view mercurial/linelog.py @ 39314:7f5e6d3e9032

manifest: proxy to revlog instance instead of inheriting

Previously, manifestrevlog inherited revlog.revlog and therefore
exposed all its APIs. This inevitably resulted in consumers calling
low-level revlog APIs.

As part of abstracting storage, we want to formalize the interface
for manifest storage. The revlog API is much too large to define as
the interface.

Like we did for filelog, this commit divorces the manifest class
from revlog so that we can standardize on a smaller API surface.

The way I went about this commit was I broke the inheritance, ran
tests, and added proxies until all tests passed. Like filelog, there
are a handful of attributes that don't belong on the interface.
And like filelog, we'll tease these out in the future.

As part of this, we formalize an interface for manifest storage and
add checks that manifestrevlog conforms to the interface.

Adding proxies will introduce some overhead due to extra attribute
lookups and function calls. On the mozilla-unified repository:

$ hg verify
before: real 627.220 secs (user 525.870+0.000 sys 18.800+0.000)
after:  real 628.930 secs (user 532.050+0.000 sys 18.320+0.000)

$ hg serve (for a clone)
before: user 223.580+0.000 sys 14.270+0.000
after:  user 227.720+0.000 sys 13.920+0.000

$ hg clone
before: user 506.390+0.000 sys 29.720+0.000
after:  user 513.080+0.000 sys 28.280+0.000

There appears to be some overhead here. But it appears to be 1-2%.
I think that is an appropriate price to pay for storage abstraction,
which will eventually let us have much nicer things. If the overhead
is noticed in other operations (whose CPU time isn't likely dwarfed by
fulltext resolution) or if we want to cut down on the overhead, we
could dynamically build up a type whose methods are effectively
aliased to a revlog instance's. I'm inclined to punt on that problem
for now. We may have to do it for the changelog. At which point it
could be implemented in a generic way and ported to filelog and
manifestrevlog easily enough I would think.

.. api:: manifest.manifestrevlog no longer inherits from revlog

   The manifestrevlog class now wraps a revlog instance instead of
   inheriting from revlog. Various attributes and methods on instances
   are no longer available.

Differential Revision: https://phab.mercurial-scm.org/D4386

# linelog - efficient cache for annotate data
#
# Copyright 2018 Google LLC.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
"""linelog is an efficient cache for annotate data inspired by SCCS Weaves.

SCCS Weaves are an implementation of
https://en.wikipedia.org/wiki/Interleaved_deltas. See
mercurial/help/internals/linelog.txt for an exploration of SCCS weaves
and how linelog works in detail.

Here's a hacker's summary: a linelog is a program which is executed in
the context of a revision. Executing the program emits information
about lines, including the revision that introduced them and the line
number in the file at the introducing revision. When an insertion or
deletion is performed on the file, a jump instruction is used to patch
in a new body of annotate information.
"""
from __future__ import absolute_import, print_function

import abc
import struct

from .thirdparty import (
    attr,
)
from . import (
    pycompat,
)

_llentry = struct.Struct('>II')

class LineLogError(Exception):
    """Error raised when something bad happens internally in linelog."""

@attr.s
class lineinfo(object):
    # Introducing revision of this line.
    rev = attr.ib()
    # Line number for this line in its introducing revision.
    linenum = attr.ib()
    # Private. Offset in the linelog program of this line. Used internally.
    _offset = attr.ib()

@attr.s
class annotateresult(object):
    rev = attr.ib()
    lines = attr.ib()
    _eof = attr.ib()

    def __iter__(self):
        return iter(self.lines)

class _llinstruction(object):

    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def __init__(self, op1, op2):
        pass

    @abc.abstractmethod
    def __str__(self):
        pass

    def __repr__(self):
        return str(self)

    @abc.abstractmethod
    def __eq__(self, other):
        pass

    @abc.abstractmethod
    def encode(self):
        """Encode this instruction to the binary linelog format."""

