Lib/linecache.py

   1 # Cache lines from files.
   2 # This is intended to read lines from modules imported -- hence if a filename
   3 # is not found, it will look down the module search path for a file by
   4 # that name.
   5
   6 import sys
   7 import os
   8 from stat import *
   9
  10 def getline(filename, lineno):
  11         lines = getlines(filename)
  12         if 1 <= lineno <= len(lines):
  13                 return lines[lineno-1]
  14         else:
  15                 return ''
  16
  17
  18 # The cache
  19
  20 cache = {} # The cache
  21
  22
  23 # Clear the cache entirely
  24
  25 def clearcache():
  26         global cache
  27         cache = {}
  28
  29
  30 # Get the lines for a file from the cache.
  31 # Update the cache if it doesn't contain an entry for this file already.
  32
  33 def getlines(filename):
  34         if cache.has_key(filename):
  35                 return cache[filename][2]
  36         else:
  37                 return updatecache(filename)
  38
  39
  40 # Discard cache entries that are out of date.
  41 # (This is not checked upon each call!)
  42
  43 def checkcache():
  44         for filename in cache.keys():
  45                 size, mtime, lines, fullname = cache[filename]
  46                 try:
  47                         stat = os.stat(fullname)
  48                 except os.error:
  49                         del cache[filename]
  50                         continue
  51                 if size <> stat[ST_SIZE] or mtime <> stat[ST_MTIME]:
  52                         del cache[filename]
  53
  54
  55 # Update a cache entry and return its list of lines.
  56 # If something's wrong, print a message, discard the cache entry,
  57 # and return an empty list.
  58
  59 def updatecache(filename):
  60         if cache.has_key(filename):
  61                 del cache[filename]
  62         if not filename or filename[0] + filename[-1] == '<>':
  63                 return []
  64         fullname = filename
  65         try:
  66                 stat = os.stat(fullname)
  67         except os.error, msg:
  68                 # Try looking through the module search path
  69                 basename = os.path.split(filename)[1]
  70                 for dirname in sys.path:
  71                         fullname = os.path.join(dirname, basename)
  72                         try:
  73                                 stat = os.stat(fullname)
  74                                 break
  75                         except os.error:
  76                                 pass
  77                 else:
  78                         # No luck
  79                         print '*** Cannot stat', filename, ':', msg
  80                         return []
  81         try:
  82                 fp = open(fullname, 'r')
  83                 lines = fp.readlines()
  84                 fp.close()
  85         except IOError, msg:
  86                 print '*** Cannot open', fullname, ':', msg
  87                 return []
  88         size, mtime = stat[ST_SIZE], stat[ST_MTIME]
  89         cache[filename] = size, mtime, lines, fullname
  90         return lines