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repository: simplify LoggedIO._read
Code gets simpler if we always only use the (shorter) header_fmt. That format ALWAYS applies, to all tags borg writes. If the tag unpacked from there indicates that there is also a chunkid to read (like for PUT and DEL), we can decide that inside _read and then read the chunkid from the fd.
This commit is contained in:
Thomas Waldmann
parent
b9ea17da77
commit
cfa34bdf71
1 changed files with 33 additions and 38 deletions
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@ -807,7 +807,7 @@ def complete_xfer(intermediate=True):
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# do not remove entry with empty shadowed_segments list here,
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# it is needed for shadowed_put_exists code (see below)!
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pass
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self.storage_quota_use -= len(data) + self.io.put_header_fmt.size
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self.storage_quota_use -= len(data) + self.io.HEADER_ID_SIZE
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elif tag == TAG_DELETE and not in_index:
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# If the shadow index doesn't contain this key, then we can't say if there's a shadowed older tag,
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# therefore we do not drop the delete, but write it to a current segment.
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@ -1208,7 +1208,7 @@ def put(self, id, data, wait=True):
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# be in the repo index (and we won't need it in the shadow_index).
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self._delete(id, segment, offset, update_shadow_index=False)
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segment, offset = self.io.write_put(id, data)
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self.storage_quota_use += len(data) + self.io.put_header_fmt.size
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self.storage_quota_use += len(data) + self.io.HEADER_ID_SIZE
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self.segments.setdefault(segment, 0)
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self.segments[segment] += 1
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self.index[id] = segment, offset
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@ -1269,8 +1269,6 @@ class SegmentFull(Exception):
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header_fmt = struct.Struct('<IIB')
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assert header_fmt.size == 9
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put_header_fmt = struct.Struct('<IIB32s')
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assert put_header_fmt.size == 41
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header_no_crc_fmt = struct.Struct('<IB')
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assert header_no_crc_fmt.size == 5
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crc_fmt = struct.Struct('<I')
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@ -1279,6 +1277,8 @@ class SegmentFull(Exception):
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_commit = header_no_crc_fmt.pack(9, TAG_COMMIT)
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COMMIT = crc_fmt.pack(crc32(_commit)) + _commit
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HEADER_ID_SIZE = header_fmt.size + 32
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def __init__(self, path, limit, segments_per_dir, capacity=90):
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self.path = path
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self.fds = LRUCache(capacity, dispose=self._close_fd)
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@ -1490,7 +1490,7 @@ def iter_objects(self, segment, offset=0, include_data=False, read_data=True):
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offset = MAGIC_LEN
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header = fd.read(self.header_fmt.size)
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while header:
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size, tag, key, data = self._read(fd, self.header_fmt, header, segment, offset,
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size, tag, key, data = self._read(fd, header, segment, offset,
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(TAG_PUT, TAG_DELETE, TAG_COMMIT),
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read_data=read_data)
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if include_data:
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@ -1549,31 +1549,25 @@ def read(self, segment, offset, id, read_data=True):
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self._write_fd.sync()
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fd = self.get_fd(segment)
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fd.seek(offset)
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header = fd.read(self.put_header_fmt.size)
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size, tag, key, data = self._read(fd, self.put_header_fmt, header, segment, offset, (TAG_PUT, ), read_data)
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header = fd.read(self.header_fmt.size)
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size, tag, key, data = self._read(fd, header, segment, offset, (TAG_PUT,), read_data)
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if id != key:
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raise IntegrityError('Invalid segment entry header, is not for wanted id [segment {}, offset {}]'.format(
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segment, offset))
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return data if read_data else size
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def _read(self, fd, fmt, header, segment, offset, acceptable_tags, read_data=True):
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def _read(self, fd, header, segment, offset, acceptable_tags, read_data=True):
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# some code shared by read() and iter_objects()
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# See comment on MAX_TAG_ID for details
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assert max(acceptable_tags) <= MAX_TAG_ID, 'Exceeding MAX_TAG_ID will break backwards compatibility'
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fmt = self.header_fmt
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try:
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hdr_tuple = fmt.unpack(header)
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except struct.error as err:
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raise IntegrityError('Invalid segment entry header [segment {}, offset {}]: {}'.format(
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segment, offset, err)) from None
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if fmt is self.put_header_fmt:
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crc, size, tag, key = hdr_tuple
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elif fmt is self.header_fmt:
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crc, size, tag = hdr_tuple
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key = None
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else:
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raise TypeError("_read called with unsupported format")
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length = size - fmt.size # we already read the header
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if size > MAX_OBJECT_SIZE:
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# if you get this on an archive made with borg < 1.0.7 and millions of files and
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# you need to restore it, you can disable this check by using "if False:" above.
