path: root/libio/iovfprintf.c

/* 
Copyright (C) 1993 Free Software Foundation

This file is part of the GNU IO Library.  This library is free
software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option)
any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this library; see the file COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

As a special exception, if you link this library with files
compiled with a GNU compiler to produce an executable, this does not cause
the resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why
the executable file might be covered by the GNU General Public License. */

/*
 * Copyright (c) 1990 Regents of the University of California.
 * 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.
 * 3. [rescinded 22 July 1999]
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 */


#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "%W% (Berkeley) %G%";
#endif /* LIBC_SCCS and not lint */

/*
 * Actual printf innards.
 *
 * This code is large and complicated...
 */

#include <sys/types.h>
#include "libioP.h"
#include <string.h>
#ifdef __STDC__
#include <stdarg.h>
#else
#include <varargs.h>
#endif

#ifndef _IO_USE_DTOA
int __cvt_double __P((double number, register int prec, int flags, int *signp, int fmtch, char *startp, char *endp));
#endif

/*
 * Define FLOATING_POINT to get floating point.
 */
#ifndef	NO_FLOATING_POINT
#define	FLOATING_POINT
#endif

/* end of configuration stuff */


/*
 * Helper "class" for `fprintf to unbuffered': creates a
 * temporary buffer. */

struct helper_file
{
  struct _IO_FILE_plus _f;
  _IO_FILE *_put_stream;
};

static int
_IO_helper_overflow (fp, c)
     _IO_FILE *fp;
     int c;
{
  _IO_FILE *target = ((struct helper_file*)fp)->_put_stream;
  int used = fp->_IO_write_ptr - fp->_IO_write_base;
  if (used)
    {
      _IO_sputn(target, fp->_IO_write_base, used);
      fp->_IO_write_ptr -= used;
    }
  return _IO_putc (c, fp);
}

static struct _IO_jump_t _IO_helper_jumps = {
  JUMP_INIT_DUMMY,
  JUMP_INIT(finish, _IO_default_finish),
  JUMP_INIT(overflow, _IO_helper_overflow),
  JUMP_INIT(underflow, _IO_default_underflow),
  JUMP_INIT(uflow, _IO_default_uflow),
  JUMP_INIT(pbackfail, _IO_default_pbackfail),
  JUMP_INIT(xsputn, _IO_default_xsputn),
  JUMP_INIT(xsgetn, _IO_default_xsgetn),
  JUMP_INIT(seekoff, _IO_default_seekoff),
  JUMP_INIT(seekpos, _IO_default_seekpos),
  JUMP_INIT(setbuf, _IO_default_setbuf),
  JUMP_INIT(sync, _IO_default_sync),
  JUMP_INIT(doallocate, _IO_default_doallocate),
  JUMP_INIT(read, _IO_default_read),
  JUMP_INIT(write, _IO_default_write),
  JUMP_INIT(seek, _IO_default_seek),
  JUMP_INIT(close, _IO_default_close),
  JUMP_INIT(stat, _IO_default_stat)
};

static int
helper_vfprintf (fp, fmt0, ap)
     _IO_FILE *fp;
     char const *fmt0;
     _IO_va_list ap;
{
  char buf[_IO_BUFSIZ];
  struct helper_file helper;
  register _IO_FILE *hp = (_IO_FILE*)&helper;
  int result, to_flush;

  /* initialize helper */
  helper._put_stream = fp;
  hp->_IO_write_base = buf;
  hp->_IO_write_ptr = buf;
  hp->_IO_write_end = buf+_IO_BUFSIZ;
  hp->_IO_file_flags = _IO_MAGIC|_IO_NO_READS;
  _IO_JUMPS(hp) = &_IO_helper_jumps;
  
  /* Now print to helper instead. */
  result = _IO_vfprintf(hp, fmt0, ap);

  /* Now flush anything from the helper to the fp. */
  if ((to_flush = hp->_IO_write_ptr - hp->_IO_write_base) > 0)
    {
      if (_IO_sputn(fp, hp->_IO_write_base, to_flush) != to_flush)
	return EOF;
    }
  return result;
}

#ifdef FLOATING_POINT

#include "floatio.h"
#define	BUF		(MAXEXP+MAXFRACT+1)	/* + decimal point */
#define	DEFPREC		6
extern double modf __P((double, double*));

