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Update pcre2demo to deal with various \K inside assertion anomalies.

This commit is contained in:
Philip.Hazel 2017-12-23 17:15:51 +00:00
parent 94d5f4a050
commit a9f7c80fa3
2 changed files with 58 additions and 0 deletions
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5
ChangeLog
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@ -95,6 +95,11 @@ not by JIT or pcre2_dfa_match(). Their settings are shown in pcre2test callouts
if the callout_extra subject modifier is set. These bits are provided to help
with tracking how a backtracking match is proceeding.
23. Updated the pcre2demo.c demonstration program, which was missing the extra
code for -g that handles the case when \K in an assertion causes the match to
end at the original start point. Also arranged for it to detect when \K causes
the end of a match to be before its start.
Version 10.30 14-August-2017
----------------------------

53
src/pcre2demo.c
View File

@ -211,6 +211,21 @@ pcre2_match_data_create_from_pattern() above. */
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. */
@ -338,6 +353,29 @@ for (;;)
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(
@ -402,6 +440,21 @@ for (;;)
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. */