fmt(1) rewrite by Gareth McCaughan.

2 files changed, 639 insertions, 556 deletions

diff --git a/usr.bin/fmt/fmt.1 b/usr.bin/fmt/fmt.1
index 3b223ff8842..a0c6d864125 100644
--- a/usr.bin/fmt/fmt.1
+++ b/usr.bin/fmt/fmt.1
@@ -1,5 +1,4 @@
-.\"	$OpenBSD: fmt.1,v 1.3 1997/02/09 23:58:42 millert Exp $
-.\"	$NetBSD: fmt.1,v 1.3 1995/09/01 01:29:40 jtc Exp $
+.\" $OpenBSD: fmt.1,v 1.4 1998/04/25 23:02:26 millert Exp $
 .\"
 .\" Copyright (c) 1980, 1990, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -34,6 +33,8 @@
 .\"
 .\"     @(#)fmt.1	8.1 (Berkeley) 6/6/93
 .\"
+.\" Modified by Gareth McCaughan to describe the new version of `fmt'
+.\" rather than the old one.
 .Dd June 6, 1993
 .Dt FMT 1
 .Os
@@ -41,8 +42,11 @@
 .Nm fmt
 .Nd simple text formatter
 .Sh SYNOPSIS
-.Nm fmt
-.Fl c
+.Nm
+.Op Fl cmps
+.Op Fl d Ar chars
+.Op Fl l Ar num
+.Op Fl t Ar num
 .Oo
 .Ar goal
 .Op Ar maximum
@@ -55,17 +59,50 @@ files (or standard input if none are given) and produces on standard
 output a version of its input with lines as close to the
 .Ar goal
 length
-as possible without exceeding the maximum.  The
+as possible without exceeding the
+.Ar maximum.
+The
 .Ar goal
 length defaults
-to 65 and the maximum to 75.  The spacing at the beginning of the
+to 65 and the
+.Ar maximum
+to 10 more than the goal length.  The spacing at the beginning of the
 input lines is preserved in the output, as are blank lines and
 interword spacing.
 .Pp
-.Fl c
-instructs
-.Nm fmt
-to center the text.
+The following options are available:
+.Bl -tag -width indent
+.It Fl c
+Center the text, line by line. In this case, most of the other
+options are ignored; no splitting or joining of lines is done.
+.It Fl m
+Try to format mail header lines contained in the input sensibly.
+.It Fl p
+Allow indented paragraphs. Without the
+.Fl p
+flag, any change in the amount of whitespace at the start of a line
+results in a new paragraph being begun.
+.It Fl s
+Collapse whitespace inside lines, so that multiple whitespace
+characters are turned into a single space. (Or, at the end of a
+sentence, a double space.)
+.It Fl d Ar chars
+Treat the
+.Ar chars
+(and no others) as sentence-ending characters. By default the
+sentence-ending characters are full stop, question mark and
+exclamation mark. Remember that some characters may need to be
+escaped to protect them from your shell.
+.It Fl l Ar number
+Replace multiple spaces with tabs at the start of each output
+line, if possible.
+.Ar number
+spaces will be replaced with one tab.
+.It Fl t Ar number
+Assume that the input files' tabs assume
+.Ar number
+spaces per tab stop. The default is 8.
+.El
 .Pp
 .Nm Fmt
 is meant to format mail messages prior to sending, but may also be useful
@@ -82,17 +119,32 @@ the command
 will reformat a paragraph,
 evening the lines.
 .Sh SEE ALSO
-.Xr nroff 1 ,
-.Xr mail 1
+.Xr mail 1 ,
+.Xr nroff 1
 .Sh HISTORY
-The
-.Nm fmt
+An
+.Nm
 command appeared in
 .Bx 3 .
+.Pp
+The version described herein is a complete rewrite and appeared in
+.\" .Ox 2.4 .
+.Bx Open
+2.4.
 .\" .Sh AUTHOR
 .\" Kurt Shoens
 .\" .br
 .\" Liz Allen (added goal length concept)
+.\" The above are the authors of the old `fmt' program;
+.\" the present one was written by Gareth McCaughan.
 .Sh BUGS
 The program was designed to be simple and fast \- for more complex
 operations, the standard text processors are likely to be more appropriate.
+.Pp
+When the first line of an indented paragraph is very long (more than
+about twice the goal length), the indentation in the output can be
+wrong.
+.Pp
+.Nm
+is not infallible in guessing what lines are mail headers and what
+lines are not.
diff --git a/usr.bin/fmt/fmt.c b/usr.bin/fmt/fmt.c
index 73de68cb516..2cb9ebe2cce 100644
--- a/usr.bin/fmt/fmt.c
+++ b/usr.bin/fmt/fmt.c
@@ -1,597 +1,628 @@
-/*	$OpenBSD: fmt.c,v 1.9 1998/02/16 07:54:29 deraadt Exp $	*/
-/*	$NetBSD: fmt.c,v 1.4 1995/09/01 01:29:41 jtc Exp $	*/
+/*	$OpenBSD: fmt.c,v 1.10 1998/04/25 23:02:28 millert Exp $	*/
 
