code/trunk/pcredemo.c

/*************************************************
*           PCRE DEMONSTRATION PROGRAM           *
*************************************************/

/* This is a demonstration program to illustrate the most straightforward ways
of calling the PCRE regular expression library from a C program. See the
pcresample documentation for a short discussion ("man pcresample" if you have 
the PCRE man pages installed).

In Unix-like environments, compile this program thuswise:

  gcc -Wall pcredemo.c -I/usr/local/include -L/usr/local/lib \
    -R/usr/local/lib -lpcre

Replace "/usr/local/include" and "/usr/local/lib" with wherever the include and
library files for PCRE are installed on your system. You don't need -I and -L
if PCRE is installed in the standard system libraries. Only some operating
systems (e.g. Solaris) use the -R option.

Building under Windows:

If you want to statically link this program against a non-dll .a file, you must
define PCRE_STATIC before including pcre.h, otherwise the pcre_malloc() and
pcre_free() exported functions will be declared __declspec(dllimport), with
unwanted results. So in this environment, uncomment the following line. */

/* #define PCRE_STATIC */

#include <stdio.h>
#include <string.h>
#include <pcre.h>

#define OVECCOUNT 30    /* should be a multiple of 3 */


int main(int argc, char **argv)
{
pcre *re;
const char *error;
char *pattern;
char *subject;
unsigned char *name_table;
int erroffset;
int find_all;
int namecount;
int name_entry_size;
int ovector[OVECCOUNT];
int subject_length;
int rc, i;


/**************************************************************************
* First, sort out the command line. There is only one possible option at  *
* the moment, "-g" to request repeated matching to find all occurrences,  *
* like Perl's /g option. We set the variable find_all to a non-zero value *
* if the -g option is present. Apart from that, there must be exactly two *
* arguments.                                                              *
**************************************************************************/

find_all = 0;
for (i = 1; i < argc; i++)
  {
  if (strcmp(argv[i], "-g") == 0) find_all = 1;
    else break;
  }

/* After the options, we require exactly two arguments, which are the pattern,
and the subject string. */

if (argc - i != 2)
  {
  printf("Two arguments required: a regex and a subject string\n");
  return 1;
  }

pattern = argv[i];
subject = argv[i+1];
subject_length = (int)strlen(subject);


/*************************************************************************
* Now we are going to compile the regular expression pattern, and handle *
* and errors that are detected.                                          *
*************************************************************************/

re = pcre_compile(
  pattern,              /* the pattern */
  0,                    /* default options */
  &error,               /* for error message */
  &erroffset,           /* for error offset */
  NULL);                /* use default character tables */

/* Compilation failed: print the error message and exit */

if (re == NULL)
  {
  printf("PCRE compilation failed at offset %d: %s\n", erroffset, error);
  return 1;
  }


/*************************************************************************
* If the compilation succeeded, we call PCRE again, in order to do a     *
* pattern match against the subject string. This does just ONE match. If *
* further matching is needed, it will be done below.                     *
*************************************************************************/

rc = pcre_exec(
  re,                   /* the compiled pattern */
  NULL,                 /* no extra data - we didn't study the pattern */
  subject,              /* the subject string */
  subject_length,       /* the length of the subject */
  0,                    /* start at offset 0 in the subject */
  0,                    /* default options */
  ovector,              /* output vector for substring information */
  OVECCOUNT);           /* number of elements in the output vector */

/* Matching failed: handle error cases */

if (rc < 0)
  {
  switch(rc)
    {
    case PCRE_ERROR_NOMATCH: printf("No match\n"); break;
    /*
    Handle other special cases if you like
    */
    default: printf("Matching error %d\n", rc); break;
    }
  pcre_free(re);     /* Release memory used for the compiled pattern */
  return 1;
  }

/* Match succeded */

printf("\nMatch succeeded at offset %d\n", ovector[0]);


