usr.bin/fmt/fmt.c

   1 /*      $OpenBSD: fmt.c,v 1.16 2000/06/25 15:35:42 pjanzen Exp $        */
   2
   3 /* Sensible version of fmt
   4  *
   5  * Syntax: fmt [ options ] [ goal [ max ] ] [ filename ... ]
   6  *
   7  * Since the documentation for the original fmt is so poor, here
   8  * is an accurate description of what this one does. It's usually
   9  * the same. The *mechanism* used may differ from that suggested
  10  * here. Note that we are *not* entirely compatible with fmt,
  11  * because fmt gets so many things wrong.
  12  *
  13  * 1. Tabs are expanded, assuming 8-space tab stops.
  14  *    If the `-t <n>' option is given, we assume <n>-space
  15  *    tab stops instead.
  16  *    Trailing blanks are removed from all lines.
  17  *    x\b == nothing, for any x other than \b.
  18  *    Other control characters are simply stripped. This
  19  *    includes \r.
  20  * 2. Each line is split into leading whitespace and
  21  *    everything else. Maximal consecutive sequences of
  22  *    lines with the same leading whitespace are considered
  23  *    to form paragraphs, except that a blank line is always
  24  *    a paragraph to itself.
  25  *    If the `-p' option is given then the first line of a
  26  *    paragraph is permitted to have indentation different
  27  *    from that of the other lines.
  28  *    If the `-m' option is given then a line that looks
  29  *    like a mail message header, if it is not immediately
  30  *    preceded by a non-blank non-message-header line, is
  31  *    taken to start a new paragraph, which also contains
  32  *    any subsequent lines with non-empty leading whitespace.
  33  *    Unless the `-n' option is given, lines beginning with
  34  *    a . (dot) are not formatted.
  35  * 3. The "everything else" is split into words; a word
  36  *    includes its trailing whitespace, and a word at the
  37  *    end of a line is deemed to be followed by a single
  38  *    space, or two spaces if it ends with a sentence-end
  39  *    character. (See the `-d' option for how to change that.)
  40  *    If the `-s' option has been given, then a word's trailing
  41  *    whitespace is replaced by what it would have had if it
  42  *    had occurred at end of line.
  43  * 4. Each paragraph is sent to standard output as follows.
  44  *    We output the leading whitespace, and then enough words
  45  *    to make the line length as near as possible to the goal
  46  *    without exceeding the maximum. (If a single word would
  47  *    exceed the maximum, we output that anyway.) Of course
  48  *    the trailing whitespace of the last word is ignored.
  49  *    We then emit a newline and start again if there are any
  50  *    words left.
  51  *    Note that for a blank line this translates as "We emit
  52  *    a newline".
  53  *    If the `-l <n>' option is given, then leading whitespace
  54  *    is modified slightly: <n> spaces are replaced by a tab.
  55  *    Indented paragraphs (see above under `-p') make matters
  56  *    more complicated than this suggests. Actually every paragraph
  57  *    has two `leading whitespace' values; the value for the first
  58  *    line, and the value for the most recent line. (While processing
  59  *    the first line, the two are equal. When `-p' has not been
  60  *    given, they are always equal.) The leading whitespace
  61  *    actually output is that of the first line (for the first
  62  *    line of *output*) or that of the most recent line (for
  63  *    all other lines of output).
  64  *    When `-m' has been given, message header paragraphs are
  65  *    taken as having first-leading-whitespace empty and
  66  *    subsequent-leading-whitespace two spaces.
  67  *
  68  * Multiple input files are formatted one at a time, so that a file
  69  * never ends in the middle of a line.
  70  *
  71  * There's an alternative mode of operation, invoked by giving
  72  * the `-c' option. In that case we just center every line,
  73  * and most of the other options are ignored. This should
  74  * really be in a separate program, but we must stay compatible
  75  * with old `fmt'.
  76  *
  77  * QUERY: Should `-m' also try to do the right thing with quoted text?
  78  * QUERY: `-b' to treat backslashed whitespace as old `fmt' does?
  79  * QUERY: Option meaning `never join lines'?
  80  * QUERY: Option meaning `split in mid-word to avoid overlong lines'?
  81  * (Those last two might not be useful, since we have `fold'.)
  82  *
  83  * Differences from old `fmt':
  84  *
  85  *   - We have many more options. Options that aren't understood
  86  *     generate a lengthy usage message, rather than being
  87  *     treated as filenames.
  88  *   - Even with `-m', our handling of message headers is
  89  *     significantly different. (And much better.)
