# -*- coding: utf-8 -*-
# Copyright 2010 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Static data and helper functions."""

from __future__ import absolute_import

import collections
import errno
import locale
import logging
import math
import multiprocessing
import os
import pkgutil
import re
import struct
import sys
import tempfile
import textwrap
import threading
import traceback
import xml.etree.ElementTree as ElementTree

import boto
from boto import config
import boto.auth
from boto.exception import NoAuthHandlerFound
from boto.gs.connection import GSConnection
from boto.provider import Provider
from boto.pyami.config import BotoConfigLocations
import httplib2
from oauth2client.client import HAS_CRYPTO
from retry_decorator import retry_decorator

import gslib
from gslib.exception import CommandException
from gslib.storage_url import StorageUrlFromString
from gslib.translation_helper import AclTranslation
from gslib.translation_helper import GenerationFromUrlAndString
from gslib.translation_helper import S3_ACL_MARKER_GUID
from gslib.translation_helper import S3_DELETE_MARKER_GUID
from gslib.translation_helper import S3_MARKER_GUIDS

# Detect platform types.
PLATFORM = str(sys.platform).lower()
IS_WINDOWS = 'win32' in PLATFORM
IS_CYGWIN = 'cygwin' in PLATFORM
IS_LINUX = 'linux' in PLATFORM
IS_OSX = 'darwin' in PLATFORM

UTF8 = 'utf-8'
WINDOWS_1252 = 'cp1252'

# pylint: disable=g-import-not-at-top
if IS_WINDOWS:
  from ctypes import c_int
  from ctypes import c_uint64
  from ctypes import c_char_p
  from ctypes import c_wchar_p
  from ctypes import windll
  from ctypes import POINTER
  from ctypes import WINFUNCTYPE
  from ctypes import WinError
  IS_CP1252 = locale.getdefaultlocale()[1] == WINDOWS_1252
else:
  IS_CP1252 = False

# pylint: disable=g-import-not-at-top
try:
  # This module doesn't necessarily exist on Windows.
  import resource
  HAS_RESOURCE_MODULE = True
except ImportError, e:
  HAS_RESOURCE_MODULE = False

ONE_KIB = 1024
ONE_MIB = 1024 * 1024
TWO_MIB = 2 * ONE_MIB
EIGHT_MIB = 8 * ONE_MIB
TEN_MIB = 10 * ONE_MIB
DEFAULT_FILE_BUFFER_SIZE = 8 * ONE_KIB
_DEFAULT_LINES = 25

# By default, the timeout for SSL read errors is infinite. This could
# cause gsutil to hang on network disconnect, so pick a more reasonable
# timeout.
SSL_TIMEOUT = 60

# Start with a progress callback every 64 KiB during uploads/downloads (JSON
# API). Callback implementation should back off until it hits the maximum size
# so that callbacks do not create huge amounts of log output.
START_CALLBACK_PER_BYTES = 1024*64
MAX_CALLBACK_PER_BYTES = 1024*1024*100

# Upload/download files in 8 KiB chunks over the HTTP connection.
TRANSFER_BUFFER_SIZE = 1024*8

# Default number of progress callbacks during transfer (XML API).
XML_PROGRESS_CALLBACKS = 10

# For files >= this size, output a message indicating that we're running an
# operation on the file (like hashing or gzipping) so it does not appear to the
# user that the command is hanging.
MIN_SIZE_COMPUTE_LOGGING = 100*1024*1024  # 100 MiB

NO_MAX = sys.maxint

VERSION_MATCHER = re.compile(r'^(?P<maj>\d+)(\.(?P<min>\d+)(?P<suffix>.*))?')

RELEASE_NOTES_URL = 'https://pub.storage.googleapis.com/gsutil_ReleaseNotes.txt'

# Binary exponentiation strings.
_EXP_STRINGS = [
    (0, 'B', 'bit'),
    (10, 'KiB', 'Kibit', 'K'),
    (20, 'MiB', 'Mibit', 'M'),
    (30, 'GiB', 'Gibit', 'G'),
    (40, 'TiB', 'Tibit', 'T'),
    (50, 'PiB', 'Pibit', 'P'),
    (60, 'EiB', 'Eibit', 'E'),
]


global manager  # pylint: disable=global-at-module-level
certs_file_lock = threading.Lock()
configured_certs_files = []


def _GenerateSuffixRegex():
  """Creates a suffix regex for human-readable byte counts."""
  human_bytes_re = r'(?P<num>\d*\.\d+|\d+)\s*(?P<suffix>%s)?'
  suffixes = []
  suffix_to_si = {}
  for i, si in enumerate(_EXP_STRINGS):
    si_suffixes = [s.lower() for s in list(si)[1:]]
    for suffix in si_suffixes:
      suffix_to_si[suffix] = i
    suffixes.extend(si_suffixes)
  human_bytes_re %= '|'.join(suffixes)
  matcher = re.compile(human_bytes_re)
  return suffix_to_si, matcher

SUFFIX_TO_SI, MATCH_HUMAN_BYTES = _GenerateSuffixRegex()

SECONDS_PER_DAY = 3600 * 24

# On Unix-like systems, we will set the maximum number of open files to avoid
# hitting the limit imposed by the OS. This number was obtained experimentally.
MIN_ACCEPTABLE_OPEN_FILES_LIMIT = 1000

