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import base64
import binascii
import re
import hashlib
def _encodeHex(s):
"""
Encode a string in hex format.
>>> _encodeHex("Hello world")
'#48656c6c6f20776f726c64#'
>>> _encodeHex("")
'##'
"""
return "#%s#"%binascii.b2a_hex(s)
def _encodeBase64(s):
"""
Encode a string in base64 format, with embedded newlines.
>>> _encodeBase64("")
'||'
>>> _encodeBase64("Hello world")
'|SGVsbG8gd29ybGQ=|'
>>> print _encodeBase64("Hello world")
|SGVsbG8gd29ybGQ=|
>>> _encodeBase64("Good night, sweet prince! A flock of angels "
... "sing thee to thy rest")
'|R29vZCBuaWdodCwgc3dlZXQgcHJpbmNlISBBIGZsb2NrIG9mIGFuZ2VscyBzaW5nIHRoZWUgdG8g\\ndGh5IHJlc3Q=|'
"""
return "|%s|"%base64.encodestring(s).strip()
# Map from a character value to its representation in a quoted-string.
_QUOTED_MAP = { '\b' : "\\b",
'\t' : "\\t",
'\v' : "\\v",
'\n' : "\\n",
'\f' : "\\f",
'\r' : "\\r",
'"' : "\"",
'\b' : "\\b",
'\\' : "\\", }
for x in xrange(256):
if 32 <= x <= 126:
_QUOTED_MAP[chr(x)] = chr(x)
elif not _QUOTED_MAP.has_key(chr(x)):
_QUOTED_MAP[chr(x)] = "\\x%02x"%x
del x
_QUOTED_CHAR_RE = re.compile(r'[^\ -\~]')
def _replaceQuotedChar(match, _Q=_QUOTED_MAP):
"""Helper function for replacing ."""
return _Q[match.group(0)]
def _encodeQuoted(s, _Q=_QUOTED_MAP):
"""
>>> _encodeQuoted("")
'""'
>>> _encodeQuoted("Hello world")
'"Hello world"'
>>> print _encodeQuoted("Hello \xff\b")
"Hello \\xff\\b"
"""
# This implementation is a slower for the case where lots of stuff
# needs quoting, but faster for the case where only some stuff
# needs quoting. If more than about 1/4 of the characters need
# quoting, then the commented-out version below is faster. Yes,
# this is a stupid overoptimization.
return '"%s"'%(_QUOTED_CHAR_RE.sub(_replaceQuotedChar, s))
#return '"%s"'%("".join(map(_QUOTED_MAP.__getitem__, s)))
def _encodeRaw(s):
"""
Encode a string in the "raw" format used for canonical encodings.
>>> _encodeRaw("")
'0:'
>>> _encodeRaw(" ")
'1: '
>>> _encodeRaw(" \\n")
'2: \\n'
"""
return "%d:%s"%(len(s),s)
_TOKEN_PAT = r"[a-zA-Z\-\.\/\_\:\*\+\=][a-zA-Z0-9\-\.\/\_\:\*\+\=]*"
_TOKEN_RE = re.compile(_TOKEN_PAT)
def _writeToken(write,s):
"""Write a string in the token (unencoded) format. Only works for strings
matching _TOKEN_RE.
"""
assert _TOKEN_RE.match(s)
return s
def _encodeCleanest(s, indent=0):
"""Encode s in whatever format seems most human-readable."""
if _TOKEN_RE.match(s):
return s
n = 0
for ch in s:
if _QUOTED_MAP[ch] != ch:
n += 1
if n > 3 and n > len(s)//4:
if len(s) > 16:
return _encodeBase64(s).replace("\n", " "*(indent+1)+"\n")
else:
return _encodeHex(s)
else:
return _encodeQuoted(s)
def _encodePrettyPrint(s, write, indent=0, niceWidth=80):
if isinstance(s, str):
write(_encodeCleanest(s))
return
elif len(s) == 0:
write("()")
return
if isinstance(s[0], str):
parts = [ " "*indent, "(", _encodeCleanest(s), "\n" ]
else:
parts = [ "(" ]
def _encodeCanonical(rep, append):
"""Given an s-expression in <rep>, encode it in canonical format,
passing each part to the function "append" as it is done.
"""
if isinstance(rep, str):
append(_encodeRaw(rep))
return
append("(")
stack = [ ]
push = stack.append
pop = stack.pop
idx = 0
while 1:
while idx == len(rep):
append(")")
try:
rep,idx = pop()
except IndexError:
return
if isinstance(rep[idx], str):
append(_encodeRaw(rep[idx]))
idx += 1
continue
push((rep,idx+1))
rep = rep[idx]
idx = 0
append("(")
def encode_canonical(rep):
"""Return the canonical encoding of the s-expression <rep>.
>>> encode_canonical("abc")
'3:abc'
>>> encode_canonical(["a"])
'(1:a)'
>>> encode_canonical(["a", "bc"])
'(1:a2:bc)'
>>> encode_canonical([[["X", "ab c"]], "d"])
'(((1:X4:ab c))1:d)'
"""
parts = []
_encodeCanonical(rep, parts.append)
return "".join(parts)
def hash_canonical(rep, hashobj):
"""Given a hashlib hash object <hashobj>, adds the canonical
encoding of the s-expression <rep> to hashobj.
>>> import hashlib
>>> s = hashlib.sha256()
>>> s.update("(3:abc(6:hello 5:world)(1:9))")
>>> s.hexdigest()
'43f7726155f2700ff0d84240f3aaa9e5a1ee2e2c9e4702f7ac3ebcd45fd2f397'
>>> s = hashlib.sha256()
>>> hash_canonical(["abc", ["hello ", "world"], ["9"] ], s)
>>> s.hexdigest()
'43f7726155f2700ff0d84240f3aaa9e5a1ee2e2c9e4702f7ac3ebcd45fd2f397'
"""
_encodeCanonical(rep, hashobj.update)
def _encodePretty(rep, append, indent_step=2, niceWidth=80):
stack = []
idx = 0
indent = 0
append("(")
pop = stack.pop
push = stack.append
while 1:
while idx == len(rep):
append(")")
indent -= indent_step
try:
rep,idx = pop()
except IndexError:
append("\n")
return
else:
append(" ")
if isinstance(rep[idx], str):
_encodePrettyPrint(rep[idx], append, indent, niceWidth)
idx += 1
if idx < len(rep):
append(" ")
continue
push((rep,idx+1))
rep = rep[idx]
idx = 0
indent += indent_step
append("\n%s("%(" "*indent))
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