msgpack: support datetime interval extended type

Tarantool supports datetime interval type since version 2.10.0 [1].
This patch introduced the support of Tarantool interval type in
msgpack decoders and encoders.

Tarantool datetime interval objects are decoded to `tarantool.Interval`
type. `tarantool.Interval` may be encoded to Tarantool interval
objects.

You can create `tarantool.Interval` objects either from msgpack
data or by using the same API as in Tarantool:

```
di = tarantool.Interval(year=-1, month=2, day=3,
                        hour=4, minute=-5, sec=6,
                        nsec=308543321,
                        adjust=tarantool.IntervalAdjust.NONE)
```

Its attrubutes (same as in init API) are exposed, so you can
use them if needed.

datetime, numpy and pandas tools doesn't seem to be sufficient to
cover all adjust cases supported by Tarantool.

This patch does not yet introduce the support of datetime interval
arithmetic.

1. tarantool/tarantool#5941

Part of #229

CHANGELOG.md

@@ -66,6 +66,25 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
   You may use `tz` property to get timezone name of a datetime object.
 
+- Datetime interval type support and tarantool.Interval type (#229).
+
+  Tarantool datetime interval objects are decoded to `tarantool.Interval`
+  type. `tarantool.Interval` may be encoded to Tarantool interval
+  objects.
+
+  You can create `tarantool.Interval` objects either from msgpack
+  data or by using the same API as in Tarantool:
+
+  ```python
+  di = tarantool.Interval(year=-1, month=2, day=3,
+                          hour=4, minute=-5, sec=6,
+                          nsec=308543321,
+                          adjust=tarantool.IntervalAdjust.NONE)
+  ```
+
+  Its attrubutes (same as in init API) are exposed, so you can
+  use them if needed.
+
 ### Changed
 - Bump msgpack requirement to 1.0.4 (PR #223).
   The only reason of this bump is various vulnerability fixes,

tarantool/__init__.py

@@ -36,6 +36,11 @@
     Datetime,
 )
 
+from tarantool.msgpack_ext.types.interval import (
+    Adjust as IntervalAdjust,
+    Interval,
+)
+
 __version__ = "0.9.0"
 
 
@@ -95,7 +100,7 @@ def connectmesh(addrs=({'host': 'localhost', 'port': 3301},), user=None,
 
 __all__ = ['connect', 'Connection', 'connectmesh', 'MeshConnection', 'Schema',
            'Error', 'DatabaseError', 'NetworkError', 'NetworkWarning',
-           'SchemaError', 'dbapi', 'Datetime']
+           'SchemaError', 'dbapi', 'Datetime', 'Interval', 'IntervalAdjust']
 
 # ConnectionPool is supported only for Python 3.7 or newer.
 if sys.version_info.major >= 3 and sys.version_info.minor >= 7:

tarantool/msgpack_ext/interval.py

@@ -0,0 +1,9 @@
+from tarantool.msgpack_ext.types.interval import Interval
+
+EXT_ID = 6
+
+def encode(obj):
+    return obj.msgpack_encode()
+
+def decode(data):
+    return Interval(data)

tarantool/msgpack_ext/packer.py

@@ -3,15 +3,18 @@
 from msgpack import ExtType
 
 from tarantool.msgpack_ext.types.datetime import Datetime
+from tarantool.msgpack_ext.types.interval import Interval
 
 import tarantool.msgpack_ext.decimal as ext_decimal
 import tarantool.msgpack_ext.uuid as ext_uuid
 import tarantool.msgpack_ext.datetime as ext_datetime
+import tarantool.msgpack_ext.interval as ext_interval
 
 encoders = [
     {'type': Decimal,  'ext': ext_decimal },
     {'type': UUID,     'ext': ext_uuid    },
     {'type': Datetime, 'ext': ext_datetime},
+    {'type': Interval, 'ext': ext_interval},
 ]
 
 def default(obj):

