The final word on GOTO
Chris Torek
chris at mimsy.UUCP
Fri Oct 13 11:43:02 AEST 1989
In many articles many people write preantepenultimate words on `goto'
when handling common code sequences with different leadins in switch
statements, specifically in a `printf' format interpreter.
If you all want to argue about something this pointless, you might as
well agree on the base code first, so here is _doprnt (in antepenultimate
form :-) i.e., not final, and untested).
/*
* Copyright (c) 1988 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that the above copyright notice and this paragraph are
* duplicated in all such forms and that any documentation,
* advertising materials, and other materials related to such
* distribution and use acknowledge that the software was developed
* by the University of California, Berkeley. The name of the
* University may not be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "%W% (Berkeley) %G%";
#endif /* LIBC_SCCS and not lint */
#include <sys/types.h>
#include <stdio.h>
#include <varargs.h>
#include <ctype.h>
/*
* Define FLOATING_POINT to get floating point.
*
* Define STDIO to get a stdio-specific version. Otherwise this
* just calls putc (and #undef's it so that it will get a real function).
*/
#define STDIO
#define FLOATING_POINT
#ifdef STDIO
#include "stdiom.h"
#else
#undef putc
#endif
#ifdef FLOATING_POINT
/* 11-bit exponent (VAX G floating point) is 308 decimal digits */
#define MAXEXP 308
/* 128 bit fraction takes up 39 decimal digits; max reasonable precision */
#define MAXFRACT 39
#define DEFPREC 6
#define BUF (MAXEXP+MAXFRACT+1) /* + decimal point */
static int cvt();
#else
#define BUF 40
#endif
/* to extend shorts properly, we need signed and unsigned versions */
#define SARG() \
_ulong = flags&LONGINT ? va_arg(argp, long) : \
flags&SHORTINT ? (long)(short)va_arg(argp, int) : \
(long)va_arg(argp, int)
#define UARG() \
_ulong = flags&LONGINT ? va_arg(argp, u_long) : \
flags&SHORTINT ? (u_long)(u_short)va_arg(argp, int) : \
(u_long)va_arg(argp, u_int)
#define todigit(c) ((c) - '0')
#define tochar(n) ((n) + '0')
#define LONGINT 0x01 /* long integer */
#define LONGDBL 0x02 /* long double; unimplemented */
#define SHORTINT 0x04 /* short integer */
#define ALT 0x08 /* alternate form */
#define LADJUST 0x10 /* left adjustment */
#define ZEROPAD 0x20 /* zero (as opposed to blank) pad */
#define HEXPREFIX 0x40 /* add 0x or 0X prefix */
_doprnt(fmt0, argp, fp)
u_char *fmt0;
va_list argp;
register FILE *fp;
{
register u_char *fmt; /* format string */
register int ch; /* character from fmt */
register int cnt; /* return value accumulator */
register int n; /* random handy integer */
register char *t; /* buffer pointer */
#ifdef FLOATING_POINT
double _double; /* double precision arguments %[eEfgG] */
int fpprec; /* `extra' floating precision in [eEfgG] */
#endif
u_long _ulong; /* integer arguments %[diouxX] */
int base; /* base for [diouxX] conversion */
int dprec; /* decimal precision in [diouxX] */
int fieldsz; /* field size expanded by sign, etc */
int flags; /* flags as above */
int prec; /* precision from format (%.3d), or -1 */
int realsz; /* field size expanded by decimal precision */
int size; /* size of converted field or string */
int width; /* width from format (%8d), or 0 */
char sign; /* sign prefix (' ', '+', '-', or \0) */
char softsign; /* temporary negative sign for floats */
char *digs; /* digits for [diouxX] conversion */
char buf[BUF]; /* space for %c, %[diouxX], %[eEfgG] */
#if defined(STDIO) && !defined(lint)
/* variant of putc that does NOT handle line buffered newlines */
#define PUTC(c) \
(--fp->_w >= 0 || fp->_flags&_IOLBF && fp->_w > fp->_bf._size ? \
*fp->_p = c, fp->_p++, 0 : __putc((int)c, fp))
/*
* Make sure we can write. A side effect is that _IOLBF is set
* if it would get set by __putc.
