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  44     """Discard cache entries that are out of date.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 = filename
  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                 try:
  92                     data = get_source(name)
  93                 except (ImportError, IOError):
  94                     pass
  95                 else:
  96                     if data is None:
  97                         # No luck, the PEP302 loader cannot find the source
  98                         # for this module.
  99                         return []
 100                     cache[filename] = (
 101                         len(data), None,
 102                         [line+'\n' for line in data.splitlines()], fullname
 103                     )
 104                     return cache[filename][2]
 105
 106         # Try looking through the module search path, which is only useful
 107         # when handling a relative filename.
 108         if os.path.isabs(filename):
 109             return []
 110
 111         for dirname in sys.path:
 112             # When using imputil, sys.path may contain things other than
 113             # strings; ignore them when it happens.
 114             try:
 115                 fullname = os.path.join(dirname, basename)
 116             except (TypeError, AttributeError):
 117                 # Not sufficiently string-like to do anything useful with.
 118                 pass
 119             else:
 120                 try:
 121                     stat = os.stat(fullname)
 122                     break
 123                 except os.error:
 124                     pass
 125         else:
 126             # No luck
 127 ##          print '*** Cannot stat', filename, ':', msg
 128             return []
 129     try:
 130         fp = open(fullname, 'rU')
 131         lines = fp.readlines()
 132         fp.close()
 133     except IOError, msg:
 134 ##      print '*** Cannot open', fullname, ':', msg
 135         return []
 136     size, mtime = stat.st_size, stat.st_mtime
 137     cache[filename] = size, mtime, lines, fullname
 138     return lines