gdtoa/FreeBSD/_ldtoa.c

   1 /*-
   2  * Copyright (c) 2003 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
  27 #include <sys/cdefs.h>
  28 __FBSDID("$FreeBSD: src/lib/libc/gdtoa/_ldtoa.c,v 1.5 2007/12/09 19:48:57 das Exp $");
  29
  30 #include <float.h>
  31 #include <inttypes.h>
  32 #include <limits.h>
  33 #include <math.h>
  34 #include <stdlib.h>
  35 #include "fpmath.h"
  36 #include "gdtoaimp.h"
  37
  38 /*
  39  * ldtoa() is a wrapper for gdtoa() that makes it smell like dtoa(),
  40  * except that the floating point argument is passed by reference.
  41  * When dtoa() is passed a NaN or infinity, it sets expt to 9999.
  42  * However, a long double could have a valid exponent of 9999, so we
  43  * use INT_MAX in ldtoa() instead.
  44  */
  45 char *
  46 __ldtoa(long double *ld, int mode, int ndigits, int *decpt, int *sign,
  47     char **rve)
  48 {
  49 #if defined(__arm__)
  50         /* On arm, double == long double, so short circuit this */
  51         char * ret = __dtoa((double)*ld, mode, ndigits, decpt, sign, rve);
  52         if (*decpt == 9999)
  53                 *decpt = INT_MAX;
  54         return ret;
  55 #else
  56         FPI fpi = {
  57                 LDBL_MANT_DIG,                  /* nbits */
  58                 LDBL_MIN_EXP - LDBL_MANT_DIG,   /* emin */
  59                 LDBL_MAX_EXP - LDBL_MANT_DIG,   /* emax */
  60                 FLT_ROUNDS,                     /* rounding */
  61 #ifdef Sudden_Underflow /* unused, but correct anyway */
  62                 1
  63 #else
  64                 0
  65 #endif
  66         };
  67         int be, kind;
  68         char *ret;
  69         union IEEEl2bits u;
  70         uint32_t bits[(LDBL_MANT_DIG + 31) / 32];
  71         void *vbits = bits;
  72         int type;
  73
  74         u.e = *ld;
  75         type = fpclassify(u.e);
  76
  77         /*
  78          * gdtoa doesn't know anything about the sign of the number, so
  79          * if the number is negative, we need to swap rounding modes of
  80          * 2 (upwards) and 3 (downwards).
  81          */
  82         *sign = u.bits.sign;
  83         fpi.rounding ^= (fpi.rounding >> 1) & u.bits.sign;
  84
  85         be = u.bits.exp - (LDBL_MAX_EXP - 1) - (LDBL_MANT_DIG - 1);
  86         LDBL_TO_ARRAY32(u, bits);
  87
  88         switch (type) {
  89         case FP_NORMAL:
  90         case FP_SUPERNORMAL:
  91                 kind = STRTOG_Normal;
  92 #ifdef  LDBL_IMPLICIT_NBIT
  93                 bits[LDBL_MANT_DIG / 32] |= 1 << ((LDBL_MANT_DIG - 1) % 32);
  94 #endif /* LDBL_IMPLICIT_NBIT */
  95                 break;
  96         case FP_ZERO:
  97                 kind = STRTOG_Zero;
  98                 break;
  99         case FP_SUBNORMAL:
 100                 kind = STRTOG_Denormal;
 101                 be++;
 102                 break;
 103         case FP_INFINITE:
 104                 kind = STRTOG_Infinite;
 105                 break;
 106         case FP_NAN:
 107                 kind = STRTOG_NaN;
 108                 break;
 109         default:
 110                 LIBC_ABORT("fpclassify returned %d", type);
 111         }
 112
 113         ret = gdtoa(&fpi, be, vbits, &kind, mode, ndigits, decpt, rve);
 114         if (*decpt == -32768)
 115                 *decpt = INT_MAX;
 116         return ret;
 117 #endif
 118 }