GSUTIL_PUB_TARBALL = 'gs://pub/gsutil.tar.gz'

Retry = retry_decorator.retry  # pylint: disable=invalid-name

# Cache the values from this check such that they're available to all callers
# without needing to run all the checks again (some of these, such as calling
# multiprocessing.Manager(), are expensive operations).
cached_multiprocessing_is_available = None
cached_multiprocessing_is_available_stack_trace = None
cached_multiprocessing_is_available_message = None


# Enum class for specifying listing style.
class ListingStyle(object):
  SHORT = 'SHORT'
  LONG = 'LONG'
  LONG_LONG = 'LONG_LONG'


def UsingCrcmodExtension(crcmod):
  return (boto.config.get('GSUtil', 'test_assume_fast_crcmod', None) or
          (getattr(crcmod, 'crcmod', None) and
           getattr(crcmod.crcmod, '_usingExtension', None)))


def CheckFreeSpace(path):
  """Return path/drive free space (in bytes)."""
  if IS_WINDOWS:
    try:
      # pylint: disable=invalid-name
      get_disk_free_space_ex = WINFUNCTYPE(c_int, c_wchar_p,
                                           POINTER(c_uint64),
                                           POINTER(c_uint64),
                                           POINTER(c_uint64))
      get_disk_free_space_ex = get_disk_free_space_ex(
          ('GetDiskFreeSpaceExW', windll.kernel32), (
              (1, 'lpszPathName'),
              (2, 'lpFreeUserSpace'),
              (2, 'lpTotalSpace'),
              (2, 'lpFreeSpace'),))
    except AttributeError:
      get_disk_free_space_ex = WINFUNCTYPE(c_int, c_char_p,
                                           POINTER(c_uint64),
                                           POINTER(c_uint64),
                                           POINTER(c_uint64))
      get_disk_free_space_ex = get_disk_free_space_ex(
          ('GetDiskFreeSpaceExA', windll.kernel32), (
              (1, 'lpszPathName'),
              (2, 'lpFreeUserSpace'),
              (2, 'lpTotalSpace'),
              (2, 'lpFreeSpace'),))

    def GetDiskFreeSpaceExErrCheck(result, unused_func, args):
      if not result:
        raise WinError()
      return args[1].value
    get_disk_free_space_ex.errcheck = GetDiskFreeSpaceExErrCheck

    return get_disk_free_space_ex(os.getenv('SystemDrive'))
  else:
    (_, f_frsize, _, _, f_bavail, _, _, _, _, _) = os.statvfs(path)
    return f_frsize * f_bavail


def CreateDirIfNeeded(dir_path, mode=0777):
  """Creates a directory, suppressing already-exists errors."""
  if not os.path.exists(dir_path):
    try:
      # Unfortunately, even though we catch and ignore EEXIST, this call will
      # output a (needless) error message (no way to avoid that in Python).
      os.makedirs(dir_path, mode)
    # Ignore 'already exists' in case user tried to start up several
    # resumable uploads concurrently from a machine where no tracker dir had
    # yet been created.
    except OSError as e:
      if e.errno != errno.EEXIST:
        raise


def DivideAndCeil(dividend, divisor):
  """Returns ceil(dividend / divisor).

  Takes care to avoid the pitfalls of floating point arithmetic that could
  otherwise yield the wrong result for large numbers.

  Args:
    dividend: Dividend for the operation.
    divisor: Divisor for the operation.

  Returns:
    Quotient.
  """
  quotient = dividend // divisor
  if (dividend % divisor) != 0:
    quotient += 1
  return quotient


def GetGsutilStateDir():
  """Returns the location of the directory for gsutil state files.

  Certain operations, such as cross-process credential sharing and
  resumable transfer tracking, need a known location for state files which
  are created by gsutil as-needed.

  This location should only be used for storing data that is required to be in
  a static location.

  Returns:
    Path to directory for gsutil static state files.
  """
  config_file_dir = config.get(
      'GSUtil', 'state_dir',
      os.path.expanduser(os.path.join('~', '.gsutil')))
  CreateDirIfNeeded(config_file_dir)
  return config_file_dir


def GetCredentialStoreFilename():
  return os.path.join(GetGsutilStateDir(), 'credstore')


def GetGceCredentialCacheFilename():
  return os.path.join(GetGsutilStateDir(), 'gcecredcache')


def GetTabCompletionLogFilename():
  return os.path.join(GetGsutilStateDir(), 'tab-completion-logs')


def GetTabCompletionCacheFilename():
  tab_completion_dir = os.path.join(GetGsutilStateDir(), 'tab-completion')
  # Limit read permissions on the directory to owner for privacy.
  CreateDirIfNeeded(tab_completion_dir, mode=0700)
  return os.path.join(tab_completion_dir, 'cache')


def GetPrintableExceptionString(exc):
  """Returns a short Unicode string describing the exception."""
  return unicode(exc).encode(UTF8) or str(exc.__class__)


def PrintTrackerDirDeprecationWarningIfNeeded():
  # TODO: Remove this along with the tracker_dir config value 1 year after
  # 4.6 release date. Use state_dir instead.
  if config.has_option('GSUtil', 'resumable_tracker_dir'):
    sys.stderr.write('Warning: you have set resumable_tracker_dir in your '
                     '.boto configuration file. This configuration option is '
                     'deprecated; please use the state_dir configuration '
                     'option instead.\n')


