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[coreutils.git] / src / fmt.c

/* GNU fmt -- simple text formatter.
   Copyright (C) 1994, 1995 Free Software Foundation, Inc.

   This program 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 program 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 program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/* Written by Ross Paterson <rap@doc.ic.ac.uk>.  */

#include <config.h>
#include <stdio.h>
#include <sys/types.h>
#include <getopt.h>

/* Redefine.  Otherwise, systems (Unicos for one) with headers that define
   it to be a type get syntax errors for the variable declaration below.  */
#define word unused_word_type

#include "system.h"
#include "version.h"
#include "error.h"

/* The following parameters represent the program's idea of what is
   "best".  Adjust to taste, subject to the caveats given.  */

/* Default longest permitted line length (max_width).  */
#define WIDTH   75

/* Prefer lines to be LEEWAY % shorter than the maximum width, giving
   room for optimization.  */
#define LEEWAY  7

/* The default secondary indent of tagged paragraph used for unindented
   one-line paragraphs not preceded by any multi-line paragraphs.  */
#define DEF_INDENT 3

/* Costs and bonuses are expressed as the equivalent departure from the
   optimal line length, multiplied by 10.  e.g. assigning something a
   cost of 50 means that it is as bad as a line 5 characters too short
   or too long.  The definition of SHORT_COST(n) should not be changed.
   However, EQUIV(n) may need tuning.  */

typedef long COST;

#define MAXCOST (~(((COST) 1) << (8 * sizeof (COST) -1)))

#define SQR(n)          ((n) * (n))
#define EQUIV(n)        SQR ((COST) (n))

/* Cost of a filled line n chars longer or shorter than best_width.  */
#define SHORT_COST(n)   EQUIV ((n) * 10)

/* Cost of the difference between adjacent filled lines.  */
#define RAGGED_COST(n)  (SHORT_COST (n) / 2)

/* Basic cost per line.  */
#define LINE_COST       EQUIV (70)

/* Cost of breaking a line after the first word of a sentence, where
   the length of the word is N.  */
#define WIDOW_COST(n)   (EQUIV (200) / ((n) + 2))

/* Cost of breaking a line before the last word of a sentence, where
   the length of the word is N.  */
#define ORPHAN_COST(n)  (EQUIV (150) / ((n) + 2))

/* Bonus for breaking a line at the end of a sentence.  */
#define SENTENCE_BONUS  EQUIV (50)

/* Cost of breaking a line after a period not marking end of a sentence.
   With the definition of sentence we are using (borrowed from emacs, see
   get_line()) such a break would then look like a sentence break.  Hence
   we assign a very high cost -- it should be avoided unless things are
   really bad.  */
#define NOBREAK_COST    EQUIV (600)

/* Bonus for breaking a line before open parenthesis.  */
#define PAREN_BONUS     EQUIV (40)

/* Bonus for breaking a line after other punctuation.  */
#define PUNCT_BONUS     EQUIV(40)

/* Credit for breaking a long paragraph one line later.  */
#define LINE_CREDIT     EQUIV(3)

/* Size of paragraph buffer, in words and characters.  Longer paragraphs
   are handled neatly (cf. flush_paragraph()), so there's little to gain
   by making these larger.  */
#define MAXWORDS        1000
#define MAXCHARS        5000

/* Extra ctype(3)-style macros.  */

#define isopen(c)       (strchr ("([`'\"", c) != NULL)
#define isclose(c)      (strchr (")]'\"", c) != NULL)
#define isperiod(c)     (strchr (".?!", c) != NULL)

/* Size of a tab stop, for expansion on input and re-introduction on
   output.  */
#define TABWIDTH        8

/* Miscellaneous definitions.  */

typedef unsigned int bool;
#define TRUE    1
#define FALSE   0

/* Word descriptor structure.  */

typedef struct Word WORD;

struct Word
  {

    /* Static attributes determined during input.  */

    const char *text;           /* the text of the word */
    short length;               /* length of this word */
    short space;                /* the size of the following space */
    bool paren:1;               /* starts with open paren */
    bool period:1;              /* ends in [.?!])* */
    bool punct:1;               /* ends in punctuation */
    bool final:1;               /* end of sentence */

