#
# Copyright (C) 2016-2018 Codethink Limited
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library. If not, see .
#
# Authors:
# Tristan Van Berkom
"""
Utilities
=========
"""
import calendar
import errno
import hashlib
import os
import re
import shutil
import signal
import stat
import string
import subprocess
import tempfile
import itertools
import functools
from contextlib import contextmanager
import psutil
from . import _signals
from ._exceptions import BstError, ErrorDomain
class UtilError(BstError):
"""Raised by utility functions when system calls fail.
This will be handled internally by the BuildStream core,
if you need to handle this error, then it should be reraised,
or either of the :class:`.ElementError` or :class:`.SourceError`
exceptions should be raised from this error.
"""
def __init__(self, message, reason=None):
super().__init__(message, domain=ErrorDomain.UTIL, reason=reason)
class ProgramNotFoundError(BstError):
"""Raised if a required program is not found.
It is normally unneeded to handle this exception from plugin code.
"""
def __init__(self, message, reason=None):
super().__init__(message, domain=ErrorDomain.PROG_NOT_FOUND, reason=reason)
class FileListResult():
"""An object which stores the result of one of the operations
which run on a list of files.
"""
def __init__(self):
self.overwritten = []
"""List of files which were overwritten in the target directory"""
self.ignored = []
"""List of files which were ignored, because they would have
replaced a non empty directory"""
self.failed_attributes = []
"""List of files for which attributes could not be copied over"""
self.files_written = []
"""List of files that were written."""
def combine(self, other):
"""Create a new FileListResult that contains the results of both.
"""
ret = FileListResult()
ret.overwritten = self.overwritten + other.overwritten
ret.ignored = self.ignored + other.ignored
ret.failed_attributes = self.failed_attributes + other.failed_attributes
ret.files_written = self.files_written + other.files_written
return ret
def list_relative_paths(directory):
"""A generator for walking directory relative paths
This generator is useful for checking the full manifest of
a directory.
Note that directories will be yielded only if they are
empty.
Symbolic links will not be followed, but will be included
in the manifest.
Args:
directory (str): The directory to list files in
Yields:
Relative filenames in `directory`
"""
for (dirpath, dirnames, filenames) in os.walk(directory):
# Modifying the dirnames directly ensures that the os.walk() generator
# allows us to specify the order in which they will be iterated.
dirnames.sort()
filenames.sort()
relpath = os.path.relpath(dirpath, directory)
# We don't want "./" pre-pended to all the entries in the root of
# `directory`, prefer to have no prefix in that case.
basepath = relpath if relpath != '.' and dirpath != directory else ''
# os.walk does not decend into symlink directories, which
# makes sense because otherwise we might have redundant
# directories, or end up descending into directories outside
# of the walk() directory.
#
# But symlinks to directories are still identified as
# subdirectories in the walked `dirpath`, so we extract
# these symlinks from `dirnames`
#
for d in dirnames:
fullpath = os.path.join(dirpath, d)
if os.path.islink(fullpath):
yield os.path.join(basepath, d)
# We've decended into an empty directory, in this case we
# want to include the directory itself, but not in any other
# case.
if not filenames:
yield relpath
# List the filenames in the walked directory
for f in filenames:
yield os.path.join(basepath, f)
# pylint: disable=anomalous-backslash-in-string
def glob(paths, pattern):
"""A generator to yield paths which match the glob pattern
Args:
paths (iterable): The paths to check
pattern (str): A glob pattern
This generator will iterate over the passed *paths* and
yield only the filenames which matched the provided *pattern*.