# Name of file where we keep the timestamp for the last time we checked whether
# a new version of gsutil is available.
PrintTrackerDirDeprecationWarningIfNeeded()
CreateDirIfNeeded(GetGsutilStateDir())
LAST_CHECKED_FOR_GSUTIL_UPDATE_TIMESTAMP_FILE = (
    os.path.join(GetGsutilStateDir(), '.last_software_update_check'))


def HasConfiguredCredentials():
  """Determines if boto credential/config file exists."""
  has_goog_creds = (config.has_option('Credentials', 'gs_access_key_id') and
                    config.has_option('Credentials', 'gs_secret_access_key'))
  has_amzn_creds = (config.has_option('Credentials', 'aws_access_key_id') and
                    config.has_option('Credentials', 'aws_secret_access_key'))
  has_oauth_creds = (
      config.has_option('Credentials', 'gs_oauth2_refresh_token'))
  has_service_account_creds = (
      HAS_CRYPTO and
      config.has_option('Credentials', 'gs_service_client_id') and
      config.has_option('Credentials', 'gs_service_key_file'))

  if (has_goog_creds or has_amzn_creds or has_oauth_creds or
      has_service_account_creds):
    return True

  valid_auth_handler = None
  try:
    valid_auth_handler = boto.auth.get_auth_handler(
        GSConnection.DefaultHost, config, Provider('google'),
        requested_capability=['s3'])
    # Exclude the no-op auth handler as indicating credentials are configured.
    # Note we can't use isinstance() here because the no-op module may not be
    # imported so we can't get a reference to the class type.
    if getattr(getattr(valid_auth_handler, '__class__', None),
               '__name__', None) == 'NoOpAuth':
      valid_auth_handler = None
  except NoAuthHandlerFound:
    pass

  return valid_auth_handler


def ConfigureNoOpAuthIfNeeded():
  """Sets up no-op auth handler if no boto credentials are configured."""
  if not HasConfiguredCredentials():
    if (config.has_option('Credentials', 'gs_service_client_id')
        and not HAS_CRYPTO):
      if os.environ.get('CLOUDSDK_WRAPPER') == '1':
        raise CommandException('\n'.join(textwrap.wrap(
            'Your gsutil is configured with an OAuth2 service account, but '
            'you do not have PyOpenSSL or PyCrypto 2.6 or later installed. '
            'Service account authentication requires one of these libraries; '
            'please reactivate your service account via the gcloud auth '
            'command and ensure any gcloud packages necessary for '
            'service accounts are present.')))
      else:
        raise CommandException('\n'.join(textwrap.wrap(
            'Your gsutil is configured with an OAuth2 service account, but '
            'you do not have PyOpenSSL or PyCrypto 2.6 or later installed. '
            'Service account authentication requires one of these libraries; '
            'please install either of them to proceed, or configure a '
            'different type of credentials with "gsutil config".')))
    else:
      # With no boto config file the user can still access publicly readable
      # buckets and objects.
      from gslib import no_op_auth_plugin  # pylint: disable=unused-variable


def GetConfigFilePath():
  config_path = 'no config found'
  for path in BotoConfigLocations:
    try:
      with open(path, 'r'):
        config_path = path
      break
    except IOError:
      pass
  return config_path


def GetBotoConfigFileList():
  """Returns list of boto config files that exist."""
  config_paths = boto.pyami.config.BotoConfigLocations
  if 'AWS_CREDENTIAL_FILE' in os.environ:
    config_paths.append(os.environ['AWS_CREDENTIAL_FILE'])
  config_files = {}
  for config_path in config_paths:
    if os.path.exists(config_path):
      config_files[config_path] = 1
  cf_list = []
  for config_file in config_files:
    cf_list.append(config_file)
  return cf_list


def GetCertsFile():
  """Configures and returns the CA Certificates file.

  If one is already configured, use it. Otherwise, amend the configuration
  (in boto.config) to use the cert roots distributed with gsutil.

  Returns:
    string filename of the certs file to use.
  """
  certs_file = boto.config.get('Boto', 'ca_certificates_file', None)
  if not certs_file:
    with certs_file_lock:
      if configured_certs_files:
        disk_certs_file = configured_certs_files[0]
      else:
        disk_certs_file = os.path.abspath(
            os.path.join(gslib.GSLIB_DIR, 'data', 'cacerts.txt'))
        if not os.path.exists(disk_certs_file):
          # If the file is not present on disk, this means the gslib module
          # doesn't actually exist on disk anywhere. This can happen if it's
          # being imported from a zip file. Unfortunately, we have to copy the
          # certs file to a local temp file on disk because the underlying SSL
          # socket requires it to be a filesystem path.
          certs_data = pkgutil.get_data('gslib', 'data/cacerts.txt')
          if not certs_data:
            raise CommandException('Certificates file not found. Please '
                                   'reinstall gsutil from scratch')
          fd, fname = tempfile.mkstemp(suffix='.txt', prefix='gsutil-cacerts')
          f = os.fdopen(fd, 'w')
          f.write(certs_data)
          f.close()
          configured_certs_files.append(fname)
          disk_certs_file = fname
      certs_file = disk_certs_file
  return certs_file


def GetCleanupFiles():
  """Returns a list of temp files to delete (if possible) when program exits."""
  cleanup_files = []
  if configured_certs_files:
    cleanup_files += configured_certs_files
  return cleanup_files


def ProxyInfoFromEnvironmentVar(proxy_env_var):
  """Reads proxy info from the environment and converts to httplib2.ProxyInfo.