*/
if (cantwrite(fp))
return (EOF);
#else /* not STDIO or lint */
#define PUTC(c) (void) putc(c, fp)
#endif
fmt = fmt0;
digs = "0123456789abcdef";
for (cnt = 0;; ++fmt) {
#ifdef STDIO
/*
* Copy characters until % or \0.
*/
n = fp->_w, t = (char *)fp->_p;
if (fp->_flags & _IOLBF) {
for (; (ch = *fmt) && ch != '%'; ++cnt, ++fmt)
if (--n > fp->_bf._size && ch != '\n')
*t++ = ch;
else {
fp->_w = n, fp->_p = (u_char *)t;
(void) __putc(ch, fp);
n = fp->_w, t = (char *)fp->_p;
}
} else {
for (; (ch = *fmt) && ch != '%'; ++cnt, ++fmt)
if (--n >= 0)
*t++ = ch;
else {
fp->_w = n, fp->_p = (u_char *)t;
(void) __putc(ch, fp);
n = fp->_w, t = (char *)fp->_p;
}
}
fp->_w = n, fp->_p = (u_char *)t;
#else /* STDIO */
for (; (ch = *fmt) && ch != '%'; ++cnt, ++fmt)
(void) putc(ch, fp);
#endif /* STDIO */
if (!ch)
return (cnt);
flags = 0;
dprec = 0;
#ifdef FLOATING_POINT
fpprec = 0;
#endif
width = 0;
prec = -1;
sign = '\0';
rflag: switch (*++fmt) {
case ' ':
/*
* ``If the space and + flags both appear, the space
* flag will be ignored.''
* -- ANSI X3J11
*/
if (!sign)
sign = ' ';
goto rflag;
case '#':
flags |= ALT;
goto rflag;
case '*':
/*
* ``A negative field width argument is taken as a
* - flag followed by a positive field width.''
* -- ANSI X3J11
* They don't exclude field widths read from args.
*/
if ((width = va_arg(argp, int)) >= 0)
goto rflag;
width = -width;
/* FALLTHROUGH */
case '-':
flags |= LADJUST;
goto rflag;
case '+':
sign = '+';
goto rflag;
case '.':
if (*++fmt == '*')
n = va_arg(argp, int);
else {
n = 0;
while (isascii(*fmt) && isdigit(*fmt))
n = 10 * n + todigit(*fmt++);
--fmt;
}
prec = n < 0 ? -1 : n;
goto rflag;
case '0':
/*
* ``Note that 0 is taken as a flag, not as the
* beginning of a field width.''
* -- ANSI X3J11
*/
flags |= ZEROPAD;
goto rflag;
case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
n = 0;
do {
n = 10 * n + todigit(*fmt);
} while (isascii(*++fmt) && isdigit(*fmt));
width = n;
--fmt;
goto rflag;
#ifdef FLOATING_POINT
case 'L':
flags |= LONGDBL;
goto rflag;
#endif
case 'h':
flags |= SHORTINT;
goto rflag;
case 'l':
flags |= LONGINT;
goto rflag;
case 'c':
*(t = buf) = va_arg(argp, int);
size = 1;
sign = '\0';
break;
case 'D':
flags |= LONGINT;
/*FALLTHROUGH*/
case 'd':
case 'i':
SARG();
if ((long)_ulong < 0) {
_ulong = -_ulong;
sign = '-';
}
base = 10;
goto number;
#ifdef FLOATING_POINT
case 'e':
case 'E':
case 'f':
case 'g':
case 'G':
_double = va_arg(argp, double);
/*
* don't do unrealistic precision; just pad it with
* zeroes later, so buffer size stays rational.