-/*
- * Copyright (c) 1980, 1993
- *	The Regents of the University of California.  All rights reserved.
+/* Sensible version of fmt
  *
- * 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
+ * Syntax: fmt [ options ] [ goal [ max ] ] [ filename ... ]
+ *
+ * Since the documentation for the original fmt is so poor, here
+ * is an accurate description of what this one does. It's usually
+ * the same. The *mechanism* used may differ from that suggested
+ * here. Note that we are *not* entirely compatible with fmt,
+ * because fmt gets so many things wrong.
+ *
+ * 1. Tabs are expanded, assuming 8-space tab stops.
+ *    If the `-t <n>' option is given, we assume <n>-space
+ *    tab stops instead.
+ *    Trailing blanks are removed from all lines.
+ *    x\b == nothing, for any x other than \b.
+ *    Other control characters are simply stripped. This
+ *    includes \r.
+ * 2. Each line is split into leading whitespace and
+ *    everything else. Maximal consecutive sequences of
+ *    lines with the same leading whitespace are considered
+ *    to form paragraphs, except that a blank line is always
+ *    a paragraph to itself.
+ *    If the `-p' option is given then the first line of a
+ *    paragraph is permitted to have indentation different
+ *    from that of the other lines.
+ *    If the `-m' option is given then a line that looks
+ *    like a mail message header, if it is not immediately
+ *    preceded by a non-blank non-message-header line, is
+ *    taken to start a new paragraph, which also contains
+ *    any subsequent lines with non-empty leading whitespace.
+ * 3. The "everything else" is split into words; a word
+ *    includes its trailing whitespace, and a word at the
+ *    end of a line is deemed to be followed by a single
+ *    space, or two spaces if it ends with a sentence-end
+ *    character. (See the `-d' option for how to change that.)
+ *    If the `-s' option has been given, then a word's trailing
+ *    whitespace is replaced by what it would have had if it
+ *    had occurred at end of line.
+ * 4. Each paragraph is sent to standard output as follows.
+ *    We output the leading whitespace, and then enough words
+ *    to make the line length as near as possible to the goal
+ *    without exceeding the maximum. (If a single word would
+ *    exceed the maximum, we output that anyway.) Of course
+ *    the trailing whitespace of the last word is ignored.
+ *    We then emit a newline and start again if there are any
+ *    words left.
+ *    Note that for a blank line this translates as "We emit
+ *    a newline".
+ *    If the `-l <n>' option is given, then leading whitespace
+ *    is modified slightly: <n> spaces are replaced by a tab.
+ *    Indented paragraphs (see above under `-p') make matters
+ *    more complicated than this suggests. Actually every paragraph
+ *    has two `leading whitespace' values; the value for the first
+ *    line, and the value for the most recent line. (While processing
+ *    the first line, the two are equal. When `-p' has not been
+ *    given, they are always equal.) The leading whitespace
+ *    actually output is that of the first line (for the first
+ *    line of *output*) or that of the most recent line (for
+ *    all other lines of output).
+ *    When `-m' has been given, message header paragraphs are
+ *    taken as having first-leading-whitespace empty and
+ *    subsequent-leading-whitespace two spaces.
+ *
+ * Multiple input files are formatted one at a time, so that a file
+ * never ends in the middle of a line.
+ *
+ * There's an alternative mode of operation, invoked by giving
+ * the `-c' option. In that case we just center every line,
+ * and most of the other options are ignored. This should
+ * really be in a separate program, but we must stay compatible
+ * with old `fmt'.
+ *
+ * QUERY: Should `-m' also try to do the right thing with quoted text?
+ * QUERY: `-b' to treat backslashed whitespace as old `fmt' does?
+ * QUERY: Option meaning `never join lines'?
+ * QUERY: Option meaning `split in mid-word to avoid overlong lines'?
+ * (Those last two might not be useful, since we have `fold'.)
+ *
+ * Differences from old `fmt':
+ *
+ *   - We have many more options. Options that aren't understood
+ *     generate a lengthy usage message, rather than being
+ *     treated as filenames.
+ *   - Even with `-m', our handling of message headers is
+ *     significantly different. (And much better.)
+ *   - We don't treat `\ ' as non-word-breaking.
+ *   - Downward changes of indentation start new paragraphs
+ *     for us, as well as upward. (I think old `fmt' behaves
+ *     in the way it does in order to allow indented paragraphs,
+ *     but this is a broken way of making indented paragraphs
+ *     behave right.)
+ *   - Given the choice of going over or under |goal_length|
+ *     by the same amount, we go over; old `fmt' goes under.
+ *   - We treat `?' as ending a sentence, and not `:'. Old `fmt'
+ *     does the reverse.
+ *   - We return approved return codes. Old `fmt' returns
+ *     1 for some errors, and *the number of unopenable files*
+ *     when that was all that went wrong.
+ *   - We have fewer crashes and more helpful error messages.
+ *   - We don't turn spaces into tabs at starts of lines unless
+ *     specifically requested.
+ *   - New `fmt' is somewhat smaller and slightly faster than
+ *     old `fmt'.
+ *
+ * Bugs:
+ *
+ *   None known. There probably are some, though.
+ *
+ * Portability:
+ *
+ *   I believe this code to be pretty portable. It does require
+ *   that you have `getopt'. If you need to include "getopt.h"
+ *   for this (e.g., if your system didn't come with `getopt'
+ *   and you installed it yourself) then you should arrange for
+ *   NEED_getopt_h to be #defined.
+ *
+ *   Everything here should work OK even on nasty 16-bit
+ *   machines and nice 64-bit ones. However, it's only really
+ *   been tested on my FreeBSD machine. Your mileage may vary.
+ */
+
+/* Copyright (c) 1997 Gareth McCaughan. All rights reserved.
+ *
+ * Redistribution and use of this code, in source or binary forms,
+ * with or without modification, are permitted subject to the following
+ * conditions:
+ *
+ *  - Redistribution 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. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *	This product includes software developed by the University of
- *	California, Berkeley and its contributors.
- * 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 you distribute modified source code it must also include
+ *    a notice saying that it has been modified, and giving a brief
+ *    description of what changes have been made.
+ *
+ * Disclaimer: I am not responsible for the results of using this code.
+ *             If it formats your hard disc, sends obscene messages to
+ *             your boss and kills your children then that's your problem
+ *             not mine. I give absolutely no warranty of any sort as to
+ *             what the program will do, and absolutely refuse to be held
+ *             liable for any consequences of your using it.
+ *             Thank you. Have a nice day.
+ */
+
+/* RCS change log:
+ * Revision 1.5  1998/03/02 18:02:21  gjm11
+ * Minor changes for portability.
+ *
+ * Revision 1.4  1997/10/01 11:51:28  gjm11
+ * Repair broken indented-paragraph handling.
+ * Add mail message header stuff.
+ * Improve comments and layout.
+ * Make usable with non-BSD systems.
+ * Add revision display to usage message.
+ *
+ * Revision 1.3  1997/09/30 16:24:47  gjm11
+ * Add copyright notice, rcsid string and log message.
+ *
+ * Revision 1.2  1997/09/30 16:13:39  gjm11
+ * Add options: -d <chars>, -l <width>, -p, -s, -t <width>, -h .
+ * Parse options with `getopt'. Clean up code generally.
+ * Make comments more accurate.
+ *
+ * Revision 1.1  1997/09/30 11:29:57  gjm11
+ * Initial revision
  */
 
