--- a/mercurial/branchmap.py	Wed Sep 25 01:16:47 2024 -0400
+++ b/mercurial/branchmap.py	Sun Sep 22 15:55:46 2024 +0200
@@ -7,8 +7,6 @@
 
 from __future__ import annotations
 
-import struct
-
 from .node import (
     bin,
     hex,
@@ -49,10 +47,6 @@
 
 subsettable = repoviewutil.subsettable
 
-calcsize = struct.calcsize
-pack_into = struct.pack_into
-unpack_from = struct.unpack_from
-
 
 class BranchMapCache:
     """mapping of filtered views of repo with their branchcache"""
@@ -1087,328 +1081,3 @@
         closednodes: Optional[Set[bytes]] = None,
     ) -> None:
         super().__init__(repo=repo, entries=entries, closed_nodes=closednodes)
-
-
-# Revision branch info cache
-
-_rbcversion = b'-v1'
-_rbcnames = b'rbc-names' + _rbcversion
-_rbcrevs = b'rbc-revs' + _rbcversion
-# [4 byte hash prefix][4 byte branch name number with sign bit indicating open]
-_rbcrecfmt = b'>4sI'
-_rbcrecsize = calcsize(_rbcrecfmt)
-_rbcmininc = 64 * _rbcrecsize
-_rbcnodelen = 4
-_rbcbranchidxmask = 0x7FFFFFFF
-_rbccloseflag = 0x80000000
-
-
-class rbcrevs:
-    """a byte string consisting of an immutable prefix followed by a mutable suffix"""
-
-    def __init__(self, revs):
-        self._prefix = revs
-        self._rest = bytearray()
-
-    def __len__(self):
-        return len(self._prefix) + len(self._rest)
-
-    def unpack_record(self, rbcrevidx):
-        if rbcrevidx < len(self._prefix):
-            return unpack_from(_rbcrecfmt, util.buffer(self._prefix), rbcrevidx)
-        else:
-            return unpack_from(
-                _rbcrecfmt,
-                util.buffer(self._rest),
-                rbcrevidx - len(self._prefix),
-            )
-
-    def make_mutable(self):
-        if len(self._prefix) > 0:
-            entirety = bytearray()
-            entirety[:] = self._prefix
-            entirety.extend(self._rest)
-            self._rest = entirety
-            self._prefix = bytearray()
-
-    def truncate(self, pos):
-        self.make_mutable()
-        del self._rest[pos:]
-
-    def pack_into(self, rbcrevidx, node, branchidx):
-        if rbcrevidx < len(self._prefix):
-            self.make_mutable()
-        buf = self._rest
-        start_offset = rbcrevidx - len(self._prefix)
-        end_offset = start_offset + _rbcrecsize
-
-        if len(self._rest) < end_offset:
-            # bytearray doesn't allocate extra space at least in Python 3.7.
-            # When multiple changesets are added in a row, precise resize would
-            # result in quadratic complexity. Overallocate to compensate by
-            # using the classic doubling technique for dynamic arrays instead.
-            # If there was a gap in the map before, less space will be reserved.
-            self._rest.extend(b'\0' * end_offset)
-        return pack_into(
-            _rbcrecfmt,
-            buf,
-            start_offset,
-            node,
-            branchidx,
-        )
-
-    def extend(self, extension):
-        return self._rest.extend(extension)
-
-    def slice(self, begin, end):
-        if begin < len(self._prefix):
-            acc = bytearray()
-            acc[:] = self._prefix[begin:end]
-            acc.extend(
-                self._rest[begin - len(self._prefix) : end - len(self._prefix)]
-            )
-            return acc
-        return self._rest[begin - len(self._prefix) : end - len(self._prefix)]
-
-
-class revbranchcache:
-    """Persistent cache, mapping from revision number to branch name and close.
-    This is a low level cache, independent of filtering.
-
-    Branch names are stored in rbc-names in internal encoding separated by 0.
-    rbc-names is append-only, and each branch name is only stored once and will
-    thus have a unique index.
-
-    The branch info for each revision is stored in rbc-revs as constant size
-    records. The whole file is read into memory, but it is only 'parsed' on
-    demand. The file is usually append-only but will be truncated if repo
-    modification is detected.
-    The record for each revision contains the first 4 bytes of the
-    corresponding node hash, and the record is only used if it still matches.
-    Even a completely trashed rbc-revs fill thus still give the right result
-    while converging towards full recovery ... assuming no incorrectly matching
-    node hashes.
-    The record also contains 4 bytes where 31 bits contains the index of the
