Update pcre2demo with match_data block size information.

git-svn-id: svn://vcs.exim.org/pcre2/code/trunk@1139 6239d852-aaf2-0410-a92c-79f79f948069

1 files changed, 18 insertions, 12 deletions

diff --git a/src/pcre2demo.c b/src/pcre2demo.c
index 5d9b321..a49f1f8 100644
--- a/src/pcre2demo.c
+++ b/src/pcre2demo.c
@@ -87,12 +87,11 @@ uint32_t newline;
 
 PCRE2_SIZE erroroffset;
 PCRE2_SIZE *ovector;
+PCRE2_SIZE subject_length;
 
-size_t subject_length;
 pcre2_match_data *match_data;
 
 
-
 /**************************************************************************
 * First, sort out the command line. There is only one possible option at  *
 * the moment, "-g" to request repeated matching to find all occurrences,  *
@@ -121,12 +120,14 @@ if (argc - i != 2)
   return 1;
   }
 
-/* As pattern and subject are char arguments, they can be straightforwardly
-cast to PCRE2_SPTR as we are working in 8-bit code units. */
+/* Pattern and subject are char arguments, so they can be straightforwardly
+cast to PCRE2_SPTR because we are working in 8-bit code units. The subject
+length is cast to PCRE2_SIZE for completeness, though PCRE2_SIZE is in fact
+defined to be size_t. */
 
 pattern = (PCRE2_SPTR)argv[i];
 subject = (PCRE2_SPTR)argv[i+1];
-subject_length = strlen((char *)subject);
+subject_length = (PCRE2_SIZE)strlen((char *)subject);
 
 
 /*************************************************************************
@@ -155,17 +156,22 @@ if (re == NULL)
 
 
 /*************************************************************************
-* If the compilation succeeded, we call PCRE again, in order to do a     *
+* If the compilation succeeded, we call PCRE2 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. Before running the  *
-* match we must set up a match_data block for holding the result.        *
+* match we must set up a match_data block for holding the result. Using  *
+* pcre2_match_data_create_from_pattern() ensures that the block is       *
+* exactly the right size for the number of capturing parentheses in the  *
+* pattern. If you need to know the actual size of a match_data block as  *
+* a number of bytes, you can find it like this:                          *
+*                                                                        *
+* PCRE2_SIZE match_data_size = pcre2_get_match_data_size(match_data);    *
 *************************************************************************/
 
-/* Using this function ensures that the block is exactly the right size for
-the number of capturing parentheses in the pattern. */
-
 match_data = pcre2_match_data_create_from_pattern(re, NULL);
 
+/* Now run the match. */
+
 rc = pcre2_match(
   re,                   /* the compiled pattern */
   subject,              /* the subject string */
@@ -188,7 +194,7 @@ if (rc < 0)
     default: printf("Matching error %d\n", rc); break;
     }
   pcre2_match_data_free(match_data);   /* Release memory used for the match */
-  pcre2_code_free(re);                 /* data and the compiled pattern. */
+  pcre2_code_free(re);                 /*   data and the compiled pattern. */
   return 1;
   }
 
@@ -232,7 +238,7 @@ application you might want to do things other than print them. */
 for (i = 0; i < rc; i++)
   {
   PCRE2_SPTR substring_start = subject + ovector[2*i];
-  size_t substring_length = ovector[2*i+1] - ovector[2*i];
+  PCRE2_SIZE substring_length = ovector[2*i+1] - ovector[2*i];
   printf("%2d: %.*s\n", i, (int)substring_length, (char *)substring_start);
   }