D5295: branchmap: define a hasbranch() to find whether a branch exists or not

[yuja (Yuya Nishihara)]

yuja added a comment.


  I don't think it's good idea to re-scan the cache file per hasbranch() call.
  Instead, we'll probably need a lazy parser backed by a in-memory cache data.
  The current cache file format is text-based, which wouldn't be easily bisected
  without loading (or memmap) the whole content.
  
  > +def hasbranch(repo, branchname):
  >  +    """check whether a branchname exists in the repo or not by reading the
  >  +    branchmap cache"""
  >  +
  >  +    if not repo.cachevfs.exists(_filename(repo)):
  >  +        # branchmap file is not present, let's go repo.branchmap() route which
  >  +        # will create that file
  >  +        return branchname in repo.branchmap()
  >  +
  >  +    # TODO: implement binary-search here for faster search
  >  +    with repo.cachevfs(_filename(repo)) as f:
  >  +        f = repo.cachevfs(_filename(repo))
  >  +        lineiter = iter(f)
  >  +        next(lineiter).rstrip('\n').split(" ", 2)
  
  Need to check if the cache file is valid.
  
  > +        for l in lineiter:
  >  +            l = l.rstrip('\n')
  >  +            if not l:
  >  +                continue
  >  +            label = l.split(" ", 2)[2]
  >  +            label = encoding.tolocal(label.strip())
  >  +            if label == branchname:
  
  And maybe need to check if the node exists.
  
  > +                return True
  >  +    return False

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D5295

To: pulkit, #hg-reviewers
Cc: yuja, mercurial-devel