cpython-lru_cache-weakref: Doc/lib/libcodecs.tex annotate

annotate Doc/lib/libcodecs.tex @ 15946:4f621708514b legacy-trunk

Rich comparisons fall-out: - Get rid of long_cmp(). - Renamed Py_TPFLAGS_NEWSTYLENUMBER to Py_TPFLAGS_CHECKTYPES.

author	Guido van Rossum <guido@python.org>
date	Wed, 17 Jan 2001 15:33:18 +0000
parents	b2892cbc63db
children	6f1fd8500398

rev	line source
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	1 \section{\module{codecs} ---
12274 559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	2 Codec registry and base classes}
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	3
12274 559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	4 \declaremodule{standard}{codecs}
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	5 \modulesynopsis{Encode and decode data and streams.}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	6 \moduleauthor{Marc-Andre Lemburg}{mal@lemburg.com}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	7 \sectionauthor{Marc-Andre Lemburg}{mal@lemburg.com}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	8
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	9
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	10 \index{Unicode}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	11 \index{Codecs}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	12 \indexii{Codecs}{encode}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	13 \indexii{Codecs}{decode}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	14 \index{streams}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	15 \indexii{stackable}{streams}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	16
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	17
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	18 This module defines base classes for standard Python codecs (encoders
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	19 and decoders) and provides access to the internal Python codec
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	20 registry which manages the codec lookup process.
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	21
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	22 It defines the following functions:
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	23
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	24 \begin{funcdesc}{register}{search_function}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	25 Register a codec search function. Search functions are expected to
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	26 take one argument, the encoding name in all lower case letters, and
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	27 return a tuple of functions \code{(\var{encoder}, \var{decoder}, \var{stream_reader},
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	28 \var{stream_writer})} taking the following arguments:
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	29
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	30 \var{encoder} and \var{decoder}: These must be functions or methods
15186 b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	31 which have the same interface as the
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	32 \method{encode()}/\method{decode()} methods of Codec instances (see
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	33 Codec Interface). The functions/methods are expected to work in a
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	34 stateless mode.
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	35
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	36 \var{stream_reader} and \var{stream_writer}: These have to be
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	37 factory functions providing the following interface:
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	38
15186 b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	39 \code{factory(\var{stream}, \var{errors}='strict')}
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	40
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	41 The factory functions must return objects providing the interfaces
12274 559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	42 defined by the base classes \class{StreamWriter} and
559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	43 \class{StreamReader}, respectively. Stream codecs can maintain
559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	44 state.
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	45
12274 559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	46 Possible values for errors are \code{'strict'} (raise an exception
559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	47 in case of an encoding error), \code{'replace'} (replace malformed
559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	48 data with a suitable replacement marker, such as \character{?}) and
559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	49 \code{'ignore'} (ignore malformed data and continue without further
559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	50 notice).
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	51
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	52 In case a search function cannot find a given encoding, it should
12274 559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	53 return \code{None}.
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	54 \end{funcdesc}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	55
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	56 \begin{funcdesc}{lookup}{encoding}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	57 Looks up a codec tuple in the Python codec registry and returns the
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	58 function tuple as defined above.
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	59
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	60 Encodings are first looked up in the registry's cache. If not found,
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	61 the list of registered search functions is scanned. If no codecs tuple
12274 559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	62 is found, a \exception{LookupError} is raised. Otherwise, the codecs
559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	63 tuple is stored in the cache and returned to the caller.
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	64 \end{funcdesc}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	65
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	66 To simplify working with encoded files or stream, the module
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	67 also defines these utility functions:
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	68
13696 bb364d6f9f69 Fix small typos and markup consistency nits. Fred Drake <fdrake@acm.org> parents: 12274 diff changeset	69 \begin{funcdesc}{open}{filename, mode\optional{, encoding\optional{,
bb364d6f9f69 Fix small typos and markup consistency nits. Fred Drake <fdrake@acm.org> parents: 12274 diff changeset	70 errors\optional{, buffering}}}}
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	71 Open an encoded file using the given \var{mode} and return
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	72 a wrapped version providing transparent encoding/decoding.
