comparison mercurial/revlog.py @ 39877:f8eb71f9e3bd

storageutil: new module for storage primitives (API)

There will exist common code between storage backends. It would
be nice to have a central place to put that code.

This commit attempts to create that place by creating the
"storageutil" module.

The first thing we move is revlog.hash(), which is the function for
computing the SHA-1 hash of revision fulltext and parents.

Differential Revision: https://phab.mercurial-scm.org/D4753

39876:a269fa55467e

from __future__ import absolute_import

import collections
import contextlib
import errno
import hashlib
import os
import re
import struct
import zlib

from .revlogutils import (
    deltas as deltautil,
)
from .utils import (
    interfaceutil,
    stringutil,
)

# blanked usage of all the name to prevent pyflakes constraints
# We need these name available in the module for extensions.

def offset_type(offset, type):
    if (type & ~REVIDX_KNOWN_FLAGS) != 0:
        raise ValueError('unknown revlog index flags')
    return int(int(offset) << 16 | type)

_nullhash = hashlib.sha1(nullid)

def hash(text, p1, p2):
    """generate a hash from the given text and its parent hashes

    This hash combines both the current file contents and its history
    in a manner that makes it easy to distinguish nodes with the same
    content in the revision graph.
    """
    # As of now, if one of the parent node is null, p2 is null
    if p2 == nullid:
        # deep copy of a hash is faster than creating one
        s = _nullhash.copy()
        s.update(p1)
    else:
        # none of the parent nodes are nullid
        if p1 < p2:
            a = p1
            b = p2
        else:
            a = p2
            b = p1
        s = hashlib.sha1(a)
        s.update(b)
    s.update(text)
    return s.digest()

@attr.s(slots=True, frozen=True)
class _revisioninfo(object):
    """Information about a revision that allows building its fulltext
    node:       expected hash of the revision

        """compare text with a given file revision

        returns True if text is different than what is stored.
        """
        p1, p2 = self.parents(node)
        return hash(text, p1, p2) != node

    def _cachesegment(self, offset, data):
        """Add a segment to the revlog cache.

        Accepts an absolute offset and the data that is at that location.

        """Compute a node hash.

        Available as a function so that subclasses can replace the hash
        as needed.
        """
        return hash(text, p1, p2)

    def _processflags(self, text, flags, operation, raw=False):
        """Inspect revision data flags and applies transforms defined by
        registered flag processors.

39877:f8eb71f9e3bd

from __future__ import absolute_import

import collections
import contextlib
import errno
import os
import re
import struct
import zlib

from .revlogutils import (
    deltas as deltautil,
)
from .utils import (
    interfaceutil,
    storageutil,
    stringutil,
)

# blanked usage of all the name to prevent pyflakes constraints
# We need these name available in the module for extensions.

def offset_type(offset, type):
    if (type & ~REVIDX_KNOWN_FLAGS) != 0:
        raise ValueError('unknown revlog index flags')
    return int(int(offset) << 16 | type)

@attr.s(slots=True, frozen=True)
class _revisioninfo(object):
    """Information about a revision that allows building its fulltext
    node:       expected hash of the revision

        """compare text with a given file revision

        returns True if text is different than what is stored.
        """
        p1, p2 = self.parents(node)
        return storageutil.hashrevisionsha1(text, p1, p2) != node

    def _cachesegment(self, offset, data):
        """Add a segment to the revlog cache.

        Accepts an absolute offset and the data that is at that location.

        """Compute a node hash.

        Available as a function so that subclasses can replace the hash
        as needed.
        """
        return storageutil.hashrevisionsha1(text, p1, p2)

    def _processflags(self, text, flags, operation, raw=False):
        """Inspect revision data flags and applies transforms defined by
        registered flag processors.