+--------+------------------------------------------------------------------+
| Meta | Description |
+========+==================================================================+
| \* | Zero or more of any character, excepting path separators |
+--------+------------------------------------------------------------------+
| \** | Zero or more of any character, including path separators |
+--------+------------------------------------------------------------------+
| ? | One of any character, except for path separators |
+--------+------------------------------------------------------------------+
| [abc] | One of any of the specified characters |
+--------+------------------------------------------------------------------+
| [a-z] | One of the characters in the specified range |
+--------+------------------------------------------------------------------+
| [!abc] | Any single character, except the specified characters |
+--------+------------------------------------------------------------------+
| [!a-z] | Any single character, except those in the specified range |
+--------+------------------------------------------------------------------+
.. note::
Escaping of the metacharacters is not possible
"""
# Ensure leading slash, just because we want patterns
# to match file lists regardless of whether the patterns
# or file lists had a leading slash or not.
if not pattern.startswith(os.sep):
pattern = os.sep + pattern
expression = _glob2re(pattern)
regexer = re.compile(expression)
for filename in paths:
filename_try = filename
if not filename_try.startswith(os.sep):
filename_try = os.sep + filename_try
if regexer.match(filename_try):
yield filename
def sha256sum(filename):
"""Calculate the sha256sum of a file
Args:
filename (str): A path to a file on disk
Returns:
(str): An sha256 checksum string
Raises:
UtilError: In the case there was an issue opening
or reading `filename`
"""
try:
h = hashlib.sha256()
with open(filename, "rb") as f:
for chunk in iter(lambda: f.read(4096), b""):
h.update(chunk)
except OSError as e:
raise UtilError("Failed to get a checksum of file '{}': {}"
.format(filename, e)) from e
return h.hexdigest()
def safe_copy(src, dest, *, result=None):
"""Copy a file while preserving attributes
Args:
src (str): The source filename
dest (str): The destination filename
result (:class:`~.FileListResult`): An optional collective result
Raises:
UtilError: In the case of unexpected system call failures
This is almost the same as shutil.copy2(), except that
we unlink *dest* before overwriting it if it exists, just
incase *dest* is a hardlink to a different file.
"""
# First unlink the target if it exists
try:
os.unlink(dest)
except OSError as e:
if e.errno != errno.ENOENT:
raise UtilError("Failed to remove destination file '{}': {}"
.format(dest, e)) from e
shutil.copyfile(src, dest)
try:
shutil.copystat(src, dest)
except PermissionError:
# If we failed to copy over some file stats, dont treat
# it as an unrecoverable error, but provide some feedback
# we can use for a warning.
#
# This has a tendency of happening when attempting to copy
# over extended file attributes.
if result:
result.failed_attributes.append(dest)
except shutil.Error as e:
raise UtilError("Failed to copy '{} -> {}': {}"
.format(src, dest, e)) from e
def safe_link(src, dest, *, result=None):
"""Try to create a hardlink, but resort to copying in the case of cross device links.
Args:
src (str): The source filename
dest (str): The destination filename
result (:class:`~.FileListResult`): An optional collective result
Raises:
UtilError: In the case of unexpected system call failures
"""
# First unlink the target if it exists
try:
os.unlink(dest)
except OSError as e:
if e.errno != errno.ENOENT:
raise UtilError("Failed to remove destination file '{}': {}"
.format(dest, e)) from e
# If we can't link it due to cross-device hardlink, copy
try:
os.link(src, dest)
except OSError as e:
if e.errno == errno.EXDEV:
safe_copy(src, dest)
else:
raise UtilError("Failed to link '{} -> {}': {}"
.format(src, dest, e)) from e
def safe_remove(path):
"""Removes a file or directory
This will remove a file if it exists, and will
remove a directory if the directory is empty.
Args:
path (str): The path to remove
Returns:
True if `path` was removed or did not exist, False
if `path` was a non empty directory.
Raises:
UtilError: In the case of unexpected system call failures
"""
if os.path.lexists(path):
# Try to remove anything that is in the way, but issue
# a warning instead if it removes a non empty directory
try:
os.unlink(path)
except OSError as e:
if e.errno != errno.EISDIR:
raise UtilError("Failed to remove '{}': {}"
.format(path, e))
try:
os.rmdir(path)
except OSError as e:
if e.errno == errno.ENOTEMPTY:
return False
else:
raise UtilError("Failed to remove '{}': {}"
.format(path, e))
return True
def copy_files(src, dest, *, files=None, ignore_missing=False, report_written=False):
"""Copy files from source to destination.
