1 /* filter - postprocessing of flex output through filters */
3 /* This file is part of flex. */
5 /* Redistribution and use in source and binary forms, with or without */
6 /* modification, are permitted provided that the following conditions */
9 /* 1. Redistributions of source code must retain the above copyright */
10 /* notice, this list of conditions and the following disclaimer. */
11 /* 2. Redistributions in binary form must reproduce the above copyright */
12 /* notice, this list of conditions and the following disclaimer in the */
13 /* documentation and/or other materials provided with the distribution. */
15 /* Neither the name of the University nor the names of its contributors */
16 /* may be used to endorse or promote products derived from this software */
17 /* without specific prior written permission. */
19 /* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR */
20 /* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED */
21 /* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR */
25 static const char * check_4_gnu_m4 =
26 "m4_dnl ifdef(`__gnu__', ,"
27 "`errprint(Flex requires GNU M4. Set the PATH or set the M4 environment variable to its path name.)"
32 struct filter *output_chain = NULL;
34 /* Allocate and initialize an external filter.
35 * @param chain the current chain or NULL for new chain
36 * @param cmd the command to execute.
37 * @param ... a NULL terminated list of (const char*) arguments to command,
38 * not including argv[0].
39 * @return newest filter in chain
41 struct filter *filter_create_ext (struct filter *chain, const char *cmd,
49 /* allocate and initialize new filter */
50 f = (struct filter *) flex_alloc (sizeof (struct filter));
52 flexerror (_("flex_alloc failed (f) in filter_create_ext"));
53 memset (f, 0, sizeof (*f));
54 f->filter_func = NULL;
60 /* append f to end of chain */
67 /* allocate argv, and populate it with the argument list. */
70 (const char **) flex_alloc (sizeof (char *) *
73 flexerror (_("flex_alloc failed (f->argv) in filter_create_ext"));
74 f->argv[f->argc++] = cmd;
77 while ((s = va_arg (ap, const char *)) != NULL) {
78 if (f->argc >= max_args) {
81 (const char **) flex_realloc (f->argv,
87 f->argv[f->argc++] = s;
89 f->argv[f->argc] = NULL;
95 /* Allocate and initialize an internal filter.
96 * @param chain the current chain or NULL for new chain
97 * @param filter_func The function that will perform the filtering.
98 * filter_func should return 0 if successful, and -1
99 * if an error occurs -- or it can simply exit().
100 * @param extra optional user-defined data to pass to the filter.
101 * @return newest filter in chain
103 struct filter *filter_create_int (struct filter *chain,
104 int (*filter_func) (struct filter *),
109 /* allocate and initialize new filter */
110 f = (struct filter *) flex_alloc (sizeof (struct filter));
112 flexerror (_("flex_alloc failed in filter_create_int"));
113 memset (f, 0, sizeof (*f));
118 f->filter_func = filter_func;
122 /* append f to end of chain */
131 /** Fork and exec entire filter chain.
132 * @param chain The head of the chain.
133 * @return true on success.
135 bool filter_apply_chain (struct filter * chain)
139 const int readsz = 512;
143 /* Tricky recursion, since we want to begin the chain
144 * at the END. Why? Because we need all the forked processes
145 * to be children of the main flex process.
148 filter_apply_chain (chain->next);
152 /* Now we are the right-most unprocessed link in the chain.
159 if (pipe (pipes) == -1)
160 flexerror (_("pipe failed"));
162 if ((pid = fork ()) == -1)
163 flexerror (_("fork failed"));
168 /* We need stdin (the FILE* stdin) to connect to this new pipe.
169 * There is no portable way to set stdin to a new file descriptor,
170 * as stdin is not an lvalue on some systems (BSD).
171 * So we dup the new pipe onto the stdin descriptor and use a no-op fseek
172 * to sync the stream. This is a Hail Mary situation. It seems to work.
176 if (dup2 (pipes[0], fileno (stdin)) == -1)
177 flexfatal (_("dup2(pipes[0],0)"));
179 fseek (stdin, 0, SEEK_CUR);
181 /* run as a filter, either internally or by exec */
182 if (chain->filter_func) {
185 if ((r = chain->filter_func (chain)) == -1)
186 flexfatal (_("filter_func failed"));
190 execvp (chain->argv[0],
191 (char **const) (chain->argv));
192 lerrsf_fatal ( _("exec of %s failed"),
201 if (dup2 (pipes[1], fileno (stdout)) == -1)
202 flexfatal (_("dup2(pipes[1],1)"));
204 fseek (stdout, 0, SEEK_CUR);
209 /** Truncate the chain to max_len number of filters.
210 * @param chain the current chain.
211 * @param max_len the maximum length of the chain.
212 * @return the resulting length of the chain.
214 int filter_truncate (struct filter *chain, int max_len)
221 while (chain->next && len < max_len) {
230 /** Splits the chain in order to write to a header file.
231 * Similar in spirit to the 'tee' program.
232 * The header file name is in extra.
233 * @return 0 (zero) on success, and -1 on failure.
235 int filter_tee_header (struct filter *chain)
237 /* This function reads from stdin and writes to both the C file and the
238 * header file at the same time.
241 const int readsz = 512;
244 FILE *to_c = NULL, *to_h = NULL;
247 write_header = (chain->extra != NULL);
249 /* Store a copy of the stdout pipe, which is already piped to C file
250 * through the running chain. Then create a new pipe to the H file as
251 * stdout, and fork the rest of the chain again.
