/*      $NetBSD: hdtoa.c,v 1.14 2024/06/09 15:06:07 jakllsch Exp $      */

/*-
 * Copyright (c) 2004, 2005 David Schultz <das@FreeBSD.ORG>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#if 0
__FBSDID("$FreeBSD: src/lib/libc/gdtoa/_hdtoa.c,v 1.4 2007/01/03 04:57:58 das Exp $");
#else
__RCSID("$NetBSD: hdtoa.c,v 1.14 2024/06/09 15:06:07 jakllsch Exp $");
#endif

#include <float.h>
#include <limits.h>
#include <math.h>
#ifndef __vax__
#include <machine/ieee.h>
#else
#include <machine/vaxfp.h>
#define ieee_double_u vax_dfloating_u
#define dblu_d dfltu_d
#define dblu_dbl dfltu_dflt
#define dbl_sign dflt_sign
#define dbl_exp dflt_exp
#define dbl_frach dflt_frach
#define dbl_fracm dflt_fracm
#define dbl_fracl dflt_fracl
#define DBL_FRACHBITS   DFLT_FRACHBITS
#define DBL_FRACMBITS   DFLT_FRACMBITS
#define DBL_FRACLBITS   DFLT_FRACLBITS
#define DBL_EXPBITS     DFLT_EXPBITS
#endif
#include "gdtoaimp.h"

/* Strings values used by dtoa() */
#define INFSTR  "Infinity"
#define NANSTR  "NaN"

#ifndef __vax__
#define DBL_ADJ         (DBL_MAX_EXP - 2 + ((DBL_MANT_DIG - 1) % 4))
#define LDBL_ADJ        (LDBL_MAX_EXP - 2 + ((LDBL_MANT_DIG - 1) % 4))
#else /* __vax__ */
#define DBL_ADJ         (DBL_MAX_EXP + 4 + ((DBL_MANT_DIG) % 4))
#endif

/*
 * Round up the given digit string.  If the digit string is fff...f,
 * this procedure sets it to 100...0 and returns 1 to indicate that
 * the exponent needs to be bumped.  Otherwise, 0 is returned.
 */
static int
roundup(char *s0, int ndigits)
{
        char *s;

        for (s = s0 + ndigits - 1; *s == 0xf; s--) {
                if (s == s0) {
                        *s = 1;
                        return (1);
                }
                *s = 0;
        }
        ++*s;
        return (0);
}

/*
 * Round the given digit string to ndigits digits according to the
 * current rounding mode.  Note that this could produce a string whose
 * value is not representable in the corresponding floating-point
 * type.  The exponent pointed to by decpt is adjusted if necessary.
 */
static void
dorounding(char *s0, int ndigits, int sign, int *decpt)
{
        int adjust = 0; /* do we need to adjust the exponent? */

        switch (FLT_ROUNDS) {
        case 0:         /* toward zero */
        default:        /* implementation-defined */
                break;
        case 1:         /* to nearest, halfway rounds to even */
                if ((s0[ndigits] > 8) ||
                    (s0[ndigits] == 8 && s0[ndigits - 1] & 1))
                        adjust = roundup(s0, ndigits);
                break;
        case 2:         /* toward +inf */
                if (sign == 0)
                        adjust = roundup(s0, ndigits);
                break;
        case 3:         /* toward -inf */
                if (sign != 0)
                        adjust = roundup(s0, ndigits);
                break;
        }

        if (adjust)
                *decpt += 4;
}

/*
 * This procedure converts a double-precision number in IEEE format
 * into a string of hexadecimal digits and an exponent of 2.  Its
 * behavior is bug-for-bug compatible with dtoa() in mode 2, with the
 * following exceptions:
 *
 * - An ndigits < 0 causes it to use as many digits as necessary to
 *   represent the number exactly.
 * - The additional xdigs argument should point to either the string
 *   "0123456789ABCDEF" or the string "0123456789abcdef", depending on
 *   which case is desired.
 * - This routine does not repeat dtoa's mistake of setting decpt
 *   to 9999 in the case of an infinity or NaN.  INT_MAX is used
 *   for this purpose instead.
 *
 * Note that the C99 standard does not specify what the leading digit
 * should be for non-zero numbers.  For instance, 0x1.3p3 is the same
 * as 0x2.6p2 is the same as 0x4.cp3.  This implementation chooses the
 * first digit so that subsequent digits are aligned on nibble
 * boundaries (before rounding).
 *
 * Inputs:      d, xdigs, ndigits
 * Outputs:     decpt, sign, rve
 */
char *
hdtoa(double d, const char *xdigs, int ndigits, int *decpt, int *sign,
    char **rve)
{
        static const int sigfigs = (DBL_MANT_DIG + 3) / 4;
        union ieee_double_u u;
        char *s, *s0;
        size_t bufsize;

