xref: /netbsd/lib/libc/stdio/vfprintf.c (revision bf9ec67e)
1 /*	$NetBSD: vfprintf.c,v 1.43 2002/05/26 14:44:00 wiz Exp $	*/
2 
3 /*-
4  * Copyright (c) 1990 The Regents of the University of California.
5  * All rights reserved.
6  *
7  * This code is derived from software contributed to Berkeley by
8  * Chris Torek.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. All advertising materials mentioning features or use of this software
19  *    must display the following acknowledgement:
20  *	This product includes software developed by the University of
21  *	California, Berkeley and its contributors.
22  * 4. Neither the name of the University nor the names of its contributors
23  *    may be used to endorse or promote products derived from this software
24  *    without specific prior written permission.
25  *
26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36  * SUCH DAMAGE.
37  */
38 
39 #include <sys/cdefs.h>
40 #if defined(LIBC_SCCS) && !defined(lint)
41 #if 0
42 static char *sccsid = "@(#)vfprintf.c	5.50 (Berkeley) 12/16/92";
43 #else
44 __RCSID("$NetBSD: vfprintf.c,v 1.43 2002/05/26 14:44:00 wiz Exp $");
45 #endif
46 #endif /* LIBC_SCCS and not lint */
47 
48 /*
49  * Actual printf innards.
50  *
51  * This code is large and complicated...
52  */
53 
54 #include "namespace.h"
55 #include <sys/types.h>
56 
57 #include <assert.h>
58 #include <errno.h>
59 #include <stdarg.h>
60 #include <stddef.h>
61 #include <stdint.h>
62 #include <stdio.h>
63 #include <stdlib.h>
64 #include <string.h>
65 #include <wchar.h>
66 
67 #include "local.h"
68 #include "fvwrite.h"
69 #include "extern.h"
70 #include "reentrant.h"
71 
72 static int __sprint __P((FILE *, struct __suio *));
73 static int __sbprintf __P((FILE *, const char *, va_list))
74      __attribute__((__format__(__printf__, 2, 0)));
75 
76 /*
77  * Flush out all the vectors defined by the given uio,
78  * then reset it so that it can be reused.
79  */
80 static int
81 __sprint(fp, uio)
82 	FILE *fp;
83 	struct __suio *uio;
84 {
85 	int err;
86 
87 	_DIAGASSERT(fp != NULL);
88 	_DIAGASSERT(uio != NULL);
89 
90 	if (uio->uio_resid == 0) {
91 		uio->uio_iovcnt = 0;
92 		return (0);
93 	}
94 	err = __sfvwrite(fp, uio);
95 	uio->uio_resid = 0;
96 	uio->uio_iovcnt = 0;
97 	return (err);
98 }
99 
100 /*
101  * Helper function for `fprintf to unbuffered unix file': creates a
102  * temporary buffer.  We only work on write-only files; this avoids
103  * worries about ungetc buffers and so forth.
104  */
105 static int
106 __sbprintf(fp, fmt, ap)
107 	FILE *fp;
108 	const char *fmt;
109 	va_list ap;
110 {
111 	int ret;
112 	FILE fake;
113 	struct __sfileext fakeext;
114 	unsigned char buf[BUFSIZ];
115 
116 	_DIAGASSERT(fp != NULL);
117 	_DIAGASSERT(fmt != NULL);
118 
119 	_FILEEXT_SETUP(&fake, &fakeext);
120 
121 	/* copy the important variables */
122 	fake._flags = fp->_flags & ~__SNBF;
123 	fake._file = fp->_file;
124 	fake._cookie = fp->_cookie;
125 	fake._write = fp->_write;
126 
127 	/* set up the buffer */
128 	fake._bf._base = fake._p = buf;
129 	fake._bf._size = fake._w = sizeof(buf);
130 	fake._lbfsize = 0;	/* not actually used, but Just In Case */
131 
132 	/* do the work, then copy any error status */
133 	ret = vfprintf(&fake, fmt, ap);
134 	if (ret >= 0 && fflush(&fake))
135 		ret = -1;
136 	if (fake._flags & __SERR)
137 		fp->_flags |= __SERR;
138 	return (ret);
139 }
140 
141 
142 #ifdef FLOATING_POINT
143 #include <locale.h>
144 #include <math.h>
145 #include "floatio.h"
146 
147 #define	BUF		(MAXEXP+MAXFRACT+1)	/* + decimal point */
148 #define	DEFPREC		6
149 
150 static char *cvt __P((double, int, int, char *, int *, int, int *));
151 static int exponent __P((char *, int, int));
152 
153 #else /* no FLOATING_POINT */
154 
155 #define	BUF		40
156 
157 #endif /* FLOATING_POINT */
158 
159 #ifdef lint
160 static __inline void *__UNCONST __P((const void *));
161 static __inline void *
162 __UNCONST(v)
163 	const void *v;
164 {
165 	/* LINTED */
166 	return (void *) v;
167 }
168 #else
169 #define __UNCONST(v)	(void *)(v)
170 #endif
171 
172 /*
173  * Macros for converting digits to letters and vice versa
174  */
175 #define	to_digit(c)	((c) - '0')
176 #define is_digit(c)	((unsigned)to_digit(c) <= 9)
177 #define	to_char(n)	((char)((n) + '0'))
178 
179 /*
180  * Flags used during conversion.