Args:
src (str): The source file or directory
dest (str): The destination directory
files (list): Optional list of files in `src` to copy
ignore_missing (bool): Dont raise any error if a source file is missing
report_written (bool): Add to the result object the full list of files written
Returns:
(:class:`~.FileListResult`): The result describing what happened during this file operation
Raises:
UtilError: In the case of unexpected system call failures
.. note::
Directories in `dest` are replaced with files from `src`,
unless the existing directory in `dest` is not empty in which
case the path will be reported in the return value.
"""
presorted = False
if files is None:
files = list_relative_paths(src)
presorted = True
result = FileListResult()
try:
_process_list(src, dest, files, safe_copy, result, ignore_missing=ignore_missing,
report_written=report_written, presorted=presorted)
except OSError as e:
raise UtilError("Failed to copy '{} -> {}': {}"
.format(src, dest, e))
return result
def link_files(src, dest, *, files=None, ignore_missing=False, report_written=False):
"""Hardlink files from source to destination.
Args:
src (str): The source file or directory
dest (str): The destination directory
files (list): Optional list of files in `src` to link
ignore_missing (bool): Dont raise any error if a source file is missing
report_written (bool): Add to the result object the full list of files written
Returns:
(:class:`~.FileListResult`): The result describing what happened during this file operation
Raises:
UtilError: In the case of unexpected system call failures
.. note::
Directories in `dest` are replaced with files from `src`,
unless the existing directory in `dest` is not empty in which
case the path will be reported in the return value.
.. note::
If a hardlink cannot be created due to crossing filesystems,
then the file will be copied instead.
"""
presorted = False
if files is None:
files = list_relative_paths(src)
presorted = True
result = FileListResult()
try:
_process_list(src, dest, files, safe_link, result, ignore_missing=ignore_missing,
report_written=report_written, presorted=presorted)
except OSError as e:
raise UtilError("Failed to link '{} -> {}': {}"
.format(src, dest, e))
return result
def get_host_tool(name):
"""Get the full path of a host tool
Args:
name (str): The name of the program to search for
Returns:
The full path to the program, if found
Raises:
:class:`.ProgramNotFoundError`
"""
search_path = os.environ.get('PATH')
program_path = shutil.which(name, path=search_path)
if not program_path:
raise ProgramNotFoundError("Did not find '{}' in PATH: {}".format(name, search_path))
return program_path
def url_directory_name(url):
"""Normalizes a url into a directory name
Args:
url (str): A url string
Returns:
A string which can be used as a directory name
"""
valid_chars = string.digits + string.ascii_letters + '%_'
def transl(x):
return x if x in valid_chars else '_'
return ''.join([transl(x) for x in url])
def get_bst_version():
"""Gets the major, minor release portion of the
BuildStream version.
Returns:
(int): The major version
(int): The minor version
"""
# Import this only conditionally, it's not resolved at bash complete time
from . import __version__
versions = __version__.split('.')[:2]
if versions[0] == '0+untagged':
raise UtilError("Your git repository has no tags - BuildStream can't "
"determine its version. Please run `git fetch --tags`.")
return (int(versions[0]), int(versions[1]))
@contextmanager
def save_file_atomic(filename, mode='w', *, buffering=-1, encoding=None,
errors=None, newline=None, closefd=True, opener=None):
"""Save a file with a temporary name and rename it into place when ready.
This is a context manager which is meant for saving data to files.
The data is written to a temporary file, which gets renamed to the target
name when the context is closed. This avoids readers of the file from
getting an incomplete file.
**Example:**
.. code:: python
with save_file_atomic('/path/to/foo', 'w') as f:
f.write(stuff)
The file will be called something like ``tmpCAFEBEEF`` until the
context block ends, at which point it gets renamed to ``foo``. The
temporary file will be created in the same directory as the output file.
