path: root/summainlib.py

# Copyright (C) 2010, 2011  Lars Wirzenius
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.


import grp
import hashlib
import os
import pwd
import stat
import time
import urllib


version = '0.5'


class NumberNormalizer(object):

    '''Normalize inode and device numbers.
    
    When we make two manifests of the same directory tree, but the
    tree may have been moved to another disk, the inode and device
    numbers may be different. This should not be a cause for concern,
    however. What is important is that if two names were hardlinked
    to the same file before, they still are, and if they weren't,
    they still aren't.
    
    To achieve this, we normalize the inode and device numbers.
    The input files are fed to the normalizer in a deterministic
    sequence, and the sequence defines the numbers we use. Thus,
    if the input files have inode numbers [42, 13, 105], we produce
    [1, 2, 3]. If one of the input numbers is repeated, that number
    is re-used.
    
    This is not a perfect solution. If the second manifest has a
    new file, it will throw off the entire remaining sequence, causing
    a big diff. But we'll live with that.
    
    '''
    
    def __init__(self):
        self.reset()

    def get(self, input_number, numbers, next):
        if input_number in numbers:
            return numbers[input_number], next
        else:
            numbers[input_number] = next
            return numbers[input_number], next + 1
    
    def get_ino(self, ino):
        output, self.next_ino = self.get(ino, self.ino_numbers, self.next_ino)
        return output
    
    def get_dev(self, dev):
        output, self.next_dev = self.get(dev, self.dev_numbers, self.next_dev)
        return output

    def reset(self):
        '''This is used by unit tests.'''
        self.ino_numbers = dict()
        self.next_ino = 1

        self.dev_numbers = dict()
        self.next_dev = 1


class PathNormalizer(object):

    '''Normalize a filesystem path.
    
    For every input path, a new output path is given. The same output
    path is given every time the same input path is given. The output
    path has the same number of elements as the input path, and if
    /foo/bar results in /a/b, then /foo/yo results in /a/b, i.e., the
    tree structure is the same.
    
    '''
    
    def __init__(self):
        self._counter = 0
        self._dict = dict()
        self._dict[os.sep] = os.sep
        self._dict['.'] = '.'
        self._dict['..'] = '..'

    def split(self, path):
        if path == os.sep:
            return [os.sep]
        parts = path.split(os.sep)
        if parts:
            if parts[0] == '':
                parts[0] = os.sep
            if parts[-1] == '':
                parts[-1] = os.sep
        return parts
        
    def _base26(self, n):
        if n == 0:
            digits = [0]
        else:
            digits = []
            while n > 0:
                digits.append(n % 26)
                n /= 26

        letters = 'abcdefghijklmnopqrstuvwxyz'
        assert len(letters) == 26
        return ''.join(letters[x] for x in reversed(digits))
        
    def normalize_part(self, part):
        if part not in self._dict:
            self._dict[part] = self._base26(self._counter)
            self._counter += 1
        return self._dict[part]
        
    def normalize(self, path):
        parts = self.split(path)
        normalized = [self.normalize_part(x) for x in parts]
        result = ''
        for x in normalized:
            if not result:
                result = x
            elif x == os.sep:
                result += x
            elif result.endswith(os.sep):
                result += x
            else:
                result += os.sep + x
        return result


class SamePath(object): # pragma: no cover

    def normalize(self, path):
        return path


class FilesystemObject(object):

    '''An object in the file system.
    
    Responsible for gathering information and formatting it for
    reporting.
    
    The optional arguments are intended for unit tests.
    
    '''
    
    def __init__(self, filename, nn, pn, exclude, stat_result=None, sha1=None,
                 open_file=None, readlink=None):
        stat_result = stat_result or os.lstat(filename)
        sha1 = sha1 or hashlib.sha1()
        self.open_file = open_file or file
        readlink = readlink or os.readlink
        
        self.values = dict()
        self['Name'] = pn.normalize(filename)
        self['Mtime'] = self.format_time(stat_result.st_mtime)
        self['Mode'] = '%o' % stat_result.st_mode
        self['Ino'] = '%d' % nn.get_ino(stat_result.st_ino)
        self['Dev'] = '%d' % nn.get_dev(stat_result.st_dev)
        self['Nlink'] = '%d' % stat_result.st_nlink
        if not stat.S_ISDIR(stat_result.st_mode):
            self['Size'] = '%d' % stat_result.st_size
        self['Uid'] = '%d' % stat_result.st_uid
        self['Username'] = self.lookup_username(stat_result.st_uid)
        self['Gid'] = '%d' % stat_result.st_gid
        self['Group'] = self.lookup_group(stat_result.st_gid)
        if stat.S_ISREG(stat_result.st_mode):
            self['Sha-1'] = self.compute_sha1(filename, sha1)
        if stat.S_ISLNK(stat_result.st_mode):
            self['Target'] = readlink(filename)

    def format_time(self, timestamp):
        return time.strftime('%Y-%m-%d %H:%M:%S +0000', 
                             time.gmtime(timestamp))

    def lookup_username(self, uid):
        return pwd.getpwuid(uid).pw_name

    def lookup_group(self, gid):
        return grp.getgrgid(gid).gr_name

    def compute_sha1(self, filename, sha1):
        f = self.open_file(filename)
        while True:
            data = f.read(64*1024) # 64 KiB seems reasonable.
            if not data:
                break
            sha1.update(data)
        f.close()
        return sha1.hexdigest()

    def hook_name(self, value):
        return urllib.quote(value)

    def __setitem__(self, key, value):
        hook_name = 'hook_%s' % key.lower()
        if hasattr(self, hook_name):
            value = getattr(self, hook_name)(value)
        self.values[key] = value
        
    def __getitem__(self, key):
        return self.values.get(key, '')

    def _isdir(self):
        '''Is this a directory?'''
        
        return stat.S_ISDIR(int(self['Mode'], 8))

    def relative_path(self, root):
        '''Return a path that is relative to root, if possible.
        
        If pathname does not start with root, then return it
        unmodified.
        
        '''
        
        if root.endswith(os.sep):
            root2 = root
        else:
            root2 = root + os.sep
        pathname = self['Name']
        if pathname.startswith(root2):
            return pathname[len(root2):]
        elif pathname == root and self._isdir():
            return '.'
        else:
            return pathname

    def format(self, root=None): # pragma: no cover
        if root is None:
            name = self['Name']
        else:
            name = self.relative_path(root)
        
        values = ([('Name', name)] + 
                  [(x, self[x])
                   for x in sorted(self.values.keys()) if x != 'Name'])
        return ''.join('%s: %s\n' % (k, v) for k, v in values)