MXS-852: Add PS response and command extraction functions

The mxs_mysql_extract_ps_response function extracts the binary protocol
prepared statement components and stores them in a common structure.

The mxs_mysql_get_command extracts the command byte from a GWBUF object
containing a complete MySQL packet.

include/maxscale/protocol/mysql.h

@@ -84,9 +84,13 @@ MXS_BEGIN_DECLS
  * [10-11] warning_count (2) -- number of warnings
  */
 #define MYSQL_PS_ID_OFFSET     MYSQL_HEADER_LEN + 1
+#define MYSQL_PS_ID_SIZE       4
 #define MYSQL_PS_COLS_OFFSET   MYSQL_HEADER_LEN + 5
+#define MYSQL_PS_COLS_SIZE     2
 #define MYSQL_PS_PARAMS_OFFSET MYSQL_HEADER_LEN + 7
+#define MYSQL_PS_PARAMS_SIZE   2
 #define MYSQL_PS_WARN_OFFSET   MYSQL_HEADER_LEN + 10
+#define MYSQL_PS_WARN_SIZE     2
 
 /** Name of the default server side authentication plugin */
 #define DEFAULT_MYSQL_AUTH_PLUGIN "mysql_native_password"
@@ -308,6 +312,14 @@ typedef struct
 #endif
 } MySQLProtocol;
 
+typedef struct
+{
+    uint32_t id;
+    uint16_t columns;
+    uint16_t parameters;
+    uint16_t warnings;
+} MXS_PS_RESPONSE;
+
 /** Defines for response codes */
 #define MYSQL_REPLY_ERR               0xff
 #define MYSQL_REPLY_OK                0x00
@@ -504,4 +516,24 @@ const char* mxs_mysql_get_current_db(MXS_SESSION* session);
  */
 void mxs_mysql_set_current_db(MXS_SESSION* session, const char* db);
 
+/**
+ * @brief Get the command byte
+ *
+ * @param buffer Buffer containing a complete MySQL packet
+ *
+ * @return The command byte
+ */
+uint8_t mxs_mysql_get_command(GWBUF* buffer);
+
+/**
+ * @brief Extract PS response values
+ *
+ * @param buffer Buffer containing a complete response to a binary protocol
+ *               preparation of a prepared statement
+ * @param out    Destination where the values are extracted
+ *
+ * @return True if values were extracted successfully
+ */
+bool mxs_mysql_extract_ps_response(GWBUF* buffer, MXS_PS_RESPONSE* out);
+
 MXS_END_DECLS

server/modules/protocol/MySQL/MySQLBackend/mysql_backend.c

@@ -629,16 +629,19 @@ static inline bool expecting_ps_response(MySQLProtocol *proto)
 static inline bool complete_ps_response(GWBUF *buffer)
 {
     ss_dassert(GWBUF_IS_CONTIGUOUS(buffer));
-    uint16_t cols = gw_mysql_get_byte2(GWBUF_DATA(buffer) + MYSQL_PS_COLS_OFFSET);
-    uint16_t params = gw_mysql_get_byte2(GWBUF_DATA(buffer) + MYSQL_PS_PARAMS_OFFSET);
+    MXS_PS_RESPONSE resp;
+    bool rval = false;
+
+    if (mxs_mysql_extract_ps_response(buffer, &resp))
+    {
         int expected_eof = 0;
 
-    if (cols > 0)
+        if (resp.columns > 0)
         {
             expected_eof++;
         }
 
-    if (params > 0)
+        if (resp.parameters > 0)
         {
             expected_eof++;
         }
@@ -648,7 +651,10 @@ static inline bool complete_ps_response(GWBUF *buffer)
 
         MXS_DEBUG("Expecting %u EOF, have %u", n_eof, expected_eof);
 
-    return n_eof == expected_eof;
+        rval = n_eof == expected_eof;
+    }
+
+    return rval;
 }
 
 static inline bool collecting_resultset(MySQLProtocol *proto, uint64_t capabilities)

server/modules/protocol/MySQL/mysql_common.c

@@ -1599,3 +1599,40 @@ void mxs_mysql_set_current_db(MXS_SESSION* session, const char* db)
     MYSQL_session* data = (MYSQL_session*)session->client_dcb->data;
     snprintf(data->db, sizeof(data->db), "%s", db);
 }
+
+uint8_t mxs_mysql_get_command(GWBUF* buffer)
+{
+    if (GWBUF_LENGTH(buffer) > MYSQL_HEADER_LEN)
+    {
+        return GWBUF_DATA(buffer)[4];
+    }
+    else
+    {
+        uint8_t command = 0;
+        gwbuf_copy_data(buffer, MYSQL_HEADER_LEN, 1, &command);
+        return command;
+    }
+}
+
+bool mxs_mysql_extract_ps_response(GWBUF* buffer, MXS_PS_RESPONSE* out)
+{
+    bool rval = false;
+    uint8_t id[MYSQL_PS_ID_SIZE];
+    uint8_t cols[MYSQL_PS_ID_SIZE];
+    uint8_t params[MYSQL_PS_ID_SIZE];
+    uint8_t warnings[MYSQL_PS_WARN_SIZE];
+
+    if (gwbuf_copy_data(buffer, MYSQL_PS_ID_OFFSET, sizeof(id), id) == sizeof(id) &&
+        gwbuf_copy_data(buffer, MYSQL_PS_COLS_OFFSET, sizeof(cols), cols) == sizeof(cols) &&
+        gwbuf_copy_data(buffer, MYSQL_PS_PARAMS_OFFSET, sizeof(params), params) == sizeof(params) &&
+        gwbuf_copy_data(buffer, MYSQL_PS_WARN_OFFSET, sizeof(warnings), warnings) == sizeof(warnings))
+    {
+        out->id = gw_mysql_get_byte4(id);
+        out->columns = gw_mysql_get_byte2(cols);
+        out->parameters = gw_mysql_get_byte2(params);
+        out->warnings = gw_mysql_get_byte2(warnings);
+        rval = true;
+    }
+
+    return rval;
+}