 #ifndef lint
-static char copyright[] =
-"@(#) Copyright (c) 1980, 1993\n\
-	The Regents of the University of California.  All rights reserved.\n";
+static const char rcsid[] =
+  "$OpenBSD: fmt.c,v 1.10 1998/04/25 23:02:28 millert Exp $";
+static const char copyright[] =
+  "Copyright (c) 1997 Gareth McCaughan. All rights reserved.\n";
 #endif /* not lint */
 
-#ifndef lint
-#if 0
-static char sccsid[] = "@(#)fmt.c	8.1 (Berkeley) 7/20/93";
+/* Cater for BSD and non-BSD systems.
+ * I hate the C preprocessor.
+ */
+
+#undef HAVE_errx
+#undef HAVE_sysexits
+
+#ifdef unix
+# include <sys/param.h>
+# ifdef BSD
+#  define HAVE_errx
+#  if BSD >= 199306
+#   define HAVE_sysexits
+#  endif
+# endif
+#endif
+
+#ifdef HAVE_errx
+# include <err.h>
 #else
-static char rcsid[] = "$OpenBSD: fmt.c,v 1.9 1998/02/16 07:54:29 deraadt Exp $";
+# define errx(rc,str) { fprintf(stderr,"fmt: %s\n",str); exit(rc); }
+#endif
+
+#ifdef HAVE_sysexits
+# include <sysexits.h>
+#else
+# define EX_USAGE 1
+# define EX_NOINPUT 1
+# define EX_SOFTWARE 1
+# define EX_OSERR 1
 #endif
-#endif /* not lint */
 
 #include <ctype.h>
-#include <err.h>
-#include <locale.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
-#ifdef	__GNUC__
-#define inline	__inline
-#else	/* !__GNUC__ */
-#define inline
-#endif	/* !__GNUC__ */
+#ifdef NEED_getopt_h
+# include "getopt.h"
+#endif
 
-/*
- * fmt -- format the concatenation of input files or standard input
- * onto standard output.  Designed for use with Mail ~|
- *
- * Syntax : fmt [ goal [ max ] ] [ name ... ]
- * Authors: Kurt Shoens (UCB) 12/7/78;
- *          Liz Allen (UMCP) 2/24/83 [Addition of goal length concept].
+/* Something that, we hope, will never be a genuine line length,
+ * indentation etc.
  */
+#define SILLY ((size_t)-1)
 
