66 lines
1.9 KiB
Python
66 lines
1.9 KiB
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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"""
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wire.py — 会话消息的打包 / 解包。
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pynng 一条消息只能是单块二进制，所以这里做一层很简单的外壳：
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b"LS01" | u32 头长度 | JSON 头（UTF-8） | 二进制体
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每个头里都带 session：
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{
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"id": "<一次运行一个 uuid>",
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"client_ip": "192.168.43.23", # 电脑自己的地址
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"board_ip": "192.168.43.50", # 板子的地址
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"started_ns": 1712345678901234567,
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"note": "..."
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}
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这样每一条请求和应答都能看出属于哪个会话、从哪台机器来。
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"""
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import json
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import struct
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import time
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import uuid
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MAGIC = b"LS01"
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_LEN = struct.Struct("<I")
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def new_session(board_ip, client_ip, note=""):
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"""新建一个会话（电脑端每次启动调一次）。"""
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return {
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"id": uuid.uuid4().hex,
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"client_ip": str(client_ip),
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"board_ip": str(board_ip),
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"started_ns": time.time_ns(),
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"note": str(note),
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}
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def pack(header, blob=b""):
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"""dict + 二进制体 -> bytes。"""
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h = json.dumps(header, separators=(",", ":"), ensure_ascii=False).encode("utf-8")
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return MAGIC + _LEN.pack(len(h)) + h + bytes(blob)
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def unpack(data):
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"""bytes -> (dict, 二进制体)。"""
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if len(data) < 8 or data[:4] != MAGIC:
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raise ValueError("bad frame magic")
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n = _LEN.unpack_from(data, 4)[0]
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if len(data) < 8 + n:
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raise ValueError("truncated header")
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header = json.loads(data[8:8 + n].decode("utf-8"))
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return header, data[8 + n:]
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def session_id(header):
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return (header.get("session") or {}).get("id")
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def check_session(header, session):
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"""应答必须属于当前会话，防止串台。"""
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got = session_id(header)
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if got != session["id"]:
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raise RuntimeError("session mismatch: got %r, want %r" % (got, session["id"]))
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