mercurial/pure/parsers.py

state: write the version number in plain text on top of state files

We will soon be using CBOR format to write the data in state files. But we
should not write the version number of the state files in CBOR format and we
should rather write it in plain text because in future we can change the format
of state files and we should be able to parse the version number of state file
without requiring to understand a certain format.

This will help us in making sure we have a good compatibility story with other
versions of state files.

Differential Revision: https://phab.mercurial-scm.org/D3579

# 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
from .. import pycompat
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 = ">Qiiiiii20s12x"
indexfirst = struct.calcsize('Q')
sizeint = struct.calcsize('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):
    def __len__(self):
        return self._lgt + len(self._extra) + 1

    def insert(self, i, tup):
        assert i == -1
        self._extra.append(tup)

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

    def __getitem__(self, i):
        i = self._fix_index(i)
        if i == len(self) - 1:
            return (0, 0, 0, -1, -1, -1, -1, nullid)
        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("deleting slices only supports a:-1 with step 1")
        i = self._fix_index(i.start)
        if i < self._lgt:
            self._data = self._data[:i * indexsize]
            self._lgt = i
            self._extra = []
        else:
            self._extra = self._extra[:i - self._lgt]

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('>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("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("deleting slices only supports a:-1 with step 1")
        i = self._fix_index(i.start)
        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_dirstate(dmap, copymap, st):
    parents = [st[:20], st[20: 40]]
    # dereference fields so they will be local in loop
    format = ">cllll"
    e_size = struct.calcsize(format)
    pos1 = 40
    l = len(st)

    # the inner loop
    while pos1 < l:
        pos2 = pos1 + e_size
        e = _unpack(">cllll", st[pos1:pos2]) # a literal here is faster
        pos1 = pos2 + e[4]
        f = st[pos2:pos1]
        if '\0' in f:
            f, c = f.split('\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("".join(pl))
    for f, e in dmap.iteritems():
        if e[0] == '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 = "%s\0%s" % (f, copymap[f])
        e = _pack(">cllll", e[0], e[1], e[2], e[3], len(f))
        write(e)
        write(f)
    return cs.getvalue()