diff options
Diffstat (limited to 'lib/libc/gdtoa/_hdtoa.c')
| -rw-r--r-- | lib/libc/gdtoa/_hdtoa.c | 319 |
1 files changed, 319 insertions, 0 deletions
diff --git a/lib/libc/gdtoa/_hdtoa.c b/lib/libc/gdtoa/_hdtoa.c new file mode 100644 index 0000000..ff7ed55 --- /dev/null +++ b/lib/libc/gdtoa/_hdtoa.c @@ -0,0 +1,319 @@ +/*- + * 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> +__FBSDID("$FreeBSD$"); + +#include <float.h> +#include <limits.h> +#include <math.h> +#include "fpmath.h" +#include "gdtoaimp.h" + +/* Strings values used by dtoa() */ +#define INFSTR "Infinity" +#define NANSTR "NaN" + +#define DBL_ADJ (DBL_MAX_EXP - 2 + ((DBL_MANT_DIG - 1) % 4)) +#define LDBL_ADJ (LDBL_MAX_EXP - 2 + ((LDBL_MANT_DIG - 1) % 4)) + +/* + * 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; + } + ++*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 IEEEd2bits u; + char *s, *s0; + int bufsize; + + u.d = d; + *sign = u.bits.sign; + + switch (fpclassify(d)) { + case FP_NORMAL: + *decpt = u.bits.exp - DBL_ADJ; + break; + case FP_ZERO: + *decpt = 1; + return (nrv_alloc("0", rve, 1)); + case FP_SUBNORMAL: + u.d *= 0x1p514; + *decpt = u.bits.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)); + 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); + + /* + * 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_MANL_SIZE / 4) - 1 && s > s0; s--) { + *s = u.bits.manl & 0xf; + u.bits.manl >>= 4; + } + for (; s > s0; s--) { + *s = u.bits.manh & 0xf; + u.bits.manh >>= 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.bits.manh | (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--) + ; + } + + if (sigfigs > ndigits && s0[ndigits] != 0) + dorounding(s0, ndigits, u.bits.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 IEEEl2bits u; + char *s, *s0; + int bufsize; + + u.e = e; + *sign = u.bits.sign; + + switch (fpclassify(e)) { + case FP_NORMAL: + *decpt = u.bits.exp - LDBL_ADJ; + break; + case FP_ZERO: + *decpt = 1; + return (nrv_alloc("0", rve, 1)); + case FP_SUBNORMAL: + u.e *= 0x1p514L; + *decpt = u.bits.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); + + /* + * 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 - (LDBL_MANL_SIZE / 4) - 1 && s > s0; s--) { + *s = u.bits.manl & 0xf; + u.bits.manl >>= 4; + } + for (; s > s0; s--) { + *s = u.bits.manh & 0xf; + u.bits.manh >>= 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.bits.manh | (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--) + ; + } + + if (sigfigs > ndigits && s0[ndigits] != 0) + dorounding(s0, ndigits, u.bits.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) */ |