/*************************************************************************
* We have found the first match within the subject string. If the output *
* vector wasn't big enough, say so. Then output any substrings that were *
* captured.                                                              *
*************************************************************************/

/* The output vector wasn't big enough */

if (rc == 0)
  {
  rc = OVECCOUNT/3;
  printf("ovector only has room for %d captured substrings\n", rc - 1);
  }

/* Show substrings stored in the output vector by number. Obviously, in a real
application you might want to do things other than print them. */

for (i = 0; i < rc; i++)
  {
  char *substring_start = subject + ovector[2*i];
  int substring_length = ovector[2*i+1] - ovector[2*i];
  printf("%2d: %.*s\n", i, substring_length, substring_start);
  }


/**************************************************************************
* That concludes the basic part of this demonstration program. We have    *
* compiled a pattern, and performed a single match. The code that follows *
* shows first how to access named substrings, and then how to code for    *
* repeated matches on the same subject.                                   *
**************************************************************************/

/* See if there are any named substrings, and if so, show them by name. First
we have to extract the count of named parentheses from the pattern. */

(void)pcre_fullinfo(
  re,                   /* the compiled pattern */
  NULL,                 /* no extra data - we didn't study the pattern */
  PCRE_INFO_NAMECOUNT,  /* number of named substrings */
  &namecount);          /* where to put the answer */

if (namecount <= 0) printf("No named substrings\n"); else
  {
  unsigned char *tabptr;
  printf("Named substrings\n");

  /* Before we can access the substrings, we must extract the table for
  translating names to numbers, and the size of each entry in the table. */

  (void)pcre_fullinfo(
    re,                       /* the compiled pattern */
    NULL,                     /* no extra data - we didn't study the pattern */
    PCRE_INFO_NAMETABLE,      /* address of the table */
    &name_table);             /* where to put the answer */

  (void)pcre_fullinfo(
    re,                       /* the compiled pattern */
    NULL,                     /* no extra data - we didn't study the pattern */
    PCRE_INFO_NAMEENTRYSIZE,  /* size of each entry in the table */
    &name_entry_size);        /* where to put the answer */

  /* Now we can scan the table and, for each entry, print the number, the name,
  and the substring itself. */

  tabptr = name_table;
  for (i = 0; i < namecount; i++)
    {
    int n = (tabptr[0] << 8) | tabptr[1];
    printf("(%d) %*s: %.*s\n", n, name_entry_size - 3, tabptr + 2,
      ovector[2*n+1] - ovector[2*n], subject + ovector[2*n]);
    tabptr += name_entry_size;
    }
  }


/*************************************************************************
* If the "-g" option was given on the command line, we want to continue  *
* to search for additional matches in the subject string, in a similar   *
* way to the /g option in Perl. This turns out to be trickier than you   *
* might think because of the possibility of matching an empty string.    *
* What happens is as follows:                                            *
*                                                                        *
* If the previous match was NOT for an empty string, we can just start   *
* the next match at the end of the previous one.                         *
*                                                                        *
* If the previous match WAS for an empty string, we can't do that, as it *
* would lead to an infinite loop. Instead, a special call of pcre_exec() *
* is made with the PCRE_NOTEMPTY and PCRE_ANCHORED flags set. The first  *
* of these tells PCRE that an empty string is not a valid match; other   *
* possibilities must be tried. The second flag restricts PCRE to one     *
* match attempt at the initial string position. If this match succeeds,  *
* an alternative to the empty string match has been found, and we can    *
* proceed round the loop.                                                *
*************************************************************************/

if (!find_all)
  {
  pcre_free(re);   /* Release the memory used for the compiled pattern */
  return 0;        /* Finish unless -g was given */
  }

/* Loop for second and subsequent matches */

for (;;)
  {
  int options = 0;                 /* Normally no options */
  int start_offset = ovector[1];   /* Start at end of previous match */

