comparison mercurial/repoview.py @ 22150:45b5cd948a4d

repoview: add caching bits

Add a caching infrastructure to cache hidden changesets. The cache tries to read
the cache lazily and falls back to recomputing if no wlock can be obtain.
To validate the cache we store a sha of the obstore content and repo heads in
the beginning of the cache which we check every request.

22149:16ef2c485f03

#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

import copy
import phases
import util
import obsolete
import tags as tagsmod


def hideablerevs(repo):
    """Revisions candidates to be hidden

    This is a standalone function to help extensions to wrap it."""

    tagsmod.readlocaltags(repo.ui, repo, tags, {})
    if tags:
        rev, nodemap = cl.rev, cl.nodemap
        blockers.update(rev(t[0]) for t in tags.values() if t[0] in nodemap)
    return blockers

def computehidden(repo):
    """compute the set of hidden revision to filter

    During most operation hidden should be filtered."""

22150:45b5cd948a4d

#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

import copy
import error
import hashlib
import phases
import util
import obsolete
import struct
import tags as tagsmod
from mercurial.i18n import _

def hideablerevs(repo):
    """Revisions candidates to be hidden

    This is a standalone function to help extensions to wrap it."""

    tagsmod.readlocaltags(repo.ui, repo, tags, {})
    if tags:
        rev, nodemap = cl.rev, cl.nodemap
        blockers.update(rev(t[0]) for t in tags.values() if t[0] in nodemap)
    return blockers

cacheversion = 1
cachefile = 'cache/hidden'

def cachehash(repo, hideable):
    """return sha1 hash of repository data to identify a valid cache.

    We calculate a sha1 of repo heads and the content of the obsstore and write
    it to the cache. Upon reading we can easily validate by checking the hash
    against the stored one and discard the cache in case the hashes don't match.
    """
    h = hashlib.sha1()
    h.update(''.join(repo.heads()))
    h.update(str(hash(frozenset(hideable))))
    return h.digest()

def trywritehiddencache(repo, hideable, hidden):
    """write cache of hidden changesets to disk

    Will not write the cache if a wlock cannot be obtained lazily.
    The cache consists of a head of 22byte:
       2 byte    version number of the cache
      20 byte    sha1 to validate the cache
     n*4 byte    hidden revs
    """
    wlock = fh = None
    try:
        wlock = repo.wlock(wait=False)
        # write cache to file
        newhash = cachehash(repo, hideable)
        sortedset = sorted(hidden)
        data = struct.pack('>%iI' % len(sortedset), *sortedset)
        fh = repo.vfs.open(cachefile, 'w+b', atomictemp=True)
        fh.write(struct.pack(">H", cacheversion))
        fh.write(newhash)
        fh.write(data)
    except (IOError, OSError):
        ui.debug('error writing hidden changesets cache')
    except error.LockHeld:
        ui.debug('cannot obtain lock to write hidden changesets cache')
    finally:
        if fh:
            fh.close()
        if wlock:
            wlock.release()

def tryreadcache(repo, hideable):
    """read a cache if the cache exists and is valid, otherwise returns None."""
    hidden = fh = None
    try:
        if repo.vfs.exists(cachefile):
            fh = repo.vfs.open(cachefile, 'rb')
            version, = struct.unpack(">H", fh.read(2))
            oldhash = fh.read(20)
            newhash = cachehash(repo, hideable)
            if (cacheversion, oldhash) == (version, newhash):
                # cache is valid, so we can start reading the hidden revs
                data = fh.read()
                count = len(data) / 4
                hidden = frozenset(struct.unpack('>%iI' % count, data))
        return hidden
    finally:
        if fh:
            fh.close()

def computehidden(repo):
    """compute the set of hidden revision to filter

    During most operation hidden should be filtered."""