| """ codecs -- Python Codec Registry, API and helpers. |
| |
| |
| Written by Marc-Andre Lemburg (mal@lemburg.com). |
| |
| (c) Copyright CNRI, All Rights Reserved. NO WARRANTY. |
| |
| """#" |
| |
| import struct,types,__builtin__ |
| |
| ### 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"] |
| |
| ### Constants |
| |
| # |
| # Byte Order Mark (BOM) and its possible values (BOM_BE, BOM_LE) |
| # |
| BOM = struct.pack('=H',0xFEFF) |
| # |
| BOM_BE = BOM32_BE = '\376\377' |
| # corresponds to Unicode U+FEFF in UTF-16 on big endian |
| # platforms == ZERO WIDTH NO-BREAK SPACE |
| BOM_LE = BOM32_LE = '\377\376' |
| # corresponds to Unicode U+FFFE in UTF-16 on little endian |
| # platforms == defined as being an illegal Unicode character |
| |
| # |
| # 64-bit Byte Order Marks |
| # |
| BOM64_BE = '\000\000\376\377' |
| # corresponds to Unicode U+0000FEFF in UCS-4 |
| BOM64_LE = '\377\376\000\000' |
| # corresponds to Unicode U+0000FFFE in UCS-4 |
| |
| |
| ### Codec base classes (defining the API) |
| |
| class Codec: |
| |
| """ Defines the interface for stateless encoders/decoders. |
| |
| The .encode()/.decode() methods may implement different error |
| handling schemes by providing the errors argument. These |
| string values are defined: |
| |
| '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. |
| |
| """ |
| 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 encodings 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 implement different error handling |
| schemes by providing the errors keyword argument. These |
| parameters are defined: |
| |
| 'strict' - raise a ValueError (or a subclass) |
| 'ignore' - ignore the character and continue with the next |
| 'replace'- replace with a suitable replacement character |
| |
| """ |
| 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 implement different error handling |
| schemes by providing the errors keyword argument. These |
| parameters are defined: |
| |
| 'strict' - raise a ValueError (or a subclass) |
| 'ignore' - ignore the character and continue with the next |
| 'replace'- replace with a suitable replacement character; |
| |
| """ |
| self.stream = stream |
| self.errors = errors |
| |
| def read(self, size=-1): |
| |
| """ Decodes data from the stream self.stream and returns the |
| resulting object. |
| |
| 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. |
| |
| 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. |
| |
| """ |
| # Unsliced reading: |
| if size < 0: |
| return self.decode(self.stream.read(), self.errors)[0] |
| |
| # Sliced reading: |
| read = self.stream.read |
| decode = self.decode |
| data = read(size) |
| i = 0 |
| while 1: |
| try: |
| object, decodedbytes = decode(data, self.errors) |
| except ValueError,why: |
| # This method is slow but should work under pretty much |
| # all conditions; at most 10 tries are made |
| i = i + 1 |
| newdata = read(1) |
| if not newdata or i > 10: |
| raise |
| data = data + newdata |
| else: |
| return object |
| |
| def readline(self, size=None): |
| |
| """ Read one line from the input stream and return the |
| decoded data. |
| |
| Note: Unlike the .readlines() method, this method inherits |
| the line breaking knowledge from the underlying stream's |
| .readline() method -- there is currently no support for |
| line breaking using the codec decoder due to lack of line |
| buffering. Sublcasses should however, if possible, try to |
| implement this method using their own knowledge of line |
| breaking. |
| |
| size, if given, is passed as size argument to the stream's |
| .readline() method. |
| |
| """ |
| if size is None: |
| line = self.stream.readline() |
| else: |
| line = self.stream.readline(size) |
| return self.decode(line,self.errors)[0] |
| |
| |
| def readlines(self, sizehint=0): |
| |
| """ 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 passed as size argument to the |
| stream's .read() method. |
| |
| """ |
| if sizehint is None: |
| data = self.stream.read() |
| else: |
| data = self.stream.read(sizehint) |
| return self.decode(data,self.errors)[0].splitlines(1) |
| |
| 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. |
| |
| """ |
| pass |
| |
| 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 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): |
| |
| if sizehint is None: |
| data = self.reader.read() |
| else: |
| data = self.reader.read(sizehint) |
| data, bytesencoded = self.encode(data, self.errors) |
| return data.splitlines(1) |
| |
| 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. Thisis 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 |
| 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 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 |
| |
| ### Tests |
| |
| if __name__ == '__main__': |
| |
| import sys |
| |
| # 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') |