-/* LIZ@UOM 6/18/85 -- Don't need LENGTH any more.
- * #define	LENGTH	72		Max line length in output
- */
-#define	NOSTR	((char *) 0)	/* Null string pointer for lint */
-
-/* LIZ@UOM 6/18/85 --New variables goal_length and max_length */
-#define GOAL_LENGTH 65
-#define MAX_LENGTH 75
-int	goal_length;		/* Target or goal line length in output */
-int	max_length;		/* Max line length in output */
-int	pfx;			/* Current leading blank count */
-int	lineno;			/* Current input line */
-int	mark;			/* Last place we saw a head line */
-int	center;			/* Did they ask to center lines? */
-
-char	*headnames[] = {"To", "Subject", "Cc", 0};
-
-void fmt __P((FILE *));
-void setout __P((void));
-void prefix __P((char *));
-void split __P((char *));
-void pack __P((char *, int));
-void oflush __P((void));
-void tabulate __P((char *));
-void leadin __P((void));
-char *savestr __P((char *));
-inline char *extstr __P((char *, int *, int));
-int  ispref __P((char *, char *));
-int  ishead __P((char *));
-
-/*
- * Drive the whole formatter by managing input files.  Also,
- * cause initialization of the output stuff and flush it out
- * at the end.
+/* I used to use |strtoul| for this, but (1) not all systems have it
+ * and (2) it's probably better to use |strtol| to detect negative
+ * numbers better.
+ * If |fussyp==0| then we don't complain about non-numbers
+ * (returning 0 instead), but we do complain about bad numbers.
  */
-
-int
-main(argc, argv)
-	int argc;
-	char **argv;
-{
-	register FILE *fi;
-	register int errs = 0;
-	int number;		/* LIZ@UOM 6/18/85 */
-
-	(void) setlocale(LC_CTYPE, "");
-
-	goal_length = GOAL_LENGTH;
-	max_length = MAX_LENGTH;
-	setout();
-	lineno = 1;
-	mark = -10;
-	/*
-	 * LIZ@UOM 6/18/85 -- Check for goal and max length arguments
-	 */
-	if (argc > 1 && !strcmp(argv[1], "-c")) {
-		center++;
-		argc--;
-		argv++;
-	}
-	if (argc > 1 && (1 == (sscanf(argv[1], "%d", &number)))) {
-		argv++;
-		argc--;
-		goal_length = abs(number);
-		if (argc > 1 && (1 == (sscanf(argv[1], "%d", &number)))) {
-			argv++;
-			argc--;
-			max_length = abs(number);
-		}
-	}
-	if (max_length <= goal_length)
-		errx(1, "Max length (%d) must be greater than goal length: %d",
-		     max_length, goal_length);
-	if (argc < 2) {
-		fmt(stdin);
-		oflush();
-		exit(0);
-	}
-	while (--argc) {
-		if ((fi = fopen(*++argv, "r")) == NULL) {
-			perror(*argv);
-			errs++;
-			continue;
-		}
-		fmt(fi);
-		fclose(fi);
-	}
-	oflush();
-	exit(errs);
+size_t get_positive(const char *s, const char *err_mess, int fussyP) {
+  char *t;
+  long result = strtol(s,&t,0);
+  if (*t) { if (fussyP) goto Lose; else return 0; }
+  if (result<=0) { Lose: errx(EX_USAGE, err_mess); }
+  return (size_t) result;
 }
 
-/*
- * Read up characters from the passed input file, forming lines,
- * doing ^H processing, expanding tabs, stripping trailing blanks,
- * and sending each line down for analysis.
- */
-void
-fmt(fi)
-	FILE *fi;
-{
-	static char *linebuf, *canonb;
-	static int lbufsize, cbufsize;
-	register char *cp, *cp2, cc;
-	register int c, col;
-#define CHUNKSIZE 1024
-
-	canonb = malloc(CHUNKSIZE);
-	if (canonb == 0)
-		errx(1, "Ran out of memory");
-
-	if (center) {
-		register int len;
-
-		linebuf = extstr(linebuf, &lbufsize, NULL);
-		for (;;) {
-			len = 0;
-			for (;;) {
-				if (!fgets(linebuf + len, lbufsize - len, fi))
-					break;
-				len = strlen(linebuf);
-				if (linebuf[len-1] == '\n' || feof(fi))
-					break;
-				linebuf = extstr(linebuf, &lbufsize, NULL);
-			}
-			if (len == 0)
-				return;
-			cp = linebuf;
-			while (*cp && isspace(*cp))
-				cp++;
-			cp2 = cp + strlen(cp) - 1;
-			while (cp2 > cp && isspace(*cp2))
-				cp2--;
-			if (cp == cp2)
-				putchar('\n');
-			col = cp2 - cp;
-			for (c = 0; c < (goal_length-col)/2; c++)
-				putchar(' ');
-			while (cp <= cp2)
-				putchar(*cp++);
-			putchar('\n');
-		}
-	}
-	c = getc(fi);
-	while (c != EOF) {
-		/*
-		 * Collect a line, doing ^H processing.
-		 * Leave tabs for now.
-		 */
-		cp = linebuf;
-		while (c != '\n' && c != EOF) {
-			if (cp - linebuf >= lbufsize) {
-				int offset = cp - linebuf;
-				linebuf = extstr(linebuf, &lbufsize, NULL);
-				cp = linebuf + offset;
-			}
-			if (c == '\b') {
-				if (cp > linebuf)
-					cp--;
-				c = getc(fi);
-				continue;
-			}
-			if (!isprint(c) && c != '\t') {
-				c = getc(fi);
-				continue;
-			}
-			*cp++ = c;
-			c = getc(fi);
-		}
-
-		/*
-		 * Toss anything remaining on the input line.
-		 */
-		while (c != '\n' && c != EOF)
-			c = getc(fi);
-
-		if (cp != NULL) {
-			*cp = '\0';
-		} else {
-			putchar('\n');
-			c = getc(fi);
-			continue;
-		}
-
-		/*
-		 * Expand tabs on the way to canonb.
-		 */
-		col = 0;
-		cp = linebuf;
-		cp2 = canonb;
-		while ((cc = *cp++)) {
-			if (cc != '\t') {
-				col++;
-				if (cp2 - canonb >= cbufsize) {
-					int offset = cp2 - canonb;
-					canonb = extstr(canonb, &cbufsize, NULL);
-					cp2 = canonb + offset;
-				}
-				*cp2++ = cc;
-				continue;
-			}
-			do {
-				if (cp2 - canonb >= cbufsize) {
-					int offset = cp2 - canonb;
-					canonb = extstr(canonb, &cbufsize, NULL);
-					cp2 = canonb + offset;
-				}
-				*cp2++ = ' ';
-				col++;
-			} while ((col & 07) != 0);
-		}
-
-		/*
-		 * Swipe trailing blanks from the line.
-		 */
-		for (cp2--; cp2 >= canonb && *cp2 == ' '; cp2--)
-			;
-		*++cp2 = '\0';
-		prefix(canonb);
-		if (c != EOF)
-			c = getc(fi);
-	}
-}
+/* Just for the sake of linguistic purity: */
+
+#ifdef BRITISH
+# define CENTER "centre"
+#else
+# define CENTER "center"
+#endif
 