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@ -1582,27 +1576,28 @@ def _read(self, fd, fmt, header, segment, offset, acceptable_tags, read_data=Tru
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if size < fmt.size:
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raise IntegrityError('Invalid segment entry size {} - too small [segment {}, offset {}]'.format(
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size, segment, offset))
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length = size - fmt.size
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if read_data:
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if tag in (TAG_PUT, TAG_DELETE):
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key = fd.read(32)
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length -= 32
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if len(key) != 32:
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raise IntegrityError(
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'Segment entry key short read [segment {}, offset {}]: expected {}, got {} bytes'.format(
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segment, offset, 32, len(key)))
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else:
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key = None
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if read_data and tag == TAG_PUT:
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data = fd.read(length)
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if len(data) != length:
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raise IntegrityError('Segment entry data short read [segment {}, offset {}]: expected {}, got {} bytes'.format(
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segment, offset, length, len(data)))
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if crc32(data, crc32(memoryview(header)[4:])) & 0xffffffff != crc:
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if crc32(data, crc32(key, crc32(memoryview(header)[4:]))) & 0xffffffff != crc:
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raise IntegrityError('Segment entry checksum mismatch [segment {}, offset {}]'.format(
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segment, offset))
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if key is None and tag in (TAG_PUT, TAG_DELETE):
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key, data = data[:32], data[32:]
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else:
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if key is None and tag in (TAG_PUT, TAG_DELETE):
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key = fd.read(32)
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length -= 32
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if len(key) != 32:
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raise IntegrityError('Segment entry key short read [segment {}, offset {}]: expected {}, got {} bytes'.format(
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segment, offset, 32, len(key)))
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data = None
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if length > 0:
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oldpos = fd.tell()
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seeked = fd.seek(length, os.SEEK_CUR) - oldpos
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data = None
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if seeked != length:
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raise IntegrityError('Segment entry data short seek [segment {}, offset {}]: expected {}, got {} bytes'.format(
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segment, offset, length, seeked))
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@ -1617,7 +1612,7 @@ def write_put(self, id, data, raise_full=False):
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# this would push the segment entry size beyond MAX_OBJECT_SIZE.
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raise IntegrityError(f'More than allowed put data [{data_size} > {MAX_DATA_SIZE}]')
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fd = self.get_write_fd(want_new=(id == Manifest.MANIFEST_ID), raise_full=raise_full)
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size = data_size + self.put_header_fmt.size
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size = data_size + self.HEADER_ID_SIZE
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offset = self.offset
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header = self.header_no_crc_fmt.pack(size, TAG_PUT)
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crc = self.crc_fmt.pack(crc32(data, crc32(id, crc32(header))) & 0xffffffff)
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@ -1627,11 +1622,11 @@ def write_put(self, id, data, raise_full=False):
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def write_delete(self, id, raise_full=False):
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fd = self.get_write_fd(want_new=(id == Manifest.MANIFEST_ID), raise_full=raise_full)
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header = self.header_no_crc_fmt.pack(self.put_header_fmt.size, TAG_DELETE)
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header = self.header_no_crc_fmt.pack(self.HEADER_ID_SIZE, TAG_DELETE)
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crc = self.crc_fmt.pack(crc32(id, crc32(header)) & 0xffffffff)
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fd.write(b''.join((crc, header, id)))
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self.offset += self.put_header_fmt.size
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return self.segment, self.put_header_fmt.size
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self.offset += self.HEADER_ID_SIZE
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return self.segment, self.HEADER_ID_SIZE
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def write_commit(self, intermediate=False):
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# Intermediate commits go directly into the current segment - this makes checking their validity more
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@ -1646,4 +1641,4 @@ def write_commit(self, intermediate=False):
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return self.segment - 1 # close_segment() increments it
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assert LoggedIO.put_header_fmt.size == 41 # see constants.MAX_OBJECT_SIZE
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assert LoggedIO.HEADER_ID_SIZE == 41 # see constants.MAX_OBJECT_SIZE
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