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Python Source | 2007-04-12 | 25.7 KB | 821 lines

""" codecs -- Python Codec Registry, API and helpers. Written by Marc-Andre Lemburg (mal@lemburg.com). (c) Copyright CNRI, All Rights Reserved. NO WARRANTY. """#" import __builtin__, sys ### Registry and builtin stateless codec functions try: from _codecs import * except ImportError, why: raise SystemError,\ 'Failed to load the builtin codecs: %s' % why __all__ = ["register", "lookup", "open", "EncodedFile", "BOM", "BOM_BE", "BOM_LE", "BOM32_BE", "BOM32_LE", "BOM64_BE", "BOM64_LE", "BOM_UTF8", "BOM_UTF16", "BOM_UTF16_LE", "BOM_UTF16_BE", "BOM_UTF32", "BOM_UTF32_LE", "BOM_UTF32_BE", "strict_errors", "ignore_errors", "replace_errors", "xmlcharrefreplace_errors", "register_error", "lookup_error"] ### Constants # # Byte Order Mark (BOM = ZERO WIDTH NO-BREAK SPACE = U+FEFF) # and its possible byte string values # for UTF8/UTF16/UTF32 output and little/big endian machines # # UTF-8 BOM_UTF8 = '\xef\xbb\xbf' # UTF-16, little endian BOM_LE = BOM_UTF16_LE = '\xff\xfe' # UTF-16, big endian BOM_BE = BOM_UTF16_BE = '\xfe\xff' # UTF-32, little endian BOM_UTF32_LE = '\xff\xfe\x00\x00' # UTF-32, big endian BOM_UTF32_BE = '\x00\x00\xfe\xff' if sys.byteorder == 'little': # UTF-16, native endianness BOM = BOM_UTF16 = BOM_UTF16_LE # UTF-32, native endianness BOM_UTF32 = BOM_UTF32_LE else: # UTF-16, native endianness BOM = BOM_UTF16 = BOM_UTF16_BE # UTF-32, native endianness BOM_UTF32 = BOM_UTF32_BE # Old broken names (don't use in new code) BOM32_LE = BOM_UTF16_LE BOM32_BE = BOM_UTF16_BE BOM64_LE = BOM_UTF32_LE BOM64_BE = BOM_UTF32_BE ### Codec base classes (defining the API) class Codec: """ Defines the interface for stateless encoders/decoders. The .encode()/.decode() methods may use different error handling schemes by providing the errors argument. These string values are predefined: 'strict' - raise a ValueError error (or a subclass) 'ignore' - ignore the character and continue with the next 'replace' - replace with a suitable replacement character; Python will use the official U+FFFD REPLACEMENT CHARACTER for the builtin Unicode codecs on decoding and '?' on encoding. 'xmlcharrefreplace' - Replace with the appropriate XML character reference (only for encoding). 'backslashreplace' - Replace with backslashed escape sequences (only for encoding). The set of allowed values can be extended via register_error. """ def encode(self, input, errors='strict'): """ Encodes the object input and returns a tuple (output object, length consumed). errors defines the error handling to apply. It defaults to 'strict' handling. The method may not store state in the Codec instance. Use StreamCodec for codecs which have to keep state in order to make encoding/decoding efficient. The encoder must be able to handle zero length input and return an empty object of the output object type in this situation. """ raise NotImplementedError def decode(self, input, errors='strict'): """ Decodes the object input and returns a tuple (output object, length consumed). input must be an object which provides the bf_getreadbuf buffer slot. Python strings, buffer objects and memory mapped files are examples of objects providing this slot. errors defines the error handling to apply. It defaults to 'strict' handling. The method may not store state in the Codec instance. Use StreamCodec for codecs which have to keep state in order to make encoding/decoding efficient. The decoder must be able to handle zero length input and return an empty object of the output object type in this situation. """ raise NotImplementedError # # The StreamWriter and StreamReader class provide generic working # interfaces which can be used to implement new encoding submodules # very easily. See encodings/utf_8.py for an example on how this is # done. # class StreamWriter(Codec): def __init__(self, stream, errors='strict'): """ Creates a StreamWriter instance. stream must be a file-like object open for writing (binary) data. The StreamWriter may use different error handling schemes by providing the errors keyword argument. These parameters are predefined: 'strict' - raise a ValueError (or a subclass) 'ignore' - ignore the character and continue with the next 'replace'- replace with a suitable replacement character 'xmlcharrefreplace' - Replace with the appropriate XML character reference. 'backslashreplace' - Replace with backslashed escape sequences (only for encoding). The set of allowed parameter values can be extended via register_error. """ self.stream = stream self.errors = errors def write(self, object): """ Writes the object's contents encoded to self.stream. """ data, consumed = self.encode(object, self.errors) self.stream.write(data) def writelines(self, list): """ Writes the concatenated list of strings to the stream using .write(). """ self.write(''.join(list)) def reset(self): """ Flushes and resets the codec buffers used for keeping state. Calling this method should ensure that the data on the output is put into a clean state, that allows appending of new fresh data without having to rescan the whole stream to recover state. """ pass def __getattr__(self, name, getattr=getattr): """ Inherit all other methods from the underlying stream. """ return getattr(self.stream, name) ### class StreamReader(Codec): def __init__(self, stream, errors='strict'): """ Creates a StreamReader instance. stream must be a file-like object open for reading (binary) data. The StreamReader may use different error handling schemes by providing the errors keyword argument. These parameters are predefined: 'strict' - raise a ValueError (or a subclass) 'ignore' - ignore the character and continue with the next 'replace'- replace with a suitable replacement character; The set of allowed parameter values can be extended via register_error. """ self.stream = stream self.errors = errors self.bytebuffer = "" # For str->str decoding this will stay a str # For str->unicode decoding the first read will promote it to unicode self.charbuffer = "" self.linebuffer = None def decode(self, input, errors='strict'): raise NotImplementedError def read(self, size=-1, chars=-1, firstline=False): """ Decodes data from the stream self.stream and returns the resulting object. chars indicates the number of characters to read from the stream. read() will never return more than chars characters, but it might return less, if there are not enough characters available. size indicates the approximate maximum number of bytes to read from the stream for decoding purposes. The decoder can modify this setting as appropriate. The default value -1 indicates to read and decode as much as possible. size is intended to prevent having to decode huge files in one step. If firstline is true, and a UnicodeDecodeError happens after the first line terminator in the input only the first line will be returned, the rest of the input will be kept until the next call to read(). The method should use a greedy read strategy meaning that it should read as much data as is allowed within the definition of the encoding and the given size, e.g. if optional encoding endings or state markers are available on the stream, these should be read too. """ # If we have lines cached, first merge them back into characters if self.linebuffer: self.charbuffer = "".join(self.linebuffer) self.linebuffer = None # read until we get the required number of characters (if available) while True: # can the request can be satisfied from the character buffer? if chars < 0: if size < 0: if self.charbuffer: break elif len(self.charbuffer) >= size: break else: if len(self.charbuffer) >= chars: break # we need more data if size < 0: newdata = self.stream.read() else: newdata = self.stream.read(size) # decode bytes (those remaining from the last call included) data = self.bytebuffer + newdata try: newchars, decodedbytes = self.decode(data, self.errors) except UnicodeDecodeError, exc: if firstline: newchars, decodedbytes = self.decode(data[:exc.start], self.errors) lines = newchars.splitlines(True) if len(lines)<=1: raise else: raise # keep undecoded bytes until the next call self.bytebuffer = data[decodedbytes:] # put new characters in the character buffer self.charbuffer += newchars # there was no data available if not newdata: break if chars < 0: # Return everything we've got result = self.charbuffer self.charbuffer = "" else: # Return the first chars characters result = self.charbuffer[:chars] self.charbuffer = self.charbuffer[chars:] return result def readline(self, size=None, keepends=True): """ Read one line from the input stream and return the decoded data. size, if given, is passed as size argument to the read() method. """ # If we have lines cached from an earlier read, return # them unconditionally if self.linebuffer: line = self.linebuffer[0] del self.linebuffer[0] if len(self.linebuffer) == 1: # revert to charbuffer mode; we might need more data # next time self.charbuffer = self.linebuffer[0] self.linebuffer = None if not keepends: line = line.splitlines(False)[0] return line readsize = size or 72 line = "" # If size is given, we call read() only once while True: data = self.read(readsize, firstline=True) if data: # If we're at a "\r" read one extra character (which might # be a "\n") to get a proper line ending. If the stream is # temporarily exhausted we return the wrong line ending. if data.endswith("\r"): data += self.read(size=1, chars=1) line += data lines = line.splitlines(True) if lines: if len(lines) > 1: # More than one line result; the first line is a full line # to return line = lines[0] del lines[0] if len(lines) > 1: # cache the remaining lines lines[-1] += self.charbuffer self.linebuffer = lines self.charbuffer = None else: # only one remaining line, put it back into charbuffer self.charbuffer = lines[0] + self.charbuffer if not keepends: line = line.splitlines(False)[0] break line0withend = lines[0] line0withoutend = lines[0].splitlines(False)[0] if line0withend != line0withoutend: # We really have a line end # Put the rest back together and keep it until the next call self.charbuffer = "".join(lines[1:]) + self.charbuffer if keepends: line = line0withend else: line = line0withoutend break # we didn't get anything or this was our only try if not data or size is not None: if line and not keepends: line = line.splitlines(False)[0] break if readsize<8000: readsize *= 2 return line def