from pathlib import Path


def u16(data, off):
    return data[off] | (data[off + 1] << 8)


def u32(data, off):
    return u16(data, off) | (u16(data, off + 2) << 16)


def get_segment(data, selector):
    ne_off = u32(data, 0x3C)
    seg_table_off = ne_off + u16(data, ne_off + 0x22)
    align_shift = u16(data, ne_off + 0x32)
    seg_index = ((selector - 0x1000) // 8) + 1
    seg_entry_off = seg_table_off + (seg_index - 1) * 8
    sector = u16(data, seg_entry_off)
    seg_len = u16(data, seg_entry_off + 2)
    if seg_len == 0:
        seg_len = 0x10000
    seg_file_off = sector << align_shift
    return seg_file_off, seg_len


def emit_runs(blob, seg_base, selector, allowed, minimum):
    start = None
    for i, byte in enumerate(blob):
        if byte in allowed:
            if start is None:
                start = i
        elif start is not None:
            length = i - start
            if length >= minimum:
                print(f'{selector:04X}:{start:04X} file=0x{seg_base + start:X} len=0x{length:X} bytes={blob[start:start+min(length,16)].hex(" ")}')
            start = None
    if start is not None:
        length = len(blob) - start
        if length >= minimum:
            print(f'{selector:04X}:{start:04X} file=0x{seg_base + start:X} len=0x{length:X} bytes={blob[start:start+min(length,16)].hex(" ")}')


def main():
    data = Path(r'd:\Ghidra\Crusader\REGRET.EXE').read_bytes()
    seg_base, seg_len = get_segment(data, 0x13F8)
    blob = data[seg_base:seg_base + seg_len]
    print(f'segment 13F8 file=0x{seg_base:X} len=0x{seg_len:X}')
    print('zero runs >= 0x20')
    emit_runs(blob, seg_base, 0x13F8, {0x00}, 0x20)
    print('nop/int3 runs >= 0x10')
    emit_runs(blob, seg_base, 0x13F8, {0x90, 0xCC}, 0x10)


if __name__ == '__main__':
    main()