响应压缩的收益边界：阈值断点、形状分流与响应头约束

import json, re, zlib
MTU_NEAR = 1400
BANDWIDTH_NEAR = 300
RANDOMISH = re.compile(r"^[0-9a-fA-F-]{32,}$")
def shape_of(payload) -> str:
    text = json.dumps(payload, ensure_ascii=False)
    if any(v.startswith("data:") for v in _leaf_strings(payload)):
        return "binary_like"
    keys = re.findall(r'"([^"]+)":', text)
    if len(keys) >= 8 and len(set(keys)) < len(keys) / 2:
        return "repeated_keys"
    if all(RANDOMISH.match(v) for v in _leaf_strings(payload)[:5] or [""]):
        return "random_like"
    return "text"
def _leaf_strings(obj):
    out = []
    if isinstance(obj, dict):
        for k in obj:
            out.extend(_leaf_strings(obj[k]))
    elif isinstance(obj, list):
        for v in obj:
            out.extend(_leaf_strings(v))
    elif isinstance(obj, str):
        out.append(obj)
    return out
def should_compress(payload, goal="latency"):
    raw = json.dumps(payload, ensure_ascii=False).encode("utf-8")
    limit = MTU_NEAR if goal == "latency" else BANDWIDTH_NEAR
    if len(raw) < limit:
        return False, 0
    if shape_of(payload) in ("binary_like", "random_like"):
        return False, 0
    return True, (1 if len(raw) < 16 * 1024 else 3)