-/*
- * Take a line devoid of tabs and other garbage and determine its
- * blank prefix.  If the indent changes, call for a linebreak.
- * If the input line is blank, echo the blank line on the output.
- * Finally, if the line minus the prefix is a mail header, try to keep
- * it on a line by itself.
+/* Global variables */
+
+static int centerP=0;		/* Try to center lines? */
+static size_t goal_length=0;	/* Target length for output lines */
+static size_t max_length=0;	/* Maximum length for output lines */
+static int coalesce_spaces_P=0;	/* Coalesce multiple whitespace -> ' ' ? */
+static int allow_indented_paragraphs=0;	/* Can first line have diff. ind.? */
+static int tab_width=8;		/* Number of spaces per tab stop */
+static int output_tab_width=0;	/* Ditto, when squashing leading spaces */
+static char *sentence_enders=".?!";	/* Double-space after these */
+static int grok_mail_headers=0;	/* treat embedded mail headers magically? */
+
+static int n_errors=0;		/* Number of failed files. Return on exit. */
+static char *output_buffer=0;	/* Output line will be built here */
+static size_t x;		/* Horizontal position in output line */
+static size_t x0;		/* Ditto, ignoring leading whitespace */
+static size_t pending_spaces;	/* Spaces to add before next word */
+static int output_in_paragraph=0;	/* Any of current para written out yet? */
+
+/* Prototypes */
+
+static void process_named_file (const char *);
+static void     process_stream (FILE *, const char *);
+static size_t    indent_length (const char *, size_t);
+static int     might_be_header (const char *);
+static void      new_paragraph (size_t, size_t);
+static void        output_word (size_t, size_t, const char *, size_t, size_t);
+static void      output_indent (size_t);
+static void      center_stream (FILE *, const char *);
+static char *         get_line (FILE *, size_t *);
+static void *         xrealloc (void *, size_t);
+
+#define XMALLOC(x) xrealloc(0,x)
+
+/* Here is perhaps the right place to mention that this code is
+ * all in top-down order. Hence, |main| comes first.
  */
-void
-prefix(line)
-	char line[];
-{
-	register char *cp, **hp;
-	register int np, h;
-
-	if (*line == '\0') {
-		oflush();
-		putchar('\n');
-		return;
-	}
-	for (cp = line; *cp == ' '; cp++)
-		;
-	np = cp - line;
-
-	/*
-	 * The following horrible expression attempts to avoid linebreaks
-	 * when the indent changes due to a paragraph.
-	 */
-	if (np != pfx && (np > pfx || abs(pfx-np) > 8))
-		oflush();
-	if ((h = ishead(cp)))
-		oflush(), mark = lineno;
-	if (lineno - mark < 3 && lineno - mark > 0)
-		for (hp = &headnames[0]; *hp != NULL; hp++)
-			if (ispref(*hp, cp)) {
-				h = 1;
-				oflush();
-				break;
-			}
-	if (!h && (h = (*cp == '.')))
-		oflush();
-	pfx = np;
-	if (h)
-		pack(cp, strlen(cp));
-	else
-		split(cp);
-	if (h)
-		oflush();
-	lineno++;
+int
+main(int argc, char *argv[]) {
+  int ch;			/* used for |getopt| processing */
+
+  /* 1. Grok parameters. */
+
+  while ((ch = getopt(argc, argv, "cd:hl:mpst:")) != EOF) switch(ch) {
+    case 'c':
+      centerP = 1;
+      continue;
+    case 'd':
+      sentence_enders = XMALLOC(strlen(optarg)+1);
+      strcpy(sentence_enders, optarg);
+      continue;
+    case 'l':
+      output_tab_width
+        = get_positive(optarg, "output tab width must be positive", 1);
+      continue;
+    case 'm':
+      grok_mail_headers = 1;
+      continue;
+    case 'p':
+      allow_indented_paragraphs = 1;
+      continue;
+    case 's':
+      coalesce_spaces_P = 1;
+      continue;
+    case 't':
+      tab_width = get_positive(optarg, "tab width must be positive", 1);
+      continue;
+    case 'h': default:
+      fprintf(stderr,
+"Usage:   fmt [-cmps] [-d chars] [-l num] [-t num] [goal [maximum]] [file...]\n"
+"Options: -c     " CENTER " each line instead of formatting\n"
+"         -d <chars> double-space after <chars> at line end\n"
+"         -l <n> turn each <n> spaces at start of line into a tab\n"
+"         -m     try to make sure mail header lines stay separate\n"
+"         -p     allow indented paragraphs\n"
+"         -s     coalesce whitespace inside lines\n"
+"         -t <n> have tabs every <n> columns\n");
+      exit(ch=='h' ? 0 : EX_USAGE);
+  }
+  argc -= optind; argv += optind;
+
+  /* [ goal [ maximum ] ] */
+
+  if (argc>0
+      && (goal_length=get_positive(*argv,"goal length must be positive", 0))
+         != 0) {
+    --argc; ++argv;
+    if (argc>0
+        && (goal_length=get_positive(*argv,"max length must be positive", 0))
+           != 0) {
+      if (max_length<goal_length)
+        errx(EX_USAGE, "max length must be >= goal length");
+    }
+  }
+  if (goal_length==0) goal_length = 65;
+  if (max_length==0) max_length = goal_length+10;
+  output_buffer = XMALLOC(max_length+1);	/* really needn't be longer */
+
+  /* 2. Process files. */
+
+  if (argc>0) {
+    while (argc-->0) process_named_file(*argv++);
+  }
+  else {
+    process_stream(stdin, "standard input");
+  }
+
+  /* We're done. */
+
+  return n_errors ? EX_NOINPUT : 0;
+
 }
 
