Add example for sqlite3 extension

example/extension/sqlite3_mod_regexp.c

@@ -0,0 +1,27 @@
+#include <regex.h>
+#include <string.h>
+#include <stdio.h>
+#include <sqlite3ext.h>
+
+SQLITE_EXTENSION_INIT1
+static void regexp_func(sqlite3_context *context, int argc, sqlite3_value **argv) {
+  if (argc >= 2) {
+    const char *target  = (const char *)sqlite3_value_text(argv[1]);
+    const char *pattern = (const char *)sqlite3_value_text(argv[0]);
+    const char* errstr = NULL;
+    int erroff = 0;
+    int vec[500];
+    int n, rc;
+    pcre* re = pcre_compile(pattern, 0, &errstr, &erroff, NULL);
+    rc = pcre_exec(re, NULL, target, strlen(target), 0, 0, vec, 500); 
+    if (rc <= 0) {
+      sqlite3_result_error(context, errstr, 0);
+      return;
+    }
+    sqlite3_result_int(context, 1);
+  }
+}
+__declspec(dllexport) int sqlite3_extension_init(sqlite3 *db, char **errmsg, const sqlite3_api_routines *api) {
+  SQLITE_EXTENSION_INIT2(api);
+  return sqlite3_create_function(db, "regexp", 2, SQLITE_UTF8, (void*)db, regexp_func, NULL, NULL);
+}