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 __all__ = ["getline","clearcache","checkcache"]
  13
  14 def getline(filename, lineno):
  15     lines = getlines(filename)
  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):
  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 cache.has_key(filename):
  39         return cache[filename][2]
  40     else:
  41         return updatecache(filename)
  42
  43
  44 def checkcache():
  45     """Discard cache entries that are out of date.
  46     (This is not checked upon each call!)"""
  47
  48     for filename in cache.keys():
  49         size, mtime, lines, fullname = cache[filename]
  50         try:
  51             stat = os.stat(fullname)
  52         except os.error:
  53             del cache[filename]
  54             continue
  55         if size != stat[ST_SIZE] or mtime != stat[ST_MTIME]:
  56             del cache[filename]
  57
  58
  59 def updatecache(filename):
  60     """Update a cache entry and return its list of lines.
  61     If something's wrong, print a message, discard the cache entry,
  62     and return an empty list."""
  63
  64     if cache.has_key(filename):
  65         del cache[filename]
  66     if not filename or filename[0] + filename[-1] == '<>':
  67         return []
  68     fullname = filename
  69     try:
  70         stat = os.stat(fullname)
  71     except os.error, msg:
  72         # Try looking through the module search path
  73         basename = os.path.split(filename)[1]
  74         for dirname in sys.path:
  75             fullname = os.path.join(dirname, basename)
  76             try:
  77                 stat = os.stat(fullname)
  78                 break
  79             except os.error:
  80                 pass
  81         else:
  82             # No luck
  83 ##          print '*** Cannot stat', filename, ':', msg
  84             return []
  85     try:
  86         fp = open(fullname, 'r')
  87         lines = fp.readlines()
  88         fp.close()
  89     except IOError, msg:
  90 ##      print '*** Cannot open', fullname, ':', msg
  91         return []
  92     size, mtime = stat[ST_SIZE], stat[ST_MTIME]
  93     cache[filename] = size, mtime, lines, fullname
  94     return lines