The ``filename`` parameter must be an absolute path.
If an exception occurs or the process is terminated, the temporary file will
be deleted.
"""
# This feature has been proposed for upstream Python in the past, e.g.:
# https://bugs.python.org/issue8604
assert os.path.isabs(filename), "The utils.save_file_atomic() parameter ``filename`` must be an absolute path"
dirname = os.path.dirname(filename)
fd, tempname = tempfile.mkstemp(dir=dirname)
os.close(fd)
f = open(tempname, mode=mode, buffering=buffering, encoding=encoding,
errors=errors, newline=newline, closefd=closefd, opener=opener)
def cleanup_tempfile():
f.close()
try:
os.remove(tempname)
except FileNotFoundError:
pass
except OSError as e:
raise UtilError("Failed to cleanup temporary file {}: {}".format(tempname, e)) from e
try:
with _signals.terminator(cleanup_tempfile):
f.real_filename = filename
yield f
f.close()
# This operation is atomic, at least on platforms we care about:
# https://bugs.python.org/issue8828
os.replace(tempname, filename)
except Exception:
cleanup_tempfile()
raise
# A sentinel to be used as a default argument for functions that need
# to distinguish between a kwarg set to None and an unset kwarg.
_sentinel = object()
# Main process pid
_main_pid = os.getpid()
# _is_main_process()
#
# Return whether we are in the main process or not.
#
def _is_main_process():
assert _main_pid is not None
return os.getpid() == _main_pid
# Recursively remove directories, ignoring file permissions as much as
# possible.
def _force_rmtree(rootpath, **kwargs):
for root, dirs, _ in os.walk(rootpath):
for d in dirs:
path = os.path.join(root, d.lstrip('/'))
if os.path.exists(path) and not os.path.islink(path):
try:
os.chmod(path, 0o755)
except OSError as e:
raise UtilError("Failed to ensure write permission on file '{}': {}"
.format(path, e))
try:
shutil.rmtree(rootpath, **kwargs)
except shutil.Error as e:
raise UtilError("Failed to remove cache directory '{}': {}"
.format(rootpath, e))
# Recursively make directories in target area
def _copy_directories(srcdir, destdir, target):
this_dir = os.path.dirname(target)
new_dir = os.path.join(destdir, this_dir)
if not os.path.lexists(new_dir):
if this_dir:
yield from _copy_directories(srcdir, destdir, this_dir)
old_dir = os.path.join(srcdir, this_dir)
if os.path.lexists(old_dir):
dir_stat = os.lstat(old_dir)
mode = dir_stat.st_mode
if stat.S_ISDIR(mode) or stat.S_ISLNK(mode):
os.makedirs(new_dir)
yield (new_dir, mode)
else:
raise UtilError('Source directory tree has file where '
'directory expected: {}'.format(old_dir))
@functools.lru_cache(maxsize=64)
def _resolve_symlinks(path):
return os.path.realpath(path)
def _ensure_real_directory(root, destpath):
# The realpath in the sandbox may refer to a file outside of the
# sandbox when any of the direcory branches are a symlink to an
# absolute path.
#
# This should not happen as we rely on relative_symlink_target() below
# when staging the actual symlinks which may lead up to this path.
#
destpath_resolved = _resolve_symlinks(destpath)
if not destpath_resolved.startswith(_resolve_symlinks(root)):
raise UtilError('Destination path resolves to a path outside ' +
'of the staging area\n\n' +
' Destination path: {}\n'.format(destpath) +
' Real path: {}'.format(destpath_resolved))
# Ensure the real destination path exists before trying to get the mode
# of the real destination path.
#
# It is acceptable that chunks create symlinks inside artifacts which
# refer to non-existing directories, they will be created on demand here
# at staging time.
#
if not os.path.exists(destpath_resolved):
os.makedirs(destpath_resolved)