  /* If the previous match was for an empty string, we are finished if we are
  at the end of the subject. Otherwise, arrange to run another match at the
  same point to see if a non-empty match can be found. */

  if (ovector[0] == ovector[1])
    {
    if (ovector[0] == subject_length) break;
    options = PCRE_NOTEMPTY | PCRE_ANCHORED;
    }

  /* Run the next matching operation */

  rc = pcre_exec(
    re,                   /* the compiled pattern */
    NULL,                 /* no extra data - we didn't study the pattern */
    subject,              /* the subject string */
    subject_length,       /* the length of the subject */
    start_offset,         /* starting offset in the subject */
    options,              /* options */
    ovector,              /* output vector for substring information */
    OVECCOUNT);           /* number of elements in the output vector */

  /* This time, a result of NOMATCH isn't an error. If the value in "options"
  is zero, it just means we have found all possible matches, so the loop ends.
  Otherwise, it means we have failed to find a non-empty-string match at a
  point where there was a previous empty-string match. In this case, we do what
  Perl does: advance the matching position by one, and continue. We do this by
  setting the "end of previous match" offset, because that is picked up at the
  top of the loop as the point at which to start again. */

  if (rc == PCRE_ERROR_NOMATCH)
    {
    if (options == 0) break;
    ovector[1] = start_offset + 1;
    continue;    /* Go round the loop again */
    }

  /* Other matching errors are not recoverable. */

  if (rc < 0)
    {
    printf("Matching error %d\n", rc);
    pcre_free(re);    /* Release memory used for the compiled pattern */
    return 1;
    }

  /* Match succeded */

  printf("\nMatch succeeded again at offset %d\n", ovector[0]);

  /* The match succeeded, but the output vector wasn't big enough. */

  if (rc == 0)
    {
    rc = OVECCOUNT/3;
    printf("ovector only has room for %d captured substrings\n", rc - 1);
    }

  /* As before, show substrings stored in the output vector by number, and then
  also any named substrings. */

  for (i = 0; i < rc; i++)
    {
    char *substring_start = subject + ovector[2*i];
    int substring_length = ovector[2*i+1] - ovector[2*i];
    printf("%2d: %.*s\n", i, substring_length, substring_start);
    }

  if (namecount <= 0) printf("No named substrings\n"); else
    {
    unsigned char *tabptr = name_table;
    printf("Named substrings\n");
    for (i = 0; i < namecount; i++)
      {
      int n = (tabptr[0] << 8) | tabptr[1];
      printf("(%d) %*s: %.*s\n", n, name_entry_size - 3, tabptr + 2,
        ovector[2*n+1] - ovector[2*n], subject + ovector[2*n]);
      tabptr += name_entry_size;
      }
    }
  }      /* End of loop to find second and subsequent matches */

printf("\n");
pcre_free(re);       /* Release memory used for the compiled pattern */
return 0;
}

