cpython/Lib/dospath.py

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# Module 'dospath' -- common operations on DOS pathnames
import os
import stat
import string
# Normalize the case of a pathname.
# On MS-DOS it maps the pathname to lowercase, turns slashes into
# backslashes and maps invalid consecutive characters to a single '_'.
# Other normalizations (such as optimizing '../' away) are not allowed
# (this is done by normpath).
#
# Amrit: Things that can be valid regular expressions cannot be normalized
# away. (which is pretty much all special characters)
#
# I am assuming that at least these chars may be used:
# [, ], |, *, +, ?
mapchar = '_'
def normcase(s):
res, s = splitdrive(s)
for c in s:
if c in '/\\':
res = res + os.sep
elif c == '.' and res[-1:] == os.sep:
res = res + mapchar + c
elif ord(c) < 32 or c in ' ",:;<=>':
if res[-1:] != mapchar:
res = res + mapchar
else:
res = res + c
return string.lower(res)
# Return wheter a path is absolute.
# Trivial in Posix, harder on the Mac or MS-DOS.
# For DOS it is absolute if it starts with a slash or backslash (current
# volume), or if a pathname after the volume letter and colon starts with
# a slash or backslash.
def isabs(s):
s = splitdrive(s)[1]
return s != '' and s[:1] in '/\\'
# Join two pathnames.
# Ignore the first part if the second part is absolute.
# Insert a '/' unless the first part is empty or already ends in '/'.
def join(a, b):
if isabs(b): return b
if a == '' or a[-1:] in '/\\': return a + b
# Note: join('x', '') returns 'x/'; is this what we want?
return a + os.sep + b
# Split a path in a drive specification (a drive letter followed by a
# colon) and the path specification.
# It is always true that drivespec + pathspec == p
def splitdrive(p):
if p[1:2] == ':':
return p[0:2], p[2:]
return '', p
# Split a path in head (everything up to the last '/') and tail (the
# rest). If the original path ends in '/' but is not the root, this
# '/' is stripped. After the trailing '/' is stripped, the invariant
# join(head, tail) == p holds.
# The resulting head won't end in '/' unless it is the root.
def split(p):
d, p = splitdrive(p)
slashes = ''
while p and p[-1:] in '/\\':
slashes = slashes + p[-1]
p = p[:-1]
if p == '':
p = p + slashes
head, tail = '', ''
for c in p:
tail = tail + c
if c in '/\\':
head, tail = head + tail, ''
slashes = ''
while head and head[-1:] in '/\\':
slashes = slashes + head[-1]
head = head[:-1]
if head == '':
head = head + slashes
return d + head, tail
# Split a path in root and extension.
# The extension is everything starting at the first dot in the last
# pathname component; the root is everything before that.
# It is always true that root + ext == p.
def splitext(p):
root, ext = '', ''
for c in p:
if c in '/\\':
root, ext = root + ext + c, ''
elif c == '.' or ext:
ext = ext + c
else:
root = root + c
return root, ext
# Return the tail (basename) part of a path.
def basename(p):
return split(p)[1]
# Return the head (dirname) part of a path.
def dirname(p):
return split(p)[0]
# Return the longest prefix of all list elements.
def commonprefix(m):
if not m: return ''
prefix = m[0]
for item in m:
for i in range(len(prefix)):
if prefix[:i+1] <> item[:i+1]:
prefix = prefix[:i]
if i == 0: return ''
break
return prefix
# Is a path a symbolic link?
# This will always return false on systems where posix.lstat doesn't exist.
def islink(path):
return false
# Does a path exist?
# This is false for dangling symbolic links.
def exists(path):
try:
st = os.stat(path)
except os.error:
return 0
return 1
# Is a path a dos directory?
# This follows symbolic links, so both islink() and isdir() can be true
# for the same path.
def isdir(path):
try:
st = os.stat(path)
except os.error:
return 0
return stat.S_ISDIR(st[stat.ST_MODE])
# Is a path a regular file?
# This follows symbolic links, so both islink() and isdir() can be true
# for the same path.
def isfile(path):
try:
st = os.stat(path)
except os.error:
return 0
return stat.S_ISREG(st[stat.ST_MODE])
# Are two filenames really pointing to the same file?
def samefile(f1, f2):
s1 = os.stat(f1)
s2 = os.stat(f2)
return samestat(s1, s2)