-/*
- * Split up the passed line into output "words" which are
- * maximal strings of non-blanks with the blank separation
- * attached at the end.  Pass these words along to the output
- * line packer.
+/* Process a single file, given its name.
  */
-void
-split(line)
-	char line[];
-{
-	register char *cp, *cp2;
-	static char *word;
-	static int wordsize;
-	int wordl;		/* LIZ@UOM 6/18/85 */
-
-	if (strlen(line) >= wordsize)
-		word = extstr(word, &wordsize, strlen(line) + 1);
-
-	cp = line;
-	while (*cp) {
-		cp2 = word;
-		wordl = 0;	/* LIZ@UOM 6/18/85 */
-
-		/*
-		 * Collect a 'word,' allowing it to contain escaped white
-		 * space.
-		 */
-		while (*cp && *cp != ' ') {
-			if (*cp == '\\' && isspace(cp[1]))
-				*cp2++ = *cp++, wordl++;
-			*cp2++ = *cp++;
-			wordl++;/* LIZ@UOM 6/18/85 */
-		}
-
-		/*
-		 * Guarantee a space at end of line. Two spaces after end of
-		 * sentence punctuation.
-		 */
-		if (*cp == '\0') {
-			*cp2++ = ' ';
-			if (strchr(".:!", cp[-1]))
-				*cp2++ = ' ';
-		}
-		while (*cp == ' ')
-			*cp2++ = *cp++;
-		*cp2 = '\0';
-		/*
-		 * LIZ@UOM 6/18/85 pack(word);
-		 */
-		pack(word, wordl);
-	}
+static void
+process_named_file(const char *name) {
+  FILE *f=fopen(name, "r");
+  if (!f) { perror(name); ++n_errors; }
+  else {
+    process_stream(f, name);
+    fclose(f);
+  }
 }
 
-/*
- * Output section.
- * Build up line images from the words passed in.  Prefix
- * each line with correct number of blanks.  The buffer "outbuf"
- * contains the current partial line image, including prefixed blanks.
- * "outp" points to the next available space therein.  When outp is NOSTR,
- * there ain't nothing in there yet.  At the bottom of this whole mess,
- * leading tabs are reinserted.
+/* Types of mail header continuation lines:
  */
-static char *outbuf;			/* Sandbagged output line image */
-static int   obufsize;			/* Size of outbuf */
-static char *outp;			/* Pointer in above */
-
-/*
- * Initialize the output section.
+typedef enum {
+  hdr_ParagraphStart = -1,
+  hdr_NonHeader      = 0,
+  hdr_Header         = 1,
+  hdr_Continuation   = 2
+} HdrType;
+
+/* Process a stream. This is where the real work happens,
+ * except that centering is handled separately.
  */
-void
-setout()
-{
-	outp = NOSTR;
+static void
+process_stream(FILE *stream, const char *name) {
+  size_t last_indent=SILLY;	/* how many spaces in last indent? */
+  size_t para_line_number=0;	/* how many lines already read in this para? */
+  size_t first_indent=SILLY;	/* indentation of line 0 of paragraph */
+  HdrType prev_header_type=hdr_ParagraphStart;
+	/* ^-- header_type of previous line; -1 at para start */
+  char *line;
+  size_t length;
+
+  if (centerP) { center_stream(stream, name); return; }
+  while ((line=get_line(stream,&length)) != NULL) {
+    size_t np=indent_length(line, length);
+    { HdrType header_type=hdr_NonHeader;
+      if (grok_mail_headers && prev_header_type!=hdr_NonHeader) {
+        if (np==0 && might_be_header(line))
+          header_type = hdr_Header;
+        else if (np>0 && prev_header_type>hdr_NonHeader)
+          header_type = hdr_Continuation;
+      }
+      /* We need a new paragraph if and only if:
+       *   this line is blank,
+       *   OR it's a mail header,
+       *   OR it's not a mail header AND the last line was one,
+       *   OR the indentation has changed
+       *      AND the line isn't a mail header continuation line
+       *      AND this isn't the second line of an indented paragraph.
+       */
+      if ( length==0
+           || header_type==hdr_Header
+           || (header_type==hdr_NonHeader && prev_header_type>hdr_NonHeader)
+           || (np!=last_indent
+               && header_type != hdr_Continuation
+               && (!allow_indented_paragraphs || para_line_number != 1)) ) {
+        new_paragraph(output_in_paragraph ? last_indent : first_indent, np);
+        para_line_number = 0;
+        first_indent = np;
+        last_indent = np;
+        if (header_type==hdr_Header) last_indent=2;	/* for cont. lines */
+        if (length==0) {
+          putchar('\n');
+          prev_header_type=hdr_ParagraphStart;
+          continue;
+        }
+      }
+      else {
+        /* If this is an indented paragraph other than a mail header
+         * continuation, set |last_indent|.
+         */
+        if (np != last_indent && header_type != hdr_Continuation)
+          last_indent=np;
+      }
+      prev_header_type = header_type;
+    }
+
+    { size_t n=np;
+      while (n<length) {
+        /* Find word end and count spaces after it */
+        size_t word_length=0, space_length=0;
+        while (n+word_length < length && line[n+word_length] != ' ')
+          ++word_length;
+        space_length = word_length;
+        while (n+space_length < length && line[n+space_length] == ' ')
+          ++space_length;
+        /* Send the word to the output machinery. */
+        output_word(first_indent, last_indent,
+                    line+n, word_length, space_length-word_length);
+        n += space_length;
+      }
+    }
+    ++para_line_number;
+  }
+  new_paragraph(output_in_paragraph ? last_indent : first_indent, 0);
+  if (ferror(stream)) { perror(name); ++n_errors; }
 }
 