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	73
12274 559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	74 \strong{Note:} The wrapped version will only accept the object format
13696 bb364d6f9f69 Fix small typos and markup consistency nits. Fred Drake <fdrake@acm.org> parents: 12274 diff changeset	75 defined by the codecs, i.e.\ Unicode objects for most built-in
bb364d6f9f69 Fix small typos and markup consistency nits. Fred Drake <fdrake@acm.org> parents: 12274 diff changeset	76 codecs. Output is also codec-dependent and will usually be Unicode as
12274 559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	77 well.
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	78
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	79 \var{encoding} specifies the encoding which is to be used for the
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	80 the file.
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	81
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	82 \var{errors} may be given to define the error handling. It defaults
13696 bb364d6f9f69 Fix small typos and markup consistency nits. Fred Drake <fdrake@acm.org> parents: 12274 diff changeset	83 to \code{'strict'} which causes a \exception{ValueError} to be raised
bb364d6f9f69 Fix small typos and markup consistency nits. Fred Drake <fdrake@acm.org> parents: 12274 diff changeset	84 in case an encoding error occurs.
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	85
12274 559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	86 \var{buffering} has the same meaning as for the built-in
559b25a79032 Make sure the \declaremodule uses the right name for the module! Fred Drake <fdrake@acm.org> parents: 12260 diff changeset	87 \function{open()} function. It defaults to line buffered.
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	88 \end{funcdesc}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	89
13696 bb364d6f9f69 Fix small typos and markup consistency nits. Fred Drake <fdrake@acm.org> parents: 12274 diff changeset	90 \begin{funcdesc}{EncodedFile}{file, input\optional{,
bb364d6f9f69 Fix small typos and markup consistency nits. Fred Drake <fdrake@acm.org> parents: 12274 diff changeset	91 output\optional{, errors}}}
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	92 Return a wrapped version of file which provides transparent
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	93 encoding translation.
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	94
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	95 Strings written to the wrapped file are interpreted according to the
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	96 given \var{input} encoding and then written to the original file as
13696 bb364d6f9f69 Fix small typos and markup consistency nits. Fred Drake <fdrake@acm.org> parents: 12274 diff changeset	97 strings using the \var{output} encoding. The intermediate encoding will
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	98 usually be Unicode but depends on the specified codecs.
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	99
13696 bb364d6f9f69 Fix small typos and markup consistency nits. Fred Drake <fdrake@acm.org> parents: 12274 diff changeset	100 If \var{output} is not given, it defaults to \var{input}.
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	101
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	102 \var{errors} may be given to define the error handling. It defaults to
13696 bb364d6f9f69 Fix small typos and markup consistency nits. Fred Drake <fdrake@acm.org> parents: 12274 diff changeset	103 \code{'strict'}, which causes \exception{ValueError} to be raised in case
12260 8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	104 an encoding error occurs.
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	105 \end{funcdesc}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	106
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	107 The module also provides the following constants which are useful
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	108 for reading and writing to platform dependent files:
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	109
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	110 \begin{datadesc}{BOM}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	111 \dataline{BOM_BE}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	112 \dataline{BOM_LE}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	113 \dataline{BOM32_BE}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	114 \dataline{BOM32_LE}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	115 \dataline{BOM64_BE}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	116 \dataline{BOM64_LE}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	117 These constants define the byte order marks (BOM) used in data
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	118 streams to indicate the byte order used in the stream or file.
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	119 \constant{BOM} is either \constant{BOM_BE} or \constant{BOM_LE}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	120 depending on the platform's native byte order, while the others
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	121 represent big endian (\samp{_BE} suffix) and little endian
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	122 (\samp{_LE} suffix) byte order using 32-bit and 64-bit encodings.
