1.Курников Иван Андреевич.612

src/part1/constants.py

@@ -1,38 +1,18 @@
-"""Bit layout and default epoch for the Twitter Snowflake ID generator.
+def my_max_value(n: int) -> int:
+    return int(2**n - 1)
 
-A Snowflake identifier is a 63-bit positive integer packed as follows, from
-the most significant bit downwards:
 
-    1 bit   unused sign bit, always zero
-    41 bits milliseconds elapsed since a custom epoch
-    10 bits node identifier
-    12 bits per-millisecond sequence counter
+EPOCH_MS_DEFAULT = 1288834974657
+NODE_ID_DEFAULT = 1
 
-The shift and mask constants should be derived from the bit widths so that
-changing a width keeps everything else consistent.
-"""
 
-from typing import Final
+TIMESTAMP_BITS = 41  # число миллисекунд прощедщих с момента пользовательской эпохи
+NODE_ID_BITS = 10  # номер узла
+SEQUENCE_ID_BITS = 12  # порядковый номер
 
+TIMESTAMP_SHIFT = NODE_ID_BITS + SEQUENCE_ID_BITS
 
-# TODO: замените заглушки (0) на корректные значения, см. TASK.md.
-# 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
-
-# Здесь можно добавить собственные вспомогательные константы
-# (например, сдвиги полей при сборке идентификатора).
+# так как номер и время(все три строчки) беззнаковые
+TIMESTAMP_MS_MAX = my_max_value(TIMESTAMP_BITS)
+NODE_ID_MAX = my_max_value(NODE_ID_BITS)
+SEQUENCE_ID_MAX = my_max_value(SEQUENCE_ID_BITS)

src/part1/snowflake.py

@@ -1,114 +1,46 @@
-"""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
-    EPOCH_MS_DEFAULT,
-    NODE_ID_DEFAULT,
-    NODE_ID_MAX,
-    SEQUENCE_ID_MAX,
-    TIMESTAMP_MS_MAX,
-)
+from .constants import *
 
 
 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
+    now_ms = time.time_ns() // 1_000_000  # текущий моент
+    return now_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
+    return (snowflake_id >> TIMESTAMP_SHIFT) + 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 >> SEQUENCE_ID_BITS) & NODE_ID_MAX
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
-    """Read the sequence counter field out of a Snowflake identifier.
+    return snowflake_id & SEQUENCE_ID_MAX
 
-    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
+    # главная функция
 
 
 def generate_snowflake_id(
-    sequence_id: int,
-    node_id: int = NODE_ID_DEFAULT,
-    epoch_ms: int = EPOCH_MS_DEFAULT,
+    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
+    local_const_time = read_current_millis(epoch_ms)
+
+    if node_id < 0 or node_id > NODE_ID_MAX:
+        print(f"node_id must be in [0, {NODE_ID_MAX}]")
+        return None
+    if sequence_id < 0 or sequence_id > SEQUENCE_ID_MAX:
+        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}]")
+        return None
+    if local_const_time > TIMESTAMP_MS_MAX:
+        print("overflows time")
+        return None
+
+    snowflake_id = (
+        (local_const_time << TIMESTAMP_SHIFT)
+        | (node_id << SEQUENCE_ID_BITS)
+        | sequence_id
+    )
+    return snowflake_id

test/test_snowflake.py

@@ -0,0 +1,41 @@
+from part1.constants import EPOCH_MS_DEFAULT, NODE_ID_MAX, SEQUENCE_ID_MAX
+from part1.snowflake import (
+    decode_node_id,
+    decode_sequence_id,
+    decode_timestamp_ms,
+    generate_snowflake_id,
+)
+
+
+def test_roundtrip_node_and_sequence():
+    for node in [0, 1, 42, 500, NODE_ID_MAX]:
+        for seq in [0, 1, 100, 4000, SEQUENCE_ID_MAX]:
+            sid = generate_snowflake_id(seq, node)
+            assert sid is not None
+            assert decode_node_id(sid) == node
+            assert decode_sequence_id(sid) == seq
+
+
+def test_timestamp_close_to_now():
+    import time
+    before = time.time_ns() // 1_000_000
+    sid = generate_snowflake_id(0, 1)
+    after = time.time_ns() // 1_000_000
+
+    ts = decode_timestamp_ms(sid)
+    assert before <= ts <= after
+
+
+def test_positive_64bit():
+    sid = generate_snowflake_id(SEQUENCE_ID_MAX, NODE_ID_MAX)
+    assert 0 < sid < 2**63
+
+
+def test_invalid_node():
+    assert generate_snowflake_id(0, NODE_ID_MAX + 1) is None
+    assert generate_snowflake_id(0, -1) is None
+
+
+def test_invalid_sequence():
+    assert generate_snowflake_id(SEQUENCE_ID_MAX + 1, 1) is None
+    assert generate_snowflake_id(-1, 1) is None