  Args:
    proxy_env_var: Environment variable string to read, such as http_proxy or
       https_proxy.

  Returns:
    httplib2.ProxyInfo constructed from the environment string.
  """
  proxy_url = os.environ.get(proxy_env_var)
  if not proxy_url or not proxy_env_var.lower().startswith('http'):
    return httplib2.ProxyInfo(httplib2.socks.PROXY_TYPE_HTTP, None, 0)
  proxy_protocol = proxy_env_var.lower().split('_')[0]
  if not proxy_url.lower().startswith('http'):
    # proxy_info_from_url requires a protocol, which is always http or https.
    proxy_url = proxy_protocol + '://' + proxy_url
  return httplib2.proxy_info_from_url(proxy_url, method=proxy_protocol)


def GetNewHttp(http_class=httplib2.Http, **kwargs):
  """Creates and returns a new httplib2.Http instance.

  Args:
    http_class: Optional custom Http class to use.
    **kwargs: Arguments to pass to http_class constructor.

  Returns:
    An initialized httplib2.Http instance.
  """
  proxy_info = httplib2.ProxyInfo(
      proxy_type=3,
      proxy_host=boto.config.get('Boto', 'proxy', None),
      proxy_port=boto.config.getint('Boto', 'proxy_port', 0),
      proxy_user=boto.config.get('Boto', 'proxy_user', None),
      proxy_pass=boto.config.get('Boto', 'proxy_pass', None),
      proxy_rdns=boto.config.get('Boto', 'proxy_rdns', False))

  if not (proxy_info.proxy_host and proxy_info.proxy_port):
    # Fall back to using the environment variable.
    for proxy_env_var in ['http_proxy', 'https_proxy', 'HTTPS_PROXY']:
      if proxy_env_var in os.environ and os.environ[proxy_env_var]:
        proxy_info = ProxyInfoFromEnvironmentVar(proxy_env_var)
        # Assume proxy_rnds is True if a proxy environment variable exists.
        proxy_info.proxy_rdns = boto.config.get('Boto', 'proxy_rdns', True)
        break

  # Some installers don't package a certs file with httplib2, so use the
  # one included with gsutil.
  kwargs['ca_certs'] = GetCertsFile()
  # Use a non-infinite SSL timeout to avoid hangs during network flakiness.
  kwargs['timeout'] = SSL_TIMEOUT
  http = http_class(proxy_info=proxy_info, **kwargs)
  http.disable_ssl_certificate_validation = (not config.getbool(
      'Boto', 'https_validate_certificates'))
  return http


# Retry for 10 minutes with exponential backoff, which corresponds to
# the maximum Downtime Period specified in the GCS SLA
# (https://cloud.google.com/storage/sla)
def GetNumRetries():
  return config.getint('Boto', 'num_retries', 23)


def GetMaxRetryDelay():
  return config.getint('Boto', 'max_retry_delay', 32)


# Resumable downloads and uploads make one HTTP call per chunk (and must be
# in multiples of 256KiB). Overridable for testing.
def GetJsonResumableChunkSize():
  chunk_size = config.getint('GSUtil', 'json_resumable_chunk_size',
                             1024*1024*100L)
  if chunk_size == 0:
    chunk_size = 1024*256L
  elif chunk_size % 1024*256L != 0:
    chunk_size += (1024*256L - (chunk_size % (1024*256L)))
  return chunk_size


def _RoundToNearestExponent(num):
  i = 0
  while i+1 < len(_EXP_STRINGS) and num >= (2 ** _EXP_STRINGS[i+1][0]):
    i += 1
  return i, round(float(num) / 2 ** _EXP_STRINGS[i][0], 2)


def MakeHumanReadable(num):
  """Generates human readable string for a number of bytes.

  Args:
    num: The number, in bytes.

  Returns:
    A string form of the number using size abbreviations (KiB, MiB, etc.).
  """
  i, rounded_val = _RoundToNearestExponent(num)
  return '%g %s' % (rounded_val, _EXP_STRINGS[i][1])


def MakeBitsHumanReadable(num):
  """Generates human readable string for a number of bits.

  Args:
    num: The number, in bits.

  Returns:
    A string form of the number using bit size abbreviations (kbit, Mbit, etc.)
  """
  i, rounded_val = _RoundToNearestExponent(num)
  return '%g %s' % (rounded_val, _EXP_STRINGS[i][2])


def HumanReadableToBytes(human_string):
  """Tries to convert a human-readable string to a number of bytes.

  Args:
    human_string: A string supplied by user, e.g. '1M', '3 GiB'.
  Returns:
    An integer containing the number of bytes.
  Raises:
    ValueError: on an invalid string.
  """
  human_string = human_string.lower()
  m = MATCH_HUMAN_BYTES.match(human_string)
  if m:
    num = float(m.group('num'))
    if m.group('suffix'):
      power = _EXP_STRINGS[SUFFIX_TO_SI[m.group('suffix')]][0]
      num *= (2.0 ** power)
    num = int(round(num))
    return num
  raise ValueError('Invalid byte string specified: %s' % human_string)


def Percentile(values, percent, key=lambda x: x):
  """Find the percentile of a list of values.

