read_recent_chunks.py

def run(limit=None):
 import os, array, struct, time, zlib
 if limit is None: limit = time.time() - 3*3600
 for i in os.listdir('.'):
  if not i.endswith('.mca'): continue
  _,ccx,ccz,_ = i.split('.')
  ccx = int(ccx) * 32; ccz = int(ccz) * 32
  with open(i, 'rb') as f:
   offsets = array.array('I', f.read(4096)); offsets.byteswap()
   timestamps = array.array('I', f.read(4096)); timestamps.byteswap()
   chunks = [(ts, (i, off/256*4096, off%256*4096), (ccx+j%32, ccz+j/32)) for j, (off, ts) in enumerate(zip(offsets, timestamps)) if off != 0 and ts >= limit]
   for ts, (fn, off, sz), (cx, cz) in chunks:
    f.seek(off)
    data = f.read(sz)
    datalen = struct.unpack('!I', data[:4])[0]
    datact = ord(data[4])
    assert datact == 2, datact
    data = zlib.decompress(data[5:4+datalen])
    print len(data)
 return data