/* End of pcredemo.c */
1	nigel	63	/*************************************************
2			* PCRE DEMONSTRATION PROGRAM *
3			*************************************************/
4	nigel	53
5	nigel	63	/* This is a demonstration program to illustrate the most straightforward ways
6			of calling the PCRE regular expression library from a C program. See the
7	ph10	315	pcresample documentation for a short discussion ("man pcresample" if you have
8			the PCRE man pages installed).
9	nigel	63
10	ph10	315	In Unix-like environments, compile this program thuswise:
11
12	nigel	75	gcc -Wall pcredemo.c -I/usr/local/include -L/usr/local/lib \
13			-R/usr/local/lib -lpcre
14	nigel	63
15	nigel	75	Replace "/usr/local/include" and "/usr/local/lib" with wherever the include and
16	ph10	200	library files for PCRE are installed on your system. You don't need -I and -L
17	ph10	199	if PCRE is installed in the standard system libraries. Only some operating
18	nigel	63	systems (e.g. Solaris) use the -R option.
19	nigel	53
20	ph10	315	Building under Windows:
21	nigel	63
22	ph10	315	If you want to statically link this program against a non-dll .a file, you must
23			define PCRE_STATIC before including pcre.h, otherwise the pcre_malloc() and
24			pcre_free() exported functions will be declared __declspec(dllimport), with
25			unwanted results. So in this environment, uncomment the following line. */
26
27			/* #define PCRE_STATIC */
28
29	nigel	63	#include <stdio.h>
30			#include <string.h>
31			#include <pcre.h>
32
33	nigel	53	#define OVECCOUNT 30 /* should be a multiple of 3 */
34
35	nigel	63
36	nigel	53	int main(int argc, char **argv)
37			{
38			pcre *re;
39			const char *error;
40	nigel	63	char *pattern;
41			char *subject;
42			unsigned char *name_table;
43	nigel	53	int erroffset;
44	nigel	63	int find_all;
45			int namecount;
46			int name_entry_size;
47	nigel	53	int ovector[OVECCOUNT];
48	nigel	63	int subject_length;
49	nigel	53	int rc, i;
50
51	nigel	63
52	nigel	75	/**************************************************************************
53			* First, sort out the command line. There is only one possible option at *
54			* the moment, "-g" to request repeated matching to find all occurrences, *
55			* like Perl's /g option. We set the variable find_all to a non-zero value *
56			* if the -g option is present. Apart from that, there must be exactly two *
57			* arguments. *
58			**************************************************************************/
59	nigel	63
60			find_all = 0;
61			for (i = 1; i < argc; i++)
62	nigel	53	{
63	nigel	63	if (strcmp(argv[i], "-g") == 0) find_all = 1;
64			else break;
65			}
66
67			/* After the options, we require exactly two arguments, which are the pattern,
68			and the subject string. */
69
70			if (argc - i != 2)
71			{
72	nigel	53	printf("Two arguments required: a regex and a subject string\n");
73			return 1;
74			}
75
76	nigel	63	pattern = argv[i];
77			subject = argv[i+1];
78			subject_length = (int)strlen(subject);
79	nigel	53
80	nigel	63
81			/*************************************************************************
82			* Now we are going to compile the regular expression pattern, and handle *
83			* and errors that are detected. *
84			*************************************************************************/
85
86	nigel	53	re = pcre_compile(
87	nigel	63	pattern, /* the pattern */
88	nigel	53	0, /* default options */
89			&error, /* for error message */
90			&erroffset, /* for error offset */
91			NULL); /* use default character tables */
92
93			/* Compilation failed: print the error message and exit */
94
95			if (re == NULL)
96			{
97			printf("PCRE compilation failed at offset %d: %s\n", erroffset, error);
98			return 1;
99			}
100
101
102	nigel	63	/*************************************************************************
103			* If the compilation succeeded, we call PCRE again, in order to do a *
104	nigel	75	* pattern match against the subject string. This does just ONE match. If *
105	nigel	63	* further matching is needed, it will be done below. *
106			*************************************************************************/
107
108	nigel	53	rc = pcre_exec(
109			re, /* the compiled pattern */
110			NULL, /* no extra data - we didn't study the pattern */
111	nigel	63	subject, /* the subject string */
112			subject_length, /* the length of the subject */
