"""position_sample_dump.py <pid> [count=10]

For a few Position hits, print the surrounding bytes raw so we can
visually inspect the layout. Goal: see if there's a heap-block
header pattern we missed.
"""
import ctypes
import ctypes.wintypes as wt
import struct
import sys

POSITION_VT = 0x00797910

PROCESS_VM_READ = 0x10
PROCESS_QUERY_INFORMATION = 0x400


class MBI(ctypes.Structure):
    _fields_ = [('BaseAddress', ctypes.c_void_p),
                ('AllocationBase', ctypes.c_void_p),
                ('AllocationProtect', wt.DWORD),
                ('PartitionId', wt.WORD),
                ('RegionSize', ctypes.c_size_t),
                ('State', wt.DWORD),
                ('Protect', wt.DWORD),
                ('Type', wt.DWORD)]


k = ctypes.windll.kernel32
k.OpenProcess.argtypes = [wt.DWORD, wt.BOOL, wt.DWORD]; k.OpenProcess.restype = wt.HANDLE
k.CloseHandle.argtypes = [wt.HANDLE]; k.CloseHandle.restype = wt.BOOL
k.ReadProcessMemory.argtypes = [wt.HANDLE, wt.LPCVOID, wt.LPVOID, ctypes.c_size_t,
                                ctypes.POINTER(ctypes.c_size_t)]
k.ReadProcessMemory.restype = wt.BOOL
k.VirtualQueryEx.argtypes = [wt.HANDLE, ctypes.c_void_p, ctypes.POINTER(MBI), ctypes.c_size_t]
k.VirtualQueryEx.restype = ctypes.c_size_t


def hexdump(addr, data, prefix=""):
    for i in range(0, len(data), 16):
        chunk = data[i:i+16]
        h = " ".join(f"{b:02x}" for b in chunk)
        a = "".join(chr(b) if 32 <= b < 127 else '.' for b in chunk)
        dws = " ".join(f"{struct.unpack_from('<I', chunk, j)[0]:08x}"
                       for j in range(0, min(16, len(chunk) - (len(chunk) % 4)), 4))
        print(f"{prefix}0x{addr+i:08x}: {h:<47}  | {dws}  | {a}")


def main():
    pid = int(sys.argv[1])
    want = int(sys.argv[2]) if len(sys.argv) > 2 else 10

    h = k.OpenProcess(PROCESS_VM_READ | PROCESS_QUERY_INFORMATION, False, pid)
    if not h:
        print(f"OpenProcess err={ctypes.get_last_error()}"); return 1

    shown = 0
    mbi = MBI()
    addr = 0
    while k.VirtualQueryEx(h, addr, ctypes.byref(mbi), ctypes.sizeof(mbi)) and shown < want:
        pr = mbi.Protect & 0xff
        if (mbi.State == 0x1000 and mbi.Type == 0x20000
                and pr in (0x04, 0x40)):
            buf = (ctypes.c_ubyte * mbi.RegionSize)()
            sz = ctypes.c_size_t(0)
            if k.ReadProcessMemory(h, mbi.BaseAddress, buf,
                                   mbi.RegionSize, ctypes.byref(sz)):
                data = bytes(buf[:sz.value])
                end = (len(data) // 4) * 4
                # find positions in this region
                pos_offs = []
                for off in range(0, end, 4):
                    if struct.unpack_from("<I", data, off)[0] == POSITION_VT:
                        pos_offs.append(off)
                # sample first few
                for off in pos_offs[:3]:
                    if shown >= want:
                        break
                    shown += 1
                    va_pos = mbi.BaseAddress + off
                    region_kb = mbi.RegionSize // 1024
                    print(f"\n=== Position #{shown} @ VA 0x{va_pos:08x} "
                          f"(region 0x{mbi.BaseAddress:08x} {region_kb}KB, "
                          f"in-region offset 0x{off:x}, "
                          f"positions-in-region={len(pos_offs)}) ===")
                    # dump 64 bytes BEFORE position vt
                    lo = max(0, off - 64)
                    hexdump(mbi.BaseAddress + lo, data[lo:off], prefix="  before  ")
                    print("  POSITION:")
                    hexdump(mbi.BaseAddress + off, data[off:off + 128], prefix="  pos+ctx ")
        addr = (mbi.BaseAddress or 0) + mbi.RegionSize
        if addr >= 0x80000000 or shown >= want:
            break

    k.CloseHandle(h)
    return 0


if __name__ == "__main__":
    sys.exit(main())