tarantool/msgpack_ext/types/interval.py

@@ -0,0 +1,149 @@
+import msgpack
+from enum import Enum
+
+from tarantool.error import MsgpackError
+
+# https://www.tarantool.io/en/doc/latest/dev_guide/internals/msgpack_extensions/#the-interval-type
+#
+# The interval MessagePack representation looks like this:
+# +--------+-------------------------+-------------+----------------+
+# | MP_EXT | Size of packed interval | MP_INTERVAL | PackedInterval |
+# +--------+-------------------------+-------------+----------------+
+# Packed interval consists of:
+# - Packed number of non-zero fields.
+# - Packed non-null fields.
+#
+# Each packed field has the following structure:
+# +----------+=====================+
+# | field ID |     field value     |
+# +----------+=====================+
+#
+# The number of defined (non-null) fields can be zero. In this case,
+# the packed interval will be encoded as integer 0.
+#
+# List of the field IDs:
+# - 0 – year
+# - 1 – month
+# - 2 – week
+# - 3 – day
+# - 4 – hour
+# - 5 – minute
+# - 6 – second
+# - 7 – nanosecond
+# - 8 – adjust
+
+id_map = {
+    0: 'year',
+    1: 'month',
+    2: 'week',
+    3: 'day',
+    4: 'hour',
+    5: 'minute',
+    6: 'sec',
+    7: 'nsec',
+    8: 'adjust',
+}
+
+# https://github.com/tarantool/c-dt/blob/cec6acebb54d9e73ea0b99c63898732abd7683a6/dt_arithmetic.h#L34
+class Adjust(Enum):
+    EXCESS = 0 # DT_EXCESS in c-dt, "excess" in Tarantool
+    NONE = 1 # DT_LIMIT in c-dt, "none" in Tarantool
+    LAST = 2 # DT_SNAP in c-dt, "last" in Tarantool
+
+class Interval():
+    def __init__(self, data=None, *, year=0, month=0, week=0,
+                 day=0, hour=0, minute=0, sec=0,
+                 nsec=0, adjust=Adjust.NONE):
+        # If msgpack data does not contain a field value, it is zero.
+        # If built not from msgpack data, set argument values later. 
+        self.year = 0
+        self.month = 0
+        self.week = 0
+        self.day = 0
+        self.hour = 0
+        self.minute = 0
+        self.sec = 0
+        self.nsec = 0
+        self.adjust = Adjust(0)
+
+        if data is not None:
+            if len(data) == 0:
+                return
+
+            # To create an unpacker is the only way to parse
+            # a sequence of values in Python msgpack module.
+            unpacker = msgpack.Unpacker()
+            unpacker.feed(data)
+            field_count = unpacker.unpack()
+            for _ in range(field_count):
+                field_id = unpacker.unpack()
+                value = unpacker.unpack()
+
+                if field_id not in id_map:
+                    raise MsgpackError(f'Unknown interval field id {field_id}')
+
+                field_name = id_map[field_id]
+
+                if field_name == 'adjust':
+                    try:
+                        value = Adjust(value)
+                    except ValueError as e:
+                        raise MsgpackError(e)
+
+                setattr(self, id_map[field_id], value)
+        else:
+            self.year = year
+            self.month = month
+            self.week = week
+            self.day = day
+            self.hour = hour
+            self.minute = minute
+            self.sec = sec
+            self.nsec = nsec
+            self.adjust = adjust
+
+    def __eq__(self, other):
+        if not isinstance(other, Interval):
+            return False
+
+        # Tarantool interval compare is naive too
+        #
+        # Tarantool 2.10.1-0-g482d91c66
+        #
+        # tarantool> datetime.interval.new{hour=1} == datetime.interval.new{min=60}
+        # ---
+        # - false
+        # ...
+
+        for field_id in id_map.keys():
+            field_name = id_map[field_id]
+            if getattr(self, field_name) != getattr(other, field_name):
+                return False
+
+        return True
+
+    def __repr__(self):
+        return f'tarantool.Interval(year={self.year}, month={self.month}, day={self.day}, ' + \
+               f'hour={self.hour}, minute={self.minute}, sec={self.sec}, ' + \
+               f'nsec={self.nsec}, adjust={self.adjust})'
+
+    __str__ = __repr__
+
+    def msgpack_encode(self):
+        buf = bytes()
+
+        count = 0
+        for field_id in id_map.keys():
+            field_name = id_map[field_id]
+            value = getattr(self, field_name)
+
+            if field_name == 'adjust':
+                value = value.value
+
+            if value != 0:
+                buf = buf + msgpack.packb(field_id) + msgpack.packb(value)
+                count = count + 1
+
+        buf = msgpack.packb(count) + buf
+
+        return buf

tarantool/msgpack_ext/unpacker.py

@@ -1,11 +1,13 @@
 import tarantool.msgpack_ext.decimal as ext_decimal
 import tarantool.msgpack_ext.uuid as ext_uuid
 import tarantool.msgpack_ext.datetime as ext_datetime
+import tarantool.msgpack_ext.interval as ext_interval
 
 decoders = {
     ext_decimal.EXT_ID : ext_decimal.decode ,
     ext_uuid.EXT_ID    : ext_uuid.decode    ,
     ext_datetime.EXT_ID: ext_datetime.decode,
+    ext_interval.EXT_ID: ext_interval.decode,
 }
 
 def ext_hook(code, data):

test/suites/__init__.py

@@ -18,13 +18,15 @@
 from .test_decimal import TestSuite_Decimal
 from .test_uuid import TestSuite_UUID
 from .test_datetime import TestSuite_Datetime
+from .test_interval import TestSuite_Interval
 
 test_cases = (TestSuite_Schema_UnicodeConnection,
               TestSuite_Schema_BinaryConnection,
               TestSuite_Request, TestSuite_Protocol, TestSuite_Reconnect,
               TestSuite_Mesh, TestSuite_Execute, TestSuite_DBAPI,
               TestSuite_Encoding, TestSuite_Pool, TestSuite_Ssl,
-              TestSuite_Decimal, TestSuite_UUID, TestSuite_Datetime)
+              TestSuite_Decimal, TestSuite_UUID, TestSuite_Datetime,
+              TestSuite_Interval)
 
 def load_tests(loader, tests, pattern):
     suite = unittest.TestSuite()