113	nigel	53	0, /* start at offset 0 in the subject */
114			0, /* default options */
115			ovector, /* output vector for substring information */
116			OVECCOUNT); /* number of elements in the output vector */
117
118			/* Matching failed: handle error cases */
119
120			if (rc < 0)
121			{
122			switch(rc)
123			{
124			case PCRE_ERROR_NOMATCH: printf("No match\n"); break;
125			/*
126			Handle other special cases if you like
127			*/
128			default: printf("Matching error %d\n", rc); break;
129			}
130	nigel	91	pcre_free(re); /* Release memory used for the compiled pattern */
131	nigel	53	return 1;
132			}
133
134			/* Match succeded */
135
136	nigel	63	printf("\nMatch succeeded at offset %d\n", ovector[0]);
137	nigel	53
138	nigel	63
139			/*************************************************************************
140			* We have found the first match within the subject string. If the output *
141	ph10	315	* vector wasn't big enough, say so. Then output any substrings that were *
142			* captured. *
143	nigel	63	*************************************************************************/
144
145	nigel	53	/* The output vector wasn't big enough */
146
147			if (rc == 0)
148			{
149			rc = OVECCOUNT/3;
150			printf("ovector only has room for %d captured substrings\n", rc - 1);
151			}
152
153	nigel	63	/* Show substrings stored in the output vector by number. Obviously, in a real
154			application you might want to do things other than print them. */
155	nigel	53
156			for (i = 0; i < rc; i++)
157			{
158	nigel	63	char substring_start = subject + ovector[2i];
159	nigel	53	int substring_length = ovector[2i+1] - ovector[2i];
160			printf("%2d: %.*s\n", i, substring_length, substring_start);
161			}
162
163	nigel	63
164	nigel	75	/**************************************************************************
165			* That concludes the basic part of this demonstration program. We have *
166			* compiled a pattern, and performed a single match. The code that follows *
167	ph10	315	* shows first how to access named substrings, and then how to code for *
168	nigel	75	* repeated matches on the same subject. *
169			**************************************************************************/
170	nigel	63
171			/* See if there are any named substrings, and if so, show them by name. First
172			we have to extract the count of named parentheses from the pattern. */
173
174			(void)pcre_fullinfo(
175			re, /* the compiled pattern */
176			NULL, /* no extra data - we didn't study the pattern */
177			PCRE_INFO_NAMECOUNT, /* number of named substrings */
178			&namecount); /* where to put the answer */
179
180			if (namecount <= 0) printf("No named substrings\n"); else
181			{
182			unsigned char *tabptr;
183			printf("Named substrings\n");
184
185			/* Before we can access the substrings, we must extract the table for
186			translating names to numbers, and the size of each entry in the table. */
187
188			(void)pcre_fullinfo(
189			re, /* the compiled pattern */
190			NULL, /* no extra data - we didn't study the pattern */
191			PCRE_INFO_NAMETABLE, /* address of the table */
192			&name_table); /* where to put the answer */
193
194			(void)pcre_fullinfo(
195			re, /* the compiled pattern */
196			NULL, /* no extra data - we didn't study the pattern */
197			PCRE_INFO_NAMEENTRYSIZE, /* size of each entry in the table */
198			&name_entry_size); /* where to put the answer */
199
200			/* Now we can scan the table and, for each entry, print the number, the name,
201			and the substring itself. */
202
203			tabptr = name_table;
204			for (i = 0; i < namecount; i++)
205			{
206			int n = (tabptr[0] << 8) \| tabptr[1];
207			printf("(%d) %s: %.s\n", n, name_entry_size - 3, tabptr + 2,
208			ovector[2n+1] - ovector[2n], subject + ovector[2*n]);
209			tabptr += name_entry_size;
210			}
211			}
212
213
214			/*************************************************************************
215			* If the "-g" option was given on the command line, we want to continue *
216			* to search for additional matches in the subject string, in a similar *
217			* way to the /g option in Perl. This turns out to be trickier than you *
218			* might think because of the possibility of matching an empty string. *
219			* What happens is as follows: *
220			* *
221			* If the previous match was NOT for an empty string, we can just start *