        u.dblu_d = d;
        *sign = u.dblu_dbl.dbl_sign;
#ifdef __vax__
        u.dfltu_dflt.dflt_fracl =
            ((u.dfltu_dflt.dflt_fracl >> 16) & 0xFFFF) |
            ((u.dfltu_dflt.dflt_fracl & 0xffff) << 16);
#endif

        switch (fpclassify(d)) {
        case FP_NORMAL:
                *decpt = u.dblu_dbl.dbl_exp - DBL_ADJ;
                break;
        case FP_ZERO:
                *decpt = 1;
                return (nrv_alloc("0", rve, 1));
#ifndef __vax__
        case FP_SUBNORMAL:
                /* (DBL_MAX_EXP=1024 / 2) + 2 = 514? */
                u.dblu_d *= 0x1p514;
                *decpt = u.dblu_dbl.dbl_exp - (514 + DBL_ADJ);
                break;
        case FP_INFINITE:
                *decpt = INT_MAX;
                return (nrv_alloc(INFSTR, rve, sizeof(INFSTR) - 1));
        case FP_NAN:
                *decpt = INT_MAX;
                return (nrv_alloc(NANSTR, rve, sizeof(NANSTR) - 1));
#endif
        default:
                abort();
        }

        /* FP_NORMAL or FP_SUBNORMAL */

        if (ndigits == 0)               /* dtoa() compatibility */
                ndigits = 1;

        /*
         * For simplicity, we generate all the digits even if the
         * caller has requested fewer.
         */
        bufsize = (sigfigs > ndigits) ? sigfigs : ndigits;
        s0 = rv_alloc(bufsize);
        if (s0 == NULL)
                return NULL;

        /*
         * We work from right to left, first adding any requested zero
         * padding, then the least significant portion of the
         * mantissa, followed by the most significant.  The buffer is
         * filled with the byte values 0x0 through 0xf, which are
         * converted to xdigs[0x0] through xdigs[0xf] after the
         * rounding phase.
         */
        for (s = s0 + bufsize - 1; s > s0 + sigfigs - 1; s--)
                *s = 0;
        for (; s > s0 + sigfigs - (DBL_FRACLBITS / 4) - 1 && s > s0; s--) {
                *s = u.dblu_dbl.dbl_fracl & 0xf;
                u.dblu_dbl.dbl_fracl >>= 4;
        }
#ifdef DBL_FRACMBITS
        for (; s > s0 + sigfigs - ((DBL_FRACLBITS + DBL_FRACMBITS) / 4) - 1
            && s > s0; s--) {
                *s = u.dblu_dbl.dbl_fracm & 0xf;
                u.dblu_dbl.dbl_fracm >>= 4;
        }
#endif
        for (; s > s0; s--) {
                *s = u.dblu_dbl.dbl_frach & 0xf;
                u.dblu_dbl.dbl_frach >>= 4;
        }

        /*
         * At this point, we have snarfed all the bits in the
         * mantissa, with the possible exception of the highest-order
         * (partial) nibble, which is dealt with by the next
         * statement.  We also tack on the implicit normalization bit.
         */
        *s = u.dblu_dbl.dbl_frach | (1U << ((DBL_MANT_DIG - 1) % 4));

        /* If ndigits < 0, we are expected to auto-size the precision. */
        if (ndigits < 0) {
                for (ndigits = sigfigs; s0[ndigits - 1] == 0; ndigits--)
                        continue;
        }

        if (sigfigs > ndigits && s0[ndigits] != 0)
                dorounding(s0, ndigits, u.dblu_dbl.dbl_sign, decpt);

        s = s0 + ndigits;
        if (rve != NULL)
                *rve = s;
        *s-- = '\0';
        for (; s >= s0; s--)
                *s = xdigs[(unsigned int)*s];

        return (s0);
}

#if (LDBL_MANT_DIG > DBL_MANT_DIG)