  90  *   - We don't treat `\ ' as non-word-breaking.
  91  *   - Downward changes of indentation start new paragraphs
  92  *     for us, as well as upward. (I think old `fmt' behaves
  93  *     in the way it does in order to allow indented paragraphs,
  94  *     but this is a broken way of making indented paragraphs
  95  *     behave right.)
  96  *   - Given the choice of going over or under |goal_length|
  97  *     by the same amount, we go over; old `fmt' goes under.
  98  *   - We treat `?' as ending a sentence, and not `:'. Old `fmt'
  99  *     does the reverse.
 100  *   - We return approved return codes. Old `fmt' returns
 101  *     1 for some errors, and *the number of unopenable files*
 102  *     when that was all that went wrong.
 103  *   - We have fewer crashes and more helpful error messages.
 104  *   - We don't turn spaces into tabs at starts of lines unless
 105  *     specifically requested.
 106  *   - New `fmt' is somewhat smaller and slightly faster than
 107  *     old `fmt'.
 108  *
 109  * Bugs:
 110  *
 111  *   None known. There probably are some, though.
 112  *
 113  * Portability:
 114  *
 115  *   I believe this code to be pretty portable. It does require
 116  *   that you have `getopt'. If you need to include "getopt.h"
 117  *   for this (e.g., if your system didn't come with `getopt'
 118  *   and you installed it yourself) then you should arrange for
 119  *   NEED_getopt_h to be #defined.
 120  *
 121  *   Everything here should work OK even on nasty 16-bit
 122  *   machines and nice 64-bit ones. However, it's only really
 123  *   been tested on my FreeBSD machine. Your mileage may vary.
 124  *
 125  * $FreeBSD: src/usr.bin/fmt/fmt.c,v 1.12.2.2 2002/01/14 09:48:26 ru Exp $
 126  * $DragonFly: src/usr.bin/fmt/fmt.c,v 1.2 2003/06/17 04:29:26 dillon Exp $
 127  */
 128
 129 /* Copyright (c) 1997 Gareth McCaughan. All rights reserved.
 130  *
 131  * Redistribution and use of this code, in source or binary forms,
 132  * with or without modification, are permitted subject to the following
 133  * conditions:
 134  *
 135  *  - Redistribution of source code must retain the above copyright
 136  *    notice, this list of conditions and the following disclaimer.
 137  *
 138  *  - If you distribute modified source code it must also include
 139  *    a notice saying that it has been modified, and giving a brief
 140  *    description of what changes have been made.
 141  *
 142  * Disclaimer: I am not responsible for the results of using this code.
 143  *             If it formats your hard disc, sends obscene messages to
 144  *             your boss and kills your children then that's your problem
 145  *             not mine. I give absolutely no warranty of any sort as to
 146  *             what the program will do, and absolutely refuse to be held
 147  *             liable for any consequences of your using it.
 148  *             Thank you. Have a nice day.
 149  */
 150
 151 /* RCS change log:
 152  * Revision 1.5  1998/03/02 18:02:21  gjm11
 153  * Minor changes for portability.
 154  *
 155  * Revision 1.4  1997/10/01 11:51:28  gjm11
 156  * Repair broken indented-paragraph handling.
 157  * Add mail message header stuff.
 158  * Improve comments and layout.
 159  * Make usable with non-BSD systems.
 160  * Add revision display to usage message.
 161  *
 162  * Revision 1.3  1997/09/30 16:24:47  gjm11
 163  * Add copyright notice, rcsid string and log message.
 164  *
 165  * Revision 1.2  1997/09/30 16:13:39  gjm11
 166  * Add options: -d <chars>, -l <width>, -p, -s, -t <width>, -h .
 167  * Parse options with `getopt'. Clean up code generally.
 168  * Make comments more accurate.
 169  *
 170  * Revision 1.1  1997/09/30 11:29:57  gjm11
 171  * Initial revision
 172  */
 173
 174 #include <ctype.h>
 175 #include <err.h>
 176 #include <locale.h>
 177 #include <stdio.h>
 178 #include <stdlib.h>
 179 #include <string.h>
 180 #include <sysexits.h>
 181 #include <unistd.h>
 182
 183 /* Something that, we hope, will never be a genuine line length,
 184  * indentation etc.
 185  */
 186 #define SILLY ((size_t)-1)
 187
 188 /* I used to use |strtoul| for this, but (1) not all systems have it
 189  * and (2) it's probably better to use |strtol| to detect negative
 190  * numbers better.
