2 from __future__ import absolute_import
3 import glob, mmap, os, struct
5 from bup import _helpers
6 from bup.compat import range
7 from bup.helpers import log, mmap_read
12 extract_bits = _helpers.extract_bits
18 """Wrapper which contains data from multiple index files.
19 Multiple index (.midx) files constitute a wrapper around index (.idx) files
20 and make it possible for bup to expand Git's indexing capabilities to vast
23 def __init__(self, filename):
25 self.force_keep = False
27 assert(filename.endswith('.midx'))
28 self.map = mmap_read(open(filename))
29 if str(self.map[0:4]) != 'MIDX':
30 log('Warning: skipping: invalid MIDX header in %r\n' % filename)
31 self.force_keep = True
32 return self._init_failed()
33 ver = struct.unpack('!I', self.map[4:8])[0]
34 if ver < MIDX_VERSION:
35 log('Warning: ignoring old-style (v%d) midx %r\n'
37 self.force_keep = False # old stuff is boring
38 return self._init_failed()
39 if ver > MIDX_VERSION:
40 log('Warning: ignoring too-new (v%d) midx %r\n'
42 self.force_keep = True # new stuff is exciting
43 return self._init_failed()
45 self.bits = _helpers.firstword(self.map[8:12])
46 self.entries = 2**self.bits
48 # fanout len is self.entries * 4
49 self.sha_ofs = self.fanout_ofs + self.entries * 4
50 self.nsha = self._fanget(self.entries - 1)
51 # sha table len is self.nsha * 20
52 self.which_ofs = self.sha_ofs + 20 * self.nsha
53 # which len is self.nsha * 4
54 self.idxnames = self.map[self.which_ofs + 4 * self.nsha:].split(b'\0')
59 def _init_failed(self):
65 if i >= self.entries * 4 or i < 0:
66 raise IndexError('invalid midx index %d' % i)
67 ofs = self.fanout_ofs + i * 4
68 return _helpers.firstword(self.map[ofs : ofs + 4])
71 if i >= self.nsha or i < 0:
72 raise IndexError('invalid midx index %d' % i)
73 ofs = self.sha_ofs + i * 20
74 return self.map[ofs : ofs + 20]
76 def _get_idx_i(self, i):
77 if i >= self.nsha or i < 0:
78 raise IndexError('invalid midx index %d' % i)
79 ofs = self.which_ofs + i * 4
80 return struct.unpack_from('!I', self.map, offset=ofs)[0]
82 def _get_idxname(self, i):
83 return self.idxnames[self._get_idx_i(i)]
86 if self.map is not None:
90 def exists(self, hash, want_source=False):
91 """Return nonempty if the object exists in the index files."""
92 global _total_searches, _total_steps
95 el = extract_bits(want, self.bits)
97 start = self._fanget(el-1)
98 startv = el << (32-self.bits)
102 end = self._fanget(el)
103 endv = (el+1) << (32-self.bits)
104 _total_steps += 1 # lookup table is a step
105 hashv = _helpers.firstword(hash)
106 #print '(%08x) %08x %08x %08x' % (extract_bits(want, 32), startv, hashv, endv)
109 #print '! %08x %08x %08x %d - %d' % (startv, hashv, endv, start, end)
110 mid = start + (hashv-startv)*(end-start-1)/(endv-startv)
111 #print ' %08x %08x %08x %d %d %d' % (startv, hashv, endv, start, mid, end)
113 #print ' %08x' % self._num(v)
116 startv = _helpers.firstword(v)
119 endv = _helpers.firstword(v)
121 return want_source and self._get_idxname(mid) or True
126 for ofs in range(start, start + self.nsha * 20, 20):
127 yield self.map[ofs : ofs + 20]
130 return int(self.nsha)
133 def clear_midxes(dir=None):
134 for midx in glob.glob(os.path.join(dir, '*.midx')):