annotate mercurial/pure/parsers.py @ 44333:50ad851efd9b

nodemap: introduce append-only incremental update of the persistent data

Rewriting the full nodemap for each transaction has a cost we would like to
avoid. We introduce a new way to write persistent nodemap data by adding new
information at the end for file. Any new and updated block as added at the end
of the file. The last block is the new root node.

With this method, some of the block already on disk get "dereferenced" and
become dead data. In later changesets, We'll start tracking the amount of dead
data to eventually re-generate a full nodemap.

Differential Revision: https://phab.mercurial-scm.org/D7886

# parsers.py - Python implementation of parsers.c
#
# Copyright 2009 Matt Mackall <[e-mail]> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import struct
import zlib

from ..node import nullid, nullrev
from .. import (
    pycompat,
    util,
)

from ..revlogutils import nodemap as nodemaputil

stringio = pycompat.bytesio


_pack = struct.pack
_unpack = struct.unpack
_compress = zlib.compress
_decompress = zlib.decompress

# Some code below makes tuples directly because it's more convenient. However,
# code outside this module should always use dirstatetuple.
def dirstatetuple(*x):
    # x is a tuple
    return x


indexformatng = b">Qiiiiii20s12x"
indexfirst = struct.calcsize(b'Q')
sizeint = struct.calcsize(b'i')
indexsize = struct.calcsize(indexformatng)


def gettype(q):
    return int(q & 0xFFFF)


def offset_type(offset, type):
    return int(int(offset) << 16 | type)


class BaseIndexObject(object):
    @property
    def nodemap(self):
        msg = b"index.nodemap is deprecated, use index.[has_node|rev|get_rev]"
        util.nouideprecwarn(msg, b'5.3', stacklevel=2)
        return self._nodemap

    @util.propertycache
    def _nodemap(self):
        nodemap = nodemaputil.NodeMap({nullid: nullrev})
        for r in range(0, len(self)):
            n = self[r][7]
            nodemap[n] = r
        return nodemap

    def has_node(self, node):
        """return True if the node exist in the index"""
        return node in self._nodemap

    def rev(self, node):
        """return a revision for a node

        If the node is unknown, raise a RevlogError"""
        return self._nodemap[node]

    def get_rev(self, node):
        """return a revision for a node

        If the node is unknown, return None"""
        return self._nodemap.get(node)

    def _stripnodes(self, start):
        if '_nodemap' in vars(self):
            for r in range(start, len(self)):
                n = self[r][7]
                del self._nodemap[n]

    def clearcaches(self):
        self.__dict__.pop('_nodemap', None)

    def __len__(self):
        return self._lgt + len(self._extra)

    def append(self, tup):
        if '_nodemap' in vars(self):
            self._nodemap[tup[7]] = len(self)
        self._extra.append(tup)

    def _check_index(self, i):
        if not isinstance(i, int):
            raise TypeError(b"expecting int indexes")
        if i < 0 or i >= len(self):
            raise IndexError

    def __getitem__(self, i):
        if i == -1:
            return (0, 0, 0, -1, -1, -1, -1, nullid)
        self._check_index(i)
        if i >= self._lgt:
            return self._extra[i - self._lgt]
        index = self._calculate_index(i)
        r = struct.unpack(indexformatng, self._data[index : index + indexsize])
        if i == 0:
            e = list(r)
            type = gettype(e[0])
            e[0] = offset_type(0, type)
            return tuple(e)
        return r


class IndexObject(BaseIndexObject):
    def __init__(self, data):
        assert len(data) % indexsize == 0
        self._data = data
        self._lgt = len(data) // indexsize
        self._extra = []

    def _calculate_index(self, i):
        return i * indexsize

    def __delitem__(self, i):
        if not isinstance(i, slice) or not i.stop == -1 or i.step is not None:
            raise ValueError(b"deleting slices only supports a:-1 with step 1")
        i = i.start
        self._check_index(i)
        self._stripnodes(i)
        if i < self._lgt:
            self._data = self._data[: i * indexsize]
            self._lgt = i
            self._extra = []
        else:
            self._extra = self._extra[: i - self._lgt]


class PersistentNodeMapIndexObject(IndexObject):
    """a Debug oriented class to test persistent nodemap