readlines(self, sizehint=None, keepends=True): """ Read all lines available on the input stream and return them as list of lines. Line breaks are implemented using the codec's decoder method and are included in the list entries. sizehint, if given, is ignored since there is no efficient way to finding the true end-of-line. """ data = self.read() return data.splitlines(keepends) def reset(self): """ Resets the codec buffers used for keeping state. Note that no stream repositioning should take place. This method is primarily intended to be able to recover from decoding errors. """ self.bytebuffer = "" self.charbuffer = u"" self.linebuffer = None def seek(self, offset, whence=0): """ Set the input stream's current position. Resets the codec buffers used for keeping state. """ self.reset() self.stream.seek(offset, whence) def next(self): """ Return the next decoded line from the input stream.""" line = self.readline() if line: return line raise StopIteration def __iter__(self): return self def __getattr__(self, name, getattr=getattr): """ Inherit all other methods from the underlying stream. """ return getattr(self.stream, name) ### class StreamReaderWriter: """ StreamReaderWriter instances allow wrapping streams which work in both read and write modes. The design is such that one can use the factory functions returned by the codec.lookup() function to construct the instance. """ # Optional attributes set by the file wrappers below encoding = 'unknown' def __init__(self, stream, Reader, Writer, errors='strict'): """ Creates a StreamReaderWriter instance. stream must be a Stream-like object. Reader, Writer must be factory functions or classes providing the StreamReader, StreamWriter interface resp. Error handling is done in the same way as defined for the StreamWriter/Readers. """ self.stream = stream self.reader = Reader(stream, errors) self.writer = Writer(stream, errors) self.errors = errors def read(self, size=-1): return self.reader.read(size) def readline(self, size=None): return self.reader.readline(size) def readlines(self, sizehint=None): return self.reader.readlines(sizehint) def next(self): """ Return the next decoded line from the input stream.""" return self.reader.next() def __iter__(self): return self def write(self, data): return self.writer.write(data) def writelines(self, list): return self.writer.writelines(list) def reset(self): self.reader.reset() self.writer.reset() def __getattr__(self, name, getattr=getattr): """ Inherit all other methods from the underlying stream. """ return getattr(self.stream, name) ### class StreamRecoder: """ StreamRecoder instances provide a frontend - backend view of encoding data. They use the complete set of APIs returned by the codecs.lookup() function to implement their task. Data written to the stream is first decoded into an intermediate format (which is dependent on the given codec combination) and then written to the stream using an instance of the provided Writer class. In the other direction, data is read from the stream using a Reader instance and then return encoded data to the caller. """ # Optional attributes set by the file wrappers below data_encoding = 'unknown' file_encoding = 'unknown' def __init__(self, stream, encode, decode, Reader, Writer, errors='strict'): """ Creates a StreamRecoder instance which implements a two-way conversion: encode and decode work on the frontend (the input to .read() and output of .write()) while Reader and Writer work on the backend (reading and writing to the stream). You can use these objects to do transparent direct recodings from e.g. latin-1 to utf-8 and back. stream must be a file-like object. encode, decode must adhere to the Codec interface, Reader, Writer must be factory functions or classes providing the StreamReader, StreamWriter interface resp. encode and decode are needed for the frontend translation, Reader and Writer for the backend translation. Unicode is used as intermediate encoding. Error handling is done in the same way as defined for the StreamWriter/Readers. """ self.stream = stream self.encode = encode self.decode = decode self.reader = Reader(stream, errors) self.writer = Writer(stream, errors) self.errors = errors def read(self, size=-1): data = self.reader.read(size) data, bytesencoded = self.encode(data, self.errors) return data def readline(self, size=None): if size is None: data = self.reader.readline() else: data = self.reader.readline(size) data, bytesencoded = self.encode(data, self.errors) return data def readlines(self, sizehint=None): data = self.reader.read() data, bytesencoded = self.encode(data, self.errors) return data.splitlines(1) def next(self): """ Return the next decoded line from the input stream.""" data = self.reader.next() data, bytesencoded = self.encode(data, self.errors) return data def __iter__(self): return self def write(self, data): data, bytesdecoded = self.decode(data, self.errors) return self.writer.write(data) def writelines(self, list): data = ''.join(list) data, bytesdecoded = self.decode(data, self.errors) return self.writer.write(data) def reset(self): self.reader.reset() self.writer.reset() def __getattr__(self, name, getattr=getattr): """ Inherit all other methods from the underlying stream. """ return getattr(self.stream, name) ### Shortcuts def open(filename, mode='rb', encoding=None, errors='strict', buffering=1): """ Open an encoded file using the given mode and return a wrapped version providing transparent encoding/decoding. Note: The wrapped version will only accept the object format defined by the codecs, i.e. Unicode objects for most builtin codecs. Output is also codec dependent and will usually by Unicode as well. Files are always opened in binary mode, even if no binary mode was specified. This is done to avoid data loss due to encodings using 8-bit values. The default file mode is 'rb' meaning to open the file in binary read mode. encoding specifies the encoding which is to be used for the file. errors may be given to define the error handling. It defaults to 'strict' which causes ValueErrors to be raised in case an encoding error occurs. buffering has the same meaning as for the builtin open() API. It defaults to line buffered. The returned wrapped file object provides an extra attribute .encoding which allows querying the used encoding. This attribute is only available if an encoding was specified as parameter. """ if encoding is not None and \ 'b' not in mode: # Force opening of the file in binary mode mode = mode + 'b' file = __builtin__.open(filename, mode, buffering) if encoding is None: return file (e, d, sr, sw) = lookup(encoding) srw = StreamReaderWriter(file, sr, sw, errors) # Add attributes to simplify introspection srw.encoding = encoding return srw def EncodedFile(file, data_encoding, file_encoding=None, errors='strict'): """ Return a wrapped version of file which provides transparent encoding translation. Strings written to the wrapped file are interpreted according to the given data_encoding and then written to the original file as string using file_encoding. The intermediate encoding will usually be Unicode but depends on the specified codecs. Strings are read from the file using file_encoding and then passed back to the caller as string using data_encoding. If file_encoding is not given, it defaults to data_encoding. errors may be given to define the error handling. It defaults to 'strict' which causes ValueErrors to be raised in case an encoding error occurs. The returned wrapped file object provides two extra attributes .data_encoding and .file_encoding which reflect the given parameters of the same name. The attributes can be used for introspection by Python programs. """ if file_encoding is None: file_encoding = data_encoding encode, decode = lookup(data_encoding)[:2] Reader, Writer = lookup(file_encoding)[2:] sr = StreamRecoder(file, encode, decode, Reader, Writer, errors) # Add attributes to simplify introspection sr.data_encoding = data_encoding sr.file_encoding = file_encoding return sr ### Helpers for codec lookup def getencoder(encoding): """ Lookup up the codec for the given encoding and return its encoder function. Raises a LookupError in case the encoding cannot be found. """ return lookup(encoding)[0] def getdecoder(encoding): """ Lookup up the codec for the given encoding and return its decoder function. Raises a LookupError in case the encoding cannot be found. """ return lookup(encoding)[1] def getreader(encoding): """ Lookup up the codec for the given encoding and return its StreamReader class or factory function. Raises a LookupError in case the encoding cannot be found. """ return lookup(encoding)[2] def getwriter(encoding): """ Lookup up the codec for the given encoding and return its StreamWriter class or factory function. Raises a LookupError in case the encoding cannot be found. """ return lookup(encoding)[3] ### Helpers for charmap-based codecs def make_identity_dict(rng): """ make_identity_dict(rng) -> dict Return a dictionary where elements of the rng sequence are mapped to themselves. """ res = {} for i in rng: res[i]=i return res def make_encoding_map(decoding_map): """ Creates an encoding map from a decoding map. If a target mapping in the decoding map occurs multiple times, then that target is mapped to None (undefined mapping), causing an exception when encountered by the charmap codec during translation. One example where this happens is cp875.py which decodes multiple character to \u001a. """ m = {} for k,v in decoding_map.items(): if not v in m: m[v] = k else: m[v] = None return m ### error handlers try: strict_errors = lookup_error("strict") ignore_errors = lookup_error("ignore") replace_errors = lookup_error("replace") xmlcharrefreplace_errors = lookup_error("xmlcharrefreplace") backslashreplace_errors = lookup_error("backslashreplace") except LookupError: # In --disable-unicode builds, these error handler are missing strict_errors = None ignore_errors = None replace_errors = None xmlcharrefreplace_errors = None backslashreplace_errors = None # Tell modulefinder that using codecs probably needs the encodings # package _false = 0 if _false: import encodings ### Tests if __name__ == '__main__': # Make stdout translate Latin-1 output into UTF-8 output sys.stdout = EncodedFile(sys.stdout, 'latin-1', 'utf-8') # Have stdin translate Latin-1 input into UTF-8 input sys.stdin = EncodedFile(sys.stdin, 'utf-8', 'latin-1')