 191  * If |fussyp==0| then we don't complain about non-numbers
 192  * (returning 0 instead), but we do complain about bad numbers.
 193  */
 194 static size_t
 195 get_positive(const char *s, const char *err_mess, int fussyP) {
 196   char *t;
 197   long result = strtol(s,&t,0);
 198   if (*t) { if (fussyP) goto Lose; else return 0; }
 199   if (result<=0) { Lose: errx(EX_USAGE, "%s", err_mess); }
 200   return (size_t) result;
 201 }
 202
 203 static size_t
 204 get_nonnegative(const char *s, const char *err_mess, int fussyP) {
 205   char *t;
 206   long result = strtol(s,&t,0);
 207   if (*t) { if (fussyP) goto Lose; else return 0; }
 208   if (result<0) { Lose: errx(EX_USAGE, "%s", err_mess); }
 209   return (size_t) result;
 210 }
 211
 212 /* Global variables */
 213
 214 static int centerP=0;           /* Try to center lines? */
 215 static size_t goal_length=0;    /* Target length for output lines */
 216 static size_t max_length=0;     /* Maximum length for output lines */
 217 static int coalesce_spaces_P=0; /* Coalesce multiple whitespace -> ' ' ? */
 218 static int allow_indented_paragraphs=0; /* Can first line have diff. ind.? */
 219 static int tab_width=8;         /* Number of spaces per tab stop */
 220 static size_t output_tab_width=8;       /* Ditto, when squashing leading spaces */
 221 static const char *sentence_enders=".?!";       /* Double-space after these */
 222 static int grok_mail_headers=0; /* treat embedded mail headers magically? */
 223 static int format_troff=0;      /* Format troff? */
 224
 225 static int n_errors=0;          /* Number of failed files. Return on exit. */
 226 static char *output_buffer=0;   /* Output line will be built here */
 227 static size_t x;                /* Horizontal position in output line */
 228 static size_t x0;               /* Ditto, ignoring leading whitespace */
 229 static size_t pending_spaces;   /* Spaces to add before next word */
 230 static int output_in_paragraph=0;       /* Any of current para written out yet? */
 231
 232 /* Prototypes */
 233
 234 static void process_named_file (const char *);
 235 static void     process_stream (FILE *, const char *);
 236 static size_t    indent_length (const char *, size_t);
 237 static int     might_be_header (const unsigned char *);
 238 static void      new_paragraph (size_t, size_t);
 239 static void        output_word (size_t, size_t, const char *, size_t, size_t);
 240 static void      output_indent (size_t);
 241 static void      center_stream (FILE *, const char *);
 242 static char *         get_line (FILE *, size_t *);
 243 static void *         xrealloc (void *, size_t);
 244
 245 #define XMALLOC(x) xrealloc(0,x)
 246
 247 /* Here is perhaps the right place to mention that this code is
 248  * all in top-down order. Hence, |main| comes first.
 249  */
 250 int
 251 main(int argc, char *argv[]) {
 252   int ch;                       /* used for |getopt| processing */
 253
 254
 255   (void) setlocale(LC_CTYPE, "");
 256
 257   /* 1. Grok parameters. */
 258
 259   while ((ch = getopt(argc, argv, "0123456789cd:hl:mnpst:w:")) != -1)
 260   switch(ch) {
 261     case 'c':
 262       centerP = 1;
 263       format_troff = 1;
 264       continue;
 265     case 'd':
 266       sentence_enders = optarg;
 267       continue;
 268     case 'l':
 269       output_tab_width
 270         = get_nonnegative(optarg, "output tab width must be non-negative", 1);
 271       continue;
 272     case 'm':
 273       grok_mail_headers = 1;
 274       continue;
 275     case 'n':
 276       format_troff = 1;
 277       continue;
 278     case 'p':
 279       allow_indented_paragraphs = 1;
 280       continue;
 281     case 's':
 282       coalesce_spaces_P = 1;
 283       continue;
 284     case 't':
 285       tab_width = get_positive(optarg, "tab width must be positive", 1);
 286       continue;
 287     case 'w':
 288       goal_length = get_positive(optarg, "width must be positive", 1);
 289       max_length = goal_length;
 290       continue;
 291     case '0': case '1': case '2': case '3': case '4': case '5':
 292     case '6': case '7': case '8': case '9':
 293     /* XXX  this is not a stylistically approved use of getopt() */
 294       if (goal_length==0) {
 295         char *p;
