内容协商与压缩：同一资源的多副面孔

Accept-Language: zh-CN, zh;q=0.9, en;q=0.5
含义：最想要 zh-CN（q=1），其次任何中文（0.9），实在不行英文（0.5）

python3 -c '
from http.server import BaseHTTPRequestHandler, HTTPServer
 
PAGES = {"zh": "你好，世界", "en": "Hello, World", "ja": "こんにちは"}
 
class H(BaseHTTPRequestHandler):
    def do_GET(self):
        al = self.headers.get("Accept-Language", "")
        # 极简协商：取第一个命中的语言标签
        chosen = "en"
        for token in al.split(","):
            lang = token.split(";")[0].strip().split("-")[0].lower()
            if lang in PAGES:
                chosen = lang
                break
        body = (PAGES[chosen] + "\n").encode()
        self.send_response(200)
        self.send_header("Content-Type", "text/plain; charset=utf-8")
        self.send_header("Content-Language", chosen)
        self.send_header("Vary", "Accept-Language")   # 关键！告诉缓存按语言分开存
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)
    def log_message(self, *a):
        pass
 
HTTPServer(("127.0.0.1", 8000), H).serve_forever()
' &
for _i in $(seq 1 50); do (exec 3<>/dev/tcp/127.0.0.1/8000) 2>/dev/null && break; sleep 0.1; done
 
curl -s http://127.0.0.1:8000/ -H "Accept-Language: zh-CN, en;q=0.5"
curl -s http://127.0.0.1:8000/ -H "Accept-Language: ja, en;q=0.8"
curl -s http://127.0.0.1:8000/ -H "Accept-Language: fr"
echo "--- 响应头里的协商结果与 Vary ---"
curl -si http://127.0.0.1:8000/ -H "Accept-Language: zh" | grep -iE "content-language|vary"

客户端: Accept-Encoding: gzip, deflate, br     "我会解这些"
服务器: Content-Encoding: gzip                 "那我用 gzip 压了"
        （Content-Length 是压缩后的字节数）

python3 -c '
from http.server import BaseHTTPRequestHandler, HTTPServer
import gzip, json
 
# 造一份 高冗余 JSON，模拟真实 API 响应
DATA = json.dumps([{"id": i, "status": "active", "role": "member"} for i in range(200)]).encode()
 
class H(BaseHTTPRequestHandler):
    def do_GET(self):
        accepts_gzip = "gzip" in self.headers.get("Accept-Encoding", "")
        body = gzip.compress(DATA) if accepts_gzip else DATA
        self.send_response(200)
        self.send_header("Content-Type", "application/json")
        if accepts_gzip:
            self.send_header("Content-Encoding", "gzip")
        self.send_header("Vary", "Accept-Encoding")
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)
    def log_message(self, *a):
        pass
 
HTTPServer(("127.0.0.1", 8000), H).serve_forever()
' &
for _i in $(seq 1 50); do (exec 3<>/dev/tcp/127.0.0.1/8000) 2>/dev/null && break; sleep 0.1; done
 
echo "== 不接受压缩 =="
curl -s -o /dev/null -w "传输 %{size_download} 字节\n" \
  -H "Accept-Encoding: identity" http://127.0.0.1:8000/api
 
echo "== 接受 gzip（--compressed 让 curl 声明并自动解压）=="
curl -s --compressed -o /dev/null -w "传输 %{size_download} 字节\n" \
  http://127.0.0.1:8000/api
 
echo "== 看响应头确认 =="
curl -si --compressed http://127.0.0.1:8000/api | grep -iE "content-encoding|content-length|vary"

Transfer-Encoding: chunked
 
响应体格式：
1a\r\n                    <- 块长度（十六进制）
abcdefghijklmnopqrstuvwxyz\r\n
10\r\n
0123456789abcdef\r\n
0\r\n                     <- 长度为 0 的块 = 结束
\r\n

python3 -c '
import socket, threading, time
 
def server():
    srv = socket.socket()
    srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    srv.bind(("127.0.0.1", 8000)); srv.listen(1)
    while True:
        conn, _ = srv.accept()
        conn.recv(65536)
        conn.sendall(b"HTTP/1.1 200 OK\r\n"
                     b"Content-Type: text/plain\r\n"
                     b"Transfer-Encoding: chunked\r\n\r\n")
        for i in range(1, 4):
            piece = ("第 " + str(i) + " 块数据\n").encode()
            # 块 = 十六进制长度 + CRLF + 数据 + CRLF
            conn.sendall(format(len(piece), "x").encode() + b"\r\n" + piece + b"\r\n")
            time.sleep(0.5)          # 模拟"边生成边发"
        conn.sendall(b"0\r\n\r\n")   # 结束块
        conn.close()
 
threading.Thread(target=server, daemon=True).start()
time.sleep(0.2)
 
import subprocess
# -N 关闭缓冲，配合 -w 展示总时间：三块分三次到达，总耗时约 1.5 秒
subprocess.run(["curl", "-sN", "-w", "总耗时 %{time_total}s\n",
                "http://127.0.0.1:8000/stream"], check=False)
'