#else /* no FLOATING_POINT */

#define	BUF		40

#endif /* FLOATING_POINT */


/*
 * Macros for converting digits to letters and vice versa
 */
#define	to_digit(c)	((c) - '0')
#define is_digit(c)	((unsigned)to_digit(c) <= 9)
#define	to_char(n)	((n) + '0')

/*
 * Flags used during conversion.
 */
#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 */

int
_IO_vfprintf (fp, fmt0, ap)
     _IO_FILE *fp;
     char const *fmt0;
     _IO_va_list ap;
{
	register const char *fmt; /* format string */
	register int ch;	/* character from fmt */
	register int n;		/* handy integer (short term usage) */
	register char *cp;	/* handy char pointer (short term usage) */
	const char *fmark;	/* for remembering a place in fmt */
	register int flags;	/* flags as above */
	int ret;		/* return value accumulator */
	int width;		/* width from format (%8d), or 0 */
	int prec;		/* precision from format (%.3d), or -1 */
	char sign;		/* sign prefix (' ', '+', '-', or \0) */
#ifdef FLOATING_POINT
	int softsign;		/* temporary negative sign for floats */
	double _double;		/* double precision arguments %[eEfgG] */
#ifndef _IO_USE_DTOA
	int fpprec;		/* `extra' floating precision in [eEfgG] */
#endif
#endif
	unsigned long _ulong;	/* integer arguments %[diouxX] */
	enum { OCT, DEC, HEX } base;/* base for [diouxX] conversion */
	int dprec;		/* a copy of prec if [diouxX], 0 otherwise */
	int dpad;		/* extra 0 padding needed for integers */
	int fieldsz;		/* field size expanded by sign, dpad etc */
	/* The initialization of 'size' is to suppress a warning that
	   'size' might be used unitialized.  It seems gcc can't
	   quite grok this spaghetti code ... */
	int size = 0;		/* size of converted field or string */
	char buf[BUF];		/* space for %c, %[diouxX], %[eEfgG] */
	char ox[2];		/* space for 0x hex-prefix */

	/*
	 * BEWARE, these `goto error' on error, and PAD uses `n'.
	 */
#define	PRINT(ptr, len) \
  do { if (_IO_sputn(fp,ptr, len) != len) goto error; } while (0)
#define PAD_SP(howmany) if (_IO_padn(fp, ' ', howmany) < (howmany)) goto error;
#define PAD_0(howmany) if (_IO_padn(fp, '0', howmany) < (howmany)) goto error;

	/*
	 * To extend shorts properly, we need both signed and unsigned
	 * argument extraction methods.
	 */
#define	SARG() \
	(flags&LONGINT ? va_arg(ap, long) : \
	    flags&SHORTINT ? (long)(short)va_arg(ap, int) : \
	    (long)va_arg(ap, int))
#define	UARG() \
	(flags&LONGINT ? va_arg(ap, unsigned long) : \
	    flags&SHORTINT ? (unsigned long)(unsigned short)va_arg(ap, int) : \
	    (unsigned long)va_arg(ap, unsigned int))

	/* optimise stderr (and other unbuffered Unix files) */
	if (fp->_IO_file_flags & _IO_UNBUFFERED)
	    return helper_vfprintf(fp, fmt0, ap);

	fmt = fmt0;
	ret = 0;

	/*
	 * Scan the format for conversions (`%' character).
	 */
	for (;;) {
		for (fmark = fmt; (ch = *fmt) != '\0' && ch != '%'; fmt++)
			/* void */;
		if ((n = fmt - fmark) != 0) {
			PRINT(fmark, n);
			ret += n;
		}
		if (ch == '\0')
			goto done;
		fmt++;		/* skip over '%' */

		flags = 0;
		dprec = 0;
#if defined(FLOATING_POINT) && !defined (_IO_USE_DTOA)
		fpprec = 0;
#endif
		width = 0;
		prec = -1;
		sign = '\0';