*/
if (prec > MAXFRACT) {
if (*fmt != 'g' && *fmt != 'G' || (flags&ALT))
fpprec = prec - MAXFRACT;
prec = MAXFRACT;
} else if (prec == -1)
prec = DEFPREC;
/*
* softsign avoids negative 0 if _double is < 0 and
* no significant digits will be shown
*/
if (_double < 0) {
softsign = '-';
_double = -_double;
} else
softsign = 0;
/*
* cvt may have to round up past the "start" of the
* buffer, i.e. ``intf("%.2f", (double)9.999);'';
* if the first char isn't NULL, it did.
*/
*buf = NULL;
size = cvt(_double, prec, flags, &softsign, *fmt, buf,
buf + sizeof(buf));
if (softsign)
sign = '-';
t = *buf ? buf : buf + 1;
break;
#endif /* FLOATING_POINT */
case 'n':
if (flags & LONGINT)
*va_arg(argp, long *) = cnt;
else if (flags & SHORTINT)
*va_arg(argp, short *) = cnt;
else
*va_arg(argp, int *) = cnt;
continue; /* no output */
case 'O':
flags |= LONGINT;
/*FALLTHROUGH*/
case 'o':
UARG();
base = 8;
goto nosign;
case 'p':
/*
* ``The argument shall be a pointer to void. The
* value of the pointer is converted to a sequence
* of printable characters, in an implementation-
* defined manner.''
* -- ANSI X3J11
*/
/* NOSTRICT */
_ulong = (u_long)va_arg(argp, void *);
base = 16;
goto nosign;
case 's':
if (!(t = va_arg(argp, char *)))
t = "(null)";
if (prec >= 0) {
/*
* can't use strlen; can only look for the
* NUL in the first `prec' characters, and
* strlen() will go further.
*/
char *p, *memchr();
if (p = memchr(t, 0, prec)) {
size = p - t;
if (size > prec)
size = prec;
} else
size = prec;
} else
size = strlen(t);
sign = '\0';
break;
case 'U':
flags |= LONGINT;
/*FALLTHROUGH*/
case 'u':
UARG();
base = 10;
goto nosign;
case 'X':
digs = "0123456789ABCDEF";
/* FALLTHROUGH */
case 'x':
UARG();
base = 16;
/* leading 0x/X only if non-zero */
if (flags & ALT && _ulong != 0)
flags |= HEXPREFIX;
/* unsigned conversions */
nosign: sign = '\0';
/*
* ``... diouXx conversions ... if a precision is
* specified, the 0 flag will be ignored.''
* -- ANSI X3J11
*/
number: if ((dprec = prec) >= 0)
flags &= ~ZEROPAD;
/*
* ``The result of converting a zero value with an
* explicit precision of zero is no characters.''
* -- ANSI X3J11
*/
t = buf + BUF;
if (_ulong != 0 || prec != 0) {
do {
*--t = digs[_ulong % base];
_ulong /= base;
} while (_ulong);
digs = "0123456789abcdef";
if (flags & ALT && base == 8 && *t != '0')
*--t = '0'; /* octal leading 0 */
}
size = buf + BUF - t;
break;
case '\0': /* "%?" prints ?, unless ? is NUL */
return (cnt);
default:
(void) putc((int)*fmt, fp);
cnt++;
continue; /* no other output */
}
/*
* All reasonable formats wind up here. At this point,
* `t' points to a string which (if not flags&LADJUST)
* should be padded out to `width' places. If
* flags&ZEROPAD, it should first be prefixed by any
* sign or other prefix; otherwise, it should be blank
* padded before the prefix is emitted. After any
* left-hand padding and prefixing, emit zeroes
* required by a decimal [diouxX] precision, then print
* the string proper, then emit zeroes required by any
* leftover floating precision; finally, if LADJUST,
* pad with blanks.