 296         p = argv[optind - 1];
 297         if (p[0] == '-' && p[1] == ch && !p[2])
 298              goal_length = get_positive(++p, "width must be nonzero", 1);
 299         else
 300              goal_length = get_positive(argv[optind]+1,
 301                  "width must be nonzero", 1);
 302         max_length = goal_length;
 303       }
 304       continue;
 305     case 'h': default:
 306       fprintf(stderr,
 307 "Usage:   fmt [-cmps] [-d chars] [-l num] [-t num]\n"
 308 "             [-w width | -width | goal [maximum]] [file ...]\n"
 309 "Options: -c     center each line instead of formatting\n"
 310 "         -d <chars> double-space after <chars> at line end\n"
 311 "         -l <n> turn each <n> spaces at start of line into a tab\n"
 312 "         -m     try to make sure mail header lines stay separate\n"
 313 "         -n     format lines beginning with a dot\n"
 314 "         -p     allow indented paragraphs\n"
 315 "         -s     coalesce whitespace inside lines\n"
 316 "         -t <n> have tabs every <n> columns\n"
 317 "         -w <n> set maximum width to <n>\n"
 318 "         goal   set target width to goal\n");
 319       exit(ch=='h' ? 0 : EX_USAGE);
 320   }
 321   argc -= optind; argv += optind;
 322
 323   /* [ goal [ maximum ] ] */
 324
 325   if (argc>0 && goal_length==0
 326       && (goal_length=get_positive(*argv,"goal length must be positive", 0))
 327          != 0) {
 328     --argc; ++argv;
 329     if (argc>0
 330         && (max_length=get_positive(*argv,"max length must be positive", 0))
 331            != 0) {
 332       --argc; ++argv;
 333       if (max_length<goal_length)
 334         errx(EX_USAGE, "max length must be >= goal length");
 335     }
 336   }
 337   if (goal_length==0) goal_length = 65;
 338   if (max_length==0) max_length = goal_length+10;
 339   output_buffer = XMALLOC(max_length+1);        /* really needn't be longer */
 340
 341   /* 2. Process files. */
 342
 343   if (argc>0) {
 344     while (argc-->0) process_named_file(*argv++);
 345   }
 346   else {
 347     process_stream(stdin, "standard input");
 348   }
 349
 350   /* We're done. */
 351
 352   return n_errors ? EX_NOINPUT : 0;
 353
 354 }
 355
 356 /* Process a single file, given its name.
 357  */
 358 static void
 359 process_named_file(const char *name) {
 360   FILE *f=fopen(name, "r");
 361   if (!f) { perror(name); ++n_errors; }
 362   else {
 363     process_stream(f, name);
 364     fclose(f);
 365   }
 366 }
 367
 368 /* Types of mail header continuation lines:
 369  */
 370 typedef enum {
 371   hdr_ParagraphStart = -1,
 372   hdr_NonHeader      = 0,
 373   hdr_Header         = 1,
 374   hdr_Continuation   = 2
 375 } HdrType;
 376
 377 /* Process a stream. This is where the real work happens,
 378  * except that centering is handled separately.
 379  */
 380 static void
 381 process_stream(FILE *stream, const char *name) {
 382   size_t last_indent=SILLY;     /* how many spaces in last indent? */
 383   size_t para_line_number=0;    /* how many lines already read in this para? */
 384   size_t first_indent=SILLY;    /* indentation of line 0 of paragraph */
 385   HdrType prev_header_type=hdr_ParagraphStart;
 386         /* ^-- header_type of previous line; -1 at para start */
 387   char *line;
 388   size_t length;
 389
 390   if (centerP) { center_stream(stream, name); return; }
 391   while ((line=get_line(stream,&length)) != NULL) {
 392     size_t np=indent_length(line, length);
 393     { HdrType header_type=hdr_NonHeader;
 394       if (grok_mail_headers && prev_header_type!=hdr_NonHeader) {
 395         if (np==0 && might_be_header(line))
 396           header_type = hdr_Header;
 397         else if (np>0 && prev_header_type>hdr_NonHeader)
 398           header_type = hdr_Continuation;
 399       }
 400       /* We need a new paragraph if and only if:
 401        *   this line is blank,
 402        *   OR it's a troff request (and we don't format troff),
 403        *   OR it's a mail header,
 404        *   OR it's not a mail header AND the last line was one,
 405        *   OR the indentation has changed
 406        *      AND the line isn't a mail header continuation line
 407        *      AND this isn't the second line of an indented paragraph.