181  */
182 #define	ALT		0x001		/* alternate form */
183 #define	HEXPREFIX	0x002		/* add 0x or 0X prefix */
184 #define	LADJUST		0x004		/* left adjustment */
185 #define	LONGDBL		0x008		/* long double; unimplemented */
186 #define	LONGINT		0x010		/* long integer */
187 #define	QUADINT		0x020		/* quad integer */
188 #define	SHORTINT	0x040		/* short integer */
189 #define	MAXINT		0x080		/* (unsigned) intmax_t */
190 #define	PTRINT		0x100		/* (unsigned) ptrdiff_t */
191 #define	SIZEINT		0x200		/* (signed) size_t */
192 #define	ZEROPAD		0x400		/* zero (as opposed to blank) pad */
193 #define FPT		0x800		/* Floating point number */
194 int
195 vfprintf(fp, fmt0, ap)
196 	FILE *fp;
197 	const char *fmt0;
198 	_BSD_VA_LIST_ ap;
199 {
200 	const char *fmt;/* format string */
201 	int ch;	/* character from fmt */
202 	int n, m;	/* handy integers (short term usage) */
203 	const char *cp;	/* handy char pointer (short term usage) */
204 	char *bp;	/* handy char pointer (short term usage) */
205 	struct __siov *iovp;/* for PRINT macro */
206 	int flags;	/* flags as above */
207 	int ret;		/* return value accumulator */
208 	int width;		/* width from format (%8d), or 0 */
209 	int prec;		/* precision from format (%.3d), or -1 */
210 	char sign;		/* sign prefix (' ', '+', '-', or \0) */
211 	wchar_t wc;
212 	mbstate_t ps;
213 #ifdef FLOATING_POINT
214 	char *decimal_point = localeconv()->decimal_point;
215 	char softsign;		/* temporary negative sign for floats */
216 	double _double = 0;	/* double precision arguments %[eEfgG] */
217 	int expt;		/* integer value of exponent */
218 	int expsize = 0;	/* character count for expstr */
219 	int ndig;		/* actual number of digits returned by cvt */
220 	char expstr[7];		/* buffer for exponent string */
221 #endif
222 
223 #ifdef __GNUC__			/* gcc has builtin quad type (long long) SOS */
224 #define	quad_t	  long long
225 #define	u_quad_t  unsigned long long
226 #endif
227 
228 #define	INTMAX_T	intmax_t
229 #define	UINTMAX_T	uintmax_t
230 
231 	UINTMAX_T _uintmax;	/* integer arguments %[diouxX] */
232 	enum { OCT, DEC, HEX } base;/* base for [diouxX] conversion */
233 	int dprec;		/* a copy of prec if [diouxX], 0 otherwise */
234 	int realsz;		/* field size expanded by dprec */
235 	int size;		/* size of converted field or string */
236 	char *xdigs = NULL;	/* digits for [xX] conversion */
237 #define NIOV 8
238 	struct __suio uio;	/* output information: summary */
239 	struct __siov iov[NIOV];/* ... and individual io vectors */
240 	char buf[BUF];		/* space for %c, %[diouxX], %[eEfgG] */
241 	char ox[2];		/* space for 0x hex-prefix */
242 
243 	/*
244 	 * Choose PADSIZE to trade efficiency vs. size.  If larger printf
245 	 * fields occur frequently, increase PADSIZE and make the initialisers
246 	 * below longer.
