diff --git a/swh/graph/pid.py b/swh/graph/pid.py index 100e642..fd7829d 100644 --- a/swh/graph/pid.py +++ b/swh/graph/pid.py @@ -1,371 +1,371 @@ # Copyright (C) 2019 The Software Heritage developers # See the AUTHORS file at the top-level directory of this distribution # License: GNU General Public License version 3, or any later version # See top-level LICENSE file for more information import mmap import os import struct from collections.abc import MutableMapping from enum import Enum -from mmap import ACCESS_READ, ACCESS_WRITE, MAP_SHARED, MAP_PRIVATE +from mmap import MAP_SHARED, MAP_PRIVATE from swh.model.identifiers import PersistentId, parse_persistent_identifier PID_BIN_FMT = 'BB20s' # 2 unsigned chars + 20 bytes INT_BIN_FMT = '>q' # big endian, 8-byte integer PID_BIN_SIZE = 22 # in bytes INT_BIN_SIZE = 8 # in bytes class PidType(Enum): """types of existing PIDs, used to serialize PID type as a (char) integer note that the order does matter also for driving the binary search in PID-indexed maps """ content = 1 directory = 2 origin = 3 release = 4 revision = 5 snapshot = 6 def str_to_bytes(pid): """Convert a PID to a byte sequence The binary format used to represent PIDs as byte sequences is as follows: - 1 byte for the namespace version represented as a C `unsigned char` - 1 byte for the object type, as the int value of :class:`PidType` enums, represented as a C `unsigned char` - 20 bytes for the SHA1 digest as a byte sequence Args: pid (str): persistent identifier Returns: bytes (bytes): byte sequence representation of pid """ pid = parse_persistent_identifier(pid) return struct.pack(PID_BIN_FMT, pid.scheme_version, PidType[pid.object_type].value, bytes.fromhex(pid.object_id)) def bytes_to_str(bytes): """Inverse function of :func:`str_to_bytes` See :func:`str_to_bytes` for a description of the binary PID format. Args: bytes (bytes): byte sequence representation of pid Returns: pid (str): persistent identifier """ (version, type, bin_digest) = struct.unpack(PID_BIN_FMT, bytes) pid = PersistentId(object_type=PidType(type).name, object_id=bin_digest) return str(pid) class _OnDiskMap(): """mmap-ed on-disk sequence of fixed size records """ def __init__(self, record_size, fname, mode='rb', length=None): """open an existing on-disk map Args: record_size (int): size of each record in bytes fname (str): path to the on-disk map mode (str): file open mode, usually either 'rb' for read-only maps, 'wb' for creating new maps, or 'rb+' for updating existing ones (default: 'rb') length (int): map size in number of logical records; used to initialize writable maps at creation time. Must be given when mode is 'wb' and the map doesn't exist on disk; ignored otherwise """ if mode not in ['rb', 'wb', 'rb+']: raise ValueError('invalid file open mode: ' + mode) new_map = (mode == 'wb') writable_map = mode in ['wb', 'rb+'] os_mode = None if mode == 'rb': os_mode = os.O_RDONLY elif mode == 'wb': os_mode = os.O_RDWR | os.O_CREAT elif mode == 'rb+': os_mode = os.O_RDWR self.record_size = record_size self.fd = os.open(fname, os_mode) if new_map: if length is None: raise ValueError('missing length when creating new map') os.truncate(self.fd, length * self.record_size) self.size = os.path.getsize(fname) (self.length, remainder) = divmod(self.size, record_size) if remainder: raise ValueError( 'map size {} is not a multiple of the record size {}'.format( self.size, record_size)) self.mm = mmap.mmap( self.fd, self.size, flags=MAP_SHARED if writable_map else MAP_PRIVATE) def close(self): """close the map shuts down both the mmap and the underlying file descriptor """ if not self.mm.closed: self.mm.close() os.close(self.fd) def __len__(self): return self.length def __delitem__(self, pos): raise NotImplementedError('cannot delete records from fixed-size map') class PidToIntMap(_OnDiskMap, MutableMapping): """memory mapped map from PID (:ref:`persistent-identifiers`) to a continuous range 0..N of (8-byte long) integers This is the converse mapping of :class:`IntToPidMap`. The on-disk serialization format is a sequence of fixed length (30 bytes) records with the following fields: - PID (22 bytes): binary PID representation as per :func:`str_to_bytes` - long (8 bytes): big endian long integer The records are sorted lexicographically by PID type and checksum, where type is the integer value of :class:`PidType`. PID lookup in the map is performed via binary search. Hence a huge map with, say, 11 B entries, will require ~30 disk seeks. Note that, due to fixed size + ordering, it is not possible to create these maps by random writing. Hence, __setitem__ can be used only to *update* the value associated to an existing key, rather than to add a missing item. To create an entire map from scratch, you should do so *sequentially*, using static method :meth:`write_record` (or, at your own risk, by hand via the mmap :attr:`mm`). """ # record binary format: PID + a big endian 8-byte big endian integer RECORD_BIN_FMT = '>' + PID_BIN_FMT + 'q' RECORD_SIZE = PID_BIN_SIZE + INT_BIN_SIZE def __init__(self, fname, mode='rb', length=None): """open an existing on-disk map Args: fname (str): path to the on-disk map mode (str): file open mode, usually either 'rb' for read-only maps, 'wb' for creating new maps, or 'rb+' for updating existing ones (default: 'rb') length (int): map size in number of logical records; used to initialize read-write maps at creation time. Must be given when mode is 'wb'; ignored otherwise """ super().