 408        */
 409       if ( length==0
 410            || (line[0]=='.' && !format_troff)
 411            || header_type==hdr_Header
 412            || (header_type==hdr_NonHeader && prev_header_type>hdr_NonHeader)
 413            || (np!=last_indent
 414                && header_type != hdr_Continuation
 415                && (!allow_indented_paragraphs || para_line_number != 1)) ) {
 416         new_paragraph(output_in_paragraph ? last_indent : first_indent, np);
 417         para_line_number = 0;
 418         first_indent = np;
 419         last_indent = np;
 420         if (header_type==hdr_Header) last_indent=2;     /* for cont. lines */
 421         if (length==0 || (line[0]=='.' && !format_troff)) {
 422           if (length==0)
 423             putchar('\n');
 424           else
 425             printf("%.*s\n", (int)length, line);
 426           prev_header_type=hdr_ParagraphStart;
 427           continue;
 428         }
 429       }
 430       else {
 431         /* If this is an indented paragraph other than a mail header
 432          * continuation, set |last_indent|.
 433          */
 434         if (np != last_indent && header_type != hdr_Continuation)
 435           last_indent=np;
 436       }
 437       prev_header_type = header_type;
 438     }
 439
 440     { size_t n=np;
 441       while (n<length) {
 442         /* Find word end and count spaces after it */
 443         size_t word_length=0, space_length=0;
 444         while (n+word_length < length && line[n+word_length] != ' ')
 445           ++word_length;
 446         space_length = word_length;
 447         while (n+space_length < length && line[n+space_length] == ' ')
 448           ++space_length;
 449         /* Send the word to the output machinery. */
 450         output_word(first_indent, last_indent,
 451                     line+n, word_length, space_length-word_length);
 452         n += space_length;
 453       }
 454     }
 455     ++para_line_number;
 456   }
 457   new_paragraph(output_in_paragraph ? last_indent : first_indent, 0);
 458   if (ferror(stream)) { perror(name); ++n_errors; }
 459 }
 460
 461 /* How long is the indent on this line?
 462  */
 463 static size_t
 464 indent_length(const char *line, size_t length) {
 465   size_t n=0;
 466   while (n<length && *line++ == ' ') ++n;
 467   return n;
 468 }
 469
 470 /* Might this line be a mail header?
 471  * We deem a line to be a possible header if it matches the
 472  * Perl regexp /^[A-Z][-A-Za-z0-9]*:\s/. This is *not* the same
 473  * as in RFC whatever-number-it-is; we want to be gratuitously
 474  * conservative to avoid mangling ordinary civilised text.
 475  */
 476 static int
 477 might_be_header(const unsigned char *line) {
 478   if (!isupper(*line++)) return 0;
 479   while (*line && (isalnum(*line) || *line=='-')) ++line;
 480   return (*line==':' && isspace(line[1]));
 481 }
 482
 483 /* Begin a new paragraph with an indent of |indent| spaces.
 484  */
 485 static void
 486 new_paragraph(size_t old_indent, size_t indent) {
 487   if (x0) {
 488     if (old_indent>0) output_indent(old_indent);
 489     fwrite(output_buffer, 1, x0, stdout);
 490     putchar('\n');
 491   }
 492   x=indent; x0=0; pending_spaces=0;
 493   output_in_paragraph = 0;
 494 }
 495
 496 /* Output spaces or tabs for leading indentation.
 497  */
 498 static void
 499 output_indent(size_t n_spaces) {
 500   if (output_tab_width) {
 501     while (n_spaces >= output_tab_width) {
 502       putchar('\t');
 503       n_spaces -= output_tab_width;
 504     }
 505   }
 506   while (n_spaces-- > 0) putchar(' ');
 507 }
 508
 509 /* Output a single word, or add it to the buffer.
 510  * indent0 and indent1 are the indents to use on the first and subsequent
 511  * lines of a paragraph. They'll often be the same, of course.
 512  */
 513 static void
 514 output_word(size_t indent0, size_t indent1, const char *word, size_t length, size_t spaces) {
 515   size_t new_x = x+pending_spaces+length;
 516   size_t indent = output_in_paragraph ? indent1 : indent0;
 517
 518   /* If either |spaces==0| (at end of line) or |coalesce_spaces_P|
 519    * (squashing internal whitespace), then add just one space;
 520    * except that if the last character was a sentence-ender we
 521    * actually add two spaces.
