feat: add record saving

src/record_file.py

@@ -0,0 +1,49 @@
+from pathlib import Path
+import struct
+import time
+from typing import Literal
+
+from src.snapshot import Snapshot
+
+
+class RecordFile:
+    VERSION = 1
+
+    def __init__(self, path: str | Path, mode: Literal["w", "r"]) -> None:
+        self.path: str | Path = path
+        self.mode: Literal["w", "r"] = mode
+        self.file = open(self.path, self.mode + "b")
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, type, value, traceback):
+        self.file.close()
+
+    def write_header(self, n_snapshots: int):
+        data: bytes = struct.pack(
+            ">IId", self.VERSION, n_snapshots, time.time())
+        self.file.write(data)
+
+    def write_snapshots(self, snapshots: list[Snapshot]):
+        self.write_header(len(snapshots))
+        for snapshot in snapshots:
+            data: bytes = snapshot.pack()
+            self.file.write(struct.pack(">I", len(data)) + data)
+
+    def read_snapshots(self) -> list[Snapshot]:
+        version: int = struct.unpack(">I", self.file.read(4))[0]
+        if version != self.VERSION:
+            raise ValueError(
+                f"Cannot parse record file with format version {version} (current version: {self.VERSION})")
+
+        n_snapshots: int
+        timestamp: float
+        n_snapshots, timestamp = struct.unpack(">Id", self.file.read(12))
+        snapshots: list[Snapshot] = []
+
+        for _ in range(n_snapshots):
+            size: int = struct.unpack(">I", self.file.read(4))[0]
+            snapshots.append(Snapshot.unpack(self.file.read(size)))
+
+        return snapshots