1. Назаров Михаил Викторович. 612.

src/part1/constants.py

@@ -19,20 +19,16 @@
 # Все константы, зависящие от ёмкостей *_BITS, должны вычисляться из них.
 
 # Twitter's original Snowflake epoch: 2010-11-04 01:42:54.657 UTC.
-EPOCH_MS_DEFAULT: Final[int] = 0
-
-# Node identifier used when the caller does not supply one.
-NODE_ID_DEFAULT: Final[int] = 0
-
-# Width of each field, in bits.
-TIMESTAMP_BITS: Final[int] = 0
-NODE_ID_BITS: Final[int] = 0
-SEQUENCE_ID_BITS: Final[int] = 0
-
-# Largest value each field can hold.
-TIMESTAMP_MS_MAX: Final[int] = 0
-NODE_ID_MAX: Final[int] = 0
-SEQUENCE_ID_MAX: Final[int] = 0
+EPOCH_MS_DEFAULT: Final[int] = 1288834974657
+NODE_ID_DEFAULT: Final[int] = 1
+TIMESTAMP_BITS: Final[int] = 41
+NODE_ID_BITS: Final[int] = 10
+SEQUENCE_ID_BITS: Final[int] = 12
+TIMESTAMP_MS_MAX: Final[int] = (1 << TIMESTAMP_BITS) - 1
+NODE_ID_MAX: Final[int] = (1 << NODE_ID_BITS) - 1
+SEQUENCE_ID_MAX: Final[int] = (1 << SEQUENCE_ID_BITS) - 1
+NODE_ID_SHIFT: Final[int] = SEQUENCE_ID_BITS
+TIMESTAMP_SHIFT: Final[int] = SEQUENCE_ID_BITS + NODE_ID_BITS
 
 # Здесь можно добавить собственные вспомогательные константы
 # (например, сдвиги полей при сборке идентификатора).

src/part1/snowflake.py

@@ -1,114 +1,58 @@
-"""Twitter Snowflake identifier generator.
+import time
 
-Snowflake produces roughly time-ordered 64-bit integer identifiers without
-coordination between nodes. Each identifier packs the milliseconds elapsed
-since a custom epoch, a node identifier and a per-millisecond sequence counter
-into a single 63-bit positive integer (see ``constants`` for the layout).
-
-The public entry point is :func:`generate_snowflake_id`. It is stateless: the
-caller passes the sequence counter on every call and is responsible for
-advancing it within a millisecond and resetting it when the clock ticks over.
-
-Each packed field can be read back on its own with :func:`decode_timestamp_ms`,
-:func:`decode_node_id` and :func:`decode_sequence_id`.
-"""
-
-import time  # noqa: F401
-
-from .constants import (  # noqa: F401
+from .constants import (
     EPOCH_MS_DEFAULT,
     NODE_ID_DEFAULT,
     NODE_ID_MAX,
+    NODE_ID_SHIFT,
     SEQUENCE_ID_MAX,
+    TIMESTAMP_BITS,
     TIMESTAMP_MS_MAX,
+    TIMESTAMP_SHIFT,
 )
 
 
 def read_current_millis(epoch_ms: int) -> int:
-    """Read the number of milliseconds elapsed since the custom epoch.
-
-    Args:
-        epoch_ms: The custom epoch expressed as Unix milliseconds.
-
-    Returns:
-        The count of whole milliseconds between ``epoch_ms`` and now. May be
-        negative if ``epoch_ms`` lies in the future.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    current_ms = int(time.time() * 1000)
+    return current_ms - epoch_ms
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
-    """Read the timestamp field out of a Snowflake identifier.
-
-    Args:
-        snowflake_id: An identifier produced against the same epoch.
-        epoch_ms: The epoch the identifier was generated against. Defaults to
-            the original Twitter epoch (2010-11-04 01:42:54.657 UTC).
-
-    Returns:
-        The absolute Unix time in milliseconds at which the identifier was
-        generated.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    timestamp_part = snowflake_id >> TIMESTAMP_SHIFT
+    return timestamp_part + epoch_ms
 
 
 def decode_node_id(snowflake_id: int) -> int:
-    """Read the node identifier field out of a Snowflake identifier.
-
-    Args:
-        snowflake_id: An identifier produced by :func:`generate_snowflake_id`.
-
-    Returns:
-        The node identifier packed into ``snowflake_id``, in the range
-        ``[0, NODE_ID_MAX]``.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    return (snowflake_id >> NODE_ID_SHIFT) & NODE_ID_MAX
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
-    """Read the sequence counter field out of a Snowflake identifier.
-
-    Args:
-        snowflake_id: An identifier produced by :func:`generate_snowflake_id`.
-
-    Returns:
-        The per-millisecond sequence counter packed into ``snowflake_id``, in
-        the range ``[0, SEQUENCE_ID_MAX]``.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    return snowflake_id & SEQUENCE_ID_MAX
 
 
 def generate_snowflake_id(
     sequence_id: int,
     node_id: int = NODE_ID_DEFAULT,
     epoch_ms: int = EPOCH_MS_DEFAULT,
 ) -> int | None:
-    """Build and return a Snowflake identifier for the current millisecond.
-
-    The function is stateless: the caller passes the per-millisecond sequence
-    counter explicitly. It is the caller's responsibility to increment
-    ``sequence_id`` for identifiers minted within the same millisecond and to
-    reset it once the clock advances.
-
-    Args:
-        sequence_id: The per-millisecond sequence counter, in the range
-            ``[0, SEQUENCE_ID_MAX]``.
-        node_id: The identifier of this node, in the range ``[0, NODE_ID_MAX]``.
-            Optional; defaults to ``NODE_ID_DEFAULT``.
-        epoch_ms: The start of the epoch as Unix milliseconds. Optional;
-            defaults to the original Twitter epoch (2010-11-04 01:42:54.657
-            UTC).
-
-    Returns:
-        The Snowflake identifier as a positive 63-bit integer, or ``None`` if
-        ``node_id`` is outside ``[0, NODE_ID_MAX]``, ``sequence_id`` is outside
-        ``[0, SEQUENCE_ID_MAX]``, or the elapsed time no longer fits in the
-        timestamp field (roughly 69 years after ``epoch_ms``). In each of those
-        cases an explanatory message is printed to stdout first.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    if not (0 <= node_id <= NODE_ID_MAX):
+        print(f"node_id must be in [0, {NODE_ID_MAX}], got {node_id}")
+        return None
+
+    if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
+        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}], got {sequence_id}")
+        return None
+
+    timestamp_ms = read_current_millis(epoch_ms)
+    if timestamp_ms > TIMESTAMP_MS_MAX:
+        print(
+            f"Timestamp overflows {TIMESTAMP_BITS} bits:"
+            f"{timestamp_ms} > {TIMESTAMP_MS_MAX}"
+        )
+        return None
+
+    snowflake_id = (
+        (timestamp_ms << TIMESTAMP_SHIFT) | (node_id << NODE_ID_SHIFT) | sequence_id
+    )
+
+    return snowflake_id