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