# Copyright 2016-present Facebook. All Rights Reserved.
#
# revmap: trivial hg hash - linelog rev bidirectional map
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
import bisect
import io
import os
import struct
from mercurial.node import hex
from mercurial.pycompat import open
from mercurial import (
error as hgerror,
)
from . import error
# the revmap file format is straightforward:
#
# 8 bytes: header
# 1 byte : flag for linelog revision 1
# ? bytes: (optional) '\0'-terminated path string
# only exists if (flag & renameflag) != 0
# 20 bytes: hg hash for linelog revision 1
# 1 byte : flag for linelog revision 2
# ? bytes: (optional) '\0'-terminated path string
# 20 bytes: hg hash for linelog revision 2
# ....
#
# the implementation is kinda stupid: __init__ loads the whole revmap.
# no laziness. benchmark shows loading 10000 revisions is about 0.015
# seconds, which looks enough for our use-case. if this implementation
# becomes a bottleneck, we can change it to lazily read the file
# from the end.
# whether the changeset is in the side branch. i.e. not in the linear main
# branch but only got referenced by lines in merge changesets.
sidebranchflag = 1
# whether the changeset changes the file path (ie. is a rename)
renameflag = 2
# len(mercurial.node.nullid)
_hshlen = 20
class revmap:
"""trivial hg bin hash - linelog rev bidirectional map
also stores a flag (uint8) for each revision, and track renames.
"""
HEADER = b'REVMAP1\0'
def __init__(self, path=None):
"""create or load the revmap, optionally associate to a file
if path is None, the revmap is entirely in-memory. the caller is
responsible for locking. concurrent writes to a same file is unsafe.
the caller needs to make sure one file is associated to at most one
revmap object at a time."""
self.path = path
self._rev2hsh = [None]
self._rev2flag = [None]
self._hsh2rev = {}
# since rename does not happen frequently, do not store path for every
# revision. self._renamerevs can be used for bisecting.
self._renamerevs = [0]
self._renamepaths = [b'']
self._lastmaxrev = -1
if path:
if os.path.exists(path):
self._load()
else:
# write the header so "append" can do incremental updates
self.flush()
def copyfrom(self, rhs):
"""copy the map data from another revmap. do not affect self.path"""
self._rev2hsh = rhs._rev2hsh[:]
self._rev2flag = rhs._rev2flag[:]
self._hsh2rev = rhs._hsh2rev.copy()
self._renamerevs = rhs._renamerevs[:]
self._renamepaths = rhs._renamepaths[:]
self._lastmaxrev = -1
@property
def maxrev(self):
"""return max linelog revision number"""
return len(self._rev2hsh) - 1
def append(self, hsh, sidebranch=False, path=None, flush=False):
"""add a binary hg hash and return the mapped linelog revision.
if flush is True, incrementally update the file.
"""
if hsh in self._hsh2rev:
raise error.CorruptedFileError(
b'%r is in revmap already' % hex(hsh)
)
if len(hsh) != _hshlen:
raise hgerror.ProgrammingError(
b'hsh must be %d-char long' % _hshlen
)
idx = len(self._rev2hsh)
flag = 0
if sidebranch:
flag |= sidebranchflag
if path is not None and path != self._renamepaths[-1]:
flag |= renameflag
self._renamerevs.append(idx)
self._renamepaths.append(path)
self._rev2hsh.append(hsh)
self._rev2flag.append(flag)
self._hsh2rev[hsh] = idx
if flush:
self.flush()
return idx
def rev2hsh(self, rev):
"""convert linelog revision to hg hash. return None if not found."""
if rev > self.maxrev or rev < 0:
return None
return self._rev2hsh[rev]
def rev2flag(self, rev):
"""get the flag (uint8) for a given linelog revision.
return None if revision does not exist.
"""
if rev > self.maxrev or rev < 0:
return None
return self._rev2flag[rev]
def rev2path(self, rev):
"""get the path for a given linelog revision.
return None if revision does not exist.
"""
if rev > self.maxrev or rev < 0:
return None
idx = bisect.bisect_right(self._renamerevs, rev) - 1
return self._renamepaths[idx]
def hsh2rev(self, hsh):
"""convert hg hash to linelog revision. return None if not found."""
return self._hsh2rev.get(hsh)
def clear(self, flush=False):
"""make the map empty. if flush is True, write to disk"""
# rev 0 is reserved, real rev starts from 1
self._rev2hsh = [None]
self._rev2flag = [None]
self._hsh2rev = {}
self._rev2path = [b'']
self._lastmaxrev = -1
if flush:
self.flush()
def flush(self):
"""write the state down to the file"""
if not self.path:
return
if self._lastmaxrev == -1: # write the entire file
with open(self.path, b'wb') as f:
f.write(self.HEADER)
for i in range(1, len(self._rev2hsh)):
self._writerev(i, f)
else: # append incrementally
with open(self.path, b'ab') as f:
for i in range(self._lastmaxrev + 1, len(self._rev2hsh)):
self._writerev(i, f)
self._lastmaxrev = self.maxrev
def _load(self):
"""load state from file"""
if not self.path:
return
# use local variables in a loop. CPython uses LOAD_FAST for them,
# which is faster than both LOAD_CONST and LOAD_GLOBAL.
flaglen = 1
hshlen = _hshlen
with open(self.path, b'rb') as f:
if f.read(len(self.HEADER)) != self.HEADER:
raise error.CorruptedFileError()
self.clear(flush=False)
while True:
buf = f.read(flaglen)
if not buf:
break
flag = ord(buf)
rev = len(self._rev2hsh)
if flag & renameflag:
path = self._readcstr(f)
self._renamerevs.append(rev)
self._renamepaths.append(path)
hsh = f.read(hshlen)
if len(hsh) != hshlen:
raise error.CorruptedFileError()
self._hsh2rev[hsh] = rev
self._rev2flag.append(flag)
self._rev2hsh.append(hsh)
self._lastmaxrev = self.maxrev
def _writerev(self, rev, f):
"""append a revision data to file"""
flag = self._rev2flag[rev]
hsh = self._rev2hsh[rev]
f.write(struct.pack(b'B', flag))
if flag & renameflag:
path = self.rev2path(rev)
if path is None:
raise error.CorruptedFileError(b'cannot find path for %s' % rev)
f.write(path + b'\0')
f.write(hsh)
@staticmethod
def _readcstr(f):
"""read a C-language-like '\0'-terminated string"""
buf = b''
while True:
ch = f.read(1)
if not ch: # unexpected eof
raise error.CorruptedFileError()
if ch == b'\0':
break
buf += ch
return buf
def __contains__(self, f):
"""(fctx or (node, path)) -> bool.
test if (node, path) is in the map, and is not in a side branch.
f can be either a tuple of (node, path), or a fctx.
"""
if isinstance(f, tuple): # f: (node, path)
hsh, path = f
else: # f: fctx
hsh, path = f.node(), f.path()
rev = self.hsh2rev(hsh)
if rev is None:
return False
if path is not None and path != self.rev2path(rev):
return False
return (self.rev2flag(rev) & sidebranchflag) == 0
def getlastnode(path):
"""return the last hash in a revmap, without loading its full content.
this is equivalent to `m = revmap(path); m.rev2hsh(m.maxrev)`, but faster.
"""
hsh = None
try:
with open(path, b'rb') as f:
f.seek(-_hshlen, io.SEEK_END)
if f.tell() > len(revmap.HEADER):
hsh = f.read(_hshlen)
except IOError:
pass
return hsh