diff options
Diffstat (limited to 'lib9/fltfmt.c')
| -rw-r--r-- | lib9/fltfmt.c | 324 |
1 files changed, 324 insertions, 0 deletions
diff --git a/lib9/fltfmt.c b/lib9/fltfmt.c new file mode 100644 index 00000000..739a4bf7 --- /dev/null +++ b/lib9/fltfmt.c @@ -0,0 +1,324 @@ +/* + * The authors of this software are Rob Pike and Ken Thompson. + * Copyright (c) 2002 by Lucent Technologies. + * Permission to use, copy, modify, and distribute this software for any + * purpose without fee is hereby granted, provided that this entire notice + * is included in all copies of any software which is or includes a copy + * or modification of this software and in all copies of the supporting + * documentation for such software. + * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED + * WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE ANY + * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY + * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE. + */ +#include "lib9.h" +#include <ctype.h> +#include "fmtdef.h" + +enum +{ + FDIGIT = 30, + FDEFLT = 6, + NSIGNIF = 17, +}; + +static int +xadd(char *a, int n, int v) +{ + char *b; + int c; + + if(n < 0 || n >= NSIGNIF) + return 0; + for(b = a+n; b >= a; b--) { + c = *b + v; + if(c <= '9') { + *b = c; + return 0; + } + *b = '0'; + v = 1; + } + *a = '1'; // overflow adding + return 1; +} + +static int +xsub(char *a, int n, int v) +{ + char *b; + int c; + + for(b = a+n; b >= a; b--) { + c = *b - v; + if(c >= '0') { + *b = c; + return 0; + } + *b = '9'; + v = 1; + } + *a = '9'; // underflow subtracting + return 1; +} + +static void +xdtoa(Fmt *fmt, char *s2, double f) +{ + char s1[NSIGNIF+10]; + double g, h; + int e, d, i, n; + int c1, c2, c3, c4, ucase, sign, chr, prec; + + prec = FDEFLT; + if(fmt->flags & FmtPrec) + prec = fmt->prec; + if(prec > FDIGIT) + prec = FDIGIT; + if(isNaN(f)) { + strcpy(s2, "NaN"); + return; + } + if(isInf(f, 1)) { + strcpy(s2, "+Inf"); + return; + } + if(isInf(f, -1)) { + strcpy(s2, "-Inf"); + return; + } + sign = 0; + if(f < 0) { + f = -f; + sign++; + } + ucase = 0; + chr = fmt->r; + if(isupper(chr)) { + ucase = 1; + chr = tolower(chr); + } + + e = 0; + g = f; + if(g != 0) { + frexp(f, &e); + e = e * .301029995664; + if(e >= -150 && e <= +150) { + d = 0; + h = f; + } else { + d = e/2; + h = f * pow10(-d); + } + g = h * pow10(d-e); + while(g < 1) { + e--; + g = h * pow10(d-e); + } + while(g >= 10) { + e++; + g = h * pow10(d-e); + } + } + + /* + * convert NSIGNIF digits and convert + * back to get accuracy. + */ + for(i=0; i<NSIGNIF; i++) { + d = g; + s1[i] = d + '0'; + g = (g - d) * 10; + } + s1[i] = 0; + + /* + * try decimal rounding to eliminate 9s + */ + c2 = prec + 1; + if(chr == 'f') + c2 += e; + if(c2 >= NSIGNIF-2) { + strcpy(s2, s1); + d = e; + s1[NSIGNIF-2] = '0'; + s1[NSIGNIF-1] = '0'; + sprint(s1+NSIGNIF, "e%d", e-NSIGNIF+1); + g = strtod(s1, nil); + if(g == f) + goto found; + if(xadd(s1, NSIGNIF-3, 1)) { + e++; + sprint(s1+NSIGNIF, "e%d", e-NSIGNIF+1); + } + g = strtod(s1, nil); + if(g == f) + goto found; + strcpy(s1, s2); + e = d; + } + + /* + * convert back so s1 gets exact answer + */ + for(;;) { + sprint(s1+NSIGNIF, "e%d", e-NSIGNIF+1); + g = strtod(s1, nil); + if(f > g) { + if(xadd(s1, NSIGNIF-1, 1)) + e--; + continue; + } + if(f < g) { + if(xsub(s1, NSIGNIF-1, 1)) + e++; + continue; + } + break; + } + +found: + /* + * sign + */ + d = 0; + i = 0; + if(sign) + s2[d++] = '-'; + else if(fmt->flags & FmtSign) + s2[d++] = '+'; + else if(fmt->flags & FmtSpace) + s2[d++] = ' '; + + /* + * copy into final place + * c1 digits of leading '0' + * c2 digits from conversion + * c3 digits of trailing '0' + * c4 digits after '.' + */ + c1 = 0; + c2 = prec + 1; + c3 = 0; + c4 = prec; + switch(chr) { + default: + if(xadd(s1, c2, 5)) + e++; + break; + case 'g': + /* + * decide on 'e' of 'f' style convers + */ + if(xadd(s1, c2, 5)) + e++; + if(e >= -5 && e <= prec) { + c1 = -e - 1; + c4 = prec - e; + chr = 'h'; // flag for 'f' style + } + break; + case 'f': + if(xadd(s1, c2+e, 5)) + e++; + c1 = -e; + if(c1 > prec) + c1 = c2; + c2 += e; + break; + } + + /* + * clean up c1 c2 and c3 + */ + if(c1 < 0) + c1 = 0; + if(c2 < 0) + c2 = 0; + if(c2 > NSIGNIF) { + c3 = c2-NSIGNIF; + c2 = NSIGNIF; + } + + /* + * copy digits + */ + while(c1 > 0) { + if(c1+c2+c3 == c4) + s2[d++] = '.'; + s2[d++] = '0'; + c1--; + } + while(c2 > 0) { + if(c2+c3 == c4) + s2[d++] = '.'; + s2[d++] = s1[i++]; + c2--; + } + while(c3 > 0) { + if(c3 == c4) + s2[d++] = '.'; + s2[d++] = '0'; + c3--; + } + + /* + * strip trailing '0' on g conv + */ + if(fmt->flags & FmtSharp) { + if(0 == c4) + s2[d++] = '.'; + } else + if(chr == 'g' || chr == 'h') { + for(n=d-1; n>=0; n--) + if(s2[n] != '0') + break; + for(i=n; i>=0; i--) + if(s2[i] == '.') { + d = n; + if(i != n) + d++; + break; + } + } + if(chr == 'e' || chr == 'g') { + if(ucase) + s2[d++] = 'E'; + else + s2[d++] = 'e'; + c1 = e; + if(c1 < 0) { + s2[d++] = '-'; + c1 = -c1; + } else + s2[d++] = '+'; + if(c1 >= 100) { + s2[d++] = c1/100 + '0'; + c1 = c1%100; + } + s2[d++] = c1/10 + '0'; + s2[d++] = c1%10 + '0'; + } + s2[d] = 0; +} + +int +_floatfmt(Fmt *fmt, double f) +{ + char s[FDIGIT+10]; + + xdtoa(fmt, s, f); + fmt->flags &= FmtWidth|FmtLeft; + _fmtcpy(fmt, s, strlen(s), strlen(s)); + return 0; +} + +int +_efgfmt(Fmt *f) +{ + double d; + + d = va_arg(f->args, double); + return _floatfmt(f, d); +} |