/*
 * This is the long double version of hdtoa().
 */
char *
hldtoa(long double e, const char *xdigs, int ndigits, int *decpt, int *sign,
    char **rve)
{
        static const int sigfigs = (LDBL_MANT_DIG + 3) / 4;
        union ieee_ext_u u;
        char *s, *s0;
        size_t bufsize;

        memset(&u, 0, sizeof u);
        u.extu_ld = e;
        *sign = u.extu_ext.ext_sign;

        switch (fpclassify(e)) {
        case FP_NORMAL:
                *decpt = u.extu_ext.ext_exp - LDBL_ADJ;
                break;
        case FP_ZERO:
                *decpt = 1;
                return (nrv_alloc("0", rve, 1));
        case FP_SUBNORMAL:
                u.extu_ld *= 0x1p514L;
                *decpt = u.extu_ext.ext_exp - (514 + LDBL_ADJ);
                break;
        case FP_INFINITE:
                *decpt = INT_MAX;
                return (nrv_alloc(INFSTR, rve, sizeof(INFSTR) - 1));
        case FP_NAN:
                *decpt = INT_MAX;
                return (nrv_alloc(NANSTR, rve, sizeof(NANSTR) - 1));
        default:
                abort();
        }

        /* FP_NORMAL or FP_SUBNORMAL */

        if (ndigits == 0)               /* dtoa() compatibility */
                ndigits = 1;

        /*
         * For simplicity, we generate all the digits even if the
         * caller has requested fewer.
         */
        bufsize = (sigfigs > ndigits) ? sigfigs : ndigits;
        s0 = rv_alloc(bufsize);
        if (s0 == NULL)
                return NULL;

        /*
         * We work from right to left, first adding any requested zero
         * padding, then the least significant portion of the
         * mantissa, followed by the most significant.  The buffer is
         * filled with the byte values 0x0 through 0xf, which are
         * converted to xdigs[0x0] through xdigs[0xf] after the
         * rounding phase.
         */
        for (s = s0 + bufsize - 1; s > s0 + sigfigs - 1; s--)
                *s = 0;
        for (; s > s0 + sigfigs - (EXT_FRACLBITS / 4) - 1 && s > s0; s--) {
                *s = u.extu_ext.ext_fracl & 0xf;
                u.extu_ext.ext_fracl >>= 4;
        }
#ifdef EXT_FRACHMBITS
        for (; s > s0; s--) {
                *s = u.extu_ext.ext_frachm & 0xf;
                u.extu_ext.ext_frachm >>= 4;
        }
#endif
#ifdef EXT_FRACLMBITS
        for (; s > s0; s--) {
                *s = u.extu_ext.ext_fraclm & 0xf;
                u.extu_ext.ext_fraclm >>= 4;
        }
#endif
        for (; s > s0; s--) {
                *s = u.extu_ext.ext_frach & 0xf;
                u.extu_ext.ext_frach >>= 4;
        }

        /*
         * At this point, we have snarfed all the bits in the
         * mantissa, with the possible exception of the highest-order
         * (partial) nibble, which is dealt with by the next
         * statement.  We also tack on the implicit normalization bit.
         */
        *s = u.extu_ext.ext_frach | (1U << ((LDBL_MANT_DIG - 1) % 4));

        /* If ndigits < 0, we are expected to auto-size the precision. */
        if (ndigits < 0) {
                for (ndigits = sigfigs; s0[ndigits - 1] == 0; ndigits--)
                        continue;
        }

        if (sigfigs > ndigits && s0[ndigits] != 0)
                dorounding(s0, ndigits, u.extu_ext.ext_sign, decpt);

        s = s0 + ndigits;
        if (rve != NULL)
                *rve = s;
        *s-- = '\0';
        for (; s >= s0; s--)
                *s = xdigs[(unsigned int)*s];

        return (s0);
}

#else   /* (LDBL_MANT_DIG == DBL_MANT_DIG) */

char *
hldtoa(long double e, const char *xdigs, int ndigits, int *decpt, int *sign,
    char **rve)
{

        return (hdtoa((double)e, xdigs, ndigits, decpt, sign, rve));
}

#endif  /* (LDBL_MANT_DIG == DBL_MANT_DIG) */