# Are two open files really referencing the same file?
# (Not necessarily the same file descriptor!)
# XXX THIS IS BROKEN UNDER DOS! ST_INO seems to indicate number of reads?
def sameopenfile(fp1, fp2):
s1 = os.fstat(fp1.fileno())
s2 = os.fstat(fp2.fileno())
return samestat(s1, s2)
# Are two stat buffers (obtained from stat, fstat or lstat)
# describing the same file?
def samestat(s1, s2):
return s1[stat.ST_INO] == s2[stat.ST_INO] and \
s1[stat.ST_DEV] == s2[stat.ST_DEV]
# Is a path a mount point?
# XXX This degenerates in: 'is this the root?' on DOS
def ismount(path):
return isabs(splitdrive(path)[1])
# Directory tree walk.
# For each directory under top (including top itself, but excluding
# '.' and '..'), func(arg, dirname, filenames) is called, where
# dirname is the name of the directory and filenames is the list
# files files (and subdirectories etc.) in the directory.
# The func may modify the filenames list, to implement a filter,
# or to impose a different order of visiting.
def walk(top, func, arg):
try:
names = os.listdir(top)
except os.error:
return
func(arg, top, names)
exceptions = ('.', '..')
for name in names:
if name not in exceptions:
name = join(top, name)
if isdir(name):
walk(name, func, arg)
# Expand paths beginning with '~' or '~user'.
# '~' means $HOME; '~user' means that user's home directory.
# If the path doesn't begin with '~', or if the user or $HOME is unknown,
# the path is returned unchanged (leaving error reporting to whatever
# function is called with the expanded path as argument).
# See also module 'glob' for expansion of *, ? and [...] in pathnames.
# (A function should also be defined to do full *sh-style environment
# variable expansion.)
def expanduser(path):
if path[:1] <> '~':
return path
i, n = 1, len(path)
while i < n and path[i] not in '/\\':
i = i+1
if i == 1:
if not os.environ.has_key('HOME'):
return path
userhome = os.environ['HOME']
else:
return path
return userhome + path[i:]
# Expand paths containing shell variable substitutions.
# The following rules apply:
# - no expansion within single quotes
# - no escape character, except for '$$' which is translated into '$'
# - ${varname} is accepted.
# - varnames can be made out of letters, digits and the character '_'
# XXX With COMMAND.COM you can use any characters in a variable name,
# XXX except '^|<>='.
varchars = string.letters + string.digits + '_-'
def expandvars(path):
if '$' not in path:
return path
res = ''
index = 0
pathlen = len(path)
while index < pathlen:
c = path[index]
if c == '\'': # no expansion within single quotes
path = path[index + 1:]
pathlen = len(path)
try:
index = string.index(path, '\'')
res = res + '\'' + path[:index + 1]
except string.index_error:
res = res + path
index = pathlen -1
elif c == '$': # variable or '$$'
if path[index + 1:index + 2] == '$':
res = res + c
index = index + 1
elif path[index + 1:index + 2] == '{':
path = path[index+2:]
pathlen = len(path)
try:
index = string.index(path, '}')
var = path[:index]
if os.environ.has_key(var):
res = res + os.environ[var]
except string.index_error:
res = res + path
index = pathlen - 1
else:
var = ''
index = index + 1
c = path[index:index + 1]
while c != '' and c in varchars:
var = var + c
index = index + 1
c = path[index:index + 1]
if os.environ.has_key(var):
res = res + os.environ[var]
if c != '':
res = res + c
else:
res = res + c
index = index + 1
return res
# Normalize a path, e.g. A//B, A/./B and A/foo/../B all become A/B.
# Also, components of the path are silently truncated to 8+3 notation.
def normpath(path):
path = normcase(path)
prefix, path = splitdrive(path)
while path[:1] == os.sep:
prefix = prefix + os.sep
path = path[1:]
comps = string.splitfields(path, os.sep)
i = 0
while i < len(comps):
if comps[i] == '.':
del comps[i]
elif comps[i] == '..' and i > 0 and \
comps[i-1] not in ('', '..'):
del comps[i-1:i+1]
i = i-1
elif comps[i] == '' and i > 0 and comps[i-1] <> '':
del comps[i]
elif '.' in comps[i]:
comp = string.splitfields(comps[i], '.')
comps[i] = comp[0][:8] + '.' + comp[1][:3]
i = i+1
elif len(comps[i]) > 8:
comps[i] = comps[i][:8]
i = i+1
else:
i = i+1
# If the path is now empty, substitute '.'
if not prefix and not comps:
comps.append('.')
return prefix + string.joinfields(comps, os.sep)