-    branch and the last bit indicate that it is a branch close commit.
-    The usage pattern for rbc-revs is thus somewhat similar to 00changelog.i
-    and will grow with it but be 1/8th of its size.
-    """
-
-    def __init__(self, repo, readonly=True):
-        assert repo.filtername is None
-        self._repo = repo
-        self._names = []  # branch names in local encoding with static index
-        self._rbcrevs = rbcrevs(bytearray())
-        self._rbcsnameslen = 0  # length of names read at _rbcsnameslen
-        try:
-            bndata = repo.cachevfs.read(_rbcnames)
-            self._rbcsnameslen = len(bndata)  # for verification before writing
-            if bndata:
-                self._names = [
-                    encoding.tolocal(bn) for bn in bndata.split(b'\0')
-                ]
-        except (IOError, OSError):
-            if readonly:
-                # don't try to use cache - fall back to the slow path
-                self.branchinfo = self._branchinfo
-
-        if self._names:
-            try:
-                usemmap = repo.ui.configbool(b'storage', b'revbranchcache.mmap')
-                with repo.cachevfs(_rbcrevs) as fp:
-                    if usemmap and repo.cachevfs.is_mmap_safe(_rbcrevs):
-                        data = util.buffer(util.mmapread(fp))
-                    else:
-                        data = fp.read()
-                self._rbcrevs = rbcrevs(data)
-            except (IOError, OSError) as inst:
-                repo.ui.debug(
-                    b"couldn't read revision branch cache: %s\n"
-                    % stringutil.forcebytestr(inst)
-                )
-        # remember number of good records on disk
-        self._rbcrevslen = min(
-            len(self._rbcrevs) // _rbcrecsize, len(repo.changelog)
-        )
-        if self._rbcrevslen == 0:
-            self._names = []
-        self._rbcnamescount = len(self._names)  # number of names read at
-        # _rbcsnameslen
-
-    def _clear(self):
-        self._rbcsnameslen = 0
-        del self._names[:]
-        self._rbcnamescount = 0
-        self._rbcrevslen = len(self._repo.changelog)
-        self._rbcrevs = rbcrevs(bytearray(self._rbcrevslen * _rbcrecsize))
-        util.clearcachedproperty(self, b'_namesreverse')
-
-    @util.propertycache
-    def _namesreverse(self):
-        return {b: r for r, b in enumerate(self._names)}
-
-    def branchinfo(self, rev):
-        """Return branch name and close flag for rev, using and updating
-        persistent cache."""
-        changelog = self._repo.changelog
-        rbcrevidx = rev * _rbcrecsize
-
-        # avoid negative index, changelog.read(nullrev) is fast without cache
-        if rev == nullrev:
-            return changelog.branchinfo(rev)
-
-        # if requested rev isn't allocated, grow and cache the rev info
-        if len(self._rbcrevs) < rbcrevidx + _rbcrecsize:
-            return self._branchinfo(rev)
-
-        # fast path: extract data from cache, use it if node is matching
-        reponode = changelog.node(rev)[:_rbcnodelen]
-        cachenode, branchidx = self._rbcrevs.unpack_record(rbcrevidx)
-        close = bool(branchidx & _rbccloseflag)
-        if close:
-            branchidx &= _rbcbranchidxmask
-        if cachenode == b'\0\0\0\0':
-            pass
-        elif cachenode == reponode:
-            try:
-                return self._names[branchidx], close
-            except IndexError:
-                # recover from invalid reference to unknown branch
-                self._repo.ui.debug(
-                    b"referenced branch names not found"
-                    b" - rebuilding revision branch cache from scratch\n"
-                )
-                self._clear()
-        else:
-            # rev/node map has changed, invalidate the cache from here up
-            self._repo.ui.debug(
-                b"history modification detected - truncating "
-                b"revision branch cache to revision %d\n" % rev
-            )
-            truncate = rbcrevidx + _rbcrecsize
-            self._rbcrevs.truncate(truncate)
-            self._rbcrevslen = min(self._rbcrevslen, truncate)
-
-        # fall back to slow path and make sure it will be written to disk
-        return self._branchinfo(rev)
-
-    def _branchinfo(self, rev):
-        """Retrieve branch info from changelog and update _rbcrevs"""
-        changelog = self._repo.changelog