  Taken from: http://code.activestate.com/recipes/511478/

  Args:
    values: a list of numeric values. Note that the values MUST BE already
            sorted.
    percent: a float value from 0.0 to 1.0.
    key: optional key function to compute value from each element of the list
         of values.

  Returns:
    The percentile of the values.
  """
  if not values:
    return None
  k = (len(values) - 1) * percent
  f = math.floor(k)
  c = math.ceil(k)
  if f == c:
    return key(values[int(k)])
  d0 = key(values[int(f)]) * (c-k)
  d1 = key(values[int(c)]) * (k-f)
  return d0 + d1


def RemoveCRLFFromString(input_str):
  """Returns the input string with all \\n and \\r removed."""
  return re.sub(r'[\r\n]', '', input_str)


def UnaryDictToXml(message):
  """Generates XML representation of a nested dict.

  This dict contains exactly one top-level entry and an arbitrary number of
  2nd-level entries, e.g. capturing a WebsiteConfiguration message.

  Args:
    message: The dict encoding the message.

  Returns:
    XML string representation of the input dict.

  Raises:
    Exception: if dict contains more than one top-level entry.
  """
  if len(message) != 1:
    raise Exception('Expected dict of size 1, got size %d' % len(message))

  name, content = message.items()[0]
  element_type = ElementTree.Element(name)
  for element_property, value in sorted(content.items()):
    node = ElementTree.SubElement(element_type, element_property)
    node.text = value
  return ElementTree.tostring(element_type)


def LookUpGsutilVersion(gsutil_api, url_str):
  """Looks up the gsutil version of the specified gsutil tarball URL.

  Version is specified in the metadata field set on that object.

  Args:
    gsutil_api: gsutil Cloud API to use when retrieving gsutil tarball.
    url_str: tarball URL to retrieve (such as 'gs://pub/gsutil.tar.gz').

  Returns:
    Version string if URL is a cloud URL containing x-goog-meta-gsutil-version
    metadata, else None.
  """
  url = StorageUrlFromString(url_str)
  if url.IsCloudUrl():
    obj = gsutil_api.GetObjectMetadata(url.bucket_name, url.object_name,
                                       provider=url.scheme,
                                       fields=['metadata'])
    if obj.metadata and obj.metadata.additionalProperties:
      for prop in obj.metadata.additionalProperties:
        if prop.key == 'gsutil_version':
          return prop.value


def GetGsutilVersionModifiedTime():
  """Returns unix timestamp of when the VERSION file was last modified."""
  if not gslib.VERSION_FILE:
    return 0
  return int(os.path.getmtime(gslib.VERSION_FILE))


def IsRunningInteractively():
  """Returns True if currently running interactively on a TTY."""
  return sys.stdout.isatty() and sys.stderr.isatty() and sys.stdin.isatty()


def _HttpsValidateCertifcatesEnabled():
  return config.get('Boto', 'https_validate_certificates', True)

CERTIFICATE_VALIDATION_ENABLED = _HttpsValidateCertifcatesEnabled()


def _BotoIsSecure():
  return config.get('Boto', 'is_secure', True)

BOTO_IS_SECURE = _BotoIsSecure()


def ResumableThreshold():
  return config.getint('GSUtil', 'resumable_threshold', EIGHT_MIB)


def AddAcceptEncoding(headers):
  """Adds accept-encoding:gzip to the dictionary of headers."""
  # If Accept-Encoding is not already set, set it to enable gzip.
  if 'accept-encoding' not in headers:
    headers['accept-encoding'] = 'gzip'


# pylint: disable=too-many-statements
def PrintFullInfoAboutObject(bucket_listing_ref, incl_acl=True):
  """Print full info for given object (like what displays for gsutil ls -L).

  Args:
    bucket_listing_ref: BucketListingRef being listed.
                        Must have ref_type OBJECT and a populated root_object
                        with the desired fields.
    incl_acl: True if ACL info should be output.

  Returns:
    Tuple (number of objects, object_length)

  Raises:
    Exception: if calling bug encountered.
  """
  url_str = bucket_listing_ref.url_string
  storage_url = StorageUrlFromString(url_str)
  obj = bucket_listing_ref.root_object

  if (obj.metadata and S3_DELETE_MARKER_GUID in
      obj.metadata.additionalProperties):
    num_bytes = 0
    num_objs = 0
    url_str += '<DeleteMarker>'
  else:
    num_bytes = obj.size
    num_objs = 1

