zram 用压缩的方式在内存里挤出交换空间

#!/usr/bin/env python3
"""Offline mm_stat parser/report demo; no device discovery or kernel access."""
from pathlib import Path
import sys
from tempfile import TemporaryDirectory


def parse_mm_stat(text):
    parts = text.split()
    if len(parts) < 3:
        raise ValueError("need orig, compr and mem_used_total")
    if any(not x.isascii() or not x.isdecimal() for x in parts):
        raise ValueError("fields must be unsigned decimal integers")
    values = tuple(int(x) for x in parts)
    if any(x > (1 << 64) - 1 for x in values):
        raise ValueError("field exceeds unsigned 64-bit range")
    orig, compr, mem_used = values[:3]
    if orig == 0 and compr != 0:
        raise ValueError("inconsistent zero-orig snapshot")
    return orig, compr, mem_used


def report(name, orig, compr, mem_used):
    prefix = f"{name}: orig={orig} compr={compr} mem_used_total={mem_used}"
    if orig == 0:
        return prefix + " ratio=n/a (no stored data)"
    if compr == 0:
        return prefix + " ratio=n/a (nonempty; zero compressed payload)"
    ratio = orig / compr
    saved = 100.0 * (1.0 - compr / orig)
    return prefix + f" ratio={ratio:.2f} payload_saved={saved:.1f}%"


def inspect_paths(paths):
    lines = []
    parsed = skipped = 0
    for path in paths:
        try:
            values = parse_mm_stat(path.read_text(encoding="ascii"))
        except (OSError, UnicodeError, ValueError) as exc:
            lines.append(f"SKIP {path.name}: {type(exc).__name__}")
            skipped += 1
            continue
        lines.append(report(path.name, *values))
        parsed += 1
    lines.append(f"SUMMARY: parsed={parsed} skipped={skipped}")
    return (0 if parsed > 0 and skipped == 0 else 1), lines


def self_test():
    if not __debug__:
        raise RuntimeError("run without Python optimization")
    with TemporaryDirectory(prefix="zram-fixture-", dir=".") as directory:
        root = Path(directory)
        cases = {
            "ratio": ("314572800 104857600 125829120 0 125829120 0 0 0 0\n",
                      "ratio: orig=314572800 compr=104857600 mem_used_total=125829120 ratio=3.00 payload_saved=66.7%"),
            "same": ("4096 0 0 0 0 1 0 0 0\n",
                     "same: orig=4096 compr=0 mem_used_total=0 ratio=n/a (nonempty; zero compressed payload)"),
            "empty": ("0 0 0\n", "empty: orig=0 compr=0 mem_used_total=0 ratio=n/a (no stored data)"),
            "overhead": ("0 0 4096\n", "overhead: orig=0 compr=0 mem_used_total=4096 ratio=n/a (no stored data)"),
            "plain": ("4096 4096 8192\n", "plain: orig=4096 compr=4096 mem_used_total=8192 ratio=1.00 payload_saved=0.0%"),
        }
        for name, (text, expected) in cases.items():
            path = root / name
            path.write_text(text, encoding="ascii")
            assert inspect_paths([path]) == (0, [expected, "SUMMARY: parsed=1 skipped=0"])
        bad = ["", "1", "1 1", "x 1 1", "1 1 x", "-1 0 0",
               "1 -1 0", "1 1 -1", "1 1 1 -1", "0 1 1", "1.0 1 1",
               "+1 1 1", "1_000 1 1", "18446744073709551616 1 1"]
        invalid_paths = []
        for index, text in enumerate(bad):
            path = root / f"bad-{index}"
            path.write_text(text, encoding="ascii")
            invalid_paths.append(path)
            assert inspect_paths([path]) == (1, [f"SKIP {path.name}: ValueError", "SUMMARY: parsed=0 skipped=1"])
        missing = root / "missing"
        assert inspect_paths([missing]) == (1, ["SKIP missing: FileNotFoundError", "SUMMARY: parsed=0 skipped=1"])
        assert inspect_paths([]) == (1, ["SUMMARY: parsed=0 skipped=0"])
        code, lines = inspect_paths(invalid_paths + [missing])
        assert code == 1 and lines[-1] == "SUMMARY: parsed=0 skipped=15"
        assert len(lines) == 16 and all(line.startswith("SKIP ") for line in lines[:-1])
        code, lines = inspect_paths([root / "ratio", missing])
        assert code == 1 and lines == [cases["ratio"][1], "SKIP missing: FileNotFoundError", "SUMMARY: parsed=1 skipped=1"]
    print("PASS: offline file fixtures; ratio, nonempty zero payload, empty, invalid/missing, all-skipped and partial results")


def main():
    if len(sys.argv) == 1:
        self_test()
        return 0
    code, lines = inspect_paths([Path(name) for name in sys.argv[1:]])
    print("\n".join(lines))
    return code


if __name__ == "__main__":
    raise SystemExit(main())