247 	 */
248 #define	PADSIZE	16		/* pad chunk size */
249 	static const char blanks[PADSIZE] =
250 	 {' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' ',' '};
251 	static const char zeroes[PADSIZE] =
252 	 {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'};
253 
254 	/*
255 	 * BEWARE, these `goto error' on error, and PAD uses `n'.
256 	 */
257 #define	PRINT(ptr, len) { \
258 	iovp->iov_base = __UNCONST(ptr); \
259 	iovp->iov_len = (len); \
260 	uio.uio_resid += (len); \
261 	iovp++; \
262 	if (++uio.uio_iovcnt >= NIOV) { \
263 		if (__sprint(fp, &uio)) \
264 			goto error; \
265 		iovp = iov; \
266 	} \
267 }
268 #define	PAD(howmany, with) { \
269 	if ((n = (howmany)) > 0) { \
270 		while (n > PADSIZE) { \
271 			PRINT(with, PADSIZE); \
272 			n -= PADSIZE; \
273 		} \
274 		PRINT(with, n); \
275 	} \
276 }
277 #define	FLUSH() { \
278 	if (uio.uio_resid && __sprint(fp, &uio)) \
279 		goto error; \
280 	uio.uio_iovcnt = 0; \
281 	iovp = iov; \
282 }
283 
284 	/*
285 	 * To extend shorts properly, we need both signed and unsigned
286 	 * argument extraction methods.
287 	 */
288 #define	SARG() \
289 	(flags&MAXINT ? va_arg(ap, intmax_t) : \
290 	    flags&PTRINT ? va_arg(ap, ptrdiff_t) : \
291 	    flags&SIZEINT ? va_arg(ap, ssize_t) : /* XXX */ \
292 	    flags&QUADINT ? va_arg(ap, quad_t) : \
293 	    flags&LONGINT ? va_arg(ap, long) : \
294 	    flags&SHORTINT ? (long)(short)va_arg(ap, int) : \
295 	    (long)va_arg(ap, int))
296 #define	UARG() \
297 	(flags&MAXINT ? va_arg(ap, uintmax_t) : \
298 	    flags&PTRINT ? va_arg(ap, uintptr_t) : /* XXX */ \
299 	    flags&SIZEINT ? va_arg(ap, size_t) : \
300 	    flags&QUADINT ? va_arg(ap, u_quad_t) : \
301 	    flags&LONGINT ? va_arg(ap, u_long) : \
302 	    flags&SHORTINT ? (u_long)(u_short)va_arg(ap, int) : \
303 	    (u_long)va_arg(ap, u_int))
304 
305 	_DIAGASSERT(fp != NULL);
306 	_DIAGASSERT(fmt0 != NULL);
307 
308 	FLOCKFILE(fp);
309 	_SET_ORIENTATION(fp, -1);
310 
311 	/* sorry, fprintf(read_only_file, "") returns -1, not 0 */
312 	if (cantwrite(fp)) {
313 		errno = EBADF;
314 		FUNLOCKFILE(fp);
315 		return (-1);
316 	}
317 
318 	/* optimise fprintf(stderr) (and other unbuffered Unix files) */
319 	if ((fp->_flags & (__SNBF|__SWR|__SRW)) == (__SNBF|__SWR) &&
320 	    fp->_file >= 0) {
321 		ret = __sbprintf(fp, fmt0, ap);
322 		FUNLOCKFILE(fp);
323 		return (ret);
324 	}
325 
326 	fmt = fmt0;
327 	uio.uio_iov = iovp = iov;
328 	uio.uio_resid = 0;
329 	uio.uio_iovcnt = 0;
330 	ret = 0;
331 
332 	memset(&ps, 0, sizeof(ps));
333 
334 	/*
335 	 * Scan the format for conversions (`%' character).
336 	 */
337 	for (;;) {
338 		cp = fmt;
339 		while ((n = mbrtowc(&wc, fmt, MB_CUR_MAX, &ps)) > 0) {
340 			fmt += n;
341 			if (wc == '%') {
342 				fmt--;
343 				break;
344 			}
345 		}
346 		if ((m = fmt - cp) != 0) {
347 			PRINT(cp, m);
348 			ret += m;
349 		}
350 		if (n <= 0)
351 			goto done;
352 		fmt++;		/* skip over '%' */
353 
354 		flags = 0;
355 		dprec = 0;
356 		width = 0;
357 		prec = -1;
358 		sign = '\0';
359 
360 rflag:		ch = *fmt++;
361 reswitch:	switch (ch) {
362 		case ' ':
363 			/*
364 			 * ``If the space and + flags both appear, the space
365 			 * flag will be ignored.''