  print '%s:' % url_str.encode(UTF8)
  if obj.updated:
    print '\tCreation time:\t\t%s' % obj.updated.strftime(
        '%a, %d %b %Y %H:%M:%S GMT')
  if obj.cacheControl:
    print '\tCache-Control:\t\t%s' % obj.cacheControl
  if obj.contentDisposition:
    print '\tContent-Disposition:\t\t%s' % obj.contentDisposition
  if obj.contentEncoding:
    print '\tContent-Encoding:\t\t%s' % obj.contentEncoding
  if obj.contentLanguage:
    print '\tContent-Language:\t%s' % obj.contentLanguage
  print '\tContent-Length:\t\t%s' % obj.size
  print '\tContent-Type:\t\t%s' % obj.contentType
  if obj.componentCount:
    print '\tComponent-Count:\t%d' % obj.componentCount
  marker_props = {}
  if obj.metadata and obj.metadata.additionalProperties:
    non_marker_props = []
    for add_prop in obj.metadata.additionalProperties:
      if add_prop.key not in S3_MARKER_GUIDS:
        non_marker_props.append(add_prop)
      else:
        marker_props[add_prop.key] = add_prop.value
    if non_marker_props:
      print '\tMetadata:'
      for ap in non_marker_props:
        meta_string = '\t\t%s:\t\t%s' % (ap.key, ap.value)
        print meta_string.encode(UTF8)
  if obj.crc32c: print '\tHash (crc32c):\t\t%s' % obj.crc32c
  if obj.md5Hash: print '\tHash (md5):\t\t%s' % obj.md5Hash
  print '\tETag:\t\t\t%s' % obj.etag.strip('"\'')
  if obj.generation:
    generation_str = GenerationFromUrlAndString(storage_url, obj.generation)
    print '\tGeneration:\t\t%s' % generation_str
  if obj.metageneration:
    print '\tMetageneration:\t\t%s' % obj.metageneration
  if incl_acl:
    # JSON API won't return acls as part of the response unless we have
    # full control scope
    if obj.acl:
      print '\tACL:\t\t%s' % AclTranslation.JsonFromMessage(obj.acl)
    elif S3_ACL_MARKER_GUID in marker_props:
      print '\tACL:\t\t%s' % marker_props[S3_ACL_MARKER_GUID]
    else:
      print ('\tACL:\t\t\tACCESS DENIED. Note: you need OWNER '
             'permission\n\t\t\t\ton the object to read its ACL.')

  return (num_objs, num_bytes)


def CompareVersions(first, second):
  """Compares the first and second gsutil version strings.

  For example, 3.33 > 3.7, and 4.1 is a greater major version than 3.33.
  Does not handle multiple periods (e.g. 3.3.4) or complicated suffixes
  (e.g., 3.3RC4 vs. 3.3RC5). A version string with a suffix is treated as
  less than its non-suffix counterpart (e.g. 3.32 > 3.32pre).

  Args:
    first: First gsutil version string.
    second: Second gsutil version string.

  Returns:
    (g, m):
       g is True if first known to be greater than second, else False.
       m is True if first known to be greater by at least 1 major version,
         else False.
  """
  m1 = VERSION_MATCHER.match(str(first))
  m2 = VERSION_MATCHER.match(str(second))

  # If passed strings we don't know how to handle, be conservative.
  if not m1 or not m2:
    return (False, False)

  major_ver1 = int(m1.group('maj'))
  minor_ver1 = int(m1.group('min')) if m1.group('min') else 0
  suffix_ver1 = m1.group('suffix')
  major_ver2 = int(m2.group('maj'))
  minor_ver2 = int(m2.group('min')) if m2.group('min') else 0
  suffix_ver2 = m2.group('suffix')

  if major_ver1 > major_ver2:
    return (True, True)
  elif major_ver1 == major_ver2:
    if minor_ver1 > minor_ver2:
      return (True, False)
    elif minor_ver1 == minor_ver2:
      return (bool(suffix_ver2) and not suffix_ver1, False)
  return (False, False)


def _IncreaseSoftLimitForResource(resource_name, fallback_value):
  """Sets a new soft limit for the maximum number of open files.

  The soft limit is used for this process (and its children), but the
  hard limit is set by the system and cannot be exceeded.

  We will first try to set the soft limit to the hard limit's value; if that
  fails, we will try to set the soft limit to the fallback_value iff this would
  increase the soft limit.

  Args:
    resource_name: Name of the resource to increase the soft limit for.
    fallback_value: Fallback value to be used if we couldn't set the
                    soft value to the hard value (e.g., if the hard value
                    is "unlimited").

  Returns:
    Current soft limit for the resource (after any changes we were able to
    make), or -1 if the resource doesn't exist.
  """

  # Get the value of the resource.
  try:
    (soft_limit, hard_limit) = resource.getrlimit(resource_name)
  except (resource.error, ValueError):
    # The resource wasn't present, so we can't do anything here.
    return -1

  # Try to set the value of the soft limit to the value of the hard limit.
  if hard_limit > soft_limit:  # Some OS's report 0 for "unlimited".
    try:
      resource.setrlimit(resource_name, (hard_limit, hard_limit))
      return hard_limit
    except (resource.error, ValueError):
      # We'll ignore this and try the fallback value.
      pass

  # Try to set the value of the soft limit to the fallback value.
  if soft_limit < fallback_value:
    try:
      resource.setrlimit(resource_name, (fallback_value, hard_limit))
      return fallback_value
    except (resource.error, ValueError):
      # We couldn't change the soft limit, so just report the current
      # value of the soft limit.
      return soft_limit
  else:
    return soft_limit


def GetCloudApiInstance(cls, thread_state=None):
  """Gets a gsutil Cloud API instance.

  Since Cloud API implementations are not guaranteed to be thread-safe, each
  thread needs its own instance. These instances are passed to each thread
  via the thread pool logic in command.

  Args:
    cls: Command class to be used for single-threaded case.
    thread_state: Per thread state from this thread containing a gsutil
                  Cloud API instance.