return destpath_resolved
# _process_list()
#
# Internal helper for copying/moving/linking file lists
#
# This will handle directories, symlinks and special files
# internally, the `actionfunc` will only be called for regular files.
#
# Args:
# srcdir: The source base directory
# destdir: The destination base directory
# filelist: List of relative file paths
# actionfunc: The function to call for regular files
# result: The FileListResult
# ignore_missing: Dont raise any error if a source file is missing
# presorted: Whether the passed list is known to be presorted
#
#
def _process_list(srcdir, destdir, filelist, actionfunc, result,
ignore_missing=False, report_written=False,
presorted=False):
# Keep track of directory permissions, since these need to be set
# *after* files have been written.
permissions = []
# Sorting the list of files is necessary to ensure that we processes
# symbolic links which lead to directories before processing files inside
# those directories.
if not presorted:
filelist = sorted(filelist)
# Now walk the list
for path in filelist:
srcpath = os.path.join(srcdir, path)
destpath = os.path.join(destdir, path)
# Add to the results the list of files written
if report_written:
result.files_written.append(path)
# Collect overlaps
if os.path.lexists(destpath) and not os.path.isdir(destpath):
result.overwritten.append(path)
# The destination directory may not have been created separately
permissions.extend(_copy_directories(srcdir, destdir, path))
# Ensure that broken symlinks to directories have their targets
# created before attempting to stage files across broken
# symlink boundaries
_ensure_real_directory(destdir, os.path.dirname(destpath))
try:
file_stat = os.lstat(srcpath)
mode = file_stat.st_mode
except FileNotFoundError as e:
# Skip this missing file
if ignore_missing:
continue
else:
raise UtilError("Source file is missing: {}".format(srcpath)) from e
if stat.S_ISDIR(mode):
# Ensure directory exists in destination
if not os.path.exists(destpath):
_ensure_real_directory(destdir, destpath)
dest_stat = os.lstat(_resolve_symlinks(destpath))
if not stat.S_ISDIR(dest_stat.st_mode):
raise UtilError('Destination not a directory. source has {}'
' destination has {}'.format(srcpath, destpath))
permissions.append((destpath, os.stat(srcpath).st_mode))
elif stat.S_ISLNK(mode):
if not safe_remove(destpath):
result.ignored.append(path)
continue
target = os.readlink(srcpath)
target = _relative_symlink_target(destdir, destpath, target)
os.symlink(target, destpath)
elif stat.S_ISREG(mode):
# Process the file.
if not safe_remove(destpath):
result.ignored.append(path)
continue
actionfunc(srcpath, destpath, result=result)
elif stat.S_ISCHR(mode) or stat.S_ISBLK(mode):
# Block or character device. Put contents of st_dev in a mknod.
if not safe_remove(destpath):
result.ignored.append(path)
continue
if os.path.lexists(destpath):
os.remove(destpath)
os.mknod(destpath, file_stat.st_mode, file_stat.st_rdev)
os.chmod(destpath, file_stat.st_mode)
else:
# Unsupported type.
raise UtilError('Cannot extract {} into staging-area. Unsupported type.'.format(srcpath))
# Write directory permissions now that all files have been written
for d, perms in permissions:
os.chmod(d, perms)
