import os import logging from twisted.internet import defer from twisted.web.client import FileBodyProducer from twisted.python.failure import Failure from lbrynet.cryptoutils import get_lbry_hash_obj from lbrynet.p2p.Error import DownloadCanceledError, InvalidDataError, InvalidBlobHashError from lbrynet.blob.writer import HashBlobWriter from lbrynet.blob.reader import HashBlobReader log = logging.getLogger(__name__) MAX_BLOB_SIZE = 2 * 2 ** 20 # digest_size is in bytes, and blob hashes are hex encoded blobhash_length = get_lbry_hash_obj().digest_size * 2 def is_valid_hashcharacter(char): return char in "0123456789abcdef" def is_valid_blobhash(blobhash): """Checks whether the blobhash is the correct length and contains only valid characters (0-9, a-f) @param blobhash: string, the blobhash to check @return: True/False """ return len(blobhash) == blobhash_length and all(is_valid_hashcharacter(l) for l in blobhash) class BlobFile: """ A chunk of data available on the network which is specified by a hashsum This class is used to create blobs on the local filesystem when we already know the blob hash before hand (i.e., when downloading blobs) Also can be used for reading from blobs on the local filesystem """ def __str__(self): return self.blob_hash[:16] def __repr__(self): return '<{}({})>'.format(self.__class__.__name__, str(self)) def __init__(self, blob_dir, blob_hash, length=None): if not is_valid_blobhash(blob_hash): raise InvalidBlobHashError(blob_hash) self.blob_hash = blob_hash self.length = length self.writers = {} # {Peer: writer, finished_deferred} self._verified = False self.readers = 0 self.blob_dir = blob_dir self.file_path = os.path.join(blob_dir, self.blob_hash) self.blob_write_lock = defer.DeferredLock() self.saved_verified_blob = False if os.path.isfile(self.file_path): self.set_length(os.path.getsize(self.file_path)) # This assumes that the hash of the blob has already been # checked as part of the blob creation process. It might # be worth having a function that checks the actual hash; # its probably too expensive to have that check be part of # this call. self._verified = True def open_for_writing(self, peer): """ open a blob file to be written by peer, supports concurrent writers, as long as they are from different peers. returns tuple of (writer, finished_deferred) writer - a file like object with a write() function, close() when finished finished_deferred - deferred that is fired when write is finished and returns a instance of itself as HashBlob """ if peer not in self.writers: log.debug("Opening %s to be written by %s", str(self), str(peer)) finished_deferred = defer.Deferred() writer = HashBlobWriter(self.get_length, self.writer_finished) self.writers[peer] = (writer, finished_deferred) return writer, finished_deferred log.warning("Tried to download the same file twice simultaneously from the same peer") return None, None def open_for_reading(self): """ open blob for reading returns a file like object that can be read() from, and closed() when finished """ if self._verified is True: f = open(self.file_path, 'rb') reader = HashBlobReader(f, self.reader_finished) self.readers += 1 return reader return None def delete(self): """ delete blob file from file system, prevent deletion if a blob is being read from or written to returns a deferred that firesback when delete is completed """ if not self.writers and not self.readers: self._verified = False self.saved_verified_blob = False try: if os.path.isfile(self.file_path): os.remove(self.file_path) except Exception as e: log.exception("An error occurred deleting %s:", str(self.file_path), exc_info=e) else: raise ValueError("File is currently being read or written and cannot be deleted") @property def verified(self): """ Protect verified from being modified by other classes. verified is True if a write to a blob has completed successfully, or a blob has been read to have the same length as specified in init """ return self._verified def set_length(self, length): if self.length is not None and length == self.length: return True if self.length is None and 0 <= length <= MAX_BLOB_SIZE: self.length = length return True log.warning("Got an invalid length. Previous length: %s, Invalid length: %s", self.length, length) return False def get_length(self): return self.length def get_is_verified(self): return self.verified def is_downloading(self): if self.writers: return True return False def reader_finished(self, reader): self.readers -= 1 return defer.succeed(True) def writer_finished(self, writer, err=None): def fire_finished_deferred(): self._verified = True for p, (w, finished_deferred) in list(self.writers.items()): if w == writer: del self.writers[p] finished_deferred.callback(self) return True log.warning( "Somehow, the writer that was accepted as being valid was already removed: %s", writer) return False def errback_finished_deferred(err): for p, (w, finished_deferred) in list(self.writers.items()): if w == writer: del self.writers[p] finished_deferred.errback(err) def cancel_other_downloads(): for p, (w, finished_deferred) in self.writers.items(): w.close() if err is None: if writer.len_so_far == self.length and writer.blob_hash == self.blob_hash: if self._verified is False: d = self.save_verified_blob(writer) d.addCallbacks(lambda _: fire_finished_deferred(), errback_finished_deferred) d.addCallback(lambda _: cancel_other_downloads()) else: d = defer.succeed(None) fire_finished_deferred() else: if writer.len_so_far != self.length: err_string = "blob length is %i vs expected %i" % (writer.len_so_far, self.length) else: err_string = f"blob hash is {writer.blob_hash} vs expected {self.blob_hash}" errback_finished_deferred(Failure(InvalidDataError(err_string))) d = defer.succeed(None) else: errback_finished_deferred(err) d = defer.succeed(None) d.addBoth(lambda _: writer.close_handle()) return d def save_verified_blob(self, writer): # we cannot have multiple _save_verified_blob interrupting # each other, can happen since startProducing is a deferred return self.blob_write_lock.run(self._save_verified_blob, writer) @defer.inlineCallbacks def _save_verified_blob(self, writer): if self.saved_verified_blob is False: writer.write_handle.seek(0) out_path = os.path.join(self.blob_dir, self.blob_hash) producer = FileBodyProducer(writer.write_handle) yield producer.startProducing(open(out_path, 'wb')) self.saved_verified_blob = True defer.returnValue(True) else: raise DownloadCanceledError()