*/
/*
* compute actual size, so we know how much to pad
* fieldsz excludes decimal prec; realsz includes it
*/
#ifdef FLOATING_POINT
fieldsz = size + fpprec;
#else
fieldsz = size;
#endif
if (sign)
fieldsz++;
if (flags & HEXPREFIX)
fieldsz += 2;
realsz = dprec > fieldsz ? dprec : fieldsz;
/* right-adjusting blank padding */
if ((flags & (LADJUST|ZEROPAD)) == 0 && width)
for (n = realsz; n < width; n++)
PUTC(' ');
/* prefix */
if (sign)
PUTC(sign);
if (flags & HEXPREFIX) {
PUTC('0');
PUTC((int)*fmt);
}
/* right-adjusting zero padding */
if ((flags & (LADJUST|ZEROPAD)) == ZEROPAD)
for (n = realsz; n < width; n++)
PUTC('0');
/* leading zeroes from decimal precision */
for (n = fieldsz; n < dprec; n++)
PUTC('0');
/* the string or number proper */
n = size;
#ifdef STDIO
if (fp->_flags & _IOLBF)
while (--n >= 0) {
ch = *t++;
if (--fp->_w > fp->_bf._size && ch != '\n')
*fp->_p++ = ch;
else
(void) __putc(ch, fp);
}
else
while (n) {
if ((ch = fp->_w) > n)
ch = n;
if (ch) {
bcopy((void *)fp->_p, (void *)t, ch);
fp->_w -= ch;
fp->_p += ch;
n -= ch;
} else {
(void) __putc(*t++, fp);
n--;
}
}
#else /* STDIO */
while (--n >= 0)
(void) putc(*t++, fp);
#endif /* STDIO */
#ifdef FLOATING_POINT
/* trailing f.p. zeroes */
while (--fpprec >= 0)
PUTC('0');
#endif
/* left-adjusting padding (always blank) */
if (flags & LADJUST)
for (n = realsz; n < width; n++)
PUTC(' ');
/* finally, adjust cnt */
cnt += width > realsz ? width : realsz;
}
/* NOTREACHED */
}
#ifdef FLOATING_POINT
static char *exponent();
static char *round();
static
cvt(number, prec, flags, signp, fmtch, startp, endp)
double number;
register int prec;
int flags;
u_char fmtch;
char *signp, *startp, *endp;
{
register char *p, *t;
register double fract;
int dotrim, expcnt, gformat;
double integer, tmp, modf();
dotrim = expcnt = gformat = 0;
fract = modf(number, &integer);
/* get an extra slot for rounding. */
t = ++startp;
/*
* get integer portion of number; put into the end of the buffer; the
* .01 is added for modf(356.0 / 10, &integer) returning .59999999...
*/
for (p = endp - 1; integer; ++expcnt) {
tmp = modf(integer / 10, &integer);
*p-- = tochar((int)((tmp + .01) * 10));
}
switch(fmtch) {
case 'f':
/* reverse integer into beginning of buffer */
if (expcnt)
for (; ++p < endp; *t++ = *p);
else
*t++ = '0';
/*
* if precision required or alternate flag set, add in a
* decimal point.
*/
if (prec || flags&ALT)
*t++ = '.';
/* if requires more precision and some fraction left */
if (fract) {
if (prec)
do {
fract = modf(fract * 10, &tmp);
*t++ = tochar((int)tmp);
} while (--prec && fract);
if (fract)
startp = round(fract, (int *)NULL, startp,
t - 1, (char)0, signp);
}
for (; prec--; *t++ = '0');
break;
case 'e':
case 'E':
eformat: if (expcnt) {
*t++ = *++p;
if (prec || flags&ALT)
*t++ = '.';
/* if requires more precision and some integer left */
for (; prec && ++p < endp; --prec)
*t++ = *p;
/*
* if done precision and more of the integer component,
* round using it; adjust fract so we don't re-round
* later.