# _relative_symlink_target()
#
# Fetches a relative path for symlink with an absolute target
#
# @root: The staging area root location
# @symlink: Location of the symlink in staging area (including the root path)
# @target: The symbolic link target, which may be an absolute path
#
# If @target is an absolute path, a relative path from the symbolic link
# location will be returned, otherwise if @target is a relative path, it will
# be returned unchanged.
#
# Using relative symlinks helps to keep the target self contained when staging
# files onto the target.
#
def _relative_symlink_target(root, symlink, target):
if os.path.isabs(target):
# First fix the input a little, the symlink itself must not have a
# trailing slash, otherwise we fail to remove the symlink filename
# from its directory components in os.path.split()
#
# The absolute target filename must have its leading separator
# removed, otherwise os.path.join() will discard the prefix
symlink = symlink.rstrip(os.path.sep)
target = target.lstrip(os.path.sep)
# We want a relative path from the directory in which symlink
# is located, not from the symlink itself.
symlinkdir, _ = os.path.split(_resolve_symlinks(symlink))
# Create a full path to the target, including the leading staging
# directory
fulltarget = os.path.join(_resolve_symlinks(root), target)
# now get the relative path from the directory where the symlink
# is located within the staging root, to the target within the same
# staging root
newtarget = os.path.relpath(fulltarget, symlinkdir)
return newtarget
else:
return target
# _set_deterministic_user()
#
# Set the uid/gid for every file in a directory tree to the process'
# euid/guid.
#
# Args:
# directory (str): The directory to recursively set the uid/gid on
#
def _set_deterministic_user(directory):
user = os.geteuid()
group = os.getegid()
for root, dirs, files in os.walk(directory.encode("utf-8"), topdown=False):
for filename in files:
os.chown(os.path.join(root, filename), user, group, follow_symlinks=False)
for dirname in dirs:
os.chown(os.path.join(root, dirname), user, group, follow_symlinks=False)
# _set_deterministic_mtime()
#
# Set the mtime for every file in a directory tree to the same.
#
# Args:
# directory (str): The directory to recursively set the mtime on
#
def _set_deterministic_mtime(directory):
# The magic number for timestamps: 2011-11-11 11:11:11
magic_timestamp = calendar.timegm([2011, 11, 11, 11, 11, 11])
for dirname, _, filenames in os.walk(directory.encode("utf-8"), topdown=False):
for filename in filenames:
pathname = os.path.join(dirname, filename)
# Python's os.utime only ever modifies the timestamp
# of the target, it is not acceptable to set the timestamp
# of the target here, if we are staging the link target we
# will also set its timestamp.
#
# We should however find a way to modify the actual link's
# timestamp, this outdated python bug report claims that
# it is impossible:
#
# http://bugs.python.org/issue623782
#
# However, nowadays it is possible at least on gnuish systems
# with with the lutimes glibc function.
if not os.path.islink(pathname):
os.utime(pathname, (magic_timestamp, magic_timestamp))
os.utime(dirname, (magic_timestamp, magic_timestamp))
# _tempdir()
#
# A context manager for doing work in a temporary directory.
#
# Args:
# dir (str): A path to a parent directory for the temporary directory
# suffix (str): A suffix for the temproary directory name
# prefix (str): A prefix for the temporary directory name
#
# Yields:
# (str): The temporary directory
#
# In addition to the functionality provided by python's
# tempfile.TemporaryDirectory() context manager, this one additionally
# supports cleaning up the temp directory on SIGTERM.
#
@contextmanager
def _tempdir(suffix="", prefix="tmp", dir=None): # pylint: disable=redefined-builtin
tempdir = tempfile.mkdtemp(suffix=suffix, prefix=prefix, dir=dir)
def cleanup_tempdir():
if os.path.isdir(tempdir):
shutil.rmtree(tempdir)
try:
with _signals.terminator(cleanup_tempdir):
yield tempdir
finally:
cleanup_tempdir()
# _kill_process_tree()
#
# Brutally murder a process and all of it's children
#
# Args:
# pid (int): Process ID
#
def _kill_process_tree(pid):
proc = psutil.Process(pid)
children = proc.children(recursive=True)
def kill_proc(p):
try:
p.kill()
except psutil.AccessDenied:
# Ignore this error, it can happen with
# some setuid bwrap processes.
pass
# Bloody Murder
for child in children:
kill_proc(child)
kill_proc(proc)
