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Editing: punycode.py
""" Codec for the Punicode encoding, as specified in RFC 3492 Written by Martin v. Löwis. """ import codecs ##################### Encoding ##################################### def segregate(str): """3.1 Basic code point segregation""" base = bytearray() extended = set() for c in str: if ord(c) < 128: base.append(ord(c)) else: extended.add(c) extended = sorted(extended) return bytes(base), extended def selective_len(str, max): """Return the length of str, considering only characters below max.""" res = 0 for c in str: if ord(c) < max: res += 1 return res def selective_find(str, char, index, pos): """Return a pair (index, pos), indicating the next occurrence of char in str. index is the position of the character considering only ordinals up to and including char, and pos is the position in the full string. index/pos is the starting position in the full string.""" l = len(str) while 1: pos += 1 if pos == l: return (-1, -1) c = str[pos] if c == char: return index+1, pos elif c < char: index += 1 def insertion_unsort(str, extended): """3.2 Insertion unsort coding""" oldchar = 0x80 result = [] oldindex = -1 for c in extended: index = pos = -1 char = ord(c) curlen = selective_len(str, char) delta = (curlen+1) * (char - oldchar) while 1: index,pos = selective_find(str,c,index,pos) if index == -1: break delta += index - oldindex result.append(delta-1) oldindex = index delta = 0 oldchar = char return result def T(j, bias): # Punycode parameters: tmin = 1, tmax = 26, base = 36 res = 36 * (j + 1) - bias if res < 1: return 1 if res > 26: return 26 return res digits = b"abcdefghijklmnopqrstuvwxyz0123456789" def generate_generalized_integer(N, bias): """3.3 Generalized variable-length integers""" result = bytearray() j = 0 while 1: t = T(j, bias) if N < t: result.append(digits[N]) return bytes(result) result.append(digits[t + ((N - t) % (36 - t))]) N = (N - t) // (36 - t) j += 1 def adapt(delta, first, numchars): if first: delta //= 700 else: delta //= 2 delta += delta // numchars # ((base - tmin) * tmax) // 2 == 455 divisions = 0 while delta > 455: delta = delta // 35 # base - tmin divisions += 36 bias = divisions + (36 * delta // (delta + 38)) return bias def generate_integers(baselen, deltas): """3.4 Bias adaptation""" # Punycode parameters: initial bias = 72, damp = 700, skew = 38 result = bytearray() bias = 72 for points, delta in enumerate(deltas): s = generate_generalized_integer(delta, bias) result.extend(s) bias = adapt(delta, points==0, baselen+points+1) return bytes(result) def punycode_encode(text): base, extended = segregate(text) deltas = insertion_unsort(text, extended) extended = generate_integers(len(base), deltas) if base: return base + b"-" + extended return extended ##################### Decoding ##################################### def decode_generalized_number(extended, extpos, bias, errors): """3.3 Generalized variable-length integers""" result = 0 w = 1 j = 0 while 1: try: char = ord(extended[extpos]) except IndexError: if errors == "strict": raise UnicodeError("incomplete punicode string") return extpos + 1, None extpos += 1 if 0x41 <= char <= 0x5A: # A-Z digit = char - 0x41 elif 0x30 <= char <= 0x39: digit = char - 22 # 0x30-26 elif errors == "strict": raise UnicodeError("Invalid extended code point '%s'" % extended[extpos-1]) else: return extpos, None t = T(j, bias) result += digit * w if digit < t: return extpos, result w = w * (36 - t) j += 1 def insertion_sort(base, extended, errors): """3.2 Insertion unsort coding""" char = 0x80 pos = -1 bias = 72 extpos = 0 while extpos < len(extended): newpos, delta = decode_generalized_number(extended, extpos, bias, errors) if delta is None: # There was an error in decoding. We can't continue because # synchronization is lost. return base pos += delta+1 char += pos // (len(base) + 1) if char > 0x10FFFF: if errors == "strict": raise UnicodeError("Invalid character U+%x" % char) char = ord('?') pos = pos % (len(base) + 1) base = base[:pos] + chr(char) + base[pos:] bias = adapt(delta, (extpos == 0), len(base)) extpos = newpos return base def punycode_decode(text, errors): if isinstance(text, str): text = text.encode("ascii") if isinstance(text, memoryview): text = bytes(text) pos = text.rfind(b"-") if pos == -1: base = "" extended = str(text, "ascii").upper() else: base = str(text[:pos], "ascii", errors) extended = str(text[pos+1:], "ascii").upper() return insertion_sort(base, extended, errors) ### Codec APIs class Codec(codecs.Codec): def encode(self, input, errors='strict'): res = punycode_encode(input) return res, len(input) def decode(self, input, errors='strict'): if errors not in ('strict', 'replace', 'ignore'): raise UnicodeError("Unsupported error handling "+errors) res = punycode_decode(input, errors) return res, len(input) class IncrementalEncoder(codecs.IncrementalEncoder): def encode(self, input, final=False): return punycode_encode(input) class IncrementalDecoder(codecs.IncrementalDecoder): def decode(self, input, final=False): if self.errors not in ('strict', 'replace', 'ignore'): raise UnicodeError("Unsupported error handling "+self.errors) return punycode_decode(input, self.errors) class StreamWriter(Codec,codecs.StreamWriter): pass class StreamReader(Codec,codecs.StreamReader): pass ### encodings module API def getregentry(): return codecs.CodecInfo( name='punycode', encode=Codec().encode, decode=Codec().decode, incrementalencoder=IncrementalEncoder, incrementaldecoder=IncrementalDecoder, streamwriter=StreamWriter, streamreader=StreamReader, )
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