__init__(self.RECORD_SIZE, fname, mode=mode, length=length) def _get_bin_record(self, pos): """seek and return the (binary) record at a given (logical) position see :func:`_get_record` for an equivalent function with additional deserialization Args: pos: 0-based record number Returns: tuple: a pair `(pid, int)`, where pid and int are bytes """ rec_pos = pos * self.RECORD_SIZE int_pos = rec_pos + PID_BIN_SIZE return (self.mm[rec_pos:int_pos], self.mm[int_pos:int_pos+INT_BIN_SIZE]) def _get_record(self, pos): """seek and return the record at a given (logical) position moral equivalent of :func:`_get_bin_record`, with additional deserialization to non-bytes types Args: pos: 0-based record number Returns: tuple: a pair `(pid, int)`, where pid is a string-based PID and int an integer """ (pid_bytes, int_bytes) = self._get_bin_record(pos) return (bytes_to_str(pid_bytes), struct.unpack(INT_BIN_FMT, int_bytes)[0]) @classmethod def write_record(cls, f, pid, int): """write a logical record to a file-like object Args: f: file-like object to write the record to pid (str): textual PID int (int): PID integer identifier """ f.write(str_to_bytes(pid)) f.write(struct.pack(INT_BIN_FMT, int)) def _find(self, pid_str): """lookup the integer identifier of a pid and its position Args: pid (str): the pid as a string Returns: tuple: a pair `(pid, pos)` with pid integer identifier and its logical record position in the map """ if not isinstance(pid_str, str): raise TypeError('PID must be a str, not ' + type(pid_str)) try: target = str_to_bytes(pid_str) # desired PID as bytes except ValueError: raise ValueError('invalid PID: "{}"'.format(pid_str)) min = 0 max = self.length - 1 while (min <= max): mid = (min + max) // 2 (pid, int) = self._get_bin_record(mid) if pid < target: min = mid + 1 elif pid > target: max = mid - 1 else: # pid == target return (struct.unpack(INT_BIN_FMT, int)[0], mid) raise KeyError(pid_str) def __getitem__(self, pid_str): """lookup the integer identifier of a PID Args: pid (str): the PID as a string Returns: int: the integer identifier of pid """ return self._find(pid_str)[0] # return element, ignore position def __setitem__(self, pid_str, int): (_pid, pos) = self._find(pid_str) # might raise KeyError and that's OK rec_pos = pos * self.RECORD_SIZE int_pos = rec_pos + PID_BIN_SIZE self.mm[rec_pos:int_pos] = str_to_bytes(pid_str) self.mm[int_pos:int_pos+INT_BIN_SIZE] = struct.pack(INT_BIN_FMT, int) def __iter__(self): for pos in range(self.length): yield self._get_record(pos) class IntToPidMap(_OnDiskMap, MutableMapping): """memory mapped map from a continuous range of 0..N (8-byte long) integers to PIDs (:ref:`persistent-identifiers`) This is the converse mapping of :class:`PidToIntMap`. The on-disk serialization format is a sequence of fixed length (22 bytes), where each record is the binary representation of PID as per :func:`str_to_bytes`. The records are sorted by long integer, so that integer lookup is possible via fixed-offset seek. """ RECORD_BIN_FMT = PID_BIN_FMT RECORD_SIZE = PID_BIN_SIZE def __init__(self, fname, mode='rb', length=None): """open an existing on-disk map Args: fname (str): path to the on-disk map mode (str): file open mode, usually either 'rb' for read-only maps, 'wb' for creating new maps, or 'rb+' for updating existing ones (default: 'rb') size (int): map size in number of logical records; used to initialize read-write maps at creation time. Must be given when mode is 'wb'; ignored otherwise """ super().__init__(self.RECORD_SIZE, fname, mode=mode, length=length) def _get_bin_record(self, pos): """seek and return the (binary) PID at a given (logical) position Args: pos: 0-based record number Returns: bytes: PID as a byte sequence """ rec_pos = pos * self.RECORD_SIZE return self.mm[rec_pos:rec_pos+self.RECORD_SIZE] @classmethod def write_record(cls, f, pid): """write a PID to a file-like object Args: f: file-like object to write the record to pid (str): textual PID """ f.write(str_to_bytes(pid)) def __getitem__(self, pos): orig_pos = pos if pos < 0: pos = len(self) + pos if not (0 <= pos < len(self)): raise IndexError(orig_pos) return bytes_to_str(self._get_bin_record(pos)) def __setitem__(self, pos, pid): rec_pos = pos * self.RECORD_SIZE self.mm[rec_pos:rec_pos+self.RECORD_SIZE] = str_to_bytes(pid) def __iter__(self): for pos in range(self.length): yield (pos, self[pos])