222			* the next match at the end of the previous one. *
223			* *
224			* If the previous match WAS for an empty string, we can't do that, as it *
225			* would lead to an infinite loop. Instead, a special call of pcre_exec() *
226			* is made with the PCRE_NOTEMPTY and PCRE_ANCHORED flags set. The first *
227			* of these tells PCRE that an empty string is not a valid match; other *
228			* possibilities must be tried. The second flag restricts PCRE to one *
229			* match attempt at the initial string position. If this match succeeds, *
230			* an alternative to the empty string match has been found, and we can *
231			* proceed round the loop. *
232			*************************************************************************/
233
234	nigel	75	if (!find_all)
235			{
236	nigel	91	pcre_free(re); /* Release the memory used for the compiled pattern */
237			return 0; /* Finish unless -g was given */
238	nigel	75	}
239	nigel	63
240			/* Loop for second and subsequent matches */
241
242			for (;;)
243			{
244			int options = 0; /* Normally no options */
245			int start_offset = ovector[1]; /* Start at end of previous match */
246
247			/* If the previous match was for an empty string, we are finished if we are
248			at the end of the subject. Otherwise, arrange to run another match at the
249			same point to see if a non-empty match can be found. */
250
251			if (ovector[0] == ovector[1])
252			{
253			if (ovector[0] == subject_length) break;
254			options = PCRE_NOTEMPTY \| PCRE_ANCHORED;
255			}
256
257			/* Run the next matching operation */
258
259			rc = pcre_exec(
260			re, /* the compiled pattern */
261			NULL, /* no extra data - we didn't study the pattern */
262			subject, /* the subject string */
263			subject_length, /* the length of the subject */
264			start_offset, /* starting offset in the subject */
265			options, /* options */
266			ovector, /* output vector for substring information */
267			OVECCOUNT); /* number of elements in the output vector */
268
269			/* This time, a result of NOMATCH isn't an error. If the value in "options"
270			is zero, it just means we have found all possible matches, so the loop ends.
271			Otherwise, it means we have failed to find a non-empty-string match at a
272			point where there was a previous empty-string match. In this case, we do what
273			Perl does: advance the matching position by one, and continue. We do this by
274			setting the "end of previous match" offset, because that is picked up at the
275			top of the loop as the point at which to start again. */
276
277			if (rc == PCRE_ERROR_NOMATCH)
278			{
279			if (options == 0) break;
280			ovector[1] = start_offset + 1;
281			continue; /* Go round the loop again */
282			}
283
284			/* Other matching errors are not recoverable. */
285
286			if (rc < 0)
287			{
288			printf("Matching error %d\n", rc);
289	nigel	91	pcre_free(re); /* Release memory used for the compiled pattern */
290	nigel	63	return 1;
291			}
292
293			/* Match succeded */
294
295			printf("\nMatch succeeded again at offset %d\n", ovector[0]);
296
297			/* The match succeeded, but the output vector wasn't big enough. */
298
299			if (rc == 0)
300			{
301			rc = OVECCOUNT/3;
302			printf("ovector only has room for %d captured substrings\n", rc - 1);
303			}
304
305			/* As before, show substrings stored in the output vector by number, and then
306			also any named substrings. */
307
308			for (i = 0; i < rc; i++)
309			{
310			char substring_start = subject + ovector[2i];
311			int substring_length = ovector[2i+1] - ovector[2i];
312			printf("%2d: %.*s\n", i, substring_length, substring_start);
313			}
314
315			if (namecount <= 0) printf("No named substrings\n"); else
316			{
317			unsigned char *tabptr = name_table;
318			printf("Named substrings\n");
319			for (i = 0; i < namecount; i++)
320			{
321			int n = (tabptr[0] << 8) \| tabptr[1];
322			printf("(%d) %s: %.s\n", n, name_entry_size - 3, tabptr + 2,
323			ovector[2n+1] - ovector[2n], subject + ovector[2*n]);
324			tabptr += name_entry_size;
325			}
326			}
327			} /* End of loop to find second and subsequent matches */
328
329			printf("\n");
330	nigel	91	pcre_free(re); /* Release memory used for the compiled pattern */
331	nigel	53	return 0;
332			}
333
334	nigel	63	/* End of pcredemo.c */
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