    We need a simple python object to test API and higher level behavior. See
    the Rust implementation for  more serious usage. This should be used only
    through the dedicated `devel.persistent-nodemap` config.
    """

    def nodemap_data_all(self):
        """Return bytes containing a full serialization of a nodemap

        The nodemap should be valid for the full set of revisions in the
        index."""
        return nodemaputil.persistent_data(self)

    def nodemap_data_incremental(self):
        """Return bytes containing a incremental update to persistent nodemap

        This containst the data for an append-only update of the data provided
        in the last call to `update_nodemap_data`.
        """
        if self._nm_root is None:
            return None
        data = nodemaputil.update_persistent_data(
            self, self._nm_root, self._nm_max_idx, self._nm_rev
        )
        self._nm_root = self._nm_max_idx = self._nm_rev = None
        return data

    def update_nodemap_data(self, nm_data):
        """provide full blokc of persisted binary data for a nodemap

        The data are expected to come from disk. See `nodemap_data_all` for a
        produceur of such data."""
        if nm_data is not None:
            self._nm_root, self._nm_max_idx = nodemaputil.parse_data(nm_data)
            if self._nm_root:
                self._nm_rev = len(self) - 1
            else:
                self._nm_root = self._nm_max_idx = self._nm_rev = None


class InlinedIndexObject(BaseIndexObject):
    def __init__(self, data, inline=0):
        self._data = data
        self._lgt = self._inline_scan(None)
        self._inline_scan(self._lgt)
        self._extra = []

    def _inline_scan(self, lgt):
        off = 0
        if lgt is not None:
            self._offsets = [0] * lgt
        count = 0
        while off <= len(self._data) - indexsize:
            (s,) = struct.unpack(
                b'>i', self._data[off + indexfirst : off + sizeint + indexfirst]
            )
            if lgt is not None:
                self._offsets[count] = off
            count += 1
            off += indexsize + s
        if off != len(self._data):
            raise ValueError(b"corrupted data")
        return count

    def __delitem__(self, i):
        if not isinstance(i, slice) or not i.stop == -1 or i.step is not None:
            raise ValueError(b"deleting slices only supports a:-1 with step 1")
        i = i.start
        self._check_index(i)
        self._stripnodes(i)
        if i < self._lgt:
            self._offsets = self._offsets[:i]
            self._lgt = i
            self._extra = []
        else:
            self._extra = self._extra[: i - self._lgt]

    def _calculate_index(self, i):
        return self._offsets[i]


def parse_index2(data, inline):
    if not inline:
        return IndexObject(data), None
    return InlinedIndexObject(data, inline), (0, data)


def parse_index_devel_nodemap(data, inline):
    """like parse_index2, but alway return a PersistentNodeMapIndexObject
    """
    return PersistentNodeMapIndexObject(data), None


def parse_dirstate(dmap, copymap, st):
    parents = [st[:20], st[20:40]]
    # dereference fields so they will be local in loop
    format = b">cllll"
    e_size = struct.calcsize(format)
    pos1 = 40
    l = len(st)

    # the inner loop
    while pos1 < l:
        pos2 = pos1 + e_size
        e = _unpack(b">cllll", st[pos1:pos2])  # a literal here is faster
        pos1 = pos2 + e[4]
        f = st[pos2:pos1]
        if b'\0' in f:
            f, c = f.split(b'\0')
            copymap[f] = c
        dmap[f] = e[:4]
    return parents


def pack_dirstate(dmap, copymap, pl, now):
    now = int(now)
    cs = stringio()
    write = cs.write
    write(b"".join(pl))
    for f, e in pycompat.iteritems(dmap):
        if e[0] == b'n' and e[3] == now:
            # The file was last modified "simultaneously" with the current
            # write to dirstate (i.e. within the same second for file-
            # systems with a granularity of 1 sec). This commonly happens
            # for at least a couple of files on 'update'.
            # The user could change the file without changing its size
            # within the same second. Invalidate the file's mtime in
            # dirstate, forcing future 'status' calls to compare the
            # contents of the file if the size is the same. This prevents
            # mistakenly treating such files as clean.
            e = dirstatetuple(e[0], e[1], e[2], -1)
            dmap[f] = e

        if f in copymap:
            f = b"%s\0%s" % (f, copymap[f])
        e = _pack(b">cllll", e[0], e[1], e[2], e[3], len(f))
        write(e)
        write(f)
    return cs.getvalue()