-extract_bits = _helpers.extract_bits
-
-
-class PackMidx:
- """Wrapper which contains data from multiple index files.
- Multiple index (.midx) files constitute a wrapper around index (.idx) files
- and make it possible for bup to expand Git's indexing capabilities to vast
- amounts of files.
- """
- def __init__(self, filename):
- self.name = filename
- self.force_keep = False
- assert(filename.endswith('.midx'))
- self.map = mmap_read(open(filename))
- if str(self.map[0:4]) != 'MIDX':
- log('Warning: skipping: invalid MIDX header in %r\n' % filename)
- self.force_keep = True
- return self._init_failed()
- ver = struct.unpack('!I', self.map[4:8])[0]
- if ver < MIDX_VERSION:
- log('Warning: ignoring old-style (v%d) midx %r\n'
- % (ver, filename))
- self.force_keep = False # old stuff is boring
- return self._init_failed()
- if ver > MIDX_VERSION:
- log('Warning: ignoring too-new (v%d) midx %r\n'
- % (ver, filename))
- self.force_keep = True # new stuff is exciting
- return self._init_failed()
-
- self.bits = _helpers.firstword(self.map[8:12])
- self.entries = 2**self.bits
- self.fanout = buffer(self.map, 12, self.entries*4)
- shaofs = 12 + self.entries*4
- nsha = self._fanget(self.entries-1)
- self.shalist = buffer(self.map, shaofs, nsha*20)
- self.idxnames = str(self.map[shaofs + 20*nsha:]).split('\0')
-
- def _init_failed(self):
- self.bits = 0
- self.entries = 1
- self.fanout = buffer('\0\0\0\0')
- self.shalist = buffer('\0'*20)
- self.idxnames = []
-
- def _fanget(self, i):
- start = i*4
- s = self.fanout[start:start+4]
- return _helpers.firstword(s)
-
- def _get(self, i):
- return str(self.shalist[i*20:(i+1)*20])
-
- def exists(self, hash):
- """Return nonempty if the object exists in the index files."""
- global _total_searches, _total_steps
- _total_searches += 1
- want = str(hash)
- el = extract_bits(want, self.bits)
- if el:
- start = self._fanget(el-1)
- startv = el << (32-self.bits)
- else:
- start = 0
- startv = 0
- end = self._fanget(el)
- endv = (el+1) << (32-self.bits)
- _total_steps += 1 # lookup table is a step
- hashv = _helpers.firstword(hash)
- #print '(%08x) %08x %08x %08x' % (extract_bits(want, 32), startv, hashv, endv)
- while start < end:
- _total_steps += 1
- #print '! %08x %08x %08x %d - %d' % (startv, hashv, endv, start, end)
- mid = start + (hashv-startv)*(end-start-1)/(endv-startv)
- #print ' %08x %08x %08x %d %d %d' % (startv, hashv, endv, start, mid, end)
- v = self._get(mid)
- #print ' %08x' % self._num(v)
- if v < want:
- start = mid+1
- startv = _helpers.firstword(v)
- elif v > want:
- end = mid
- endv = _helpers.firstword(v)
- else: # got it!
- return True
- return None
-
- def __iter__(self):
- for i in xrange(self._fanget(self.entries-1)):
- yield buffer(self.shalist, i*20, 20)
-
- def __len__(self):
- return int(self._fanget(self.entries-1))
-
-