ref: 496817c742f8bc9a625c3fb77dd7332e75f89be6
dir: /libc/fltfmt.c/
#include <u.h> #include <libc.h> #include <float.h> #include <ctype.h> #include "fmtdef.h" enum { FDIGIT = 30, FDEFLT = 6, NSIGNIF = 17 }; /* * first few powers of 10, enough for about 1/2 of the * total space for doubles. */ static double pows10[] = { 1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19, 1e20, 1e21, 1e22, 1e23, 1e24, 1e25, 1e26, 1e27, 1e28, 1e29, 1e30, 1e31, 1e32, 1e33, 1e34, 1e35, 1e36, 1e37, 1e38, 1e39, 1e40, 1e41, 1e42, 1e43, 1e44, 1e45, 1e46, 1e47, 1e48, 1e49, 1e50, 1e51, 1e52, 1e53, 1e54, 1e55, 1e56, 1e57, 1e58, 1e59, 1e60, 1e61, 1e62, 1e63, 1e64, 1e65, 1e66, 1e67, 1e68, 1e69, 1e70, 1e71, 1e72, 1e73, 1e74, 1e75, 1e76, 1e77, 1e78, 1e79, 1e80, 1e81, 1e82, 1e83, 1e84, 1e85, 1e86, 1e87, 1e88, 1e89, 1e90, 1e91, 1e92, 1e93, 1e94, 1e95, 1e96, 1e97, 1e98, 1e99, 1e100, 1e101, 1e102, 1e103, 1e104, 1e105, 1e106, 1e107, 1e108, 1e109, 1e110, 1e111, 1e112, 1e113, 1e114, 1e115, 1e116, 1e117, 1e118, 1e119, 1e120, 1e121, 1e122, 1e123, 1e124, 1e125, 1e126, 1e127, 1e128, 1e129, 1e130, 1e131, 1e132, 1e133, 1e134, 1e135, 1e136, 1e137, 1e138, 1e139, 1e140, 1e141, 1e142, 1e143, 1e144, 1e145, 1e146, 1e147, 1e148, 1e149, 1e150, 1e151, 1e152, 1e153, 1e154, 1e155, 1e156, 1e157, 1e158, 1e159, }; #undef pow10 #define pow10(x) fmtpow10(x) static double pow10(int n) { double d; int neg; neg = 0; if(n < 0){ if(n < DBL_MIN_10_EXP){ return 0.; } neg = 1; n = -n; }else if(n > DBL_MAX_10_EXP){ return HUGE_VAL; } if(n < (int)(sizeof(pows10)/sizeof(pows10[0]))) d = pows10[n]; else{ d = pows10[sizeof(pows10)/sizeof(pows10[0]) - 1]; for(;;){ n -= sizeof(pows10)/sizeof(pows10[0]) - 1; if(n < (int)(sizeof(pows10)/sizeof(pows10[0]))){ d *= pows10[n]; break; } d *= pows10[sizeof(pows10)/sizeof(pows10[0]) - 1]; } } if(neg){ return 1./d; } return d; } 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; } static int floatfmt(Fmt *fmt, double f) { char s[341]; /* precision+exponent+sign+'.'+null */ 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); }