rflag:		ch = *fmt++;
reswitch:	switch (ch) {
		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(ap, int)) >= 0)
				goto rflag;
			width = -width;
			/* FALLTHROUGH */
		case '-':
			flags |= LADJUST;
			flags &= ~ZEROPAD; /* '-' disables '0' */
			goto rflag;
		case '+':
			sign = '+';
			goto rflag;
		case '.':
			if ((ch = *fmt++) == '*') {
				n = va_arg(ap, int);
				prec = n < 0 ? -1 : n;
				goto rflag;
			}
			n = 0;
			while (is_digit(ch)) {
				n = 10 * n + to_digit(ch);
				ch = *fmt++;
			}
			prec = n < 0 ? -1 : n;
			goto reswitch;
		case '0':
			/*
			 * ``Note that 0 is taken as a flag, not as the
			 * beginning of a field width.''
			 *	-- ANSI X3J11
			 */
			if (!(flags & LADJUST))
			    flags |= ZEROPAD; /* '-' disables '0' */
			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 + to_digit(ch);
				ch = *fmt++;
			} while (is_digit(ch));
			width = n;
			goto reswitch;
#ifdef FLOATING_POINT
		case 'L':
			flags |= LONGDBL;
			goto rflag;
#endif
		case 'h':
			flags |= SHORTINT;
			goto rflag;
		case 'l':
			flags |= LONGINT;
			goto rflag;
		case 'c':
			*(cp = buf) = va_arg(ap, int);
			size = 1;
			sign = '\0';
			break;
		case 'D':
			flags |= LONGINT;
			/*FALLTHROUGH*/
		case 'd':
		case 'i':
			_ulong = SARG();
			if ((long)_ulong < 0) {
				_ulong = -_ulong;
				sign = '-';
			}
			base = DEC;
			goto number;
#ifdef FLOATING_POINT
		case 'e':
		case 'E':
		case 'f':
		case 'F':
		case 'g':
		case 'G':
			_double = va_arg(ap, double);
#ifdef _IO_USE_DTOA
			{
			    int fmt_flags = 0;
			    int fill = ' ';
			    if (flags & ALT)
				fmt_flags |= _IO_SHOWPOINT;
			    if (flags & LADJUST)
				fmt_flags |= _IO_LEFT;
			    else if (flags & ZEROPAD)
				fmt_flags |= _IO_INTERNAL, fill = '0';
			    n = _IO_outfloat(_double, fp, ch, width,
					     prec < 0 ? DEFPREC : prec,
					     fmt_flags, sign, fill);
			    if (n < 0)
				goto error;
			    ret += n;
			}
			/* CHECK ERROR! */
			continue;
#else
			/*
			 * don't do unrealistic precision; just pad it with
			 * zeroes later, so buffer size stays rational.
			 */
			if (prec > MAXFRACT) {
				if ((ch != 'g' && ch != 'G') || (flags&ALT))
					fpprec = prec - MAXFRACT;
				prec = MAXFRACT;
			} else if (prec == -1)
				prec = DEFPREC;
			/* __cvt_double may have to round up before the
			   "start" of its buffer, i.e.
			   ``intf("%.2f", (double)9.999);'';
			   if the first character is still NUL, it did.
			   softsign avoids negative 0 if _double < 0 but
			   no significant digits will be shown. */
			cp = buf;
			*cp = '\0';
			size = __cvt_double(_double, prec, flags, &softsign,
					    ch, cp, buf + sizeof(buf));
			if (softsign)
				sign = '-';
			if (*cp == '\0')
				cp++;
			break;
#endif
#endif /* FLOATING_POINT */
		case 'n':
			if (flags & LONGINT)
				*va_arg(ap, long *) = ret;
			else if (flags & SHORTINT)
				*va_arg(ap, short *) = ret;
			else
				*va_arg(ap, int *) = ret;
			continue;	/* no output */
		case 'O':
			flags |= LONGINT;
			/*FALLTHROUGH*/
		case 'o':
			_ulong = UARG();
			base = OCT;
			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 = (unsigned long)va_arg(ap, void *);
			base = HEX;
			flags |= HEXPREFIX;
			ch = 'x';
			goto nosign;
		case 's':
			if ((cp = va_arg(ap, char *)) == NULL)
				cp = "(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 = (char*)memchr(cp, 0, prec);

				if (p != NULL) {
					size = p - cp;
					if (size > prec)
						size = prec;
				} else
					size = prec;
			} else
				size = strlen(cp);
			sign = '\0';
			break;
		case 'U':
			flags |= LONGINT;
			/*FALLTHROUGH*/
		case 'u':
			_ulong = UARG();
			base = DEC;
			goto nosign;
		case 'X':
		case 'x':
			_ulong = UARG();
			base = HEX;
			/* 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
			 */
			cp = buf + BUF;
			if (_ulong != 0 || prec != 0) {
			        char *xdigs; /* digits for [xX] conversion */
				/*
				 * unsigned mod is hard, and unsigned mod
				 * by a constant is easier than that by
				 * a variable; hence this switch.
				 */
				switch (base) {
				case OCT:
					do {
						*--cp = to_char(_ulong & 7);
						_ulong >>= 3;
					} while (_ulong);
					/* handle octal leading 0 */
					if (flags & ALT && *cp != '0')
						*--cp = '0';
					break;

