MDEV-20844 RBR from binary(16) to inet6 fails with error 171: The event was corrupt, leading to illegal data being read

This patch changes the way how INET6 is packed to the RBR binary log:
- from fixed length 16 bytes
- to BINARY(16) compatible variable length style
  with trailing 0x00 byte compression.

This is to make INET6 fully compatible with BINARY(16) in RBR binary logs,
so RBR replication works in this scenarios:

- Old master BINARY(16) -> New slave INET6
- New master INET6      -> Old slave BINARY(16)

A new class StringPack was added to share the code between
Field_string and Field_inet6.

1 files changed, 48 insertions, 0 deletions

diff --git a/sql/sql_type_string.h b/sql/sql_type_string.h
new file mode 100644
index 00000000000..fca46e91394
--- /dev/null
+++ b/sql/sql_type_string.h
@@ -0,0 +1,48 @@
+/* Copyright (c) 2019 MariaDB
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA */
+
+#ifndef SQL_TYPE_STRING_INCLUDED
+#define SQL_TYPE_STRING_INCLUDED
+
+class StringPack
+{
+  CHARSET_INFO *m_cs;
+  uint32 m_octet_length;
+  CHARSET_INFO *charset() const { return m_cs; }
+  uint mbmaxlen() const { return m_cs->mbmaxlen; };
+  uint32 char_length() const { return m_octet_length / mbmaxlen(); }
+public:
+  StringPack(CHARSET_INFO *cs, uint32 octet_length)
+   :m_cs(cs),
+    m_octet_length(octet_length)
+  { }
+  uchar *pack(uchar *to, const uchar *from, uint max_length) const;
+  const uchar *unpack(uchar *to, const uchar *from, const uchar *from_end,
+                      uint param_data) const;
+public:
+  static uint max_packed_col_length(uint max_length)
+  {
+    return (max_length > 255 ? 2 : 1) + max_length;
+  }
+  static uint packed_col_length(const uchar *data_ptr, uint length)
+  {
+    if (length > 255)
+      return uint2korr(data_ptr)+2;
+    return (uint) *data_ptr + 1;
+  }
+};
+
+
+#endif // SQL_TYPE_STRING_INCLUDED