Revision: 895
http://www.exim.org/viewvc/pcre2?view=rev&revision=895
Author: ph10
Date: 2017-12-24 10:27:13 +0000 (Sun, 24 Dec 2017)
Log Message:
-----------
Documentation update.
Modified Paths:
--------------
code/trunk/doc/html/pcre2demo.html
code/trunk/doc/pcre2demo.3
Modified: code/trunk/doc/html/pcre2demo.html
===================================================================
--- code/trunk/doc/html/pcre2demo.html 2017-12-23 17:15:51 UTC (rev 894)
+++ code/trunk/doc/html/pcre2demo.html 2017-12-24 10:27:13 UTC (rev 895)
@@ -228,6 +228,21 @@
if (rc == 0)
printf("ovector was not big enough for all the captured substrings\n");
+/* We must guard against patterns such as /(?=.\K)/ that use \K in an assertion
+to set the start of a match later than its end. In this demonstration program,
+we just detect this case and give up. */
+
+if (ovector[0] > ovector[1])
+ {
+ printf("\\K was used in an assertion to set the match start after its end.\n"
+ "From end to start the match was: %.*s\n", (int)(ovector[0] - ovector[1]),
+ (char *)(subject + ovector[1]));
+ printf("Run abandoned\n");
+ pcre2_match_data_free(match_data);
+ pcre2_code_free(re);
+ return 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. */
@@ -355,6 +370,29 @@
options = PCRE2_NOTEMPTY_ATSTART | PCRE2_ANCHORED;
}
+ /* If the previous match was not an empty string, there is one tricky case to
+ consider. If a pattern contains \K within a lookbehind assertion at the
+ start, the end of the matched string can be at the offset where the match
+ started. Without special action, this leads to a loop that keeps on matching
+ the same substring. We must detect this case and arrange to move the start on
+ by one character. The pcre2_get_startchar() function returns the starting
+ offset that was passed to pcre2_match(). */
+
+ else
+ {
+ PCRE2_SIZE startchar = pcre2_get_startchar(match_data);
+ if (start_offset <= startchar)
+ {
+ if (startchar >= subject_length) break; /* Reached end of subject. */
+ start_offset = startchar + 1; /* Advance by one character. */
+ if (utf8) /* If UTF-8, it may be more */
+ { /* than one code unit. */
+ for (; start_offset < subject_length; start_offset++)
+ if ((subject[start_offset] & 0xc0) != 0x80) break;
+ }
+ }
+ }
+
/* Run the next matching operation */
rc = pcre2_match(
@@ -419,6 +457,21 @@
if (rc == 0)
printf("ovector was not big enough for all the captured substrings\n");
+ /* We must guard against patterns such as /(?=.\K)/ that use \K in an
+ assertion to set the start of a match later than its end. In this
+ demonstration program, we just detect this case and give up. */
+
+ if (ovector[0] > ovector[1])
+ {
+ printf("\\K was used in an assertion to set the match start after its end.\n"
+ "From end to start the match was: %.*s\n", (int)(ovector[0] - ovector[1]),
+ (char *)(subject + ovector[1]));
+ printf("Run abandoned\n");
+ pcre2_match_data_free(match_data);
+ pcre2_code_free(re);
+ return 1;
+ }
+
/* As before, show substrings stored in the output vector by number, and then
also any named substrings. */
Modified: code/trunk/doc/pcre2demo.3
===================================================================
--- code/trunk/doc/pcre2demo.3 2017-12-23 17:15:51 UTC (rev 894)
+++ code/trunk/doc/pcre2demo.3 2017-12-24 10:27:13 UTC (rev 895)
@@ -228,6 +228,21 @@
if (rc == 0)
printf("ovector was not big enough for all the captured substrings\en");
+/* We must guard against patterns such as /(?=.\eK)/ that use \eK in an assertion
+to set the start of a match later than its end. In this demonstration program,
+we just detect this case and give up. */
+
+if (ovector[0] > ovector[1])
+ {
+ printf("\e\eK was used in an assertion to set the match start after its end.\en"
+ "From end to start the match was: %.*s\en", (int)(ovector[0] - ovector[1]),
+ (char *)(subject + ovector[1]));
+ printf("Run abandoned\en");
+ pcre2_match_data_free(match_data);
+ pcre2_code_free(re);
+ return 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. */
@@ -355,6 +370,29 @@
options = PCRE2_NOTEMPTY_ATSTART | PCRE2_ANCHORED;
}
+ /* If the previous match was not an empty string, there is one tricky case to
+ consider. If a pattern contains \eK within a lookbehind assertion at the
+ start, the end of the matched string can be at the offset where the match
+ started. Without special action, this leads to a loop that keeps on matching
+ the same substring. We must detect this case and arrange to move the start on
+ by one character. The pcre2_get_startchar() function returns the starting
+ offset that was passed to pcre2_match(). */
+
+ else
+ {
+ PCRE2_SIZE startchar = pcre2_get_startchar(match_data);
+ if (start_offset <= startchar)
+ {
+ if (startchar >= subject_length) break; /* Reached end of subject. */
+ start_offset = startchar + 1; /* Advance by one character. */
+ if (utf8) /* If UTF-8, it may be more */
+ { /* than one code unit. */
+ for (; start_offset < subject_length; start_offset++)
+ if ((subject[start_offset] & 0xc0) != 0x80) break;
+ }
+ }
+ }
+
/* Run the next matching operation */
rc = pcre2_match(
@@ -419,6 +457,21 @@
if (rc == 0)
printf("ovector was not big enough for all the captured substrings\en");
+ /* We must guard against patterns such as /(?=.\eK)/ that use \eK in an
+ assertion to set the start of a match later than its end. In this
+ demonstration program, we just detect this case and give up. */
+
+ if (ovector[0] > ovector[1])
+ {
+ printf("\e\eK was used in an assertion to set the match start after its end.\en"
+ "From end to start the match was: %.*s\en", (int)(ovector[0] - ovector[1]),
+ (char *)(subject + ovector[1]));
+ printf("Run abandoned\en");
+ pcre2_match_data_free(match_data);
+ pcre2_code_free(re);
+ return 1;
+ }
+
/* As before, show substrings stored in the output vector by number, and then
also any named substrings. */