				case DEC:
					/* many numbers are 1 digit */
					while (_ulong >= 10) {
						*--cp = to_char(_ulong % 10);
						_ulong /= 10;
					}
					*--cp = to_char(_ulong);
					break;

				case HEX:
					if (ch == 'X')
					    xdigs = "0123456789ABCDEF";
					else /* ch == 'x' || ch == 'p' */
					    xdigs = "0123456789abcdef";
					do {
						*--cp = xdigs[_ulong & 15];
						_ulong >>= 4;
					} while (_ulong);
					break;

				default:
					cp = "bug in vform: bad base";
					goto skipsize;
				}
			}
			size = buf + BUF - cp;
		skipsize:
			break;
		default:	/* "%?" prints ?, unless ? is NUL */
			if (ch == '\0')
				goto done;
			/* pretend it was %c with argument ch */
			cp = buf;
			*cp = ch;
			size = 1;
			sign = '\0';
			break;
		}

		/*
		 * All reasonable formats wind up here.  At this point,
		 * `cp' 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.
		 */
#if defined(FLOATING_POINT) && !defined (_IO_USE_DTOA)
		fieldsz = size + fpprec;
#else
		fieldsz = size;
#endif
		dpad = dprec - size;
		if (dpad < 0)
		    dpad = 0;

		if (sign)
			fieldsz++;
		else if (flags & HEXPREFIX)
			fieldsz += 2;
		fieldsz += dpad;

		/* right-adjusting blank padding */
		if ((flags & (LADJUST|ZEROPAD)) == 0)
			PAD_SP(width - fieldsz);

		/* prefix */
		if (sign) {
			PRINT(&sign, 1);
		} else if (flags & HEXPREFIX) {
			ox[0] = '0';
			ox[1] = ch;
			PRINT(ox, 2);
		}

		/* right-adjusting zero padding */
		if ((flags & (LADJUST|ZEROPAD)) == ZEROPAD)
			PAD_0(width - fieldsz);

		/* leading zeroes from decimal precision */
		PAD_0(dpad);

		/* the string or number proper */
		PRINT(cp, size);

#if defined(FLOATING_POINT) && !defined (_IO_USE_DTOA)
		/* trailing f.p. zeroes */
		PAD_0(fpprec);
#endif

		/* left-adjusting padding (always blank) */
		if (flags & LADJUST)
			PAD_SP(width - fieldsz);

		/* finally, adjust ret */
		ret += width > fieldsz ? width : fieldsz;

	}
done:
	return ret;
error:
	return EOF;
	/* NOTREACHED */
}

#if defined(FLOATING_POINT) && !defined(_IO_USE_DTOA)

static char *exponent(register char *p, register int exp, int 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 = to_char(exp % 10);
		} while ((exp /= 10) > 9);
		*--t = to_char(exp);
		for (; t < expbuf + MAXEXP; *p++ = *t++);
	}
	else {
		*p++ = '0';
		*p++ = to_char(exp);
	}
	return (p);
}

static char * round(double fract, int *exp,
		    register char *start, register char *end,
		    char ch, int *signp)
{
	double tmp;

	if (fract)
	(void)modf(fract * 10, &tmp);
	else
		tmp = to_digit(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);
}

int __cvt_double(double number, register int prec, int flags, int *signp,
		 int fmtch, char *startp, char *endp)
{
	register char *p, *t;
	register double fract;
	int dotrim = 0, expcnt, gformat = 0;
	double integer, tmp;

	expcnt = 0;
	if (number < 0) {
		number = -number;
		*signp = '-';
	} else
		*signp = 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; p >= startp && integer; ++expcnt) {
		tmp = modf(integer / 10, &integer);
		*p-- = to_char((int)((tmp + .01) * 10));
	}
	switch (fmtch) {
	case 'f':
	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++ = to_char((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++ = to_char((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++ = to_char((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) {
				/* If no integer part, don't count initial
				 * zeros as significant digits. */
				do {
					fract = modf(fract * 10, &tmp);
					*t++ = to_char((int)tmp);
				} while(!tmp && !expcnt);
				while (--prec && fract) {
					fract = modf(fract * 10, &tmp);
					*t++ = to_char((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);
}

#endif /* defined(FLOATING_POINT) && !defined(_IO_USE_DTOA) */