    /* The remaining fields are computed during the optimization.  */

    short line_length;          /* length of the best line starting here */
    COST best_cost;             /* cost of best paragraph starting here */
    WORD *next_break;           /* break which achieves best_cost */
  };

/* Forward declarations.  */

static void set_prefix __P ((char *p));
static void fmt __P ((FILE *f));
static bool get_paragraph __P ((FILE *f));
static int get_line __P ((FILE *f, int c));
static int get_prefix __P ((FILE *f));
static int get_space __P ((FILE *f, int c));
static int copy_rest __P ((FILE *f, int c));
static bool same_para __P ((int c));
static void flush_paragraph __P ((void));
static void fmt_paragraph __P ((void));
static void check_punctuation __P ((WORD *w));
static COST base_cost __P ((WORD *this));
static COST line_cost __P ((WORD *next, int len));
static void put_paragraph __P ((WORD *finish));
static void put_line __P ((WORD *w, int indent));
static void put_word __P ((WORD *w));
static void put_space __P ((int space));

/* The name this program was run with.  */
const char *program_name;

/* If nonzero, display usage information and exit.  */
static int show_help = 0;

/* If nonzero, print the version on standard output and exit.  */
static int show_version = 0;

/* Option values.  */

/* If TRUE, first 2 lines may have different indent (default FALSE).  */
static bool crown;

/* If TRUE, first 2 lines _must_ have different indent (default FALSE).  */
static bool tagged;

/* If TRUE, each line is a paragraph on its own (default FALSE).  */
static bool split;

/* If TRUE, don't preserve inter-word spacing (default FALSE).  */
static bool uniform;

/* Prefix minus leading and trailing spaces (default "").  */
static const char *prefix;

/* User-supplied maximum line width (default WIDTH).  The only output
   lines
   longer than this will each comprise a single word.  */
static int max_width;

/* Values derived from the option values.  */

/* The length of prefix minus leading space.  */
static int prefix_full_length;

/* The length of the leading space trimmed from the prefix.  */
static int prefix_lead_space;

/* The length of prefix minus leading and trailing space.  */
static int prefix_length;

/* The preferred width of text lines, set to LEEWAY % less than max_width.  */
static int best_width;

/* Dynamic variables.  */

/* Start column of the character most recently read from the input file.  */
static int in_column;

/* Start column of the next character to be written to stdout.  */
static int out_column;

/* Space for the paragraph text -- longer paragraphs are handled neatly
   (cf. flush_paragraph()).  */
static char parabuf[MAXCHARS];

/* A pointer into parabuf, indicating the first unused character position.  */
static char *wptr;

/* The words of a paragraph -- longer paragraphs are handled neatly
   (cf. flush_paragraph()).  */
static WORD word[MAXWORDS];

/* A pointer into the above word array, indicating the first position
   after the last complete word.  Sometimes it will point at an incomplete
   word.  */
static WORD *word_limit;

/* If TRUE, current input file contains tab characters, and so tabs can be
   used for white space on output.  */
static bool tabs;

/* Space before trimmed prefix on each line of the current paragraph.  */
static int prefix_indent;

/* Indentation of the first line of the current paragraph.  */
static int first_indent;

/* Indentation of other lines of the current paragraph */
static int other_indent;

/* To detect the end of a paragraph, we need to look ahead to the first
   non-blank character after the prefix on the next line, or the first
   character on the following line that failed to match the prefix.
   We can reconstruct the lookahead from that character (next_char), its
   position on the line (in_column) and the amount of space before the
   prefix (next_prefix_indent).  See get_paragraph() and copy_rest().  */

/* The last character read from the input file.  */
static int next_char;

/* The space before the trimmed prefix (or part of it) on the next line
   after the current paragraph.  */
static int next_prefix_indent;

