view mercurial/cffi/osutil.py @ 45059:79f6f9fa18c1

documentation: add some internals documentation about bid merge

This is an important algorithm that was only documented on the wiki so far.

Some update to the algorithm (and associated doc) is to expected in the future
since the bid merge algorithm is bug-ridden when it comes to file deletion comes
to play.

Differential Revision: https://phab.mercurial-scm.org/D8711

# osutil.py - CFFI version of osutil.c
#
# Copyright 2016 Maciej Fijalkowski <[e-mail]>
#
# 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 os
import stat as statmod

from ..pure.osutil import *

from .. import pycompat

if pycompat.isdarwin:
    from . import _osutil

    ffi = _osutil.ffi
    lib = _osutil.lib

    listdir_batch_size = 4096
    # tweakable number, only affects performance, which chunks
    # of bytes do we get back from getattrlistbulk

    attrkinds = [None] * 20  # we need the max no for enum VXXX, 20 is plenty

    attrkinds[lib.VREG] = statmod.S_IFREG
    attrkinds[lib.VDIR] = statmod.S_IFDIR
    attrkinds[lib.VLNK] = statmod.S_IFLNK
    attrkinds[lib.VBLK] = statmod.S_IFBLK
    attrkinds[lib.VCHR] = statmod.S_IFCHR
    attrkinds[lib.VFIFO] = statmod.S_IFIFO
    attrkinds[lib.VSOCK] = statmod.S_IFSOCK

    class stat_res(object):
        def __init__(self, st_mode, st_mtime, st_size):
            self.st_mode = st_mode
            self.st_mtime = st_mtime
            self.st_size = st_size

    tv_sec_ofs = ffi.offsetof(b"struct timespec", b"tv_sec")
    buf = ffi.new(b"char[]", listdir_batch_size)

    def listdirinternal(dfd, req, stat, skip):
        ret = []
        while True:
            r = lib.getattrlistbulk(dfd, req, buf, listdir_batch_size, 0)
            if r == 0:
                break
            if r == -1:
                raise OSError(ffi.errno, os.strerror(ffi.errno))
            cur = ffi.cast(b"val_attrs_t*", buf)
            for i in range(r):
                lgt = cur.length
                assert lgt == ffi.cast(b'uint32_t*', cur)[0]
                ofs = cur.name_info.attr_dataoffset
                str_lgt = cur.name_info.attr_length
                base_ofs = ffi.offsetof(b'val_attrs_t', b'name_info')
                name = str(
                    ffi.buffer(
                        ffi.cast(b"char*", cur) + base_ofs + ofs, str_lgt - 1
                    )
                )
                tp = attrkinds[cur.obj_type]
                if name == b"." or name == b"..":
                    continue
                if skip == name and tp == statmod.S_ISDIR:
                    return []
                if stat:
                    mtime = cur.mtime.tv_sec
                    mode = (cur.accessmask & ~lib.S_IFMT) | tp
                    ret.append(
                        (
                            name,
                            tp,
                            stat_res(
                                st_mode=mode,
                                st_mtime=mtime,
                                st_size=cur.datalength,
                            ),
                        )
                    )
                else:
                    ret.append((name, tp))
                cur = ffi.cast(
                    b"val_attrs_t*", int(ffi.cast(b"intptr_t", cur)) + lgt
                )
        return ret

    def listdir(path, stat=False, skip=None):
        req = ffi.new(b"struct attrlist*")
        req.bitmapcount = lib.ATTR_BIT_MAP_COUNT
        req.commonattr = (
            lib.ATTR_CMN_RETURNED_ATTRS
            | lib.ATTR_CMN_NAME
            | lib.ATTR_CMN_OBJTYPE
            | lib.ATTR_CMN_ACCESSMASK
            | lib.ATTR_CMN_MODTIME
        )
        req.fileattr = lib.ATTR_FILE_DATALENGTH
        dfd = lib.open(path, lib.O_RDONLY, 0)
        if dfd == -1:
            raise OSError(ffi.errno, os.strerror(ffi.errno))

        try:
            ret = listdirinternal(dfd, req, stat, skip)
        finally:
            try:
                lib.close(dfd)
            except BaseException:
                pass  # we ignore all the errors from closing, not
                # much we can do about that
        return ret