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  45     """Discard cache entries that are out of date.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