/* If nonzero, the length of the last line output in the current
   paragraph, used to charge for raggedness at the split point for long
   paragraphs chosen by fmt_paragraph().  */
static int last_line_length;

static void
usage (int status)
{
  if (status != 0)
    fprintf (stderr, _("Try `%s --help' for more information.\n"),
             program_name);
  else
    {
      printf (_("Usage: %s [-DIGITS] [OPTION]... [FILE]...\n"), program_name);
      fputs (_("\
Reformat each paragraph in the FILE(s), writing to standard output.\n\
If no FILE or if FILE is `-', read standard input.\n\
\n\
Mandatory arguments to long options are mandatory for short options too.\n\
  -c, --crown-margin        preserve indentation of first two lines\n\
  -s, --split-only          split long lines, but do not refill\n\
  -t, --tagged-paragraph    indentation of first line different from second\n\
  -u, --uniform-spacing     one space between words, two after sentences\n\
  -w, --width=NUMBER        maximum line width (default of 75 columns)\n\
  -p, --prefix=STRING       combine only lines having STRING as prefix\n\
      --help                display this help and exit\n\
      --version             output version information and exit\n\
\n\
In -wNUMBER, the letter `w' may be omitted.\n"),
             stdout);
    }
  exit (status);
}

/* Decode options and launch execution.  */

static const struct option long_options[] =
{
  {"crown-margin", no_argument, NULL, 'c'},
  {"help", no_argument, &show_help, 1},
  {"prefix", required_argument, NULL, 'p'},
  {"split-only", no_argument, NULL, 's'},
  {"tagged-paragraph", no_argument, NULL, 't'},
  {"uniform-spacing", no_argument, NULL, 'u'},
  {"version", no_argument, &show_version, 1},
  {"width", required_argument, NULL, 'w'},
  {0, 0, 0, 0},
};

int
main (register int argc, register char **argv)
{
  int optchar;
  FILE *infile;

  program_name = argv[0];

  crown = tagged = split = uniform = FALSE;
  max_width = WIDTH;
  prefix = "";
  prefix_length = prefix_lead_space = prefix_full_length = 0;

  if (argc > 1 && argv[1][0] == '-' && ISDIGIT (argv[1][1]))
    {
      max_width = 0;
      /* Old option syntax; a dash followed by one or more digits.
         Move past the number. */
      for (++argv[1]; ISDIGIT (*argv[1]); ++argv[1])
        {
          /* FIXME: use strtol to detect overflow.  */
          max_width = max_width * 10 + *argv[1] - '0';
        }
      /* Make the options we just parsed invisible to getopt. */
      argv[1] = argv[0];
      argv++;
      argc--;
    }

  while ((optchar = getopt_long (argc, argv, "0123456789cstuw:p:",
                                 long_options, NULL))
         != EOF)
    switch (optchar)
      {
      default:
        usage (1);

      case 0:
        break;

      case 'c':
        crown = TRUE;
        break;

      case 's':
        split = TRUE;
        break;

      case 't':
        tagged = TRUE;
        break;

      case 'u':
        uniform = TRUE;
        break;

      case 'w':
        /* FIXME: use strtol.  */
        max_width = atoi (optarg);
        break;

      case 'p':
        set_prefix (optarg);
        break;

      }

  if (show_version)
    {
      printf ("fmt - %s\n", version_string);
      exit (0);
    }

  if (show_help)
    usage (0);

  best_width = max_width * (2 * (100 - LEEWAY) + 1) / 200;

  if (optind == argc)
    fmt (stdin);
  else
    for (; optind < argc; optind++)
      if (strcmp (argv[optind], "-") == 0)
        fmt (stdin);
      else
        {
          infile = fopen (argv[optind], "r");
          if (infile != NULL)
            {
              fmt (infile);
              fclose (infile);
            }
          else
            error (0, errno, argv[optind]);
        }

  exit (0);
}

/* Trim space from the front and back of the string P, yielding the prefix,
   and record the lengths of the prefix and the space trimmed.  */

static void
set_prefix (register char *p)
{
  register char *s;

  prefix_lead_space = 0;
  while (*p == ' ')
    {
      prefix_lead_space++;
      p++;
    }
  prefix = p;
  prefix_full_length = strlen (p);
  s = p + prefix_full_length;
  while (s > p && s[-1] == ' ')
    s--;
  *s = '\0';
  prefix_length = s - p;
}

