cvs2svn_lib/log.py

   1 # (Be in -*- python -*- mode.)
   2 #
   3 # ====================================================================
   4 # Copyright (c) 2000-2008 CollabNet.  All rights reserved.
   5 #
   6 # This software is licensed as described in the file COPYING, which
   7 # you should have received as part of this distribution.  The terms
   8 # are also available at http://subversion.tigris.org/license-1.html.
   9 # If newer versions of this license are posted there, you may use a
  10 # newer version instead, at your option.
  11 #
  12 # This software consists of voluntary contributions made by many
  13 # individuals.  For exact contribution history, see the revision
  14 # history and logs, available at http://cvs2svn.tigris.org/.
  15 # ====================================================================
  16
  17 """This module contains a simple logging facility for cvs2svn."""
  18
  19
  20 import sys
  21 import time
  22 import threading
  23
  24
  25 class Log:
  26   """A Simple logging facility.
  27
  28   If self.log_level is DEBUG or higher, each line will be timestamped
  29   with the number of wall-clock seconds since the time when this
  30   module was first imported.
  31
  32   The public methods of this class are thread-safe.
  33
  34   This class is a Borg; see
  35   http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66531."""
  36
  37   # These constants represent the log levels that this class supports.
  38   # The increase_verbosity() and decrease_verbosity() methods rely on
  39   # these constants being consecutive integers:
  40   ERROR = -2
  41   WARN = -1
  42   QUIET = 0
  43   NORMAL = 1
  44   VERBOSE = 2
  45   DEBUG = 3
  46
  47   start_time = time.time()
  48
  49   __shared_state = {}
  50
  51   def __init__(self):
  52     self.__dict__ = self.__shared_state
  53     if self.__dict__:
  54       return
  55
  56     self.log_level = Log.NORMAL
  57
  58     # The output file to use for errors:
  59     self._err = sys.stderr
  60
  61     # The output file to use for lower-priority messages:
  62     self._out = sys.stdout
  63
  64     # Lock to serialize writes to the log:
  65     self.lock = threading.Lock()
  66
  67   def increase_verbosity(self):
  68     self.lock.acquire()
  69     try:
  70       self.log_level = min(self.log_level + 1, Log.DEBUG)
  71     finally:
  72       self.lock.release()
  73
  74   def decrease_verbosity(self):
  75     self.lock.acquire()
  76     try:
  77       self.log_level = max(self.log_level - 1, Log.ERROR)
  78     finally:
  79       self.lock.release()
  80
  81   def is_on(self, level):
  82     """Return True iff messages at the specified LEVEL are currently on.
  83
  84     LEVEL should be one of the constants Log.WARN, Log.QUIET, etc."""
  85
  86     return self.log_level >= level
  87
  88   def _timestamp(self):
  89     """Return a timestamp if needed, as a string with a trailing space."""
  90
  91     retval = []
  92
  93     if self.log_level >= Log.DEBUG:
  94       retval.append('%f: ' % (time.time() - self.start_time,))
  95
  96     return ''.join(retval)
  97
  98   def _write(self, out, *args):
  99     """Write a message to OUT.
 100
 101     If there are multiple ARGS, they will be separated by spaces.  If
 102     there are multiple lines, they will be output one by one with the
 103     same timestamp prefix."""
 104
 105     timestamp = self._timestamp()
 106     s = ' '.join(map(str, args))
 107     lines = s.split('\n')
 108     if lines and not lines[-1]:
 109       del lines[-1]
 110
 111     self.lock.acquire()
 112     try:
 113       for s in lines:
 114         out.write('%s%s\n' % (timestamp, s,))
 115       # Ensure that log output doesn't get out-of-order with respect to
 116       # stderr output.
 117       out.flush()
 118     finally:
 119       self.lock.release()
 120
 121   def write(self, *args):
 122     """Write a message to SELF._out.
 123
 124     This is a public method to use for writing to the output log
 125     unconditionally."""
 126
 127     self._write(self._out, *args)
 128
 129   def error(self, *args):
 130     """Log a message at the ERROR level."""
 131
 132     if self.is_on(Log.ERROR):
 133       self._write(self._err, *args)
 134
 135   def warn(self, *args):
 136     """Log a message at the WARN level."""
 137
 138     if self.is_on(Log.WARN):
 139       self._write(self._out, *args)
 140
 141   def quiet(self, *args):
 142     """Log a message at the QUIET level."""
 143
 144     if self.is_on(Log.QUIET):
 145       self._write(self._out, *args)
 146
 147   def normal(self, *args):
 148     """Log a message at the NORMAL level."""
 149
 150     if self.is_on(Log.NORMAL):
 151       self._write(self._out, *args)
 152
 153   def verbose(self, *args):
 154     """Log a message at the VERBOSE level."""
 155
 156     if self.is_on(Log.VERBOSE):
 157       self._write(self._out, *args)
 158
 159   def debug(self, *args):
 160     """Log a message at the DEBUG level."""
 161
 162     if self.is_on(Log.DEBUG):
 163       self._write(self._out, *args)
 164
 165
 166 # Create an instance that everybody can use:
 167 logger = Log()
 168
 169