view hglib/util.py @ 145:f3c430afa598

hglib: abstract out use of cStringIO.StringIO (issue4520)

The cStringIO module does not exist in Python 3, but io.BytesIO does.
This change prepares for the use of io.BytesIO when available by
replacing all uses of cStringIO.StringIO with an object named BytesIO.

import itertools, error, os, subprocess, sys
from cStringIO import StringIO as BytesIO

if sys.version_info[0] > 2:
    def b(s):
        """Encode the string as bytes."""
        return s.encode('latin-1')
else:
    def b(s):
        """Encode the string as bytes."""
        return s

def grouper(n, iterable):
    ''' list(grouper(2, range(4))) -> [(0, 1), (2, 3)] '''
    args = [iter(iterable)] * n
    return itertools.izip(*args)

def eatlines(s, n):
    """
    >>> eatlines("1\\n2", 1)
    '2'
    >>> eatlines("1\\n2", 2)
    ''
    >>> eatlines("1\\n2", 3)
    ''
    >>> eatlines("1\\n2\\n3", 1)
    '2\\n3'
    """
    cs = BytesIO(s)

    for line in cs:
        n -= 1
        if n == 0:
            return cs.read()
    return b('')

def skiplines(s, prefix):
    """
    Skip lines starting with prefix in s

    >>> skiplines('a\\nb\\na\\n', 'a')
    'b\\na\\n'
    >>> skiplines('a\\na\\n', 'a')
    ''
    >>> skiplines('', 'a')
    ''
    >>> skiplines('a\\nb', 'b')
    'a\\nb'
    """
    cs = BytesIO(s)

    for line in cs:
        if not line.startswith(prefix):
            return line + cs.read()

    return b('')

def cmdbuilder(name, *args, **kwargs):
    """
    A helper for building the command arguments

    args are the positional arguments

    kwargs are the options
    keys that are single lettered are prepended with '-', others with '--',
    underscores are replaced with dashes

    keys with False boolean values are ignored, lists add the key multiple times

    None arguments are skipped

    >>> cmdbuilder('cmd', a=True, b=False, c=None)
    ['cmd', '-a']
    >>> cmdbuilder('cmd', long=True)
    ['cmd', '--long']
    >>> cmdbuilder('cmd', str='s')
    ['cmd', '--str', 's']
    >>> cmdbuilder('cmd', d_ash=True)
    ['cmd', '--d-ash']
    >>> cmdbuilder('cmd', _=True)
    ['cmd', '-']
    >>> cmdbuilder('cmd', list=[1, 2])
    ['cmd', '--list', '1', '--list', '2']
    >>> cmdbuilder('cmd', None)
    ['cmd']
    """
    cmd = [name]
    for arg, val in kwargs.items():
        if val is None:
            continue

        arg = arg.replace(b('_'), b('-'))
        if arg != b('-'):
            if len(arg) == 1:
                arg = b('-') + arg
            else:
                arg = b('--') + arg
        if isinstance(val, bool):
            if val:
                cmd.append(arg)
        elif isinstance(val, list):
            for v in val:
                cmd.append(arg)
                cmd.append(str(v))
        else:
            cmd.append(arg)
            cmd.append(str(val))

    for a in args:
        if a is not None:
            cmd.append(a)

    return cmd

class reterrorhandler(object):
    """This class is meant to be used with rawcommand() error handler
    argument. It remembers the return value the command returned if
    it's one of allowed values, which is only 1 if none are given.
    Otherwise it raises a CommandError.

    >>> e = reterrorhandler('')
    >>> bool(e)
    True
    >>> e(1, 'a', '')
    'a'
    >>> bool(e)
    False

    """
    def __init__(self, args, allowed=None):
        self.args = args
        self.ret = 0
        if allowed is None:
            self.allowed = [1]
        else:
            self.allowed = allowed

    def __call__(self, ret, out, err):
        self.ret = ret
        if ret not in self.allowed:
            raise error.CommandError(self.args, ret, out, err)
        return out

    def __nonzero__(self):
        """ Returns True if the return code was 0, False otherwise """
        return self.ret == 0

class propertycache(object):
    """
    Decorator that remembers the return value of a function call.

    >>> class obj(object):
    ...     def func(self):
    ...         print 'func'
    ...         return []
    ...     func = propertycache(func)
    >>> o = obj()
    >>> o.func
    func
    []
    >>> o.func
    []
    """
    def __init__(self, func):
        self.func = func
        self.name = func.__name__
    def __get__(self, obj, type=None):
        result = self.func(obj)
        setattr(obj, self.name, result)
        return result

close_fds = os.name == 'posix'

startupinfo = None
if os.name == 'nt':
    startupinfo = subprocess.STARTUPINFO()
    startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW

def popen(args, env={}):
    environ = None
    if env:
        environ = dict(os.environ)
        environ.update(env)

    return subprocess.Popen(args, stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                            stderr=subprocess.PIPE, close_fds=close_fds,
                            startupinfo=startupinfo, env=environ)