 522    */
 523   if (coalesce_spaces_P || spaces==0)
 524     spaces = strchr(sentence_enders, word[length-1]) ? 2 : 1;
 525
 526   if (new_x<=goal_length) {
 527     /* After adding the word we still aren't at the goal length,
 528      * so clearly we add it to the buffer rather than outputing it.
 529      */
 530     memset(output_buffer+x0, ' ', pending_spaces);
 531     x0 += pending_spaces; x += pending_spaces;
 532     memcpy(output_buffer+x0, word, length);
 533     x0 += length; x += length;
 534     pending_spaces = spaces;
 535   }
 536   else {
 537     /* Adding the word takes us past the goal. Print the line-so-far,
 538      * and the word too iff either (1) the lsf is empty or (2) that
 539      * makes us nearer the goal but doesn't take us over the limit,
 540      * or (3) the word on its own takes us over the limit.
 541      * In case (3) we put a newline in between.
 542      */
 543     if (indent>0) output_indent(indent);
 544     fwrite(output_buffer, 1, x0, stdout);
 545     if (x0==0 || (new_x <= max_length && new_x-goal_length <= goal_length-x)) {
 546       printf("%*s", (int)pending_spaces, "");
 547       goto write_out_word;
 548     }
 549     else {
 550       /* If the word takes us over the limit on its own, just
 551        * spit it out and don't bother buffering it.
 552        */
 553       if (indent+length > max_length) {
 554         putchar('\n');
 555         if (indent>0) output_indent(indent);
 556 write_out_word:
 557         fwrite(word, 1, length, stdout);
 558         x0 = 0; x = indent1; pending_spaces = 0;
 559       }
 560       else {
 561         memcpy(output_buffer, word, length);
 562         x0 = length; x = length+indent1; pending_spaces = spaces;
 563       }
 564     }
 565     putchar('\n');
 566     output_in_paragraph = 1;
 567   }
 568 }
 569
 570 /* Process a stream, but just center its lines rather than trying to
 571  * format them neatly.
 572  */
 573 static void
 574 center_stream(FILE *stream, const char *name) {
 575   char *line;
 576   size_t length;
 577   while ((line=get_line(stream, &length)) != 0) {
 578     size_t l=length;
 579     while (l>0 && isspace(*line)) { ++line; --l; }
 580     length=l;
 581     while (l<goal_length) { putchar(' '); l+=2; }
 582     fwrite(line, 1, length, stdout);
 583     putchar('\n');
 584   }
 585   if (ferror(stream)) { perror(name); ++n_errors; }
 586 }
 587
 588 /* Get a single line from a stream. Expand tabs, strip control
 589  * characters and trailing whitespace, and handle backspaces.
 590  * Return the address of the buffer containing the line, and
 591  * put the length of the line in |lengthp|.
 592  * This can cope with arbitrarily long lines, and with lines
 593  * without terminating \n.
 594  * If there are no characters left or an error happens, we
 595  * return 0.
 596  * Don't confuse |spaces_pending| here with the global
 597  * |pending_spaces|.
 598  */
 599 static char *
 600 get_line(FILE *stream, size_t *lengthp) {
 601   static char *buf=NULL;
 602   static size_t length=0;
 603   size_t len=0;
 604   int ch;
 605   size_t spaces_pending=0;
 606   int troff=0;
 607
 608   if (buf==NULL) { length=100; buf=XMALLOC(length); }
 609   while ((ch=getc(stream)) != '\n' && ch != EOF) {
 610     if (len+spaces_pending==0 && ch=='.' && !format_troff) troff=1;
 611     if (ch==' ') ++spaces_pending;
 612     else if (troff || isprint(ch)) {
 613       while (len+spaces_pending >= length) {
 614         length*=2; buf=xrealloc(buf, length);
 615       }
 616       while (spaces_pending > 0) { --spaces_pending; buf[len++]=' '; }
 617       buf[len++] = ch;
 618     }
 619     else if (ch=='\t')
 620       spaces_pending += tab_width - (len+spaces_pending)%tab_width;
 621     else if (ch=='\b') { if (len) --len; }
 622   }
 623   *lengthp=len;
 624   return (len>0 || ch!=EOF) ? buf : 0;
 625 }
 626
 627 /* (Re)allocate some memory, exiting with an error if we can't.
 628  */
 629 static void *
 630 xrealloc(void *ptr, size_t nbytes) {
 631   void *p = realloc(ptr, nbytes);
 632   if (p == NULL) errx(EX_OSERR, "out of memory");
 633   return p;
 634 }