/* read file F and send formatted output to stdout.  */

static void
fmt (FILE *f)
{
  tabs = FALSE;
  other_indent = 0;
  next_char = get_prefix (f);
  while (get_paragraph (f))
    {
      fmt_paragraph ();
      put_paragraph (word_limit);
    }
}

/* Read a paragraph from input file F.  A paragraph consists of a
   maximal number of non-blank (excluding any prefix) lines subject to:
   * In split mode, a paragraph is a single non-blank line.
   * In crown mode, the second and subsequent lines must have the
   same indentation, but possibly different from the indent of the
   first line.
   * Tagged mode is similar, but the first and second lines must have
   different indentations.
   * Otherwise, all lines of a paragraph must have the same indent.
   If a prefix is in effect, it must be present at the same indent for
   each line in the paragraph.

   Return FALSE if end-of-file was encountered before the start of a
   paragraph, else TRUE.  */

static bool
get_paragraph (FILE *f)
{
  register int c;

  last_line_length = 0;
  c = next_char;

  /* Scan (and copy) blank lines, and lines not introduced by the prefix.  */

  while (c == '\n' || c == EOF
         || next_prefix_indent < prefix_lead_space
         || in_column < next_prefix_indent + prefix_full_length)
    {
      c = copy_rest (f, c);
      if (c == EOF)
        {
          next_char = EOF;
          return FALSE;
        }
      putchar ('\n');
      c = get_prefix (f);
    }

  /* Got a suitable first line for a paragraph.  */

  prefix_indent = next_prefix_indent;
  first_indent = in_column;
  wptr = parabuf;
  word_limit = word;
  c = get_line (f, c);

  /* Read rest of paragraph (unless split is specified).  */

  if (split)
    other_indent = first_indent;
  else if (crown)
    {
      if (same_para (c))
        {
          other_indent = in_column;
          do
            {                   /* for each line till the end of the para */
              c = get_line (f, c);
            }
          while (same_para (c) && in_column == other_indent);
        }
      else
        other_indent = first_indent;
    }
  else if (tagged)
    {
      if (same_para (c) && in_column != first_indent)
        {
          other_indent = in_column;
          do
            {                   /* for each line till the end of the para */
              c = get_line (f, c);
            }
          while (same_para (c) && in_column == other_indent);
        }

      /* Only one line: use the secondary indent from last time if it
         splits, or 0 if there have been no multi-line paragraphs in the
         input so far.  But if these rules make the two indents the same,
         pick a new secondary indent.  */

      else if (other_indent == first_indent)
        other_indent = first_indent == 0 ? DEF_INDENT : 0;
    }
  else
    {
      other_indent = first_indent;
      while (same_para (c) && in_column == other_indent)
        c = get_line (f, c);
    }
  (word_limit - 1)->period = (word_limit - 1)->final = TRUE;
  next_char = c;
  return TRUE;
}

/* Copy to the output a line that failed to match the prefix, or that
   was blank after the prefix.  In the former case, C is the character
   that failed to match the prefix.  In the latter, C is \n or EOF.
   Return the character (\n or EOF) ending the line.  */

static int
copy_rest (FILE *f, register int c)
{
  register const char *s;

  out_column = 0;
  if (in_column > next_prefix_indent && c != '\n' && c != EOF)
    {
      put_space (next_prefix_indent);
      for (s = prefix; out_column != in_column; out_column++)
        putchar (*s++);
    }
  while (c != '\n' && c != EOF)
    {
      putchar (c);
      c = getc (f);
    }
  return c;
}

/* Return TRUE if a line whose first non-blank character after the
   prefix (if any) is C could belong to the current paragraph,
   otherwise FALSE.  */

static bool
same_para (register int c)
{
  return (next_prefix_indent == prefix_indent
          && in_column >= next_prefix_indent + prefix_full_length
          && c != '\n' && c != EOF);
}

/* Read a line from input file F, given first non-blank character C
   after the prefix, and the following indent, and break it into words.
   A word is a maximal non-empty string of non-white characters.  A word
   ending in [.?!]["')\]]* and followed by end-of-line or at least two
   spaces ends a sentence, as in emacs.

