL:
  98 #ifdef __i386__
  99                 oldprec = fpsetprec(FP_PE);
 100 #endif
 101                 u.e *= 0x1p514L;
 102                 *decpt = u.bits.exp - (514 + LDBL_ADJ);
 103 #ifdef __i386__
 104                 fpsetprec(oldprec);
 105 #endif
 106                 break;
 107         case FP_INFINITE:
 108                 *decpt = INT_MAX;
 109                 return (nrv_alloc(INFSTR, rve, sizeof(INFSTR) - 1));
 110         default:        /* FP_NAN or unrecognized */
 111                 *decpt = INT_MAX;
 112                 return (nrv_alloc(NANSTR, rve, sizeof(NANSTR) - 1));
 113         }
 114
 115         /* FP_NORMAL or FP_SUBNORMAL */
 116
 117         if (ndigits == 0)               /* dtoa() compatibility */
 118                 ndigits = 1;
 119
 120         /*
 121          * If ndigits < 0, we are expected to auto-size, so we allocate
 122          * enough space for all the digits.
 123          */
 124         bufsize = (ndigits > 0) ? ndigits : SIGFIGS;
 125         s0 = rv_alloc(bufsize);
 126
 127         /* Round to the desired number of digits. */
 128         if (SIGFIGS > ndigits && ndigits > 0) {
 129                 float redux = one[u.bits.sign];
 130                 int offset = 4 * ndigits + LDBL_MAX_EXP - 4 - LDBL_MANT_DIG;
 131 #ifdef __i386__
 132                 oldprec = fpsetprec(FP_PE);
 133 #endif
 134                 u.bits.exp = offset;
 135                 u.e += redux;
 136                 u.e -= redux;
 137                 *decpt += u.bits.exp - offset;
 138 #ifdef __i386__
 139                 fpsetprec(oldprec);
 140 #endif
 141         }
 142
 143         mask_nbit_l(u);
 144         manh = u.bits.manh;
 145         manl = u.bits.manl;
 146         *s0 = '1';
 147         for (s = s0 + 1; s < s0 + bufsize; s++) {
 148                 *s = xdigs[(manh >> (MANH_SIZE - 4)) & 0xf];
 149                 manh = (manh << 4) | (manl >> (LDBL_MANL_SIZE - 4));
 150                 manl <<= 4;
 151         }
 152
 153         /* If ndigits < 0, we are expected to auto-size the precision. */
 154         if (ndigits < 0) {
 155                 for (ndigits = SIGFIGS; s0[ndigits - 1] == '0'; ndigits--)
 156                         ;
 157         }
 158
 159         s = s0 + ndigits;
 160         *s = '\0';
 161         if (rve != NULL)
 162                 *rve = s;
 163         return (s0);
 164 }
 165
 166 #else   /* (LDBL_MANT_DIG == DBL_MANT_DIG) */
 167
 168 char *
 169 __hldtoa(long double e, const char *xdigs, int ndigits, int *decpt, int *sign,
 170     char **rve)
 171 {
 172
 173         return (__hdtoa((double)e, xdigs, ndigits, decpt, sign, rve));
 174 }
 175
 176 #endif  /* (LDBL_MANT_DIG == DBL_MANT_DIG) */