*/
if (!prec && ++p < endp) {
fract = 0;
startp = round((double)0, &expcnt, startp,
t - 1, *p, signp);
}
/* adjust expcnt for digit in front of decimal */
--expcnt;
}
/* until first fractional digit, decrement exponent */
else if (fract) {
/* adjust expcnt for digit in front of decimal */
for (expcnt = -1;; --expcnt) {
fract = modf(fract * 10, &tmp);
if (tmp)
break;
}
*t++ = tochar((int)tmp);
if (prec || flags&ALT)
*t++ = '.';
}
else {
*t++ = '0';
if (prec || flags&ALT)
*t++ = '.';
}
/* if requires more precision and some fraction left */
if (fract) {
if (prec)
do {
fract = modf(fract * 10, &tmp);
*t++ = tochar((int)tmp);
} while (--prec && fract);
if (fract)
startp = round(fract, &expcnt, startp,
t - 1, (char)0, signp);
}
/* if requires more precision */
for (; prec--; *t++ = '0');
/* unless alternate flag, trim any g/G format trailing 0's */
if (gformat && !(flags&ALT)) {
while (t > startp && *--t == '0');
if (*t == '.')
--t;
++t;
}
t = exponent(t, expcnt, fmtch);
break;
case 'g':
case 'G':
/* a precision of 0 is treated as a precision of 1. */
if (!prec)
++prec;
/*
* ``The style used depends on the value converted; style e
* will be used only if the exponent resulting from the
* conversion is less than -4 or greater than the precision.''
* -- ANSI X3J11
*/
if (expcnt > prec || !expcnt && fract && fract < .0001) {
/*
* g/G format counts "significant digits, not digits of
* precision; for the e/E format, this just causes an
* off-by-one problem, i.e. g/G considers the digit
* before the decimal point significant and e/E doesn't
* count it as precision.
*/
--prec;
fmtch -= 2; /* G->E, g->e */
gformat = 1;
goto eformat;
}
/*
* reverse integer into beginning of buffer,
* note, decrement precision
*/
if (expcnt)
for (; ++p < endp; *t++ = *p, --prec);
else
*t++ = '0';
/*
* if precision required or alternate flag set, add in a
* decimal point. If no digits yet, add in leading 0.
*/
if (prec || flags&ALT) {
dotrim = 1;
*t++ = '.';
}
else
dotrim = 0;
/* if requires more precision and some fraction left */
if (fract) {
if (prec) {
do {
fract = modf(fract * 10, &tmp);
*t++ = tochar((int)tmp);
} while(!tmp);
while (--prec && fract) {
fract = modf(fract * 10, &tmp);
*t++ = tochar((int)tmp);
}
}
if (fract)
startp = round(fract, (int *)NULL, startp,
t - 1, (char)0, signp);
}
/* alternate format, adds 0's for precision, else trim 0's */
if (flags&ALT)
for (; prec--; *t++ = '0');
else if (dotrim) {
while (t > startp && *--t == '0');
if (*t != '.')
++t;
}
}
return(t - startp);
}
static char *
round(fract, exp, start, end, ch, signp)
double fract;
int *exp;
register char *start, *end;
char ch, *signp;
{
double tmp;
if (fract)
(void)modf(fract * 10, &tmp);
else
tmp = todigit(ch);
if (tmp > 4)
for (;; --end) {
if (*end == '.')
--end;
if (++*end <= '9')
break;
*end = '0';
if (end == start) {
if (exp) { /* e/E; increment exponent */
*end = '1';
++*exp;
}
else { /* f; add extra digit */
*--end = '1';
--start;
}
break;
}
}
/* ``"%.3f", (double)-0.0004'' gives you a negative 0. */
else if (*signp == '-')
for (;; --end) {
if (*end == '.')
--end;
if (*end != '0')
break;
if (end == start)
*signp = 0;
}
return(start);
}
static char *
exponent(p, exp, fmtch)
register char *p;
register int exp;
u_char fmtch;
{
register char *t;
char expbuf[MAXEXP];
*p++ = fmtch;
if (exp < 0) {
exp = -exp;
*p++ = '-';
}
else
*p++ = '+';
t = expbuf + MAXEXP;
if (exp > 9) {
do {
*--t = tochar(exp % 10);
} while ((exp /= 10) > 9);
*--t = tochar(exp);
for (; t < expbuf + MAXEXP; *p++ = *t++);
}
else {
*p++ = '0';
*p++ = tochar(exp);
}
return(p);
}
#endif /* FLOATING_POINT */
--
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain: chris at cs.umd.edu Path: uunet!mimsy!chris
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