254 if ((to_cfd = dup (1)) == -1)
255 flexfatal (_("dup(1) failed"));
256 to_c = fdopen (to_cfd, "w");
259 if (freopen ((char *) chain->extra, "w", stdout) == NULL)
260 flexfatal (_("freopen(headerfilename) failed"));
262 filter_apply_chain (chain->next);
266 /* Now to_c is a pipe to the C branch, and to_h is a pipe to the H branch.
270 fputs (check_4_gnu_m4, to_h);
271 fputs ("m4_changecom`'m4_dnl\n", to_h);
272 fputs ("m4_changequote`'m4_dnl\n", to_h);
273 fputs ("m4_changequote([[,]])[[]]m4_dnl\n", to_h);
274 fputs ("m4_define([[M4_YY_NOOP]])[[]]m4_dnl\n", to_h);
275 fputs ("m4_define( [[M4_YY_IN_HEADER]],[[]])m4_dnl\n",
277 fprintf (to_h, "#ifndef %sHEADER_H\n", prefix);
278 fprintf (to_h, "#define %sHEADER_H 1\n", prefix);
279 fprintf (to_h, "#define %sIN_HEADER 1\n\n", prefix);
281 "m4_define( [[M4_YY_OUTFILE_NAME]],[[%s]])m4_dnl\n",
282 headerfilename ? headerfilename : "<stdout>");
286 fputs (check_4_gnu_m4, to_c);
287 fputs ("m4_changecom`'m4_dnl\n", to_c);
288 fputs ("m4_changequote`'m4_dnl\n", to_c);
289 fputs ("m4_changequote([[,]])[[]]m4_dnl\n", to_c);
290 fputs ("m4_define([[M4_YY_NOOP]])[[]]m4_dnl\n", to_c);
291 fprintf (to_c, "m4_define( [[M4_YY_OUTFILE_NAME]],[[%s]])m4_dnl\n",
292 outfilename ? outfilename : "<stdout>");
294 buf = (char *) flex_alloc (readsz);
296 flexerror (_("flex_alloc failed in filter_tee_header"));
297 while (fgets (buf, readsz, stdin)) {
304 fprintf (to_h, "\n");
306 /* write a fake line number. It will get fixed by the linedir filter. */
307 fprintf (to_h, "#line 4000 \"M4_YY_OUTFILE_NAME\"\n");
309 fprintf (to_h, "#undef %sIN_HEADER\n", prefix);
310 fprintf (to_h, "#endif /* %sHEADER_H */\n", prefix);
311 fputs ("m4_undefine( [[M4_YY_IN_HEADER]])m4_dnl\n", to_h);
315 lerrsf (_("error writing output file %s"),
316 (char *) chain->extra);
318 else if (fclose (to_h))
319 lerrsf (_("error closing output file %s"),
320 (char *) chain->extra);
325 lerrsf (_("error writing output file %s"),
326 outfilename ? outfilename : "<stdout>");
328 else if (fclose (to_c))
329 lerrsf (_("error closing output file %s"),
330 outfilename ? outfilename : "<stdout>");
332 while (wait (0) > 0) ;
338 /** Adjust the line numbers in the #line directives of the generated scanner.
339 * After the m4 expansion, the line numbers are incorrect since the m4 macros
340 * can add or remove lines. This only adjusts line numbers for generated code,
341 * not user code. This also happens to be a good place to squeeze multiple
342 * blank lines into a single blank line.
344 int filter_fix_linedirs (struct filter *chain)
347 const int readsz = 512;
349 bool in_gen = true; /* in generated code */
350 bool last_was_blank = false;
355 buf = (char *) flex_alloc (readsz);
357 flexerror (_("flex_alloc failed in filter_fix_linedirs"));
359 while (fgets (buf, readsz, stdin)) {
363 /* Check for #line directive. */
365 && regexec (®ex_linedir, buf, 3, m, 0) == 0) {
370 /* extract the line number and filename */
371 num = regmatch_strtol (&m[1], buf, NULL, 0);
372 fname = regmatch_dup (&m[2], buf);
375 outfilename ? outfilename : "<stdout>")
378 headerfilename ? headerfilename : "<stdout>")
382 char filename[MAXLINE];
387 while ((s2 - filename) < (MAXLINE - 1) && *s1) {
388 /* Escape the backslash */
391 /* Escape the double quote */
394 /* Copy the character as usual */
400 /* Adjust the line directives. */
402 snprintf (buf, readsz, "#line %d \"%s\"\n",
403 lineno + 1, filename);
406 /* it's a #line directive for code we didn't write */
411 last_was_blank = false;
414 /* squeeze blank lines from generated code */
416 && regexec (®ex_blank_line, buf, 0, NULL,
421 last_was_blank = true;
425 /* it's a line of normal, non-empty code. */
426 last_was_blank = false;
434 lerrsf (_("error writing output file %s"),
435 outfilename ? outfilename : "<stdout>");
437 else if (fclose (stdout))
438 lerrsf (_("error closing output file %s"),
439 outfilename ? outfilename : "<stdout>");
444 /* vim:set expandtab cindent tabstop=4 softtabstop=4 shiftwidth=4 textwidth=0: */