  Returns:
    gsutil Cloud API instance.
  """
  return thread_state or cls.gsutil_api


def GetFileSize(fp, position_to_eof=False):
  """Returns size of file, optionally leaving fp positioned at EOF."""
  if not position_to_eof:
    cur_pos = fp.tell()
  fp.seek(0, os.SEEK_END)
  cur_file_size = fp.tell()
  if not position_to_eof:
    fp.seek(cur_pos)
  return cur_file_size


def GetStreamFromFileUrl(storage_url):
  if storage_url.IsStream():
    return sys.stdin
  else:
    return open(storage_url.object_name, 'rb')


def UrlsAreForSingleProvider(url_args):
  """Tests whether the URLs are all for a single provider.

  Args:
    url_args: Strings to check.

  Returns:
    True if URLs are for single provider, False otherwise.
  """
  provider = None
  url = None
  for url_str in url_args:
    url = StorageUrlFromString(url_str)
    if not provider:
      provider = url.scheme
    elif url.scheme != provider:
      return False
  return provider is not None


def HaveFileUrls(args_to_check):
  """Checks whether args_to_check contain any file URLs.

  Args:
    args_to_check: Command-line argument subset to check.

  Returns:
    True if args_to_check contains any file URLs.
  """
  for url_str in args_to_check:
    storage_url = StorageUrlFromString(url_str)
    if storage_url.IsFileUrl():
      return True
  return False


def HaveProviderUrls(args_to_check):
  """Checks whether args_to_check contains any provider URLs (like 'gs://').

  Args:
    args_to_check: Command-line argument subset to check.

  Returns:
    True if args_to_check contains any provider URLs.
  """
  for url_str in args_to_check:
    storage_url = StorageUrlFromString(url_str)
    if storage_url.IsCloudUrl() and storage_url.IsProvider():
      return True
  return False

# This must be defined at the module level for pickling across processes.
MultiprocessingIsAvailableResult = collections.namedtuple(
    'MultiprocessingIsAvailableResult', ['is_available', 'stack_trace'])


def CheckMultiprocessingAvailableAndInit(logger=None):
  """Checks if multiprocessing is available.

  There are some environments in which there is no way to use multiprocessing
  logic that's built into Python (e.g., if /dev/shm is not available, then
  we can't create semaphores). This simply tries out a few things that will be
  needed to make sure the environment can support the pieces of the
  multiprocessing module that we need.

  If multiprocessing is available, this performs necessary initialization for
  multiprocessing.  See gslib.command.InitializeMultiprocessingVariables for
  an explanation of why this is necessary.

  Args:
    logger: logging.logger to use for debug output.

  Returns:
    (multiprocessing_is_available, stack_trace):
      multiprocessing_is_available: True iff the multiprocessing module is
                                    available for use.
      stack_trace: The stack trace generated by the call we tried that failed.
  """
  # pylint: disable=global-variable-undefined
  global cached_multiprocessing_is_available
  global cached_multiprocessing_check_stack_trace
  global cached_multiprocessing_is_available_message
  if cached_multiprocessing_is_available is not None:
    if logger:
      logger.debug(cached_multiprocessing_check_stack_trace)
      logger.warn(cached_multiprocessing_is_available_message)
    return MultiprocessingIsAvailableResult(
        is_available=cached_multiprocessing_is_available,
        stack_trace=cached_multiprocessing_check_stack_trace)

  if IS_WINDOWS:
    message = """
Multiple processes are not supported on Windows. Operations requesting
parallelism will be executed with multiple threads in a single process only.    
"""
    if logger:
      logger.warn(message)
    return MultiprocessingIsAvailableResult(is_available=False,
                                            stack_trace=None)

  stack_trace = None
  multiprocessing_is_available = True
  message = """
You have requested multiple processes for an operation, but the
required functionality of Python\'s multiprocessing module is not available.
Operations requesting parallelism will be executed with multiple threads in a
single process only.
"""
  try:
    # Fails if /dev/shm (or some equivalent thereof) is not available for use
    # (e.g., there's no implementation, or we can't write to it, etc.).
    try:
      multiprocessing.Value('i', 0)
    except:
      message += """
Please ensure that you have write access to both /dev/shm and /run/shm.
"""
      raise  # We'll handle this in one place below.

    # Manager objects and Windows are generally a pain to work with, so try it
    # out as a sanity check. This definitely works on some versions of Windows,
    # but it's certainly possible that there is some unknown configuration for
    # which it won't.
    global manager  # pylint: disable=global-variable-undefined

    manager = multiprocessing.Manager()

    # Check that the max number of open files is reasonable. Always check this
    # after we're sure that the basic multiprocessing functionality is
    # available, since this won't matter unless that's true.
    limit = -1
    if HAS_RESOURCE_MODULE:
      # Try to set this with both resource names - RLIMIT_NOFILE for most Unix
      # platforms, and RLIMIT_OFILE for BSD. Ignore AttributeError because the
      # "resource" module is not guaranteed to know about these names.
      try:
        limit = max(limit,
                    _IncreaseSoftLimitForResource(
                        resource.RLIMIT_NOFILE,
                        MIN_ACCEPTABLE_OPEN_FILES_LIMIT))
      except AttributeError:
        pass
      try:
        limit = max(limit,
                    _IncreaseSoftLimitForResource(
                        resource.RLIMIT_OFILE, MIN_ACCEPTABLE_OPEN_FILES_LIMIT))
      except AttributeError:
        pass

    if limit < MIN_ACCEPTABLE_OPEN_FILES_LIMIT:
      message += ("""
Your max number of open files, %s, is too low to allow safe multiprocessing.
On Linux you can fix this by adding something like "ulimit -n 10000" to your
~/.bashrc or equivalent file and opening a new terminal.

