MXS-1216: Fix DATETIME(n) value interpretation

The DATETIME(n) values generated by a MariaDB 10.0 server were not
interpreted correctly as the wrong algorithm was used to extract the
values.

DATETIME(0) values still do not work properly and they require further
debugging and changes to the code.

server/core/mysql_binlog.c

@@ -26,6 +26,10 @@
 #include <strings.h>
 #include <math.h>
 
+#include "mysql_client_server_protocol.h"
+
+static uint64_t unpack_bytes(uint8_t *ptr, size_t bytes);
+
 /**
  * @brief Convert a table column type to a string
  *
@@ -217,6 +221,35 @@ static void unpack_year(uint8_t *ptr, struct tm *dest)
     dest->tm_year = *ptr;
 }
 
+/** Base-10 logarithm values */
+int64_t log_10_values[] =
+{
+    1,
+    10,
+    100,
+    1000,
+    10000,
+    100000,
+    1000000,
+    10000000,
+    100000000
+};
+
+/**
+ * If the TABLE_COL_TYPE_DATETIME type field is declared as a datetime with
+ * extra precision, the packed length is shorter than 8 bytes.
+ */
+size_t datetime_sizes[] =
+{
+    5, // DATETIME(0)
+    6, // DATETIME(1)
+    6, // DATETIME(2)
+    7, // DATETIME(3)
+    7, // DATETIME(4)
+    7, // DATETIME(5)
+    8  // DATETIME(6)
+};
+
 /**
  * @brief Unpack a DATETIME
  *
@@ -225,21 +258,52 @@ static void unpack_year(uint8_t *ptr, struct tm *dest)
  * @param val Value read from the binary log
  * @param dest Pointer where the unpacked value is stored
  */
-static void unpack_datetime(uint8_t *ptr, struct tm *dest)
+static void unpack_datetime(uint8_t *ptr, int length, struct tm *dest)
 {
-    uint64_t val = 0;
-    memcpy(&val, ptr, sizeof(val));
-    uint32_t second = val - ((val / 100) * 100);
-    val /= 100;
-    uint32_t minute = val - ((val / 100) * 100);
-    val /= 100;
-    uint32_t hour = val - ((val / 100) * 100);
-    val /= 100;
-    uint32_t day = val - ((val / 100) * 100);
-    val /= 100;
-    uint32_t month = val - ((val / 100) * 100);
-    val /= 100;
-    uint32_t year = val;
+    int64_t val = 0;
+    uint32_t second, minute, hour, day, month, year;
+
+    if (length == -1)
+    {
+        val = gw_mysql_get_byte8(ptr);
+        second = val - ((val / 100) * 100);
+        val /= 100;
+        minute = val - ((val / 100) * 100);
+        val /= 100;
+        hour = val - ((val / 100) * 100);
+        val /= 100;
+        day = val - ((val / 100) * 100);
+        val /= 100;
+        month = val - ((val / 100) * 100);
+        val /= 100;
+        year = val;
+    }
+    else
+    {
+        // TODO: Figure out why DATETIME(0) doesn't work like it others do
+        val = unpack_bytes(ptr, datetime_sizes[length]);
+        val *= log_10_values[6 - length];
+
+        if (val < 0)
+        {
+            val = -val;
+        }
+
+        int subsecond = val % 1000000;
+        val /= 1000000;
+
+        second = val % 60;
+        val /= 60;
+        minute = val % 60;
+        val /= 60;
+        hour = val % 24;
+        val /= 24;
+        day = val % 32;
+        val /= 32;
+        month = val % 13;
+        val /= 13;
+        year = val;
+    }
 
     memset(dest, 0, sizeof(struct tm));
     dest->tm_year = year - 1900;
@@ -392,21 +456,6 @@ size_t unpack_bit(uint8_t *ptr, uint8_t *null_mask, uint32_t col_count,
     return metadata[1];
 }
 
-/**
- * If the TABLE_COL_TYPE_DATETIME type field is declared as a datetime with
- * extra precision, the packed length is shorter than 8 bytes.
- */
-size_t datetime_sizes[] =
-{
-    5, // DATETIME(0)
-    6, // DATETIME(1)
-    6, // DATETIME(2)
-    7, // DATETIME(3)
-    7, // DATETIME(4)
-    7, // DATETIME(5)
-    8  // DATETIME(6)
-};
-
 /**
  * @brief Get the length of a temporal field
  * @param type Field type
@@ -465,7 +514,7 @@ size_t unpack_temporal_value(uint8_t type, uint8_t *ptr, uint8_t *metadata, int
             break;
 
         case TABLE_COL_TYPE_DATETIME:
-            unpack_datetime(ptr, tm);
+            unpack_datetime(ptr, length, tm);
             break;
 
         case TABLE_COL_TYPE_DATETIME2: