"""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
import tokenize
__all__ = ["getline", "clearcache", "checkcache"]
def getline(filename, lineno, module_globals=None):
lines = getlines(filename, module_globals)
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, module_globals=None):
"""Get the lines for a file from the cache.
Update the cache if it doesn't contain an entry for this file already."""
if filename in cache:
return cache[filename][2]
else:
return updatecache(filename, module_globals)
def checkcache(filename=None):
"""Discard cache entries that are out of date.
(This is not checked upon each call!)"""
if filename is None:
filenames = list(cache.keys())
else:
if filename in cache:
filenames = [filename]
else:
return
for filename in filenames:
size, mtime, lines, fullname = cache[filename]
if mtime is None:
continue # no-op for files loaded via a __loader__
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, module_globals=None):
"""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 filename in cache:
del cache[filename]
if not filename or filename[0] + filename[-1] == '<>':
return []
fullname = filename
try:
stat = os.stat(fullname)
except os.error as msg:
basename = filename
# Try for a __loader__, if available
if module_globals and '__loader__' in module_globals:
name = module_globals.get('__name__')
loader = module_globals['__loader__']
get_source = getattr(loader, 'get_source', None)
if name and get_source:
try:
data = get_source(name)
except (ImportError, IOError):
pass
else:
if data is None:
# No luck, the PEP302 loader cannot find the source
# for this module.
return []
cache[filename] = (
len(data), None,
[line+'\n' for line in data.splitlines()], fullname
)
return cache[filename][2]
# Try looking through the module search path, which is only useful
# when handling a relative filename.
if os.path.isabs(filename):
return []
for dirname in sys.path:
try:
fullname = os.path.join(dirname, basename)
except (TypeError, AttributeError):
# Not sufficiently string-like to do anything useful with.
pass
else:
try:
stat = os.stat(fullname)
break
except os.error:
pass
else:
# No luck
return []
with open(fullname, 'rb') as fp:
coding, line = tokenize.detect_encoding(fp.readline)
with open(fullname, 'r', encoding=coding) as fp:
lines = fp.readlines()
size, mtime = stat.st_size, stat.st_mtime
cache[filename] = size, mtime, lines, fullname
return lines
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