Lib/linecache.py

   1 """Cache lines from files.
   2
   3 This is intended to read lines from modules imported -- hence if a filename
   4 is not found, it will look down the module search path for a file by
   5 that name.
   6 """
   7
   8 import sys
   9 import os
  10
  11 __all__ = ["getline", "clearcache", "checkcache"]
  12
  13 def getline(filename, lineno, module_globals=None):
  14     lines = getlines(filename, module_globals)
  15     if 1 <= lineno <= len(lines):
  16         return lines[lineno-1]
  17     else:
  18         return ''
  19
  20
  21 # The cache
  22
  23 cache = {} # The cache
  24
  25
  26 def clearcache():
  27     """Clear the cache entirely."""
  28
  29     global cache
  30     cache = {}
  31
  32
  33 def getlines(filename, module_globals=None):
  34     """Get the lines for a file from the cache.
  35     Update the cache if it doesn't contain an entry for this file already."""
  36
  37     if filename in cache:
  38         return cache[filename][2]
  39     else:
  40         return updatecache(filename, module_globals)
  41
  42
  43 def checkcache(filename=None):
  44     """Discard cache entries that are out of date.
  45     (This is not checked upon each call!)"""
  46
  47     if filename is None:
  48         filenames = cache.keys()
  49     else:
  50         if filename in cache:
  51             filenames = [filename]
  52         else:
  53             return
  54
  55     for filename in filenames:
  56         size, mtime, lines, fullname = cache[filename]
  57         if mtime is None:
  58             continue   # no-op for files loaded via a __loader__
  59         try:
  60             stat = os.stat(fullname)
  61         except os.error:
  62             del cache[filename]
  63             continue
  64         if size != stat.st_size or mtime != stat.st_mtime:
  65             del cache[filename]
  66
  67
  68 def updatecache(filename, module_globals=None):
  69     """Update a cache entry and return its list of lines.
  70     If something's wrong, print a message, discard the cache entry,
  71     and return an empty list."""
  72
  73     if filename in cache:
  74         del cache[filename]
  75     if not filename or filename[0] + filename[-1] == '<>':
  76         return []
  77
  78     fullname = filename
  79     try:
  80         stat = os.stat(fullname)
  81     except os.error, msg:
  82         basename = os.path.split(filename)[1]
  83
  84         # Try for a __loader__, if available
  85         if module_globals and '__loader__' in module_globals:
  86             name = module_globals.get('__name__')
  87             loader = module_globals['__loader__']
  88             get_source = getattr(loader, 'get_source', None)
  89
  90             if name and get_source:
  91                 if basename.startswith(name.split('.')[-1]+'.'):
  92                     try:
  93                         data = get_source(name)
  94                     except (ImportError, IOError):
  95                         pass
  96                     else:
  97                         if data is None:
  98                             # No luck, the PEP302 loader cannot find the source
  99                             # for this module.
 100                             return []
 101                         cache[filename] = (
 102                             len(data), None,
 103                             [line+'\n' for line in data.splitlines()], fullname
 104                         )
 105                         return cache[filename][2]
 106
 107         # Try looking through the module search path.
 108
 109         for dirname in sys.path:
 110             # When using imputil, sys.path may contain things other than
 111             # strings; ignore them when it happens.
 112             try:
 113                 fullname = os.path.join(dirname, basename)
 114             except (TypeError, AttributeError):
 115                 # Not sufficiently string-like to do anything useful with.
 116                 pass
 117             else:
 118                 try:
 119                     stat = os.stat(fullname)
 120                     break
 121                 except os.error:
 122                     pass
 123         else:
 124             # No luck
 125 ##          print '*** Cannot stat', filename, ':', msg
 126             return []
 127     try:
 128         fp = open(fullname, 'rU')
 129         lines = fp.readlines()
 130         fp.close()
 131     except IOError, msg:
 132 ##      print '*** Cannot open', fullname, ':', msg
 133         return []
 134     size, mtime = stat.st_size, stat.st_mtime
 135     cache[filename] = size, mtime, lines, fullname
 136     return lines