query_classifier: implemented skygw_get_canonical which returns a copy of original string with given substrings being replaced with questionmarks.

skygw_utils.cc: added string replacement function for use of skygw_get_canonical

query_classifier/query_classifier.cc

@@ -816,3 +816,45 @@ char* skygw_query_classifier_get_stmtname(
         return ((THD *)(mysql->thd))->lex->prepared_stmt_name.str;
         
 }
+
+char* skygw_get_canonical(
+        MYSQL* mysql, 
+        char*  querystr)
+{
+        THD*  thd;
+        LEX*  lex;
+        bool  found = false;
+        char* newstr;
+        
+        thd = (THD *)mysql->thd;
+        lex = thd->lex;
+        Item* item;
+        
+        for (item=thd->free_list; item != NULL; item=item->next) 
+        {
+                Item::Type itype;
+                
+                itype = item->type();
+                
+                if (itype == Item::STRING_ITEM || itype == Item::INT_ITEM)
+                {
+                        if (!found)
+                        {
+                                newstr = replace_str(querystr, 
+                                                        item->name,
+                                                        "?");
+                                found = true;
+                        }
+                        else 
+                        {
+                                char* prevstr = newstr;
+                                
+                                newstr = replace_str(prevstr, 
+                                                     item->name,
+                                                     "?");
+                                free(prevstr);
+                        }
+                }
+        } /*< for */
+        return newstr;
+}

query_classifier/query_classifier.h

@@ -60,6 +60,8 @@ skygw_query_type_t skygw_query_classifier_get_type(
 /** Free THD context and close MYSQL */
 void  skygw_query_classifier_free(MYSQL* mysql);
 char* skygw_query_classifier_get_stmtname(MYSQL* mysql);
+char* skygw_get_canonical(MYSQL* mysql, char* querystr);
+
 
 EXTERN_C_BLOCK_END
 

utils/skygw_utils.cc

@@ -23,7 +23,7 @@
 #include <errno.h>
 #include <string.h>
 #include <time.h>
-
+#include <stddef.h>
 #include "skygw_debug.h"
 #include "skygw_types.h"
 #include "skygw_utils.h"
@@ -1863,3 +1863,69 @@ void skygw_file_done(
                 free(file);
         }
 }
+
+/**
+ * Replaces in the string str all the occurrences of the source string old with 
+ * the destination string new. The lengths of the strings old and new may differ. 
+ * The string new may be of any length, but the string "old" must be of non-zero 
+ * length - the penalty for providing an empty string for the "old" parameter is 
+ * an infinite loop. In addition, none of the three parameters may be NULL.
+ * 
+ * @param       str String to be modified
+ * @param       old Substring to be replaced
+ * @param       new Replacement
+ * @return      String with replacements in new memory area or NULL if memory 
+ *              allocation failed.
+ * Dependencies:        For this function to compile, you will need to also #include 
+ * the following files: <string.h>, <stdlib.h> and <stddef.h>.
+ * 
+ * Thanks, to Laird Shaw who implemented most of this function.
+ */
+char* replace_str (
+        const char *str, 
+        const char *old, 
+        const char *replacement)
+{
+        char* ret;
+        char* r;
+        const char* p;
+        const char* q;
+        size_t oldlen;
+        size_t count;
+        size_t retlen;
+        size_t newlen;
+        
+        oldlen = strlen(old);
+        newlen = strlen(replacement);
+        
+        if (oldlen != newlen) 
+        {
+                for (count = 0, p = str; (q = strstr(p, old)) != NULL; p = q + oldlen)
+                {
+                        count++;
+                }
+                /* this is undefined if p - str > PTRDIFF_MAX */
+                retlen = p - str + strlen(p) + count * (newlen - oldlen);
+        } 
+        else
+        {
+                retlen = strlen(str);
+        }
+        if ((ret = (char *)malloc(retlen + 1)) == NULL)
+        {
+                return NULL;
+        }
+        
+        for (r = ret, p = str; (q = strstr(p, old)) != NULL; p = q + oldlen) 
+        {
+                /* this is undefined if q - p > PTRDIFF_MAX */
+                ptrdiff_t l = q - p;
+                memcpy(r, p, l);
+                r += l;
+                memcpy(r, replacement, newlen);
+                r += newlen;
+        }
+        strcpy(r, p);
+        
+        return ret;
+}

utils/skygw_utils.h

@@ -191,5 +191,7 @@ int skygw_rwlock_unlock(skygw_rwlock_t* rwlock);
 int skygw_rwlock_init(skygw_rwlock_t** rwlock);
 
 int atomic_add(int *variable, int value);
+char* replace_str(const char* str, const char* old, const char* replacement);
+
 
 #endif /* SKYGW_UTILS_H */