Source Code for Module qm.trace

  1  ######################################################################## 
  2  # 
  3  # File:   trace.py 
  4  # Author: Mark Mitchell 
  5  # Date:   01/25/2002 
  6  # 
  7  # Contents: 
  8  #   Tracer 
  9  # 
 10  # Copyright (c) 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  import os 
 21  import sys 
 22   
 23  ######################################################################## 
 24  # Classes 
 25  ######################################################################## 
 26   
 27 -class Tracer: 
 28      """A 'Tracer' outputs trace messages useful for debugging.""" 
 29   
 30      prefix = 'QM_THRESHOLD_' 
 31      """The prefix for an environment variable that indicates a 
 32      threshold for a particular trace category.  The string following 
 33      the prefix gives the name of the trace category.  If the 
 34      environment variable has no associated level, the associated level 
 35      is one.  Otherwise, the associated level is given by the value of 
 36      the environment variable.""" 
 37       
 38 -    def __init__(self, file=sys.stderr): 
 39          """Construct a new 'Tracer'. 
 40   
 41          'file' -- The file object to which output should be written.""" 
 42   
 43          self.__file = file 
 44          self.__thresholds = {} 
 45   
 46          # Take any environment variables that begin with QM_THRESHOLD_ 
 47          # as the initial values for thresholds. 
 48          keys = filter (lambda key: (key[:len(Tracer.prefix)] 
 49                                      == Tracer.prefix), 
 50                         os.environ.keys()) 
 51          for key in keys: 
 52              level = os.environ[key] 
 53              if level: 
 54                  level = int(level) 
 55              else: 
 56                  level = 1 
 57              self.SetThreshold(key[len(Tracer.prefix):], level) 
 58                                 
 59                                       
 60 -    def Write(self, message, category, level=0): 
 61          """Output a trace message. 
 62   
 63          'message' -- A string giving the contents of the message.  The 
 64          message should begin with a capital letter and end with a 
 65          period. 
 66   
 67          'category' -- A string indicating the category to which this 
 68          message belongs. 
 69   
 70          'level' -- A non-negative integer indicating the level at 
 71          which the message should be output. 
 72   
 73          Every category has an associated threshold.  If the level of 
 74          the 'message' is less than the threshold, the mesage will be 
 75          output.""" 
 76   
 77          if level < self.GetThreshold(category): 
 78              self.__file.write("[%s]: %s\n" % (category, message)) 
 79              self.__file.flush() 
 80   
 81   
 82 -    def GetThreshold(self, category): 
 83          """Return the current threshold for 'category'. 
 84   
 85          'category' -- A string giving a trace category. 
 86   
 87          returns -- The threshold associated with 'category'.  If no 
 88          threshold has been set, the threshold is considered to be 
 89          zero.""" 
 90   
 91          return self.__thresholds.get(category, 0) 
 92   
 93   
 94 -    def SetThreshold(self, category, level): 
 95          """Set the threshold associated with 'category'. 
 96   
 97          'category' --A string giving a trace category. 
 98   
 99          'level' -- A non-negative integer indicating the threshold 
100          level for 'category'.""" 
101   
102          self.__thresholds[category] = level 
103