stdio/linewrap.c

   1 /* Word-wrapping and line-truncating streams.
   2 Copyright (C) 1996 Free Software Foundation, Inc.
   3 This file is part of the GNU C Library.
   4
   5 The GNU C Library is free software; you can redistribute it and/or
   6 modify it under the terms of the GNU Library General Public License as
   7 published by the Free Software Foundation; either version 2 of the
   8 License, or (at your option) any later version.
   9
  10 The GNU C Library is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 Library General Public License for more details.
  14
  15 You should have received a copy of the GNU Library General Public
  16 License along with the GNU C Library; see the file COPYING.LIB.  If
  17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  18 Cambridge, MA 02139, USA.  */
  19
  20 #include <stdio.h>
  21 #include <ctype.h>
  22 #include <string.h>
  23 #include <stdlib.h>
  24
  25 #include <linewrap.h>
  26 \f
  27 void __line_wrap_output (FILE *, int);
  28
  29 /* Install our hooks into a stream.  */
  30 static inline void
  31 wrap_stream (FILE *stream, struct line_wrap_data *d)
  32 {
  33   static __io_close_fn lwclose;
  34   static __io_fileno_fn lwfileno;
  35
  36   stream->__cookie = d;
  37   stream->__room_funcs.__output = &__line_wrap_output;
  38   stream->__io_funcs.__close = &lwclose;
  39   stream->__io_funcs.__fileno = &lwfileno;
  40   stream->__io_funcs.__seek = NULL; /* Cannot seek.  */
  41 }
  42
  43 /* Restore a stream to its original state.  */
  44 static inline void
  45 unwrap_stream (FILE *stream, struct line_wrap_data *d)
  46 {
  47   stream->__cookie = d->cookie;
  48   stream->__room_funcs.__output = d->output;
  49   stream->__io_funcs.__close = d->close;
  50   stream->__io_funcs.__fileno = d->fileno;
  51   stream->__io_funcs.__seek = d->seek;
  52 }
  53 \f
  54 /* Cookie io functions that might get called on a wrapped stream.
  55    Must pass the original cookie to the original functions.  */
  56
  57 static int
  58 lwclose (void *cookie)
  59 {
  60   struct line_wrap_data *d = cookie;
  61   return (*d->close) (d->cookie);
  62 }
  63
  64 static int
  65 lwfileno (void *cookie)
  66 {
  67   struct line_wrap_data *d = cookie;
  68   return (*d->fileno) (d->cookie);
  69 }
  70 \f
  71 /* This function is called when STREAM must be flushed.
  72    C is EOF or a character to be appended to the buffer contents.  */
  73 void
  74 __line_wrap_output (FILE *stream, int c)
  75 {
  76   char *buf, *nl;
  77   size_t len;
  78
  79   /* Extract our data and restore the stream's original cookie
  80      and output function so writes we do really go out.  */
  81   struct line_wrap_data *d = stream->__cookie;
  82   unwrap_stream (stream, d);
  83
  84   /* Scan the buffer for newlines.  */
  85   buf = stream->__buffer;
  86   while ((buf < stream->__bufp || (c != EOF && c != '\n')) && !stream->__error)
  87     {
  88       size_t r;
  89
  90       if (d->point == 0 && d->lmargin != 0)
  91         {
  92           /* We are starting a new line.  Print spaces to the left margin.  */
  93           const size_t pad = d->lmargin;
  94           if (stream->__bufp + pad < stream->__put_limit)
  95             {
  96               /* We can fit in them in the buffer by moving the
  97                  buffer text up and filling in the beginning.  */
  98               memmove (buf + pad, buf, stream->__bufp - buf);
  99               stream->__bufp += pad; /* Compensate for bigger buffer. */
 100               memset (buf, ' ', pad); /* Fill in the spaces.  */
 101               buf += pad; /* Don't bother searching them.  */
 102             }
 103           else
 104             {
 105               /* No buffer space for spaces.  Must flush.  */
 106               size_t i;
 107               char *olimit;
 108
 109               len = stream->__bufp - buf;
 110               olimit = stream->__put_limit;
 111               stream->__bufp = stream->__put_limit = buf;
 112               for (i = 0; i < pad; ++i)
 113                 (*d->output) (stream, ' ');
 114               stream->__put_limit = olimit;
 115               memcpy (stream->__bufp, buf, len);
 116               stream->__bufp += len;
 117             }
 118           d->point = pad;
 119         }
 120
 121       len = stream->__bufp - buf;
 122       nl = memchr (buf, '\n', len);
 123
 124       if (!nl)
 125         {
 126           /* The buffer ends in a partial line.  */
 127
 128           if (d->point + len + (c != EOF && c != '\n') <= d->rmargin)
 129             {
 130               /* The remaining buffer text is a partial line and fits
 131                  within the maximum line width.  Advance point for the
 132                  characters to be written and stop scanning.  */
 133               d->point += len;
 134               break;
 135             }
