comparison mercurial/tags.py @ 45787:225e513c444e

tags: add safety check for len(record) while reading hgtagsfnodescache

I am trying to fix a breakage where somehow we end up getting a node of 12
length from `getfnode()`. Understanding the hgtagsfnodescache code, it seems
highly unlikely that it can happen unless one of `mctx.readfast().get()` or
`ctx.filenode()` is returning a node of 12 length.

For safety, I think it's better to add a check to make sure that record which we
are parsing is of same length we are expecting otherwise we consider that as
invalid record.

Differential Revision: https://phab.mercurial-scm.org/D9169

45786:37c65704869d

        offset = rev * _fnodesrecsize
        record = b'%s' % self._raw[offset : offset + _fnodesrecsize]
        properprefix = node[0:4]

        # Validate and return existing entry.
        if record != _fnodesmissingrec:
            fileprefix = record[0:4]

            if fileprefix == properprefix:
                self.hitcount += 1
                return record[4:]

45787:225e513c444e

        offset = rev * _fnodesrecsize
        record = b'%s' % self._raw[offset : offset + _fnodesrecsize]
        properprefix = node[0:4]

        # Validate and return existing entry.
        if record != _fnodesmissingrec and len(record) == _fnodesrecsize:
            fileprefix = record[0:4]

            if fileprefix == properprefix:
                self.hitcount += 1
                return record[4:]