    @abc.abstractmethod
    def execute(self, rev, pc, emit):
        """Execute this instruction.

        Args:
          rev: The revision we're annotating.
          pc: The current offset in the linelog program.
          emit: A function that accepts a single lineinfo object.

        Returns:
          The new value of pc. Returns None if exeuction should stop
          (that is, we've found the end of the file.)
        """

class _jge(_llinstruction):
    """If the current rev is greater than or equal to op1, jump to op2."""

    def __init__(self, op1, op2):
        self._cmprev = op1
        self._target = op2

    def __str__(self):
        return r'JGE %d %d' % (self._cmprev, self._target)

    def __eq__(self, other):
        return (type(self) == type(other)
                and self._cmprev == other._cmprev
                and self._target == other._target)

    def encode(self):
        return _llentry.pack(self._cmprev << 2, self._target)

    def execute(self, rev, pc, emit):
        if rev >= self._cmprev:
            return self._target
        return pc + 1

class _jump(_llinstruction):
    """Unconditional jumps are expressed as a JGE with op1 set to 0."""

    def __init__(self, op1, op2):
        if op1 != 0:
            raise LineLogError("malformed JUMP, op1 must be 0, got %d" % op1)
        self._target = op2

    def __str__(self):
        return r'JUMP %d' % (self._target)

    def __eq__(self, other):
        return (type(self) == type(other)
                and self._target == other._target)

    def encode(self):
        return _llentry.pack(0, self._target)

    def execute(self, rev, pc, emit):
        return self._target

class _eof(_llinstruction):
    """EOF is expressed as a JGE that always jumps to 0."""

    def __init__(self, op1, op2):
        if op1 != 0:
            raise LineLogError("malformed EOF, op1 must be 0, got %d" % op1)
        if op2 != 0:
            raise LineLogError("malformed EOF, op2 must be 0, got %d" % op2)

    def __str__(self):
        return r'EOF'

    def __eq__(self, other):
        return type(self) == type(other)

    def encode(self):
        return _llentry.pack(0, 0)

    def execute(self, rev, pc, emit):
        return None

class _jl(_llinstruction):
    """If the current rev is less than op1, jump to op2."""

    def __init__(self, op1, op2):
        self._cmprev = op1
        self._target = op2

    def __str__(self):
        return r'JL %d %d' % (self._cmprev, self._target)

    def __eq__(self, other):
        return (type(self) == type(other)
                and self._cmprev == other._cmprev
                and self._target == other._target)

    def encode(self):
        return _llentry.pack(1 | (self._cmprev << 2), self._target)

    def execute(self, rev, pc, emit):
        if rev < self._cmprev:
            return self._target
        return pc + 1

class _line(_llinstruction):
    """Emit a line."""

    def __init__(self, op1, op2):
        # This line was introduced by this revision number.
        self._rev = op1
        # This line had the specified line number in the introducing revision.
        self._origlineno = op2

    def __str__(self):
        return r'LINE %d %d' % (self._rev, self._origlineno)

    def __eq__(self, other):
        return (type(self) == type(other)
                and self._rev == other._rev
                and self._origlineno == other._origlineno)

    def encode(self):
        return _llentry.pack(2 | (self._rev << 2), self._origlineno)

    def execute(self, rev, pc, emit):
        emit(lineinfo(self._rev, self._origlineno, pc))
        return pc + 1

def _decodeone(data, offset):
    """Decode a single linelog instruction from an offset in a buffer."""
    try:
        op1, op2 = _llentry.unpack_from(data, offset)
    except struct.error as e:
        raise LineLogError('reading an instruction failed: %r' % e)
    opcode = op1 & 0b11
    op1 = op1 >> 2
    if opcode == 0:
        if op1 == 0:
            if op2 == 0:
                return _eof(op1, op2)
            return _jump(op1, op2)
        return _jge(op1, op2)
    elif opcode == 1:
        return _jl(op1, op2)
    elif opcode == 2:
        return _line(op1, op2)
    raise NotImplementedError('Unimplemented opcode %r' % opcode)

class linelog(object):
    """Efficient cache for per-line history information."""

