path: root/src/engine/SCons/dblite.py

# dblite.py module contributed by Ralf W. Grosse-Kunstleve.
# Extended for Unicode by Steven Knight.
from __future__ import print_function

import os
import pickle
import shutil
import time

from SCons.compat import PICKLE_PROTOCOL

keep_all_files = 00000
ignore_corrupt_dbfiles = 0


def corruption_warning(filename):
    print("Warning: Discarding corrupt database:", filename)


try:
    unicode
except NameError:
    def is_string(s):
        return isinstance(s, str)
else:
    def is_string(s):
        return type(s) in (str, unicode)


def is_bytes(s):
    return isinstance(s, bytes)


try:
    unicode('a')
except NameError:
    def unicode(s):
        return s

dblite_suffix = '.dblite'

# TODO: Does commenting this out break switching from py2/3?
# if bytes is not str:
#     dblite_suffix += '.p3'
tmp_suffix = '.tmp'


class dblite(object):
    """
    Squirrel away references to the functions in various modules
    that we'll use when our __del__() method calls our sync() method
    during shutdown.  We might get destroyed when Python is in the midst
    of tearing down the different modules we import in an essentially
    arbitrary order, and some of the various modules's global attributes
    may already be wiped out from under us.

    See the discussion at:
      http://mail.python.org/pipermail/python-bugs-list/2003-March/016877.html
    """

    _open = open
    _pickle_dump = staticmethod(pickle.dump)
    _pickle_protocol = PICKLE_PROTOCOL
    _os_chmod = os.chmod

    try:
        _os_chown = os.chown
    except AttributeError:
        _os_chown = None

    _os_rename = os.rename
    _os_unlink = os.unlink
    _shutil_copyfile = shutil.copyfile
    _time_time = time.time

    def __init__(self, file_base_name, flag, mode):
        assert flag in (None, "r", "w", "c", "n")
        if flag is None:
            flag = "r"

        base, ext = os.path.splitext(file_base_name)
        if ext == dblite_suffix:
            # There's already a suffix on the file name, don't add one.
            self._file_name = file_base_name
            self._tmp_name = base + tmp_suffix
        else:
            self._file_name = file_base_name + dblite_suffix
            self._tmp_name = file_base_name + tmp_suffix

        self._flag = flag
        self._mode = mode
        self._dict = {}
        self._needs_sync = 00000

        if self._os_chown is not None and (os.geteuid() == 0 or os.getuid() == 0):
            # running as root; chown back to current owner/group when done
            try:
                statinfo = os.stat(self._file_name)
                self._chown_to = statinfo.st_uid
                self._chgrp_to = statinfo.st_gid
            except OSError as e:
                # db file doesn't exist yet.
                # Check os.environ for SUDO_UID, use if set
                self._chown_to = int(os.environ.get('SUDO_UID', -1))
                self._chgrp_to = int(os.environ.get('SUDO_GID', -1))
        else:
            self._chown_to = -1  # don't chown
            self._chgrp_to = -1  # don't chgrp

        if self._flag == "n":
            with self._open(self._file_name, "wb", self._mode):
                pass  # just make sure it exists
        else:
            try:
                f = self._open(self._file_name, "rb")
            except IOError as e:
                if self._flag != "c":
                    raise e
                with self._open(self._file_name, "wb", self._mode):
                    pass  # just make sure it exists
            else:
                p = f.read()
                f.close()
                if len(p) > 0:
                    try:
                        if bytes is not str:
                            self._dict = pickle.loads(p, encoding='bytes')
                        else:
                            self._dict = pickle.loads(p)
                    except (pickle.UnpicklingError, EOFError, KeyError):
                        # Note how we catch KeyErrors too here, which might happen
                        # when we don't have cPickle available (default pickle
                        # throws it).
                        if (ignore_corrupt_dbfiles == 0): raise
                        if (ignore_corrupt_dbfiles == 1):
                            corruption_warning(self._file_name)

    def close(self):
        if self._needs_sync:
            self.sync()

    def __del__(self):
        self.close()

    def sync(self):
        self._check_writable()
        f = self._open(self._tmp_name, "wb", self._mode)
        self._pickle_dump(self._dict, f, self._pickle_protocol)
        f.close()

