AppPkg/Applications/Python/Python-2.7.10/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
  40     try:
  41         return updatecache(filename, module_globals)
  42     except MemoryError:
  43         clearcache()
  44         return []
  45
  46
  47 def checkcache(filename=None):
  48     """Discard cache entries that are out of date.
  49     (This is not checked upon each call!)"""
  50
  51     if filename is None:
  52         filenames = cache.keys()
  53     else:
  54         if filename in cache:
  55             filenames = [filename]
  56         else:
  57             return
  58
  59     for filename in filenames:
  60         size, mtime, lines, fullname = cache[filename]
  61         if mtime is None:
  62             continue   # no-op for files loaded via a __loader__
  63         try:
  64             stat = os.stat(fullname)
  65         except os.error:
  66             del cache[filename]
  67             continue
  68         if size != stat.st_size or mtime != stat.st_mtime:
  69             del cache[filename]
  70
  71
  72 def updatecache(filename, module_globals=None):
  73     """Update a cache entry and return its list of lines.
  74     If something's wrong, print a message, discard the cache entry,
  75     and return an empty list."""
  76
  77     if filename in cache:
  78         del cache[filename]
  79     if not filename or (filename.startswith('<') and filename.endswith('>')):
  80         return []
  81
  82     fullname = filename
  83     try:
  84         stat = os.stat(fullname)
  85     except OSError:
  86         basename = filename
  87
  88         # Try for a __loader__, if available
  89         if module_globals and '__loader__' in module_globals:
  90             name = module_globals.get('__name__')
  91             loader = module_globals['__loader__']
  92             get_source = getattr(loader, 'get_source', None)
  93
  94             if name and get_source:
  95                 try:
  96                     data = get_source(name)
  97                 except (ImportError, IOError):
  98                     pass
  99                 else:
 100                     if data is None:
 101                         # No luck, the PEP302 loader cannot find the source
 102                         # for this module.
 103                         return []
 104                     cache[filename] = (
 105                         len(data), None,
 106                         [line+'\n' for line in data.splitlines()], fullname
 107                     )
 108                     return cache[filename][2]
 109
 110         # Try looking through the module search path, which is only useful
 111         # when handling a relative filename.
 112         if os.path.isabs(filename):
 113             return []
 114
 115         for dirname in sys.path:
 116             # When using imputil, sys.path may contain things other than
 117             # strings; ignore them when it happens.
 118             try:
 119                 fullname = os.path.join(dirname, basename)
 120             except (TypeError, AttributeError):
 121                 # Not sufficiently string-like to do anything useful with.
 122                 continue
 123             try:
 124                 stat = os.stat(fullname)
 125                 break
 126             except os.error:
 127                 pass
 128         else:
 129             return []
 130     try:
 131         with open(fullname, 'rU') as fp:
 132             lines = fp.readlines()
 133     except IOError:
 134         return []
 135     if lines and not lines[-1].endswith('\n'):
 136         lines[-1] += '\n'
 137     size, mtime = stat.st_size, stat.st_mtime
 138     cache[filename] = size, mtime, lines, fullname
 139     return lines