From 1a5c27bb0cac9819d3b7192612acefc406cb01b2 Mon Sep 17 00:00:00 2001
From: Verum <whyverum@gmail.com>
Date: Thu, 5 Mar 2026 18:48:12 +0700
Subject: [PATCH] =?UTF-8?q?=D0=94=D0=B5=D0=BA=D0=BE=D0=B4=D0=B5=D1=80=20ba?=
 =?UTF-8?q?se64?=
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---
 backend/utils/encoding.py | 48 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 backend/utils/encoding.py

diff --git a/backend/utils/encoding.py b/backend/utils/encoding.py
new file mode 100644
index 0000000..ef10989
--- /dev/null
+++ b/backend/utils/encoding.py
@@ -0,0 +1,48 @@
+from typing import Dict
+
+# Таблица Base64-подобного варианта
+VariantBase64Table: str = (
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
+)
+VariantBase64Dict: Dict[int, str] = {
+    i: VariantBase64Table[i] for i in range(len(VariantBase64Table))
+}
+VariantBase64ReverseDict: Dict[str, int] = {
+    VariantBase64Table[i]: i for i in range(len(VariantBase64Table))
+}
+
+
+def variant_base64_encode(bs: bytes) -> bytes:
+    """
+    Пользовательский Base64 encode (малые блоки, little-endian).
+
+    Аргументы:
+    - bs: bytes - исходные данные
+
+    Возвращает:
+    - bytes: закодированные данные
+    """
+    result: bytearray = bytearray()
+    blocks_count, left_bytes = divmod(len(bs), 3)
+
+    # Полные блоки по 3 байта
+    for i in range(blocks_count):
+        b: bytes = bs[3*i:3*i+3]
+        coding_int: int = int.from_bytes(b, "little")
+        block: str = "".join(
+            VariantBase64Dict[(coding_int >> shift) & 0x3F]
+            for shift in (0, 6, 12, 18)
+        )
+        result.extend(block.encode("ascii"))
+
+    # Обработка оставшихся байт
+    if left_bytes:
+        b: bytes = bs[-left_bytes:]
+        coding_int: int = int.from_bytes(b, "little")
+        block: str = "".join(
+            VariantBase64Dict[(coding_int >> shift) & 0x3F]
+            for shift in range(0, left_bytes * 8 + 1, 6)
+        )
+        result.extend(block.encode("ascii"))
+
+    return bytes(result)