Field::quote_data():

  don't call escape_string_for_mysql() unnecesary
  don't overwrite local buffer
escape_string_for_mysql():
  take a length of the destination buffer as an argument

include/my_sys.h

@@ -845,7 +845,8 @@ extern char *get_charsets_dir(char *buf);
 extern my_bool my_charset_same(CHARSET_INFO *cs1, CHARSET_INFO *cs2);
 extern my_bool init_compiled_charsets(myf flags);
 extern void add_compiled_collation(CHARSET_INFO *cs);
-extern ulong escape_string_for_mysql(CHARSET_INFO *charset_info, char *to,
+extern ulong escape_string_for_mysql(CHARSET_INFO *charset_info,
+                                     char *to, ulong to_length,
                                      const char *from, ulong length);
 
 extern void thd_increment_bytes_sent(ulong length);

libmysql/libmysql.c

@@ -1575,14 +1575,14 @@ mysql_hex_string(char *to, const char *from, ulong length)
 ulong STDCALL
 mysql_escape_string(char *to,const char *from,ulong length)
 {
-  return escape_string_for_mysql(default_charset_info, to, from, length);
+  return escape_string_for_mysql(default_charset_info, to, 0, from, length);
 }
 
 ulong STDCALL
 mysql_real_escape_string(MYSQL *mysql, char *to,const char *from,
 			 ulong length)
 {
-  return escape_string_for_mysql(mysql->charset, to, from, length);
+  return escape_string_for_mysql(mysql->charset, to, 0, from, length);
 }
 
 

mysys/charset.c

@@ -547,10 +547,10 @@ CHARSET_INFO *get_charset_by_csname(const char *cs_name,
   DBUG_PRINT("enter",("name: '%s'", cs_name));
 
   (void) init_available_charsets(MYF(0));	/* If it isn't initialized */
-  
+
   cs_number= get_charset_number(cs_name, cs_flags);
   cs= cs_number ? get_internal_charset(cs_number, flags) : NULL;
-  
+
   if (!cs && (flags & MY_WME))
   {
     char index_file[FN_REFLEN];
@@ -561,21 +561,34 @@ CHARSET_INFO *get_charset_by_csname(const char *cs_name,
   DBUG_RETURN(cs);
 }
 
-
-ulong escape_string_for_mysql(CHARSET_INFO *charset_info, char *to,
+/*
+  NOTE
+    to keep old C API, to_length may be 0 to mean "big enough"
+  RETURN
+    the length of the escaped string or ~0 if it did not fit.
+*/
+ulong escape_string_for_mysql(CHARSET_INFO *charset_info,
+                              char *to, ulong to_length,
                               const char *from, ulong length)
 {
   const char *to_start= to;
-  const char *end;
+  const char *end, *to_end=to_start + (to_length ? to_length-1 : 2*length);
+  my_bool overflow=0;
 #ifdef USE_MB
   my_bool use_mb_flag= use_mb(charset_info);
 #endif
-  for (end= from + length; from != end; from++)
+  for (end= from + length; from < end; from++)
   {
+    char escape=0;
 #ifdef USE_MB
     int l;
     if (use_mb_flag && (l= my_ismbchar(charset_info, from, end)))
     {
+      if (to + l >= to_end)
+      {
+        overflow=1;
+        break;
+      }
       while (l--)
 	*to++= *from++;
       from--;
@@ -593,45 +606,53 @@ ulong escape_string_for_mysql(CHARSET_INFO *charset_info, char *to,
      a valid GBK character, but 0xbf5c is. (0x27 = ', 0x5c = \)
     */
     if (use_mb_flag && (l= my_mbcharlen(charset_info, *from)) > 1)
-    {
-      *to++= '\\';
-      *to++= *from;
-      continue;
-    }
+      escape= *from;
+    else
 #endif
     switch (*from) {
     case 0:				/* Must be escaped for 'mysql' */
-      *to++= '\\';
-      *to++= '0';
+      escape= '0';
       break;
     case '\n':				/* Must be escaped for logs */
-      *to++= '\\';
-      *to++= 'n';
+      escape= 'n';
       break;
     case '\r':
-      *to++= '\\';
-      *to++= 'r';
+      escape= 'r';
       break;
     case '\\':
-      *to++= '\\';
-      *to++= '\\';
+      escape= '\\';
       break;
     case '\'':
-      *to++= '\\';
-      *to++= '\'';
+      escape= '\'';
       break;
     case '"':				/* Better safe than sorry */
-      *to++= '\\';
-      *to++= '"';
+      escape= '"';
       break;
     case '\032':			/* This gives problems on Win32 */
-      *to++= '\\';
-      *to++= 'Z';
+      escape= 'Z';
       break;
-    default:
+    }
+    if (escape)
+    {
+      if (to + 2 >= to_end)
+      {
+        overflow=1;
+        break;
+      }
+      *to++= '\\';
+      *to++= escape;
+    }
+    else
+    {
+      if (to + 1 >= to_end)
+      {
+        overflow=1;
+        break;
+      }
       *to++= *from;
     }
   }
   *to= 0;
-  return (ulong) (to - to_start);
+  return overflow ? (ulong)~0 : (ulong) (to - to_start);
 }
+

sql/field.cc

@@ -752,25 +752,22 @@ bool Field::quote_data(String *unquoted_string)
 {
   char escaped_string[IO_SIZE];
   char *unquoted_string_buffer= (char *)(unquoted_string->ptr());
-  uint need_quotes;
   DBUG_ENTER("Field::quote_data");
 
-  // this is the same call that mysql_real_escape_string() calls
-  escape_string_for_mysql(&my_charset_bin, (char *)escaped_string,
-    unquoted_string->ptr(), unquoted_string->length());
-
-  need_quotes= needs_quotes();
-
-  if (need_quotes == 0)
+  if (!needs_quotes())
     DBUG_RETURN(0);
 
+  // this is the same call that mysql_real_escape_string() calls
+  if (escape_string_for_mysql(&my_charset_bin, (char *)escaped_string,
+                              sizeof(escaped_string), unquoted_string->ptr(),
+                              unquoted_string->length()) == (ulong)~0)
+    DBUG_RETURN(1);
+
   // reset string, then re-append with quotes and escaped values
   unquoted_string->length(0);
-  if (unquoted_string->append('\''))
-    DBUG_RETURN(1);
-  if (unquoted_string->append((char *)escaped_string))
-    DBUG_RETURN(1);
-  if (unquoted_string->append('\''))
+  if (unquoted_string->append('\'') ||
+      unquoted_string->append((char *)escaped_string) ||
+      unquoted_string->append('\''))
     DBUG_RETURN(1);
   DBUG_RETURN(0);
 }

sql/item.cc

@@ -2038,7 +2038,7 @@ const String *Item_param::query_val_str(String* str) const
       buf= str->c_ptr_quick();
       ptr= buf;
       *ptr++= '\'';
-      ptr+= escape_string_for_mysql(str_value.charset(), ptr,
+      ptr+= escape_string_for_mysql(str_value.charset(), ptr, 0,
                                     str_value.ptr(), str_value.length());
       *ptr++= '\'';
       str->length(ptr - buf);

sql/sql_prepare.cc

@@ -865,7 +865,7 @@ static bool insert_params_from_vars_with_log(Prepared_statement *stmt,
     *ptr++= '\'';
     ptr+=
       escape_string_for_mysql(&my_charset_utf8_general_ci,
-                              ptr, entry->name.str, entry->name.length);
+                              ptr, 0, entry->name.str, entry->name.length);
     *ptr++= '\'';
     str.length(ptr - buf);