366 			 *	-- ANSI X3J11
367 			 */
368 			if (!sign)
369 				sign = ' ';
370 			goto rflag;
371 		case '#':
372 			flags |= ALT;
373 			goto rflag;
374 		case '*':
375 			/*
376 			 * ``A negative field width argument is taken as a
377 			 * - flag followed by a positive field width.''
378 			 *	-- ANSI X3J11
379 			 * They don't exclude field widths read from args.
380 			 */
381 			if ((width = va_arg(ap, int)) >= 0)
382 				goto rflag;
383 			width = -width;
384 			/* FALLTHROUGH */
385 		case '-':
386 			flags |= LADJUST;
387 			goto rflag;
388 		case '+':
389 			sign = '+';
390 			goto rflag;
391 		case '.':
392 			if ((ch = *fmt++) == '*') {
393 				n = va_arg(ap, int);
394 				prec = n < 0 ? -1 : n;
395 				goto rflag;
396 			}
397 			n = 0;
398 			while (is_digit(ch)) {
399 				n = 10 * n + to_digit(ch);
400 				ch = *fmt++;
401 			}
402 			prec = n < 0 ? -1 : n;
403 			goto reswitch;
404 		case '0':
405 			/*
406 			 * ``Note that 0 is taken as a flag, not as the
407 			 * beginning of a field width.''
408 			 *	-- ANSI X3J11
409 			 */
410 			flags |= ZEROPAD;
411 			goto rflag;
412 		case '1': case '2': case '3': case '4':
413 		case '5': case '6': case '7': case '8': case '9':
414 			n = 0;
415 			do {
416 				n = 10 * n + to_digit(ch);
417 				ch = *fmt++;
418 			} while (is_digit(ch));
419 			width = n;
420 			goto reswitch;
421 #ifdef FLOATING_POINT
422 		case 'L':
423 			flags |= LONGDBL;
424 			goto rflag;
425 #endif
426 		case 'h':
427 			flags |= SHORTINT;
428 			goto rflag;
429 		case 'j':
430 			flags |= MAXINT;
431 			goto rflag;
432 		case 'l':
433 			if (*fmt == 'l') {
434 				fmt++;
435 				flags |= QUADINT;
436 			} else {
437 				flags |= LONGINT;
438 			}
439 			goto rflag;
440 		case 'q':
441 			flags |= QUADINT;
442 			goto rflag;
443 		case 't':
444 			flags |= PTRINT;
445 			goto rflag;
446 		case 'z':
447 			flags |= SIZEINT;
448 			goto rflag;
449 		case 'c':
450 			*buf = va_arg(ap, int);
451 			cp = buf;
452 			size = 1;
453 			sign = '\0';
454 			break;
455 		case 'D':
456 			flags |= LONGINT;
457 			/*FALLTHROUGH*/
458 		case 'd':
459 		case 'i':
460 			_uintmax = SARG();
461 			if ((intmax_t)_uintmax < 0) {
462 				_uintmax = -_uintmax;
463 				sign = '-';
464 			}
465 			base = DEC;
466 			goto number;
467 #ifdef FLOATING_POINT
468 		case 'e':
469 		case 'E':
470 		case 'f':
471 		case 'F':
472 		case 'g':
473 		case 'G':
474 			if (prec == -1) {
475 				prec = DEFPREC;
476 			} else if ((ch == 'g' || ch == 'G') && prec == 0) {
477 				prec = 1;
478 			}
479 
480 			if (flags & LONGDBL) {
481 				_double = (double) va_arg(ap, long double);
482 			} else {
483 				_double = va_arg(ap, double);
484 			}
485 
486 			/* do this before tricky precision changes */
487 			if (isinf(_double)) {
488 				if (_double < 0)
489 					sign = '-';
490 				if (ch == 'E' || ch == 'F' || ch == 'G')
491 					cp = "INF";
492 				else
493 					cp = "inf";
494 				size = 3;
495 				break;
496 			}
497 			if (isnan(_double)) {
498 				if (ch == 'E' || ch == 'F' || ch == 'G')
499 					cp = "NAN";
500 				else
501 					cp = "nan";
502 				size = 3;
503 				break;
504 			}
505 
506 			flags |= FPT;