On MacOS, you may also need to run a command like this once (in addition to the
above instructions), which might require a restart of your system to take
effect:
  launchctl limit maxfiles 10000

Alternatively, edit /etc/launchd.conf with something like:
  limit maxfiles 10000 10000

""" % limit)
      raise Exception('Max number of open files, %s, is too low.' % limit)
  except:  # pylint: disable=bare-except
    stack_trace = traceback.format_exc()
    multiprocessing_is_available = False
    if logger is not None:
      logger.debug(stack_trace)
      logger.warn(message)

  # Set the cached values so that we never need to do this check again.
  cached_multiprocessing_is_available = multiprocessing_is_available
  cached_multiprocessing_check_stack_trace = stack_trace
  cached_multiprocessing_is_available_message = message
  return MultiprocessingIsAvailableResult(
      is_available=cached_multiprocessing_is_available,
      stack_trace=cached_multiprocessing_check_stack_trace)


def CreateLock():
  """Returns either a multiprocessing lock or a threading lock.

  Use Multiprocessing lock iff we have access to the parts of the
  multiprocessing module that are necessary to enable parallelism in operations.

  Returns:
    Multiprocessing or threading lock.
  """
  if CheckMultiprocessingAvailableAndInit().is_available:
    return manager.Lock()
  else:
    return threading.Lock()


def IsCloudSubdirPlaceholder(url, blr=None):
  """Determines if URL is a cloud subdir placeholder.

  This function is needed because GUI tools (like the GCS cloud console) allow
  users to create empty "folders" by creating a placeholder object; and parts
  of gsutil need to treat those placeholder objects specially. For example,
  gsutil rsync needs to avoid downloading those objects because they can cause
  conflicts (see comments in rsync command for details).

  We currently detect two cases:
    - Cloud objects whose name ends with '_$folder$'
    - Cloud objects whose name ends with '/'

  Args:
    url: The URL to be checked.
    blr: BucketListingRef to check, or None if not available.
         If None, size won't be checked.

  Returns:
    True/False.
  """
  if not url.IsCloudUrl():
    return False
  url_str = url.url_string
  if url_str.endswith('_$folder$'):
    return True
  if blr and blr.IsObject():
    size = blr.root_object.size
  else:
    size = 0
  return size == 0 and url_str.endswith('/')


def GetTermLines():
  """Returns number of terminal lines."""
  # fcntl isn't supported in Windows.
  try:
    import fcntl    # pylint: disable=g-import-not-at-top
    import termios  # pylint: disable=g-import-not-at-top
  except ImportError:
    return _DEFAULT_LINES
  def ioctl_GWINSZ(fd):  # pylint: disable=invalid-name
    try:
      return struct.unpack(
          'hh', fcntl.ioctl(fd, termios.TIOCGWINSZ, '1234'))[0]
    except:  # pylint: disable=bare-except
      return 0  # Failure (so will retry on different file descriptor below).
  # Try to find a valid number of lines from termio for stdin, stdout,
  # or stderr, in that order.
  ioc = ioctl_GWINSZ(0) or ioctl_GWINSZ(1) or ioctl_GWINSZ(2)
  if not ioc:
    try:
      fd = os.open(os.ctermid(), os.O_RDONLY)
      ioc = ioctl_GWINSZ(fd)
      os.close(fd)
    except:  # pylint: disable=bare-except
      pass
  if not ioc:
    ioc = os.environ.get('LINES', _DEFAULT_LINES)
  return int(ioc)


def FixWindowsEncodingIfNeeded(str):
  """Attempts to detect Windows CP1252 encoding and convert to UTF8.

  Windows doesn't provide a way to set UTF-8 for string encodings; you can set
  the system locale (see
  http://windows.microsoft.com/en-us/windows/change-system-locale#1TC=windows-7)
  but that takes you to a "Change system locale" dropdown that just lists
  languages (e.g., "English (United States)". Instead, we're forced to check if
  a encoding as UTF8 raises an exception and if so, try converting from CP1252
  to Unicode.

  Args:
    str: The input string.
  Returns:
    The converted string (or the original, if conversion wasn't needed).
  """
  if IS_CP1252:
    return str.decode(WINDOWS_1252).encode(UTF8)
  else:
    return str


class GsutilStreamHandler(logging.StreamHandler):
  """A subclass of StreamHandler for use in gsutil."""

  def flush(self):
    # Note: we override the flush method here due to a python 2.6 bug. The
    # python logging module will try to flush all stream handlers at exit.
    # If the StreamHandler is pointing to a file that is already closed, the
    # method throws an exception. Our unit tests temporarily redirect stderr,
    # which causes the default StreamHandler to open its stream against a
    # temporary file. By the time the process shuts down, the underlying file
    # is closed, causing an exception. This was fixed in Python 2.7, but to
    # remove the flake from Python 2.6, we maintain this here.
    try:
      logging.StreamHandler.flush(self)
    except ValueError:
      pass


def StdinIterator():
  """A generator function that returns lines from stdin."""
  for line in sys.stdin:
    # Strip CRLF.
    yield line.rstrip()
