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      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     48     """Discard cache entries that are out of date.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
    140