507 			cp = cvt(_double, prec, flags, &softsign,
508 				&expt, ch, &ndig);
509 			if (ch == 'g' || ch == 'G') {
510 				if (expt <= -4 || expt > prec)
511 					ch = (ch == 'g') ? 'e' : 'E';
512 				else
513 					ch = 'g';
514 			}
515 			if (ch == 'e' || ch == 'E') {
516 				--expt;
517 				expsize = exponent(expstr, expt, ch);
518 				size = expsize + ndig;
519 				if (ndig > 1 || flags & ALT)
520 					++size;
521 			} else if (ch == 'f' || ch == 'F') {
522 				if (expt > 0) {
523 					size = expt;
524 					if (prec || flags & ALT)
525 						size += prec + 1;
526 				} else	/* "0.X" */
527 					size = prec + 2;
528 			} else if (expt >= ndig) {	/* fixed g fmt */
529 				size = expt;
530 				if (flags & ALT)
531 					++size;
532 			} else
533 				size = ndig + (expt > 0 ?
534 					1 : 2 - expt);
535 
536 			if (softsign)
537 				sign = '-';
538 			break;
539 #endif /* FLOATING_POINT */
540 		case 'n':
541 			if (flags & MAXINT)
542 				*va_arg(ap, intmax_t *) = ret;
543 			else if (flags & PTRINT)
544 				*va_arg(ap, ptrdiff_t *) = ret;
545 			else if (flags & SIZEINT)
546 				*va_arg(ap, ssize_t *) = ret;	/* XXX */
547 			else if (flags & QUADINT)
548 				*va_arg(ap, quad_t *) = ret;
549 			else if (flags & LONGINT)
550 				*va_arg(ap, long *) = ret;
551 			else if (flags & SHORTINT)
552 				*va_arg(ap, short *) = ret;
553 			else
554 				*va_arg(ap, int *) = ret;
555 			continue;	/* no output */
556 		case 'O':
557 			flags |= LONGINT;
558 			/*FALLTHROUGH*/
559 		case 'o':
560 			_uintmax = UARG();
561 			base = OCT;
562 			goto nosign;
563 		case 'p':
564 			/*
565 			 * ``The argument shall be a pointer to void.  The
566 			 * value of the pointer is converted to a sequence
567 			 * of printable characters, in an implementation-
568 			 * defined manner.''
569 			 *	-- ANSI X3J11
570 			 */
571 			/* NOSTRICT */
572 			_uintmax = (u_long)va_arg(ap, void *);
573 			base = HEX;
574 			xdigs = "0123456789abcdef";
575 			flags |= HEXPREFIX;
576 			ch = 'x';
577 			goto nosign;
578 		case 's':
579 			if ((cp = va_arg(ap, char *)) == NULL)
580 				cp = "(null)";
581 			if (prec >= 0) {
582 				/*
583 				 * can't use strlen; can only look for the
584 				 * NUL in the first `prec' characters, and
585 				 * strlen() will go further.
586 				 */
587 				char *p = memchr(cp, 0, (size_t)prec);
588 
589 				if (p != NULL) {
590 					size = p - cp;
591 					if (size > prec)
592 						size = prec;
593 				} else
594 					size = prec;
595 			} else
596 				size = strlen(cp);
597 			sign = '\0';
598 			break;
599 		case 'U':
600 			flags |= LONGINT;
601 			/*FALLTHROUGH*/
602 		case 'u':
603 			_uintmax = UARG();
604 			base = DEC;
605 			goto nosign;
606 		case 'X':
607 			xdigs = "0123456789ABCDEF";
608 			goto hex;
609 		case 'x':
610 			xdigs = "0123456789abcdef";
611 hex:			_uintmax = UARG();
612 			base = HEX;
613 			/* leading 0x/X only if non-zero */
614 			if (flags & ALT && _uintmax != 0)
615 				flags |= HEXPREFIX;
616 
617 			/* unsigned conversions */
618 nosign:			sign = '\0';
619 			/*
620 			 * ``... diouXx conversions ... if a precision is
621 			 * specified, the 0 flag will be ignored.''
