Source Code for Module qm.label

  1  ######################################################################## 
  2  # 
  3  # File:   label.py 
  4  # Author: Alex Samuel 
  5  # Date:   2001-03-17 
  6  # 
  7  # Contents: 
  8  #   Label 
  9  # 
 10  # Copyright (c) 2001, 2002 by CodeSourcery, LLC.  All rights reserved.  
 11  # 
 12  # For license terms see the file COPYING. 
 13  # 
 14  ######################################################################## 
 15   
 16  ######################################################################## 
 17  # Imports 
 18  ######################################################################## 
 19   
 20  from   __future__ import nested_scopes 
 21  import os 
 22  import re 
 23  import string 
 24  import types 
 25   
 26  ######################################################################## 
 27  # Classes 
 28  ######################################################################## 
 29   
 30 -class Label: 
 31      """A 'Label' identifies an entity. 
 32   
 33      A 'Label' is a generalization of a filename.  Like filenames, labels 
 34      consist of one or more directories followed by a basename.  However, 
 35      the format used for a label need not be the same as that used by 
 36      filenames. 
 37   
 38      Each label class defines a separator character to take the place of 
 39      the '/' character used by many file systems. 
 40       
 41      All labels are relative labels; no label may begin with a separator 
 42      character.""" 
 43   
 44 -    def __init__(self, label): 
 45          """Construct a new 'Label'. 
 46   
 47          'label' -- A string giving the value of the label.""" 
 48   
 49          assert type(label) in (types.StringType, types.UnicodeType) 
 50          self._label = label 
 51           
 52   
 53 -    def Join(self, *labels): 
 54          """Combine this label and the 'labels' into a single label. 
 55   
 56          'labels' -- A sequence of strings giving the components of the 
 57          new label.  All but the last are taken as directory names; the 
 58          last is treated as a basename.""" 
 59   
 60          result = self._label 
 61          for l in labels: 
 62              if not result: 
 63                  # If the label is empty so far, l is the first component. 
 64                  result = l 
 65              elif result and result[-1] == self._sep: 
 66                  # If the label thus far ends with a separator, we do not 
 67                  # want to add another one. 
 68                  result += l 
 69              else: 
 70                  result = result + self._sep + l 
 71   
 72          return self.__class__(result) 
 73       
 74           
 75 -    def Split(self): 
 76          """Split the label into a pair '(directory, basename)'. 
 77   
 78          returns -- A pair '(directory, basename)', each of which is 
 79          a label. 
 80   
 81          It is always true that 'directory.join(basename)' will return a 
 82          label equivalent to the original label.""" 
 83   
 84          last_sep = self._label.rfind(self._sep) 
 85          if last_sep != -1: 
 86              return (self.__class__(self._label[:last_sep]), 
 87                      self.__class__(self._label[last_sep + 1:])) 
 88          else: 
 89              return (self.__class__(""), 
 90                      self.__class__(self._label)) 
 91   
 92   
 93 -    def SplitLeft(self): 
 94          """Split the label into a pair '(parent, subpath)'.  This is 
 95          the same operation as Split, except the split occurs at the 
 96          leftmost separator, not the rightmost. 
 97   
 98          returns -- A pair '(directory, basename)', each of which is 
 99          a label. 
100   
101          It is always true that 'directory.join(basename)' will return a 
102          label equivalent to the original label.""" 
103   
104          first_sep = self._label.find(self._sep) 
105          if first_sep != -1: 
106              return (self.__class__(self._label[:first_sep]), 
107                      self.__class__(self._label[first_sep + 1:])) 
108          else: 
109              return (self.__class__(self._label), 
110                      self.__class__("")) 
111   
112   
113 -    def Basename(self): 
114          """Return the basename for the label. 
115   
116          returns -- A string giving the basename for the label.  The 
117          value returned for 'l.basename()' is always the same as 
118          'l.split()[1]'.""" 
119   
120          return self.Split()[1] 
121       
122       
123 -    def Dirname(self): 
124          """Return the directory name for the 'label'. 
125   
126          returns -- A string giving the directory name for the 'label'. 
127          The value returned for 'l.dirname()' is always the same as 
128          'l.split()[0]'.""" 
129   
130          return self.Split()[0] 
131   
132   
133 -    def IsValid(self, label, is_component): 
134          """Returns true if 'label' is valid. 
135   
136          'label' -- The string being tested for validity. 
137           
138          'is_component' -- True if the string being tested is just a 
139          single component of a label path. 
140           
141          returns -- True if 'label' is not valid.""" 
142   
143          if label and label[0] == self._sep: 
144              # All labels are relative; a valid label cannot begin with a 
145              # separator. 
146              return 0 
147          elif is_component and self._sep in label: 
148              # A component label cannot contain a separator. 
149              return 0 
150          elif label.find(self._sep + self._sep) != -1: 
151              # It is invalid to have two separators in a row. 
152              return 0 
153               
154          return 1 
155   
156   
157 -    def __str__(self): 
158          """Return the string form of this label.""" 
159   
160          return self._label 
161       
162  ######################################################################## 
163  # Functions 
164  ######################################################################## 
165   
166  __thunk_regex = re.compile("[^a-z0-9_]") 
167   
168 -def thunk(label): 
169      """Sanitize and convert 'label' to a valid label. 
170   
171      Makes a best-effort attempt to keep 'label' recognizable during 
172      the conversion. 
173   
174      returns -- A valid label.""" 
175   
176      # Strip leading and trailing whitespace. 
177      label = string.strip(label) 
178      # Lower capital letters. 
179      label = string.lower(label) 
180      # Replace all invalid characters with underscores. 
181      label = string.replace(label, "+", "x") 
182      label = __thunk_regex.sub("_", label) 
183      # Trim leading underscores. 
184      while len(label) > 0 and label[0] == "_": 
185          label = label[1:] 
186      # Make sure the label isn't empty. 
187      if label == "": 
188          raise ValueError, "Empty label" 
189      return label 
190   
191  ######################################################################## 
192  # Local Variables: 
193  # mode: python 
194  # indent-tabs-mode: nil 
195  # fill-column: 72 
196  # End: 
197