        # Windows doesn't allow renaming if the file exists, so unlink
        # it first, chmod'ing it to make sure we can do so.  On UNIX, we
        # may not be able to chmod the file if it's owned by someone else
        # (e.g. from a previous run as root).  We should still be able to
        # unlink() the file if the directory's writable, though, so ignore
        # any OSError exception  thrown by the chmod() call.
        try:
            self._os_chmod(self._file_name, 0o777)
        except OSError:
            pass
        self._os_unlink(self._file_name)
        self._os_rename(self._tmp_name, self._file_name)
        if self._os_chown is not None and self._chown_to > 0:  # don't chown to root or -1
            try:
                self._os_chown(self._file_name, self._chown_to, self._chgrp_to)
            except OSError:
                pass
        self._needs_sync = 00000
        if (keep_all_files):
            self._shutil_copyfile(
                self._file_name,
                self._file_name + "_" + str(int(self._time_time())))

    def _check_writable(self):
        if (self._flag == "r"):
            raise IOError("Read-only database: %s" % self._file_name)

    def __getitem__(self, key):
        return self._dict[key]

    def __setitem__(self, key, value):
        self._check_writable()
        if (not is_string(key)):
            raise TypeError("key `%s' must be a string but is %s" % (key, type(key)))
        if (not is_bytes(value)):
            raise TypeError("value `%s' must be a bytes but is %s" % (value, type(value)))
        self._dict[key] = value
        self._needs_sync = 0o001

    def keys(self):
        return list(self._dict.keys())

    def has_key(self, key):
        return key in self._dict

    def __contains__(self, key):
        return key in self._dict

    def iterkeys(self):
        # Wrapping name in () prevents fixer from "fixing" this
        return (self._dict.iterkeys)()

    __iter__ = iterkeys

    def __len__(self):
        return len(self._dict)


def open(file, flag=None, mode=0o666):
    return dblite(file, flag, mode)


def _exercise():
    db = open("tmp", "n")
    assert len(db) == 0
    db["foo"] = "bar"
    assert db["foo"] == "bar"
    db[unicode("ufoo")] = unicode("ubar")
    assert db[unicode("ufoo")] == unicode("ubar")
    db.sync()
    db = open("tmp", "c")
    assert len(db) == 2, len(db)
    assert db["foo"] == "bar"
    db["bar"] = "foo"
    assert db["bar"] == "foo"
    db[unicode("ubar")] = unicode("ufoo")
    assert db[unicode("ubar")] == unicode("ufoo")
    db.sync()
    db = open("tmp", "r")
    assert len(db) == 4, len(db)
    assert db["foo"] == "bar"
    assert db["bar"] == "foo"
    assert db[unicode("ufoo")] == unicode("ubar")
    assert db[unicode("ubar")] == unicode("ufoo")
    try:
        db.sync()
    except IOError as e:
        assert str(e) == "Read-only database: tmp.dblite"
    else:
        raise RuntimeError("IOError expected.")
    db = open("tmp", "w")
    assert len(db) == 4
    db["ping"] = "pong"
    db.sync()
    try:
        db[(1, 2)] = "tuple"
    except TypeError as e:
        assert str(e) == "key `(1, 2)' must be a string but is <type 'tuple'>", str(e)
    else:
        raise RuntimeError("TypeError exception expected")
    try:
        db["list"] = [1, 2]
    except TypeError as e:
        assert str(e) == "value `[1, 2]' must be a string but is <type 'list'>", str(e)
    else:
        raise RuntimeError("TypeError exception expected")
    db = open("tmp", "r")
    assert len(db) == 5
    db = open("tmp", "n")
    assert len(db) == 0
    dblite._open("tmp.dblite", "w")
    db = open("tmp", "r")
    dblite._open("tmp.dblite", "w").write("x")
    try:
        db = open("tmp", "r")
    except pickle.UnpicklingError:
        pass
    else:
        raise RuntimeError("pickle exception expected.")
    global ignore_corrupt_dbfiles
    ignore_corrupt_dbfiles = 2
    db = open("tmp", "r")
    assert len(db) == 0
    os.unlink("tmp.dblite")
    try:
        db = open("tmp", "w")
    except IOError as e:
        assert str(e) == "[Errno 2] No such file or directory: 'tmp.dblite'", str(e)
    else:
        raise RuntimeError("IOError expected.")


if (__name__ == "__main__"):
    _exercise()

# Local Variables:
# tab-width:4
# indent-tabs-mode:nil
# End:
# vim: set expandtab tabstop=4 shiftwidth=4: