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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Server Message Data 编解码工具
用于处理 Base64URL 编码的 protobuf 消息
"""
import base64
from typing import Dict, Optional, Tuple, Any
from datetime import datetime, timezone
try:
from zoneinfo import ZoneInfo # Python 3.9+
except Exception:
ZoneInfo = None # type: ignore
class MessageCodec:
"""Server Message Data 编解码器"""
@staticmethod
def b64url_decode_padded(s: str) -> bytes:
"""Base64URL解码（带填充）"""
t = s.replace("-", "+").replace("_", "/")
pad = (-len(t)) % 4
if pad:
t += "=" * pad
return base64.b64decode(t)
@staticmethod
def b64url_encode_nopad(b: bytes) -> str:
"""Base64URL编码（无填充）"""
return base64.urlsafe_b64encode(b).decode("ascii").rstrip("=")
@staticmethod
def read_varint(buf: bytes, i: int) -> Tuple[int, int]:
"""读取varint格式的整数"""
shift = 0
val = 0
while i < len(buf):
b = buf[i]
i += 1
val |= (b & 0x7F) << shift
if not (b & 0x80):
return val, i
shift += 7
if shift > 63:
break
raise ValueError("invalid varint")
@staticmethod
def write_varint(v: int) -> bytes:
"""写入varint格式的整数"""
out = bytearray()
vv = int(v)
while True:
to_write = vv & 0x7F
vv >>= 7
if vv:
out.append(to_write | 0x80)
else:
out.append(to_write)
break
return bytes(out)
@classmethod
def make_key(cls, field_no: int, wire_type: int) -> bytes:
"""创建protobuf字段键"""
return cls.write_varint((field_no << 3) | wire_type)
@classmethod
def decode_timestamp(cls, buf: bytes) -> Tuple[Optional[int], Optional[int]]:
"""解码google.protobuf.Timestamp"""
i = 0
seconds: Optional[int] = None
nanos: Optional[int] = None
while i < len(buf):
key, i = cls.read_varint(buf, i)
field_no = key >> 3
wt = key & 0x07
if wt == 0: # varint
val, i = cls.read_varint(buf, i)
if field_no == 1:
seconds = int(val)
elif field_no == 2:
nanos = int(val)
elif wt == 2: # length-delimited
ln, i2 = cls.read_varint(buf, i)
i = i2 + ln
elif wt == 1:
i += 8
elif wt == 5:
i += 4
else:
break
return seconds, nanos
@classmethod
def encode_timestamp(cls, seconds: Optional[int], nanos: Optional[int]) -> bytes:
"""编码google.protobuf.Timestamp"""
parts = bytearray()
if seconds is not None:
parts += cls.make_key(1, 0) # field 1, varint
parts += cls.write_varint(int(seconds))
if nanos is not None:
parts += cls.make_key(2, 0) # field 2, varint
parts += cls.write_varint(int(nanos))
return bytes(parts)
@classmethod
def decode_server_message_data(cls, b64url: str) -> Dict:
"""解码 Base64URL 的 server_message_data"""
try:
raw = cls.b64url_decode_padded(b64url)
except Exception as e:
return {"error": f"base64url decode failed: {e}", "raw_b64url": b64url}
i = 0
uuid: Optional[str] = None
seconds: Optional[int] = None
nanos: Optional[int] = None
while i < len(raw):
key, i = cls.read_varint(raw, i)
field_no = key >> 3
wt = key & 0x07
if wt == 2: # length-delimited
ln, i2 = cls.read_varint(raw, i)
i = i2
data = raw[i:i+ln]
i += ln
if field_no == 1: # uuid string
try:
uuid = data.decode("utf-8")
except Exception:
uuid = None
elif field_no == 3: # google.protobuf.Timestamp
seconds, nanos = cls.decode_timestamp(data)
elif wt == 0: # varint
_, i = cls.read_varint(raw, i)
elif wt == 1:
i += 8
elif wt == 5:
i += 4
else:
break
out: Dict[str, Any] = {}
if uuid is not None:
out["uuid"] = uuid
if seconds is not None:
out["seconds"] = seconds
if nanos is not None:
out["nanos"] = nanos
return out
@classmethod
def encode_server_message_data(cls, uuid: str = None, seconds: int = None, nanos: int = None) -> str:
"""将 uuid/seconds/nanos 组合编码为 Base64URL 字符串"""
parts = bytearray()
if uuid:
b = uuid.encode("utf-8")
parts += cls.make_key(1, 2) # field 1, length-delimited
parts += cls.write_varint(len(b))
parts += b
if seconds is not None or nanos is not None:
ts = cls.encode_timestamp(seconds, nanos)
parts += cls.make_key(3, 2) # field 3, length-delimited
parts += cls.write_varint(len(ts))
parts += ts
return cls.b64url_encode_nopad(bytes(parts))
# 为了向后兼容，提供简单的函数接口
decode_server_message_data = MessageCodec.decode_server_message_data
encode_server_message_data = MessageCodec.encode_server_message_data |