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  43     """Discard cache entries that are out of date.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