# _call()
#
# A wrapper for subprocess.call() supporting suspend and resume
#
# Args:
# popenargs (list): Popen() arguments
# terminate (bool): Whether to attempt graceful termination before killing
# rest_of_args (kwargs): Remaining arguments to subprocess.call()
#
# Returns:
# (int): The process exit code.
# (str): The program output.
#
def _call(*popenargs, terminate=False, **kwargs):
kwargs['start_new_session'] = True
process = None
# Handle termination, suspend and resume
def kill_proc():
if process:
# Some callers know that their subprocess can be
# gracefully terminated, make an attempt first
if terminate:
proc = psutil.Process(process.pid)
proc.terminate()
try:
proc.wait(20)
except psutil.TimeoutExpired:
# Did not terminate within the timeout: murder
_kill_process_tree(process.pid)
else:
# FIXME: This is a brutal but reliable approach
#
# Other variations I've tried which try SIGTERM first
# and then wait for child processes to exit gracefully
# have not reliably cleaned up process trees and have
# left orphaned git or ssh processes alive.
#
# This cleans up the subprocesses reliably but may
# cause side effects such as possibly leaving stale
# locks behind. Hopefully this should not be an issue
# as long as any child processes only interact with
# the temp directories which we control and cleanup
# ourselves.
#
_kill_process_tree(process.pid)
def suspend_proc():
if process:
group_id = os.getpgid(process.pid)
os.killpg(group_id, signal.SIGSTOP)
def resume_proc():
if process:
group_id = os.getpgid(process.pid)
os.killpg(group_id, signal.SIGCONT)
with _signals.suspendable(suspend_proc, resume_proc), _signals.terminator(kill_proc):
process = subprocess.Popen(*popenargs, **kwargs)
output, _ = process.communicate()
exit_code = process.poll()
# Program output is returned as bytes, we want utf8 strings
if output is not None:
output = output.decode('UTF-8')
return (exit_code, output)
# _glob2re()
#
# Function to translate a glob style pattern into a regex
#
# Args:
# pat (str): The glob pattern
#
# This is a modified version of the python standard library's
# fnmatch.translate() function which supports path like globbing
# a bit more correctly, and additionally supports recursive glob
# patterns with double asterisk.
#
# Note that this will only support the most basic of standard
# glob patterns, and additionally the recursive double asterisk.
#
# Support includes:
#
# * Match any pattern except a path separator
# ** Match any pattern, including path separators
# ? Match any single character
# [abc] Match one of the specified characters
# [A-Z] Match one of the characters in the specified range
# [!abc] Match any single character, except the specified characters
# [!A-Z] Match any single character, except those in the specified range
#
def _glob2re(pat):
i, n = 0, len(pat)
res = ''
while i < n:
c = pat[i]
i = i + 1
if c == '*':
# fnmatch.translate() simply uses the '.*' separator here,
# we only want that for double asterisk (bash 'globstar' behavior)
#
if i < n and pat[i] == '*':
res = res + '.*'
i = i + 1
else:
res = res + '[^/]*'
elif c == '?':
# fnmatch.translate() simply uses the '.' wildcard here, but
# we dont want to match path separators here
res = res + '[^/]'
elif c == '[':
j = i
if j < n and pat[j] == '!':
j = j + 1
if j < n and pat[j] == ']':
j = j + 1
while j < n and pat[j] != ']':
j = j + 1
if j >= n:
res = res + '\\['
else:
stuff = pat[i:j].replace('\\', '\\\\')
i = j + 1
if stuff[0] == '!':
stuff = '^' + stuff[1:]
elif stuff[0] == '^':
stuff = '\\' + stuff
res = '{}[{}]'.format(res, stuff)
else:
res = res + re.escape(c)
return res + r'\Z(?ms)'
# _deduplicate()
#
# Remove duplicate entries in a list or other iterable.
#
# Copied verbatim from the unique_everseen() example at
# https://docs.python.org/3/library/itertools.html#itertools-recipes
#
# Args:
# iterable (iterable): What to deduplicate
# key (callable): Optional function to map from list entry to value
#
# Returns:
# (generator): Generator that produces a deduplicated version of 'iterable'
#
def _deduplicate(iterable, key=None):
seen = set()
seen_add = seen.add
if key is None:
for element in itertools.filterfalse(seen.__contains__, iterable):
seen_add(element)
yield element
else:
for element in iterable:
k = key(element)
if k not in seen:
seen_add(k)
yield element