622 			 *	-- ANSI X3J11
623 			 */
624 number:			if ((dprec = prec) >= 0)
625 				flags &= ~ZEROPAD;
626 
627 			/*
628 			 * ``The result of converting a zero value with an
629 			 * explicit precision of zero is no characters.''
630 			 *	-- ANSI X3J11
631 			 */
632 			bp = buf + BUF;
633 			if (_uintmax != 0 || prec != 0) {
634 				/*
635 				 * Unsigned mod is hard, and unsigned mod
636 				 * by a constant is easier than that by
637 				 * a variable; hence this switch.
638 				 */
639 				switch (base) {
640 				case OCT:
641 					do {
642 						*--bp = to_char(_uintmax & 7);
643 						_uintmax >>= 3;
644 					} while (_uintmax);
645 					/* handle octal leading 0 */
646 					if (flags & ALT && *bp != '0')
647 						*--bp = '0';
648 					break;
649 
650 				case DEC:
651 					/* many numbers are 1 digit */
652 					while (_uintmax >= 10) {
653 						*--bp = to_char(_uintmax % 10);
654 						_uintmax /= 10;
655 					}
656 					*--bp = to_char(_uintmax);
657 					break;
658 
659 				case HEX:
660 					do {
661 						*--bp = xdigs[(size_t)
662 						    (_uintmax & 15)];
663 						_uintmax >>= 4;
664 					} while (_uintmax);
665 					break;
666 
667 				default:
668 					cp = "bug in vfprintf: bad base";
669 					size = strlen(cp);
670 					goto skipsize;
671 				}
672 			}
673 			cp = bp;
674 			size = buf + BUF - bp;
675 		skipsize:
676 			break;
677 		default:	/* "%?" prints ?, unless ? is NUL */
678 			if (ch == '\0')
679 				goto done;
680 			/* pretend it was %c with argument ch */
681 			*buf = ch;
682 			cp = buf;
683 			size = 1;
684 			sign = '\0';
685 			break;
686 		}
687 
688 		/*
689 		 * All reasonable formats wind up here.  At this point, `cp'
690 		 * points to a string which (if not flags&LADJUST) should be
691 		 * padded out to `width' places.  If flags&ZEROPAD, it should
692 		 * first be prefixed by any sign or other prefix; otherwise,
693 		 * it should be blank padded before the prefix is emitted.
694 		 * After any left-hand padding and prefixing, emit zeroes
695 		 * required by a decimal [diouxX] precision, then print the
696 		 * string proper, then emit zeroes required by any leftover
697 		 * floating precision; finally, if LADJUST, pad with blanks.
698 		 *
699 		 * Compute actual size, so we know how much to pad.
700 		 * size excludes decimal prec; realsz includes it.
701 		 */
702 		realsz = dprec > size ? dprec : size;
703 		if (sign)
704 			realsz++;
705 		else if (flags & HEXPREFIX)
706 			realsz+= 2;
707 
708 		/* right-adjusting blank padding */
709 		if ((flags & (LADJUST|ZEROPAD)) == 0)
710 			PAD(width - realsz, blanks);
711 
712 		/* prefix */
713 		if (sign) {
714 			PRINT(&sign, 1);
715 		} else if (flags & HEXPREFIX) {
716 			ox[0] = '0';
717 			ox[1] = ch;
718 			PRINT(ox, 2);
719 		}
720 
721 		/* right-adjusting zero padding */
722 		if ((flags & (LADJUST|ZEROPAD)) == ZEROPAD)
723 			PAD(width - realsz, zeroes);
724 
725 		/* leading zeroes from decimal precision */
726 		PAD(dprec - size, zeroes);
727 
728 		/* the string or number proper */
729 #ifdef FLOATING_POINT
730 		if ((flags & FPT) == 0) {
731 			PRINT(cp, size);
732 		} else {	/* glue together f_p fragments */
733 			if (ch >= 'f') {	/* 'f' or 'g' */
734 				if (_double == 0) {
735 					/* kludge for __dtoa irregularity */
736 					PRINT("0", 1);
