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from __future__ import absolute_import

from __future__ import division

from __future__ import unicode_literals

import concurrent.futures

import contextlib

import math

import os

import sys

import six

from pre_commit import parse_shebang

from pre_commit.util import cmd_output

def _environ_size(_env=None):

environ = _env if _env is not None else getattr(os, 'environb', os.environ)

size = 8 * len(environ) # number of pointers in `envp`

for k, v in environ.items():

size += len(k) + len(v) + 2 # c strings in `envp`

return size

def _get_platform_max_length(): # pragma: no cover (platform specific)

if os.name == 'posix':

maximum = os.sysconf(str('SC_ARG_MAX')) - 2048 - _environ_size()

maximum = max(min(maximum, 2 ** 17), 2 ** 12)

return maximum

elif os.name == 'nt':

return 2 ** 15 - 2048 # UNICODE_STRING max - headroom

else:

# posix minimum

return 2 ** 12

def _command_length(*cmd):

full_cmd = ' '.join(cmd)

# win32 uses the amount of characters, more details at:

# https://github.com/pre-commit/pre-commit/pull/839

if sys.platform == 'win32':

# the python2.x apis require bytes, we encode as UTF-8

if six.PY2:

return len(full_cmd.encode('utf-8'))

else:

return len(full_cmd.encode('utf-16le')) // 2

else:

return len(full_cmd.encode(sys.getfilesystemencoding()))

class ArgumentTooLongError(RuntimeError):

pass

def partition(cmd, varargs, target_concurrency, _max_length=None):

_max_length = _max_length or _get_platform_max_length()

# Generally, we try to partition evenly into at least `target_concurrency`

# partitions, but we don't want a bunch of tiny partitions.

max_args = max(4, math.ceil(len(varargs) / target_concurrency))

cmd = tuple(cmd)

ret = []

ret_cmd = []

# Reversed so arguments are in order

varargs = list(reversed(varargs))

total_length = _command_length(*cmd) + 1

while varargs:

arg = varargs.pop()

arg_length = _command_length(arg) + 1

if (

total_length + arg_length <= _max_length and

len(ret_cmd) < max_args

ret_cmd.append(arg)

total_length += arg_length

elif not ret_cmd:

raise ArgumentTooLongError(arg)

else:

# We've exceeded the length, yield a command

ret.append(cmd + tuple(ret_cmd))

ret_cmd = []

total_length = _command_length(*cmd) + 1

varargs.append(arg)

ret.append(cmd + tuple(ret_cmd))

return tuple(ret)

@contextlib.contextmanager

def _thread_mapper(maxsize):

if maxsize == 1:

yield map

else:

with concurrent.futures.ThreadPoolExecutor(maxsize) as ex:

yield ex.map

def xargs(cmd, varargs, **kwargs):

"""A simplified implementation of xargs.

negate: Make nonzero successful and zero a failure

target_concurrency: Target number of partitions to run concurrently

"""

negate = kwargs.pop('negate', False)

target_concurrency = kwargs.pop('target_concurrency', 1)

max_length = kwargs.pop('_max_length', _get_platform_max_length())

retcode = 0

stdout = b''

stderr = b''

try:

cmd = parse_shebang.normalize_cmd(cmd)

except parse_shebang.ExecutableNotFoundError as e:

return e.to_output()

partitions = partition(cmd, varargs, target_concurrency, max_length)

def run_cmd_partition(run_cmd):

return cmd_output(*run_cmd, encoding=None, retcode=None, **kwargs)

threads = min(len(partitions), target_concurrency)

with _thread_mapper(threads) as thread_map:

results = thread_map(run_cmd_partition, partitions)

for proc_retcode, proc_out, proc_err in results:

# This is *slightly* too clever so I'll explain it.

# First the xor boolean table:

# T | F |

# +-------+

# T | F | T |

# --+-------+

# F | T | F |

# --+-------+

# When negate is True, it has the effect of flipping the return

# code. Otherwise, the returncode is unchanged.

retcode |= bool(proc_retcode) ^ negate

stdout += proc_out

stderr += proc_err

return retcode, stdout, stderr

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