-/*
- * Pack a word onto the output line.  If this is the beginning of
- * the line, push on the appropriately-sized string of blanks first.
- * If the word won't fit on the current line, flush and begin a new
- * line.  If the word is too long to fit all by itself on a line,
- * just give it its own and hope for the best.
- *
- * LIZ@UOM 6/18/85 -- If the new word will fit in at less than the
- *	goal length, take it.  If not, then check to see if the line
- *	will be over the max length; if so put the word on the next
- *	line.  If not, check to see if the line will be closer to the
- *	goal length with or without the word and take it or put it on
- *	the next line accordingly.
+/* How long is the indent on this line?
  */
+static size_t
+indent_length(const char *line, size_t length) {
+  size_t n=0;
+  while (n<length && *line++ == ' ') ++n;
+  return n;
+}
 
-/*
- * LIZ@UOM 6/18/85 -- pass in the length of the word as well
- * pack(word)
- *	char word[];
+/* Might this line be a mail header?
+ * We deem a line to be a possible header if it matches the
+ * Perl regexp /^[A-Z][-A-Za-z0-9]*:\s/. This is *not* the same
+ * as in RFC whatever-number-it-is; we want to be gratuitously
+ * conservative to avoid mangling ordinary civilised text.
  */
-void
-pack(word, wl)
-	char word[];
-	int wl;
-{
-	register char *cp;
-	register int s, t;
-
-	if (outp == NOSTR)
-		leadin();
-	/*
-	 * LIZ@UOM 6/18/85 -- change condition to check goal_length; s is the
-	 * length of the line before the word is added; t is now the length
-	 * of the line after the word is added
-	 *	t = strlen(word);
-	 *	if (t+s <= LENGTH)
-	 */
-	s = outp - outbuf;
-	t = wl + s;
-	if (t + 1 > obufsize) {
-		outbuf = extstr(outbuf, &obufsize, t + 1);
-		outp = outbuf + s;
-	}
-	if ((t <= goal_length) ||
-	    ((t <= max_length) && (t - goal_length <= goal_length - s))) {
-		/*
-		 * In like flint!
-		 */
-		for (cp = word; *cp; *outp++ = *cp++)
-			;
-		return;
-	}
-	if (s > pfx) {
-		oflush();
-		leadin();
-	}
-	for (cp = word; *cp; *outp++ = *cp++)
-		;
+static int
+might_be_header(const char *line) {
+  if (!isupper(*line++)) return 0;
+  while (*line && (isalnum(*line) || *line=='-')) ++line;
+  return (*line==':' && isspace(line[1]));
 }
 
-/*
- * If there is anything on the current output line, send it on
- * its way.  Set outp to NOSTR to indicate the absence of the current
- * line prefix.
+/* Begin a new paragraph with an indent of |indent| spaces.
  */
-void
-oflush()
-{
-	if (outp == NOSTR)
-		return;
-	*outp = '\0';
-	tabulate(outbuf);
-	outp = NOSTR;
+static void
+new_paragraph(size_t old_indent, size_t indent) {
+  if (x0) {
+    if (old_indent>0) output_indent(old_indent);
+    fwrite(output_buffer, 1, x0, stdout);
+    putchar('\n');
+  }
+  x=indent; x0=0; pending_spaces=0;
+  output_in_paragraph = 0;
 }
 
-/*
- * Take the passed line buffer, insert leading tabs where possible, and
- * output on standard output (finally).
+/* Output spaces or tabs for leading indentation.
  */
-void
-tabulate(line)
-	char line[];
-{
-	register char *cp;
-	register int b, t;
-
-	/*
-	 * Toss trailing blanks in the output line.
-	 */
-	cp = line + strlen(line) - 1;
-	while (cp >= line && *cp == ' ')
-		cp--;
-	*++cp = '\0';
-
-	/*
-	 * Count the leading blank space and tabulate.
-	 */
-	for (cp = line; *cp == ' '; cp++)
-		;
-	b = cp-line;
-	t = b >> 3;
-	b &= 07;
-	if (t > 0)
-		do
-			putc('\t', stdout);
-		while (--t);
-	if (b > 0)
-		do
-			putc(' ', stdout);
-		while (--b);
-	while (*cp)
-		putc(*cp++, stdout);
-	putc('\n', stdout);
+static void
+output_indent(size_t n_spaces) {
+  if (output_tab_width) {
+    while (n_spaces >= output_tab_width) {
+      putchar('\t');
+      n_spaces -= output_tab_width;
+    }
+  }
+  while (n_spaces-- > 0) putchar(' ');
 }
 