   Return the first non-blank character of the next line.  */

static int
get_line (FILE *f, register int c)
{
  int start;
  register char *end_of_parabuf;
  register WORD *end_of_word;

  end_of_parabuf = &parabuf[MAXCHARS];
  end_of_word = &word[MAXWORDS - 2];

  do
    {                           /* for each word in a line */

      /* Scan word.  */

      word_limit->text = wptr;
      do
        {
          if (wptr == end_of_parabuf)
            flush_paragraph ();
          *wptr++ = c;
          c = getc (f);
        }
      while (c != EOF && !isspace (c));
      in_column += word_limit->length = wptr - word_limit->text;
      check_punctuation (word_limit);

      /* Scan inter-word space.  */

      start = in_column;
      c = get_space (f, c);
      word_limit->space = in_column - start;
      word_limit->final = (c == EOF
                           || (word_limit->period
                               && (c == '\n' || word_limit->space > 1)));
      if (c == '\n' || c == EOF || uniform)
        word_limit->space = word_limit->final ? 2 : 1;
      if (word_limit == end_of_word)
        flush_paragraph ();
      word_limit++;
      if (c == EOF)
        return EOF;
    }
  while (c != '\n');
  return get_prefix (f);
}

/* Read a prefix from input file F.  Return either first non-matching
   character, or first non-blank character after the prefix.  */

static int
get_prefix (FILE *f)
{
  register int c;
  register const char *p;

  in_column = 0;
  c = get_space (f, getc (f));
  if (prefix_length == 0)
    next_prefix_indent = prefix_lead_space < in_column ?
      prefix_lead_space : in_column;
  else
    {
      next_prefix_indent = in_column;
      for (p = prefix; *p != '\0'; p++)
        {
          if (c != *p)
            return c;
          in_column++;
          c = getc (f);
        }
      c = get_space (f, c);
    }
  return c;
}

/* Read blank characters from input file F, starting with C, and keeping
   in_column up-to-date.  Return first non-blank character.  */

static int
get_space (FILE *f, register int c)
{
  for (;;)
    {
      if (c == ' ')
        in_column++;
      else if (c == '\t')
        {
          tabs = TRUE;
          in_column = (in_column / TABWIDTH + 1) * TABWIDTH;
        }
      else
        return c;
      c = getc (f);
    }
}

/* Set extra fields in word W describing any attached punctuation.  */

static void
check_punctuation (register WORD *w)
{
  register const char *start, *finish;

  start = w->text;
  finish = start + (w->length - 1);
  w->paren = isopen (*start);
  w->punct = ispunct (*finish);
  while (isclose (*finish) && finish > start)
    finish--;
  w->period = isperiod (*finish);
}

/* Flush part of the paragraph to make room.  This function is called on
   hitting the limit on the number of words or characters.  */

static void
flush_paragraph (void)
{
  WORD *split_point;
  register WORD *w;
  int shift;
  COST best_break;

  /* In the special case where it's all one word, just flush it.  */

  if (word_limit == word)
    {
      printf ("%*s", wptr - parabuf, parabuf);
      wptr = parabuf;
      return;
    }

  /* Otherwise:
     - format what you have so far as a paragraph,
     - find a low-cost line break near the end,
     - output to there,
     - make that the start of the paragraph.  */

  fmt_paragraph ();

  /* Choose a good split point.  */

  split_point = word_limit;
  best_break = MAXCOST;
  for (w = word->next_break; w != word_limit; w = w->next_break)
    {
      if (w->best_cost - w->next_break->best_cost < best_break)
        {
          split_point = w;
          best_break = w->best_cost - w->next_break->best_cost;
        }
      if (best_break <= MAXCOST - LINE_CREDIT)
        best_break += LINE_CREDIT;
    }
  put_paragraph (split_point);

  /* Copy text of words down to start of parabuf -- we use memmove because
     the source and target may overlap.  */

  memmove (parabuf, split_point->text, (size_t) (wptr - split_point->text));
  shift = split_point->text - parabuf;
  wptr -= shift;

  /* Adjust text pointers.  */

  for (w = split_point; w <= word_limit; w++)
    w->text -= shift;