737 					if (expt < ndig || (flags & ALT) != 0) {
738 						PRINT(decimal_point, 1);
739 						PAD(ndig - 1, zeroes);
740 					}
741 				} else if (expt <= 0) {
742 					PRINT("0", 1);
743 					PRINT(decimal_point, 1);
744 					PAD(-expt, zeroes);
745 					PRINT(cp, ndig);
746 				} else if (expt >= ndig) {
747 					PRINT(cp, ndig);
748 					PAD(expt - ndig, zeroes);
749 					if (flags & ALT)
750 						PRINT(".", 1);
751 				} else {
752 					PRINT(cp, expt);
753 					cp += expt;
754 					PRINT(".", 1);
755 					PRINT(cp, ndig-expt);
756 				}
757 			} else {	/* 'e' or 'E' */
758 				if (ndig > 1 || flags & ALT) {
759 					ox[0] = *cp++;
760 					ox[1] = '.';
761 					PRINT(ox, 2);
762 					if (_double) {
763 						PRINT(cp, ndig-1);
764 					} else	/* 0.[0..] */
765 						/* __dtoa irregularity */
766 						PAD(ndig - 1, zeroes);
767 				} else	/* XeYYY */
768 					PRINT(cp, 1);
769 				PRINT(expstr, expsize);
770 			}
771 		}
772 #else
773 		PRINT(cp, size);
774 #endif
775 		/* left-adjusting padding (always blank) */
776 		if (flags & LADJUST)
777 			PAD(width - realsz, blanks);
778 
779 		/* finally, adjust ret */
780 		ret += width > realsz ? width : realsz;
781 
782 		FLUSH();	/* copy out the I/O vectors */
783 	}
784 done:
785 	FLUSH();
786 error:
787 	if (__sferror(fp))
788 		ret = -1;
789 	FUNLOCKFILE(fp);
790 	return (ret);
791 }
792 
793 #ifdef FLOATING_POINT
794 
795 static char *
796 cvt(value, ndigits, flags, sign, decpt, ch, length)
797 	double value;
798 	int ndigits, flags, *decpt, ch, *length;
799 	char *sign;
800 {
801 	int mode, dsgn;
802 	char *digits, *bp, *rve;
803 
804 	_DIAGASSERT(decpt != NULL);
805 	_DIAGASSERT(length != NULL);
806 	_DIAGASSERT(sign != NULL);
807 
808 	if (ch == 'f') {
809 		mode = 3;		/* ndigits after the decimal point */
810 	} else {
811 		/* To obtain ndigits after the decimal point for the 'e'
812 		 * and 'E' formats, round to ndigits + 1 significant
813 		 * figures.
814 		 */
815 		if (ch == 'e' || ch == 'E') {
816 			ndigits++;
817 		}
818 		mode = 2;		/* ndigits significant digits */
819 	}
820 
821 	digits = __dtoa(value, mode, ndigits, decpt, &dsgn, &rve);
822 	if (dsgn) {
823 		value = -value;
824 		*sign = '-';
825 	} else
826 		*sign = '\000';
827 	if ((ch != 'g' && ch != 'G') || flags & ALT) {	/* Print trailing zeros */
828 		bp = digits + ndigits;
829 		if (ch == 'f') {
830 			if (*digits == '0' && value)
831 				*decpt = -ndigits + 1;
832 			bp += *decpt;
833 		}
834 		if (value == 0)	/* kludge for __dtoa irregularity */
835 			rve = bp;
836 		while (rve < bp)
837 			*rve++ = '0';
838 	}
839 	*length = rve - digits;
840 	return (digits);
841 }
842 
843 static int
844 exponent(p0, expon, fmtch)
845 	char *p0;
846 	int expon, fmtch;
847 {
848 	char *p, *t;
849 	char expbuf[MAXEXP];
850 
851 	_DIAGASSERT(p0 != NULL);
852 
853 	p = p0;
854 	*p++ = fmtch;
855 	if (expon < 0) {
856 		expon = -expon;
857 		*p++ = '-';
858 	}
859 	else
860 		*p++ = '+';
861 	t = expbuf + MAXEXP;
862 	if (expon > 9) {
863 		do {
864 			*--t = to_char(expon % 10);
865 		} while ((expon /= 10) > 9);
866 		*--t = to_char(expon);
867 		for (; t < expbuf + MAXEXP; *p++ = *t++);
868 	}
869 	else {
870 		*p++ = '0';
871 		*p++ = to_char(expon);
872 	}
873 	return (p - p0);
874 }
875 #endif /* FLOATING_POINT */
876