"""count_vtable_instances.py <dump.dmp> <vtable_va>
Count how many objects in the dump have <vtable_va> as their first DWORD.
Print the count and a few sample addresses.
"""
import struct, sys
from minidump.minidumpfile import MinidumpFile


def _ei(v):
    if v is None: return 0
    if hasattr(v, 'value'): return int(v.value)
    return int(v)


md = MinidumpFile.parse(sys.argv[1])
vt = int(sys.argv[2], 16)
rdr = md.get_reader().get_buffered_reader()

scan = []
for r in md.memory_info.infos:
    st, ty, pr = _ei(r.State), _ei(r.Type), _ei(r.Protect) & 0xff
    if st != 0x1000 or ty == 0x1000000 or pr not in (0x04, 0x40): continue
    scan.append((r.BaseAddress, r.RegionSize))

count = 0
samples = []
for base, size in scan:
    try:
        rdr.move(base); buf = rdr.read(size)
    except Exception: continue
    if not buf: continue
    end = (len(buf) // 4) * 4
    for off in range(0, end - 4, 4):
        if struct.unpack_from("<I", buf, off)[0] == vt:
            count += 1
            if len(samples) < 5:
                samples.append(base + off)

print(f"instances of vtable 0x{vt:08x}: {count}")
for s in samples:
    print(f"  0x{s:08x}")