    def __init__(self, program=None, maxrev=0):
        if program is None:
            # We pad the program with an extra leading EOF so that our
            # offsets will match the C code exactly. This means we can
            # interoperate with the C code.
            program = [_eof(0, 0), _eof(0, 0)]
        self._program = program
        self._lastannotate = None
        self._maxrev = maxrev

    def __eq__(self, other):
        return (type(self) == type(other)
                and self._program == other._program
                and self._maxrev == other._maxrev)

    def __repr__(self):
        return '<linelog at %s: maxrev=%d size=%d>' % (
            hex(id(self)), self._maxrev, len(self._program))

    def debugstr(self):
        fmt = r'%%%dd %%s' % len(str(len(self._program)))
        return pycompat.sysstr('\n').join(
            fmt % (idx, i) for idx, i in enumerate(self._program[1:], 1))

    @classmethod
    def fromdata(cls, buf):
        if len(buf) % _llentry.size != 0:
            raise LineLogError(
                "invalid linelog buffer size %d (must be a multiple of %d)" % (
                    len(buf), _llentry.size))
        expected = len(buf) / _llentry.size
        fakejge = _decodeone(buf, 0)
        if isinstance(fakejge, _jump):
            maxrev = 0
        else:
            maxrev = fakejge._cmprev
        numentries = fakejge._target
        if expected != numentries:
            raise LineLogError("corrupt linelog data: claimed"
                               " %d entries but given data for %d entries" % (
                                   expected, numentries))
        instructions = [_eof(0, 0)]
        for offset in pycompat.xrange(1, numentries):
            instructions.append(_decodeone(buf, offset * _llentry.size))
        return cls(instructions, maxrev=maxrev)

    def encode(self):
        hdr = _jge(self._maxrev, len(self._program)).encode()
        return hdr + ''.join(i.encode() for i in self._program[1:])

    def clear(self):
        self._program = []
        self._maxrev = 0
        self._lastannotate = None

    def replacelines_vec(self, rev, a1, a2, blines):
        return self.replacelines(rev, a1, a2, 0, len(blines),
                                 _internal_blines=blines)

    def replacelines(self, rev, a1, a2, b1, b2, _internal_blines=None):
        """Replace lines [a1, a2) with lines [b1, b2)."""
        if self._lastannotate:
            # TODO(augie): make replacelines() accept a revision at
            # which we're editing as well as a revision to mark
            # responsible for the edits. In hg-experimental it's
            # stateful like this, so we're doing the same thing to
            # retain compatibility with absorb until that's imported.
            ar = self._lastannotate
        else:
            ar = self.annotate(rev)
            #        ar = self.annotate(self._maxrev)
        if a1 > len(ar.lines):
            raise LineLogError(
                '%d contains %d lines, tried to access line %d' % (
                    rev, len(ar.lines), a1))
        elif a1 == len(ar.lines):
            # Simulated EOF instruction since we're at EOF, which
            # doesn't have a "real" line.
            a1inst = _eof(0, 0)
            a1info = lineinfo(0, 0, ar._eof)
        else:
            a1info = ar.lines[a1]
            a1inst = self._program[a1info._offset]
        programlen = self._program.__len__
        oldproglen = programlen()
        appendinst = self._program.append