 136           else
 137             /* Set the end-of-line pointer for the code below to
 138                the end of the buffer.  */
 139             nl = stream->__bufp;
 140         }
 141       else if (d->point + (nl - buf) <= d->rmargin)
 142         {
 143           /* The buffer contains a full line that fits within the maximum
 144              line width.  Reset point and scan the next line.  */
 145           d->point = 0;
 146           buf = nl + 1;
 147           continue;
 148         }
 149
 150       /* This line is too long.  */
 151       r = d->rmargin;
 152
 153       if (d->wmargin < 0)
 154         {
 155           /* Truncate the line by overwriting the excess with the
 156              newline and anything after it in the buffer.  */
 157           if (nl < stream->__bufp)
 158             {
 159               memcpy (buf + (r - d->point), nl, stream->__bufp - nl);
 160               stream->__bufp -= buf + (r - d->point) - nl;
 161               /* Reset point for the next line and start scanning it.  */
 162               d->point = 0;
 163               buf += r + 1; /* Skip full line plus \n. */
 164             }
 165           else
 166             {
 167               /* The buffer ends with a partial line that is beyond the
 168                  maximum line width.  Advance point for the characters
 169                  written, and discard those past the max from the buffer.  */
 170               d->point += len;
 171               stream->__bufp -= d->point - r;
 172               if (c != '\n')
 173                 /* Swallow the extra character too.  */
 174                 c = EOF;
 175               break;
 176             }
 177         }
 178       else
 179         {
 180           /* Do word wrap.  Go to the column just past the maximum line
 181              width and scan back for the beginning of the word there.
 182              Then insert a line break.  */
 183
 184           char *p, *nextline;
 185           int i;
 186
 187           p = buf + (r + 1 - d->point);
 188           while (p >= buf && !isblank (*p))
 189             --p;
 190           nextline = p + 1;     /* This will begin the next line.  */
 191
 192           if (nextline > buf)
 193             {
 194               /* Swallow separating blanks.  */
 195               do
 196                 --p;
 197               while (isblank (*p));
 198               nl = p + 1;       /* The newline will replace the first blank. */
 199             }
 200           else
 201             {
 202               /* A single word that is greater than the maximum line width.
 203                  Oh well.  Put it on an overlong line by itself.  */
 204               p = buf + (r + 1 - d->point);
 205               /* Find the end of the long word.  */
 206               do
 207                 ++p;
 208               while (p < nl && !isblank (*p));
 209               if (p == nl)
 210                 {
 211                   /* It already ends a line.  No fussing required.  */
 212                   d->point = 0;
 213                   buf = nl + 1;
 214                   continue;
 215                 }
 216               /* We will move the newline to replace the first blank.  */
 217               nl = p;
 218               /* Swallow separating blanks.  */
 219               do
 220                 ++p;
 221               while (isblank (*p));
 222               /* The next line will start here.  */
 223               nextline = p;
 224             }
 225
 226           /* Temporarily reset bufp to include just the first line.  */
 227           stream->__bufp = nl;
 228           if (nextline - (nl + 1) < d->wmargin)
 229             /* The margin needs more blanks than we removed.
 230                Output the first line so we can use the space.  */
 231             (*d->output) (stream, '\n');
 232           else
 233             /* We can fit the newline and blanks in before
 234                the next word.  */
 235             *stream->__bufp++ = '\n';
 236
 237           /* Reset the counter of what has been output this line.  */
 238           d->point = 0;
 239
 240           /* Add blanks up to the wrap margin column.  */
 241           for (i = 0; i < d->wmargin; ++i)
 242             *stream->__bufp++ = ' ';
 243
 244           /* Copy the tail of the original buffer into the current buffer
 245              position.  */
 246           if (stream->__bufp != nextline)
 247             memcpy (stream->__bufp, nextline, buf + len - nextline);
 248           len -= nextline - buf;
 249
 250           /* Continue the scan on the remaining lines in the buffer.  */
 251           buf = stream->__bufp;
 252
 253           /* Restore bufp to include all the remaining text.  */
 254           stream->__bufp += len;
 255         }
 256     }
 257
 258   if (!stream->__error)
 259     {
 260       (*d->output) (stream, c);
