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Documentation update.

This commit is contained in:
Philip.Hazel 2017-12-24 10:27:13 +00:00
parent a9f7c80fa3
commit 07de1b1a9f
2 changed files with 106 additions and 0 deletions
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53
doc/html/pcre2demo.html
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@ -228,6 +228,21 @@ 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. */
@ -355,6 +370,29 @@ 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(
@ -419,6 +457,21 @@ 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. */

53
doc/pcre2demo.3
View File

@ -228,6 +228,21 @@ pcre2_match_data_create_from_pattern() above. */
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 @@ 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 \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 @@ for (;;)
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. */