        # insert
        blineinfos = []
        bappend = blineinfos.append
        if b1 < b2:
            # Determine the jump target for the JGE at the start of
            # the new block.
            tgt = oldproglen + (b2 - b1 + 1)
            # Jump to skip the insert if we're at an older revision.
            appendinst(_jl(rev, tgt))
            for linenum in pycompat.xrange(b1, b2):
                if _internal_blines is None:
                    bappend(lineinfo(rev, linenum, programlen()))
                    appendinst(_line(rev, linenum))
                else:
                    newrev, newlinenum = _internal_blines[linenum]
                    bappend(lineinfo(newrev, newlinenum, programlen()))
                    appendinst(_line(newrev, newlinenum))
        # delete
        if a1 < a2:
            if a2 > len(ar.lines):
                raise LineLogError(
                    '%d contains %d lines, tried to access line %d' % (
                        rev, len(ar.lines), a2))
            elif a2 == len(ar.lines):
                endaddr = ar._eof
            else:
                endaddr = ar.lines[a2]._offset
            if a2 > 0 and rev < self._maxrev:
                # If we're here, we're deleting a chunk of an old
                # commit, so we need to be careful and not touch
                # invisible lines between a2-1 and a2 (IOW, lines that
                # are added later).
                endaddr = ar.lines[a2 - 1]._offset + 1
            appendinst(_jge(rev, endaddr))
        # copy instruction from a1
        a1instpc = programlen()
        appendinst(a1inst)
        # if a1inst isn't a jump or EOF, then we need to add an unconditional
        # jump back into the program here.
        if not isinstance(a1inst, (_jump, _eof)):
            appendinst(_jump(0, a1info._offset + 1))
        # Patch instruction at a1, which makes our patch live.
        self._program[a1info._offset] = _jump(0, oldproglen)

        # Update self._lastannotate in place. This serves as a cache to avoid
        # expensive "self.annotate" in this function, when "replacelines" is
        # used continuously.
        if len(self._lastannotate.lines) > a1:
            self._lastannotate.lines[a1]._offset = a1instpc
        else:
            assert isinstance(a1inst, _eof)
            self._lastannotate._eof = a1instpc
        self._lastannotate.lines[a1:a2] = blineinfos
        self._lastannotate.rev = max(self._lastannotate.rev, rev)

        if rev > self._maxrev:
            self._maxrev = rev

    def annotate(self, rev):
        pc = 1
        lines = []
        executed = 0
        # Sanity check: if instructions executed exceeds len(program), we
        # hit an infinite loop in the linelog program somehow and we
        # should stop.
        while pc is not None and executed < len(self._program):
            inst = self._program[pc]
            lastpc = pc
            pc = inst.execute(rev, pc, lines.append)
            executed += 1
        if pc is not None:
            raise LineLogError(
                r'Probably hit an infinite loop in linelog. Program:\n' +
                self.debugstr())
        ar = annotateresult(rev, lines, lastpc)
        self._lastannotate = ar
        return ar

    @property
    def maxrev(self):
        return self._maxrev

    # Stateful methods which depend on the value of the last
    # annotation run. This API is for compatiblity with the original
    # linelog, and we should probably consider refactoring it.
    @property
    def annotateresult(self):
        """Return the last annotation result. C linelog code exposed this."""
        return [(l.rev, l.linenum) for l in self._lastannotate.lines]

    def getoffset(self, line):
        return self._lastannotate.lines[line]._offset

    def getalllines(self, start=0, end=0):
        """Get all lines that ever occurred in [start, end).

        Passing start == end == 0 means "all lines ever".

        This works in terms of *internal* program offsets, not line numbers.
        """
        pc = start or 1
        lines = []
        # only take as many steps as there are instructions in the
        # program - if we don't find an EOF or our stop-line before
        # then, something is badly broken.
        for step in pycompat.xrange(len(self._program)):
            inst = self._program[pc]
            nextpc = pc + 1
            if isinstance(inst, _jump):
                nextpc = inst._target
            elif isinstance(inst, _eof):
                return lines
            elif isinstance(inst, (_jl, _jge)):
                pass
            elif isinstance(inst, _line):
                lines.append((inst._rev, inst._origlineno))
            else:
                raise LineLogError("Illegal instruction %r" % inst)
            if nextpc == end:
                return lines
            pc = nextpc
        raise LineLogError("Failed to perform getalllines")