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