import hashlib import os import zlib from avro import io from cStringIO import StringIO import cPickle from dedupestore import archive_schema NS_ARCHIVES = 'ARCHIVES' NS_CHUNKS = 'CHUNKS' class Cache(object): """Client Side cache """ def __init__(self, store): self.store = store self.path = os.path.join(os.path.expanduser('~'), '.dedupestore', 'cache', '%s.cache' % self.store.uuid) self.tid = -1 self.open() if self.tid != self.store.tid: self.init() def open(self): if not os.path.exists(self.path): return data = open(self.path, 'rb').read() id = data[:32] data = data[32:] if hashlib.sha256(data).digest() != id: raise Exception('Cache hash did not match') data = cPickle.loads(zlib.decompress(data)) if data['uuid'] != self.store.uuid: raise Exception('Cache UUID mismatch') self.chunkmap = data['chunkmap'] self.archives = data['archives'] self.tid = data['tid'] def init(self): """Initializes cache by fetching and reading all archive indicies """ self.chunkmap = {} self.archives = {} self.tid = self.store.tid if self.store.tid == 0: return for id in list(self.store.list(NS_ARCHIVES)): data = self.store.get(NS_ARCHIVES, id) if hashlib.sha256(data).digest() != id: raise Exception('Archive hash did not match') buffer = StringIO(zlib.decompress(data)) reader = io.DatumReader(archive_schema) decoder = io.BinaryDecoder(buffer) archive = reader.read(decoder) self.archives[archive['name']] = id for id, size in archive['chunks']: if self.seen_chunk(id): self.chunk_incref(id) else: self.init_chunk(id, size) def save(self): assert self.store.state == self.store.OPEN data = {'uuid': self.store.uuid, 'chunkmap': self.chunkmap, 'tid': self.store.tid, 'archives': self.archives} cachedir = os.path.dirname(self.path) if not os.path.exists(cachedir): os.makedirs(cachedir) with open(self.path, 'wb') as fd: data = zlib.compress(cPickle.dumps(data)) id = hashlib.sha256(data).digest() fd.write(id + data) def add_chunk(self, data): id = hashlib.sha256(data).digest() if self.seen_chunk(id): return self.chunk_incref(id) osize = len(data) data = zlib.compress(data) data = hashlib.sha256(data).digest() + data csize = len(data) self.store.put(NS_CHUNKS, id, data) return self.init_chunk(id, csize) def init_chunk(self, id, size): self.chunkmap[id] = (1, size) return id, size def seen_chunk(self, id): count, size = self.chunkmap.get(id, (0, 0)) return count def chunk_incref(self, id): count, size = self.chunkmap[id] self.chunkmap[id] = (count + 1, size) return id, size def chunk_decref(self, id): count, size = self.chunkmap[id] if count == 1: del self.chunkmap[id] self.store.delete(NS_CHUNKS, id) else: self.chunkmap[id] = (count - 1, size)