 261       if (c == '\n')
 262         d->point = 0;
 263       else if (c != EOF)
 264         ++d->point;
 265     }
 266
 267   wrap_stream (stream, d);
 268 }
 269 \f
 270 /* Modify STREAM so that it prefixes lines written on it with LMARGIN spaces
 271    and limits them to RMARGIN columns total.  If WMARGIN >= 0, words that
 272    extend past RMARGIN are wrapped by replacing the whitespace before them
 273    with a newline and WMARGIN spaces.  Otherwise, chars beyond RMARGIN are
 274    simply dropped until a newline.  Returns STREAM after modifying it, or
 275    NULL if there was an error.  */
 276 FILE *
 277 line_wrap_stream (FILE *stream, size_t lmargin, size_t rmargin, size_t wmargin)
 278 {
 279   struct line_wrap_data *d = malloc (sizeof *d);
 280
 281   if (!d)
 282     return NULL;
 283
 284   /* Ensure full setup before we start tweaking.  */
 285   fflush (stream);
 286
 287   /* Initialize our wrapping state.  */
 288   d->point = 0;
 289
 290   /* Save the original cookie and output and close hooks.  */
 291   d->cookie = stream->__cookie;
 292   d->output = stream->__room_funcs.__output;
 293   d->close = stream->__io_funcs.__close;
 294   d->fileno = stream->__io_funcs.__fileno;
 295
 296   /* Take over the stream.  */
 297   wrap_stream (stream, d);
 298
 299   /* Line-wrapping streams are normally line-buffered.  This is not
 300      required, just assumed desired.  The wrapping feature should continue
 301      to work if the stream is switched to full or no buffering.  */
 302   stream->__linebuf = 1;
 303
 304   d->lmargin = lmargin;
 305   d->rmargin = rmargin;
 306   d->wmargin = wmargin;
 307
 308   return stream;
 309 }
 310
 311 /* Remove the hooks placed in STREAM by `line_wrap_stream'.  */
 312 void
 313 line_unwrap_stream (FILE *stream)
 314 {
 315   struct line_wrap_data *d = stream->__cookie;
 316   unwrap_stream (stream, d);
 317   free (d);
 318 }
 319 \f
 320 /* Functions on wrapped streams.  */
 321
 322 /* Returns true if STREAM is line wrapped.  */
 323 inline int
 324 line_wrapped (FILE *stream)
 325 {
 326   return (stream->__room_funcs.__output == &__line_wrap_output);
 327 }
 328
 329 /* If STREAM is not line-wrapped return -1, else return its left margin.  */
 330 size_t
 331 line_wrap_lmargin (FILE *stream)
 332 {
 333   if (! line_wrapped (stream))
 334     return -1;
 335   return ((struct line_wrap_data *)stream->__cookie)->lmargin;
 336 }
 337
 338 /* If STREAM is not line-wrapped return -1, else set its left margin to
 339    LMARGIN and return the old value.  */
 340 size_t
 341 line_wrap_set_lmargin (FILE *stream, size_t lmargin)
 342 {
 343   if (! line_wrapped (stream))
 344     return -1;
 345   else
 346     {
 347       struct line_wrap_data *d = stream->__cookie;
 348       size_t old = d->lmargin;
 349       d->lmargin = lmargin;
 350       return old;
 351     }
 352 }
 353
 354 /* If STREAM is not line-wrapped return -1, else return its left margin.  */
 355 size_t
 356 line_wrap_rmargin (FILE *stream)
 357 {
 358   if (! line_wrapped (stream))
 359     return -1;
 360   return ((struct line_wrap_data *)stream->__cookie)->rmargin;
 361 }
 362
 363 /* If STREAM is not line-wrapped return -1, else set its right margin to
 364    RMARGIN and return the old value.  */
 365 size_t
 366 line_wrap_set_rmargin (FILE *stream, size_t rmargin)
 367 {
 368   if (! line_wrapped (stream))
 369     return -1;
 370   else
 371     {
 372       struct line_wrap_data *d = stream->__cookie;
 373       size_t old = d->rmargin;
 374       d->rmargin = rmargin;
 375       return old;
 376     }
 377 }
 378
 379 /* If STREAM is not line-wrapped return -1, else return its wrap margin.  */
 380 size_t
 381 line_wrap_wmargin (FILE *stream)
 382 {
 383   if (! line_wrapped (stream))
 384     return -1;
 385   return ((struct line_wrap_data *)stream->__cookie)->wmargin;
 386 }
 387
 388 /* If STREAM is not line-wrapped return -1, else set its left margin to
 389    WMARGIN and return the old value.  */
 390 size_t
 391 line_wrap_set_wmargin (FILE *stream, size_t wmargin)
 392 {
 393   if (! line_wrapped (stream))
 394     return -1;
 395   else
 396     {
 397       struct line_wrap_data *d = stream->__cookie;
 398       size_t old = d->wmargin;
 399       d->wmargin = wmargin;
 400       return old;
 401     }
 402 }
 403
 404 /* If STREAM is not line-wrapped return -1, else return the column number of
 405    the current output point.  */
 406 size_t
 407 line_wrap_point (FILE *stream)
 408 {
 409   if (! line_wrapped (stream))
 410     return -1;
 411   return ((struct line_wrap_data *)stream->__cookie)->point;
 412 }
 413 \f
 414 #ifdef TEST
 415 int
 416 main (int argc, char **argv)
 417 {
 418   int c;
 419   puts ("stopme");
 420   line_wrap_stream (stdout, atoi (argv[1]), atoi (argv[2] ?: "-1"));
 421   while ((c = getchar()) != EOF) putchar (c);
 422   return 0;
 423 }
 424 #endif