comparison mercurial/revlogutils/docket.py @ 47312:7ea39d633cf3

docket: move the uid logic in the `revlogutils.docket` module

We want to use it for revlog-v2 (& Co), it seems more logical to have the logic
lives inside the `docket` file than the `nodemap` file.

Differential Revision: https://phab.mercurial-scm.org/D10755

47311:5bc6d2fc1cfc

#
# * a data file, containing variable width data for these revisions,

from __future__ import absolute_import

import struct

from .. import (
    error,
    util,
)

from . import (
    constants,
)

# Docket format
#
# * 4 bytes: revlog version
#          |   This is mandatory as docket must be compatible with the previous

47312:7ea39d633cf3

#
# * a data file, containing variable width data for these revisions,

from __future__ import absolute_import

import errno
import os
import random
import struct

from .. import (
    encoding,
    error,
    node,
    pycompat,
    util,
)

from . import (
    constants,
)


def make_uid(id_size=8):
    """return a new unique identifier.

    The identifier is random and composed of ascii characters."""
    # size we "hex" the result we need half the number of bits to have a final
    # uuid of size ID_SIZE
    return node.hex(os.urandom(id_size // 2))


# some special test logic to avoid anoying random output in the test
stable_docket_file = encoding.environ.get(b'HGTEST_UUIDFILE')

if stable_docket_file:

    def make_uid(id_size=8):
        try:
            with open(stable_docket_file, mode='rb') as f:
                seed = f.read().strip()
        except IOError as inst:
            if inst.errno != errno.ENOENT:
                raise
            seed = b'04'  # chosen by a fair dice roll. garanteed to be random
        if pycompat.ispy3:
            iter_seed = iter(seed)
        else:
            iter_seed = (ord(c) for c in seed)
        # some basic circular sum hashing on 64 bits
        int_seed = 0
        low_mask = int('1' * 35, 2)
        for i in iter_seed:
            high_part = int_seed >> 35
            low_part = (int_seed & low_mask) << 28
            int_seed = high_part + low_part + i
        r = random.Random()
        if pycompat.ispy3:
            r.seed(int_seed, version=1)
        else:
            r.seed(int_seed)
        # once we drop python 3.8 support we can simply use r.randbytes
        raw = r.getrandbits(id_size * 4)
        assert id_size == 8
        p = struct.pack('>L', raw)
        new = node.hex(p)
        with open(stable_docket_file, 'wb') as f:
            f.write(new)
        return new


# Docket format
#
# * 4 bytes: revlog version
#          |   This is mandatory as docket must be compatible with the previous