-        b, close = changelog.branchinfo(rev)
-        if b in self._namesreverse:
-            branchidx = self._namesreverse[b]
-        else:
-            branchidx = len(self._names)
-            self._names.append(b)
-            self._namesreverse[b] = branchidx
-        reponode = changelog.node(rev)
-        if close:
-            branchidx |= _rbccloseflag
-        self._setcachedata(rev, reponode, branchidx)
-        return b, close
-
-    def setdata(self, rev, changelogrevision):
-        """add new data information to the cache"""
-        branch, close = changelogrevision.branchinfo
-
-        if branch in self._namesreverse:
-            branchidx = self._namesreverse[branch]
-        else:
-            branchidx = len(self._names)
-            self._names.append(branch)
-            self._namesreverse[branch] = branchidx
-        if close:
-            branchidx |= _rbccloseflag
-        self._setcachedata(rev, self._repo.changelog.node(rev), branchidx)
-        # If no cache data were readable (non exists, bad permission, etc)
-        # the cache was bypassing itself by setting:
-        #
-        #   self.branchinfo = self._branchinfo
-        #
-        # Since we now have data in the cache, we need to drop this bypassing.
-        if 'branchinfo' in vars(self):
-            del self.branchinfo
-
-    def _setcachedata(self, rev, node, branchidx):
-        """Writes the node's branch data to the in-memory cache data."""
-        if rev == nullrev:
-            return
-        rbcrevidx = rev * _rbcrecsize
-        self._rbcrevs.pack_into(rbcrevidx, node, branchidx)
-        self._rbcrevslen = min(self._rbcrevslen, rev)
-
-        tr = self._repo.currenttransaction()
-        if tr:
-            tr.addfinalize(b'write-revbranchcache', self.write)
-
-    def write(self, tr=None):
-        """Save branch cache if it is dirty."""
-        repo = self._repo
-        wlock = None
-        step = b''
-        try:
-            # write the new names
-            if self._rbcnamescount < len(self._names):
-                wlock = repo.wlock(wait=False)
-                step = b' names'
-                self._writenames(repo)
-
-            # write the new revs
-            start = self._rbcrevslen * _rbcrecsize
-            if start != len(self._rbcrevs):
-                step = b''
-                if wlock is None:
-                    wlock = repo.wlock(wait=False)
-                self._writerevs(repo, start)
-
-        except (IOError, OSError, error.Abort, error.LockError) as inst:
-            repo.ui.debug(
-                b"couldn't write revision branch cache%s: %s\n"
-                % (step, stringutil.forcebytestr(inst))
-            )
-        finally:
-            if wlock is not None:
-                wlock.release()
-
-    def _writenames(self, repo):
-        """write the new branch names to revbranchcache"""
-        if self._rbcnamescount != 0:
-            f = repo.cachevfs.open(_rbcnames, b'ab')
-            if f.tell() == self._rbcsnameslen:
-                f.write(b'\0')
-            else:
-                f.close()
-                repo.ui.debug(b"%s changed - rewriting it\n" % _rbcnames)
-                self._rbcnamescount = 0
-                self._rbcrevslen = 0
-        if self._rbcnamescount == 0:
-            # before rewriting names, make sure references are removed
-            repo.cachevfs.unlinkpath(_rbcrevs, ignoremissing=True)
-            f = repo.cachevfs.open(_rbcnames, b'wb')
-        f.write(
-            b'\0'.join(
-                encoding.fromlocal(b)
-                for b in self._names[self._rbcnamescount :]
-            )
-        )
-        self._rbcsnameslen = f.tell()
-        f.close()
-        self._rbcnamescount = len(self._names)
-
-    def _writerevs(self, repo, start):
-        """write the new revs to revbranchcache"""
-        revs = min(len(repo.changelog), len(self._rbcrevs) // _rbcrecsize)
-        with repo.cachevfs.open(_rbcrevs, b'ab') as f:
-            if f.tell() != start:
-                repo.ui.debug(
-                    b"truncating cache/%s to %d\n" % (_rbcrevs, start)
-                )
-                f.seek(start)
-                if f.tell() != start:
-                    start = 0
-                    f.seek(start)
-                f.truncate()
-            end = revs * _rbcrecsize
-            f.write(self._rbcrevs.slice(start, end))
-        self._rbcrevslen = revs