python
diff --git a/‎Lib/linecache.py‎
Lines changed: 71 additions & 0 deletions b/‎Lib/linecache.py‎
Lines changed: 71 additions & 0 deletions
@@ -0,0 +1,71 @@
+# Cache lines from files.
+
+import os
+from stat import *
+
+def getline(filename, lineno):
+	lines = getlines(filename)
+	if 1 <= lineno <= len(lines):
+		return lines[lineno-1]
+	else:
+		return ''
+
+
+# The cache
+
+cache = {} # The cache
+
+
+# Clear the cache entirely
+
+def clearcache():
+	global cache
+	cache = {}
+
+
+# Get the lines for a file from the cache.
+# Update the cache if it doesn't contain an entry for this file already.
+
+def getlines(filename):
+	if cache.has_key(filename):
+		return cache[filename][2]
+	else:
+		return updatecache(filename)
+
+
+# Discard cache entries that are out of date.
+# (This is not checked upon each call
+
+def checkcache():
+	for filename in cache.keys():
+		size, mtime, lines = cache[filename]
+		try:	stat = os.stat(filename)
+		except os.error:
+			del cache[filename]
+			continue
+		if size <> stat[ST_SIZE] or mtime <> stat[ST_MTIME]:
+			del cache[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.
+
+def updatecache(filename):
+	try:	del cache[filename]
+	except KeyError: pass
+	try:	stat = os.stat(filename)
+	except os.error, msg:
+		if filename[0] + filename[-1] <> '<>':
+			print '*** Cannot stat', filename, ':', msg
+		return []
+	try:
+		fp = open(filename, 'r')
+		lines = fp.readlines()
+		fp.close()
+	except IOError, msg:
+		print '*** Cannot open', filename, ':', msg
+		return []
+	size, mtime = stat[ST_SIZE], stat[ST_MTIME]
+	cache[filename] = size, mtime, lines
+	return lines