# Independent GPT validator (does not share code with gptedit.py)
import struct, zlib, sys
DISK_SECTORS = 7634944
def check(prim_path, back_path):
    P = open(prim_path, "rb").read(); B = open(back_path, "rb").read()
    ok = True
    def fail(m):
        nonlocal ok; ok = False; print("  FAIL:", m)
    def hdr(buf, label, expect_my, expect_alt):
        h = buf
        sig, rev, hsz, hcrc, _, my, alt, fu, lu = struct.unpack("<8sIII4sQQQQ", h[:56])
        guid = h[56:72]; ent_lba, n, esz, ecrc = struct.unpack("<QIII", h[72:92])
        calc = zlib.crc32(h[:16] + b"\0\0\0\0" + h[20:hsz]) & 0xffffffff
        if sig != b"EFI PART": fail(label + " signature")
        if calc != hcrc: fail("%s header CRC stored %08x calc %08x" % (label, hcrc, calc))
        if my != expect_my: fail("%s my_lba %d != %d" % (label, my, expect_my))
        if alt != expect_alt: fail("%s alternate_lba %d != %d" % (label, alt, expect_alt))
        return dict(fu=fu, lu=lu, guid=guid, ent_lba=ent_lba, n=n, esz=esz, ecrc=ecrc)
    hp = hdr(P[512:1024], "primary", 1, DISK_SECTORS - 1)
    hb = hdr(B[32*512:33*512], "backup", DISK_SECTORS - 1, 1)
    ep = P[hp["ent_lba"]*512: hp["ent_lba"]*512 + hp["n"]*hp["esz"]]
    if hb["ent_lba"] != DISK_SECTORS - 33: fail("backup entries LBA %d" % hb["ent_lba"])
    eb = B[:hb["n"]*hb["esz"]]
    for lab, e, h in (("primary", ep, hp), ("backup", eb, hb)):
        c = zlib.crc32(e) & 0xffffffff
        if c != h["ecrc"]: fail("%s entries CRC stored %08x calc %08x" % (lab, h["ecrc"], c))
    if ep != eb: fail("primary and backup entry arrays differ")
    for k in ("fu", "lu", "guid", "n", "esz"):
        if hp[k] != hb[k]: fail("header field %s differs" % k)
    parts = []
    for i in range(hp["n"]):
        e = ep[i*128:(i+1)*128]
        if e[:16] == b"\0"*16: continue
        s, l = struct.unpack("<QQ", e[32:48]); nm = e[56:128].decode("utf-16le").rstrip("\0")
        if not (hp["fu"] <= s <= l <= hp["lu"]): fail("%s outside usable range" % nm)
        parts.append((s, l, nm))
    parts.sort()
    for a, b in zip(parts, parts[1:]):
        if b[0] <= a[1]: fail("overlap %s / %s" % (a[2], b[2]))
    if P[0x1fe:0x200] != b"\x55\xaa" or P[0x1c2] != 0xee: fail("protective MBR")
    print("  %s: %d partitions, usable %d..%d -> %s" % (prim_path, len(parts), hp["fu"], hp["lu"], "OK" if ok else "INVALID"))
    return ok
for p, b in (("../gpt/gpt-primary-34sectors.bin", "../gpt/gpt-backup-33sectors.bin"), ("aurora-new-gpt-primary-34sectors.bin", "aurora-new-gpt-backup-33sectors.bin")):
    check(p, b)