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"""Cache lines from files.
This is intended to read lines from modules imported -- hence if a filename
is not found, it will look down the module search path for a file by
that name.
"""
import sys
import os
from stat import *
__all__ = ["getline","clearcache","checkcache"]
def getline(filename, lineno):
lines = getlines(filename)
if 1 <= lineno <= len(lines):
return lines[lineno-1]
else:
return ''
# The cache
cache = {} # The cache
def clearcache():
"""Clear the cache entirely."""
global cache
cache = {}
def getlines(filename):
"""Get the lines for a file from the cache.
Update the cache if it doesn't contain an entry for this file already."""
if cache.has_key(filename):
return cache[filename][2]
else:
return updatecache(filename)
def checkcache():
"""Discard cache entries that are out of date.
(This is not checked upon each call!)"""
for filename in cache.keys():
size, mtime, lines, fullname = cache[filename]
try:
stat = os.stat(fullname)
except os.error:
del cache[filename]
continue
if size != stat[ST_SIZE] or mtime != stat[ST_MTIME]:
del cache[filename]
def updatecache(filename):
"""Update a cache entry and return its list of lines.
If something's wrong, print a message, discard the cache entry,
and return an empty list."""
if cache.has_key(filename):
del cache[filename]
if not filename or filename[0] + filename[-1] == '<>':
return []
fullname = filename
try:
stat = os.stat(fullname)
except os.error, msg:
# Try looking through the module search path
basename = os.path.split(filename)[1]
for dirname in sys.path:
fullname = os.path.join(dirname, basename)
try:
stat = os.stat(fullname)
break
except os.error:
pass
else:
# No luck
## print '*** Cannot stat', filename, ':', msg
return []
try:
fp = open(fullname, 'r')
lines = fp.readlines()
fp.close()
except IOError, msg:
## print '*** Cannot open', fullname, ':', msg
return []
size, mtime = stat[ST_SIZE], stat[ST_MTIME]
cache[filename] = size, mtime, lines, fullname
return lines
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