-/*
- * Initialize the output line with the appropriate number of
- * leading blanks.
+/* Output a single word, or add it to the buffer.
+ * indent0 and indent1 are the indents to use on the first and subsequent
+ * lines of a paragraph. They'll often be the same, of course.
  */
-void
-leadin()
-{
-	register int b;
-	register char *cp;
-
-	if (obufsize == 0 || (outp != NULL && outp - outbuf <= pfx))
-		outbuf = extstr(outbuf, &obufsize, pfx);
-	for (b = 0, cp = outbuf; b < pfx; b++)
-		*cp++ = ' ';
-	outp = cp;
+static void
+output_word(size_t indent0, size_t indent1, const char *word, size_t length, size_t spaces) {
+  size_t new_x = x+pending_spaces+length;
+  size_t indent = output_in_paragraph ? indent1 : indent0;
+
+  /* If either |spaces==0| (at end of line) or |coalesce_spaces_P|
+   * (squashing internal whitespace), then add just one space;
+   * except that if the last character was a sentence-ender we
+   * actually add two spaces.
+   */
+  if (coalesce_spaces_P || spaces==0)
+    spaces = strchr(sentence_enders, word[length-1]) ? 2 : 1;
+
+  if (new_x<=goal_length) {
+    /* After adding the word we still aren't at the goal length,
+     * so clearly we add it to the buffer rather than outputing it.
+     */
+    memset(output_buffer+x0, ' ', pending_spaces);
+    x0 += pending_spaces; x += pending_spaces;
+    memcpy(output_buffer+x0, word, length);
+    x0 += length; x += length;
+    pending_spaces = spaces;
+  }
+  else {
+    /* Adding the word takes us past the goal. Print the line-so-far,
+     * and the word too iff either (1) the lsf is empty or (2) that
+     * makes us nearer the goal but doesn't take us over the limit,
+     * or (3) the word on its own takes us over the limit.
+     * In case (3) we put a newline in between.
+     */
+    if (indent>0) output_indent(indent);
+    fwrite(output_buffer, 1, x0, stdout);
+    if (x0==0 || (new_x <= max_length && new_x-goal_length <= goal_length-x)) {
+      printf("%*s", pending_spaces, "");
+      goto write_out_word;
+    }
+    else {
+      /* If the word takes us over the limit on its own, just
+       * spit it out and don't bother buffering it.
+       */
+      if (indent+length > max_length) {
+        putchar('\n');
+        if (indent>0) output_indent(indent);
+write_out_word:
+        fwrite(word, 1, length, stdout);
+        x0 = 0; x = indent1; pending_spaces = 0;
+      }
+      else {
+        memcpy(output_buffer, word, length);
+        x0 = length; x = length+indent1; pending_spaces = spaces;
+      }
+    }
+    putchar('\n');
+    output_in_paragraph = 1;
+  }
 }
 
-/*
- * Save a string in dynamic space.
- * This little goodie is needed for
- * a headline detector in head.c
+/* Process a stream, but just center its lines rather than trying to
+ * format them neatly.
  */
-char *
-savestr(str)
-	char str[];
-{
-	char *top;
-
-	top = strdup(str);
-	if (top == NOSTR)
-		errx(1, "Ran out of memory");
-	return (top);
+static void
+center_stream(FILE *stream, const char *name) {
+  char *line;
+  size_t length;
+  while ((line=get_line(stream, &length)) != 0) {
+    size_t l=length;
+    while (l>0 && isspace(*line)) { ++line; --l; }
+    length=l;
+    while (l<goal_length) { putchar(' '); l+=2; }
+    fwrite(line, 1, length, stdout);
+    putchar('\n');
+  }
+  if (ferror(stream)) { perror(name); ++n_errors; }
 }
 
-/*
- * Is s1 a prefix of s2??
+/* Get a single line from a stream. Expand tabs, strip control
+ * characters and trailing whitespace, and handle backspaces.
+ * Return the address of the buffer containing the line, and
+ * put the length of the line in |lengthp|.
+ * This can cope with arbitrarily long lines, and with lines
+ * without terminating \n.
+ * If there are no characters left or an error happens, we
+ * return 0.
+ * Don't confuse |spaces_pending| here with the global
+ * |pending_spaces|.
  */
-int
-ispref(s1, s2)
-	register char *s1, *s2;
-{
-
-	while (*s1++ == *s2)
-		;
-	return (*s1 == '\0');
+static char *
+get_line(FILE *stream, size_t *lengthp) {
+  static char *buf=NULL;
+  static size_t length=0;
+  size_t len=0;
+  int ch;
+  size_t spaces_pending=0;
+
+  if (buf==NULL) { length=100; buf=XMALLOC(length); }
+  while ((ch=getc(stream)) != '\n' && ch != EOF) {
+    if (ch==' ') ++spaces_pending;
+    else if (isprint(ch)) {
+      while (len+spaces_pending >= length) {
+        length*=2; buf=xrealloc(buf, length);
+      }
+      while (spaces_pending > 0) { --spaces_pending; buf[len++]=' '; }
+      buf[len++] = ch;
+    }
+    else if (ch=='\t')
+      spaces_pending += tab_width - (len+spaces_pending)%tab_width;
+    else if (ch=='\b') { if (len) --len; }
+  }
+  *lengthp=len;
+  return (len>0 || ch!=EOF) ? buf : 0;
 }
 
-inline char *
-extstr(str, size, gsize)
-	char *str;
-	int *size;
-	int gsize;
-{
-	do {
-		*size += CHUNKSIZE;
-	} while (gsize && *size < gsize);
-
-	if ((str = realloc(str, *size)) == NULL)
-		errx(1, "Ran out of memory");
-	
-	return(str);
+/* (Re)allocate some memory, exiting with an error if we can't.
+ */
+static void *
+xrealloc(void *ptr, size_t nbytes) {
+  void *p = realloc(ptr, nbytes);
+  if (p == NULL) errx(EX_OSERR, "out of memory");
+  return p;
 }