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annotate src/libsys/sprintf/float.c @ 27:cb3f6fe694e1 default tip

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README: document SE K2x0 addition
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 21 Dec 2023 21:44:43 +0000
parents 92470e5d0b9e
children
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1 /*
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2 * Embedded [v]sprintf() implementation by Mychaela Falconia,
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3 * loosely based on the 4.3BSD-Tahoe version.
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4 *
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5 * This module contains the floating point conversion functions.
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6 */
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7
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8 #include <sys/types.h>
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9 #include <ctype.h>
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10 #include "defs.h"
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11
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12 extern double modf();
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13
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14 extern u_char * _sprintf_field(u_char *op, int width, int flags, int sign,
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15 u_char *body, int size, int dprec, int fpprec);
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16
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17 #define MAX_INT_DIGITS 10 /* 2^32-1 in decimal */
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18 #define MAXFRACT 16 /* max sensible for 64-bit double */
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19 #define DEFPREC 6
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20
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21 static char *
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22 emit_integer_portion(unsigned number, char *endp)
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23 {
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24 char *t = endp;
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25
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26 do {
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27 *--t = tochar(number % 10);
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28 number /= 10;
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29 } while (number);
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30 return (t);
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31 }
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32
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33 static int
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34 f_round(double fract, char *start, char *end, int sign)
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35 {
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36 double tmp;
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37
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38 (void)modf(fract * 10, &tmp);
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39 if (tmp > 4)
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40 for (;; --end) {
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41 if (*end == '.')
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42 --end;
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43 if (++*end <= '9')
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44 break;
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45 *end = '0';
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46 if (end == start) {
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47 *--end = '1';
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48 return(1);
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49 }
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50 }
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51 /* ``"%.3f", (double)-0.0004'' gives you a negative 0. */
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52 else if (sign == '-')
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53 for (;; --end) {
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54 if (*end == '.')
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55 --end;
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56 if (*end != '0')
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57 break;
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58 if (end == start)
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59 return(-1); /* clear the -ve */
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60 }
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61 return(0);
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62 }
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63
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64 u_char *
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65 _sprintf_percent_f(u_char *op, int width, int flags, int sign,
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66 double number, int prec)
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67 {
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68 char buf[MAX_INT_DIGITS + 1 + MAXFRACT];
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69 int extra_prec = 0;
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70 int origsign = sign;
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71 int round_stat;
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72 double fract, tmp;
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73 char *start, *t;
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74
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75 /* first order of business: weed out infinities and NaNs */
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76 if (isinf(number)) {
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77 if (number < 0)
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78 sign = '-';
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79 return _sprintf_field(op, width, flags, sign, "Inf", 3, 0, 0);
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80 }
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81 if (isnan(number))
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82 return _sprintf_field(op, width, flags, sign, "NaN", 3, 0, 0);
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83 /* OK, we know it's a valid real like in the good old VAX days */
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84 if (number < 0) {
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85 sign = '-';
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86 number = -number;
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87 }
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88 fract = modf(number, &tmp);
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89 if (tmp > (double) 0xFFFFFFFF)
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90 return _sprintf_field(op, width, flags, sign, "Toobig", 6,
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91 0, 0);
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92 start = emit_integer_portion((unsigned) tmp, buf + MAX_INT_DIGITS);
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93 if (prec > MAXFRACT) {
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94 extra_prec = prec - MAXFRACT;
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95 prec = MAXFRACT;
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96 } else if (prec == -1)
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97 prec = DEFPREC;
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98 t = buf + MAX_INT_DIGITS;
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99 /*
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100 * if precision required or alternate flag set, add in a
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101 * decimal point.
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102 */
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103 if (prec || flags&ALT)
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104 *t++ = '.';
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105 /* if requires more precision and some fraction left */
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106 if (fract) {
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107 if (prec)
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108 do {
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109 fract = modf(fract * 10, &tmp);
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110 *t++ = tochar((int)tmp);
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111 } while (--prec && fract);
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112 if (fract) {
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113 round_stat = f_round(fract, start, t - 1, sign);
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114 if (round_stat == 1)
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115 start--;
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116 else if (round_stat == -1)
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117 sign = origsign;
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118 }
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119 }
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120 return _sprintf_field(op, width, flags, sign, start, t - start,
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121 0, prec + extra_prec);
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122 }