  /* Copy words from split_point down to word -- we use memmove because
     the source and target may overlap.  */

  memmove ((char *) word, (char *) split_point,
         (word_limit - split_point + 1) * sizeof (WORD));
  word_limit -= split_point - word;
}

/* Compute the optimal formatting for the whole paragraph by computing
   and remembering the optimal formatting for each suffix from the empty
   one to the whole paragraph.  */

static void
fmt_paragraph (void)
{
  register WORD *start, *w;
  register int len;
  register COST wcost, best;
  int saved_length;

  word_limit->best_cost = 0;
  saved_length = word_limit->length;
  word_limit->length = max_width;       /* sentinel */

  for (start = word_limit - 1; start >= word; start--)
    {
      best = MAXCOST;
      len = start == word ? first_indent : other_indent;

      /* At least one word, however long, in the line.  */

      w = start;
      len += w->length;
      do
        {
          w++;

          /* Consider breaking before w.  */

          wcost = line_cost (w, len) + w->best_cost;
          if (start == word && last_line_length > 0)
            wcost += RAGGED_COST (len - last_line_length);
          if (wcost < best)
            {
              best = wcost;
              start->next_break = w;
              start->line_length = len;
            }
          len += (w - 1)->space + w->length;    /* w > start >= word */
        }
      while (len < max_width);
      start->best_cost = best + base_cost (start);
    }

  word_limit->length = saved_length;
}

/* Return the constant component of the cost of breaking before the
   word THIS.  */

static COST
base_cost (register WORD *this)
{
  register COST cost;

  cost = LINE_COST;

  if (this > word)
    {
      if ((this - 1)->period)
        {
          if ((this - 1)->final)
            cost -= SENTENCE_BONUS;
          else
            cost += NOBREAK_COST;
        }
      else if ((this - 1)->punct)
        cost -= PUNCT_BONUS;
      else if (this > word + 1 && (this - 2)->final)
        cost += WIDOW_COST ((this - 1)->length);
    }

  if (this->paren)
    cost -= PAREN_BONUS;
  else if (this->final)
    cost += ORPHAN_COST (this->length);

  return cost;
}

/* Return the component of the cost of breaking before word NEXT that
   depends on LEN, the length of the line beginning there.  */

static COST
line_cost (register WORD *next, register int len)
{
  register int n;
  register COST cost;

  if (next == word_limit)
    return 0;
  n = best_width - len;
  cost = SHORT_COST (n);
  if (next->next_break != word_limit)
    {
      n = len - next->line_length;
      cost += RAGGED_COST (n);
    }
  return cost;
}

/* Output to stdout a paragraph from word up to (but not including)
   FINISH, which must be in the next_break chain from word.  */

static void
put_paragraph (register WORD *finish)
{
  register WORD *w;

  put_line (word, first_indent);
  for (w = word->next_break; w != finish; w = w->next_break)
    put_line (w, other_indent);
}

/* Output to stdout the line beginning with word W, beginning in column
   INDENT, including the prefix (if any).  */

static void
put_line (register WORD *w, int indent)
{
  register WORD *endline;

  out_column = 0;
  put_space (prefix_indent);
  fputs (prefix, stdout);
  out_column += prefix_length;
  put_space (indent - out_column);

  endline = w->next_break - 1;
  for (; w != endline; w++)
    {
      put_word (w);
      put_space (w->space);
    }
  put_word (w);
  last_line_length = out_column;
  putchar ('\n');
}

/* Output to stdout the word W.  */

static void
put_word (register WORD *w)
{
  register const char *s;
  register int n;

  s = w->text;
  for (n = w->length; n != 0; n--)
    putchar (*s++);
  out_column += w->length;
}

/* Output to stdout SPACE spaces, or equivalent tabs.  */

static void
put_space (int space)
{
  register int space_target, tab_target;

  space_target = out_column + space;
  if (tabs)
    {
      tab_target = space_target / TABWIDTH * TABWIDTH;
      if (out_column + 1 < tab_target)
        while (out_column < tab_target)
          {
            putchar ('\t');
            out_column = (out_column / TABWIDTH + 1) * TABWIDTH;
          }
    }
  while (out_column < space_target)
    {
      putchar (' ');
      out_column++;
    }
}