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	123 \end{datadesc}
8c0f863ba50c Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: diff changeset	124
15186 b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	125 \subsection{Codec Base Classes}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	126
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	127 The \module{codecs} defines a set of base classes which define the
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	128 interface and can also be used to easily write you own codecs for use
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	129 in Python.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	130
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	131 Each codec has to define four interfaces to make it usable as codec in
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	132 Python: stateless encoder, stateless decoder, stream reader and stream
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	133 writer. The stream reader and writers typically reuse the stateless
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	134 encoder/decoder to implement the file protocols.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	135
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	136 The \class{Codec} class defines the interface for stateless
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	137 encoders/decoders.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	138
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	139 To simplify and standardize error handling, the \method{encode()} and
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	140 \method{decode()} methods may implement different error handling
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	141 schemes by providing the \var{errors} string argument. The following
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	142 string values are defined and implemented by all standard Python
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	143 codecs:
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	144
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	145 \begin{itemize}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	146 \item \code{'strict'} Raise \exception{ValueError} (or a subclass);
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	147 this is the default.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	148 \item \code{'ignore'} Ignore the character and continue with the next.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	149 \item \code{'replace'} Replace with a suitable replacement character;
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	150 Python will use the official U+FFFD REPLACEMENT
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	151 CHARACTER for the builtin Unicode codecs.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	152 \end{itemize}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	153
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	154
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	155 \subsubsection{Codec Objects \label{codec-objects}}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	156
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	157 The \class{Codec} class defines these methods which also define the
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	158 function interfaces of the stateless encoder and decoder:
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	159
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	160 \begin{methoddesc}{encode}{input\optional{, errors}}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	161 Encodes the object \var{input} and returns a tuple (output object,
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	162 length consumed).
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	163
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	164 \var{errors} defines the error handling to apply. It defaults to
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	165 \code{'strict'} handling.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	166
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	167 The method may not store state in the \class{Codec} instance. Use
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	168 \class{StreamCodec} for codecs which have to keep state in order to
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	169 make encoding/decoding efficient.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	170
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	171 The encoder must be able to handle zero length input and return an
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	172 empty object of the output object type in this situation.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	173 \end{methoddesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	174
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	175 \begin{methoddesc}{decode}{input\optional{, errors}}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	176 Decodes the object \var{input} and returns a tuple (output object,
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	177 length consumed).
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	178
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	179 \var{input} must be an object which provides the \code{bf_getreadbuf}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	180 buffer slot. Python strings, buffer objects and memory mapped files
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	181 are examples of objects providing this slot.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	182
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	183 \var{errors} defines the error handling to apply. It defaults to
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	184 \code{'strict'} handling.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	185
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	186 The method may not store state in the \class{Codec} instance. Use
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	187 \class{StreamCodec} for codecs which have to keep state in order to
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	188 make encoding/decoding efficient.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	189
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	190 The decoder must be able to handle zero length input and return an
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	191 empty object of the output object type in this situation.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	192 \end{methoddesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	193
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	194 The \class{StreamWriter} and \class{StreamReader} classes provide
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	195 generic working interfaces which can be used to implement new
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	196 encodings submodules very easily. See \module{encodings.utf_8} for an
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	197 example on how this is done.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	198
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	199
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	200 \subsubsection{StreamWriter Objects \label{stream-writer-objects}}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	201
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	202 The \class{StreamWriter} class is a subclass of \class{Codec} and
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	203 defines the following methods which every stream writer must define in
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	204 order to be compatible to the Python codec registry.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	205
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	206 \begin{classdesc}{StreamWriter}{stream\optional{, errors}}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	207 Constructor for a \class{StreamWriter} instance.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	208
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	209 All stream writers must provide this constructor interface. They are
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	210 free to add additional keyword arguments, but only the ones defined
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	211 here are used by the Python codec registry.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	212
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	213 \var{stream} must be a file-like object open for writing (binary)
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	214 data.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	215
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	216 The \class{StreamWriter} may implement different error handling
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	217 schemes by providing the \var{errors} keyword argument. These
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	218 parameters are defined:
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	219
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	220 \begin{itemize}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	221 \item \code{'strict'} Raise \exception{ValueError} (or a subclass);
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	222 this is the default.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	223 \item \code{'ignore'} Ignore the character and continue with the next.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	224 \item \code{'replace'} Replace with a suitable replacement character
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	225 \end{itemize}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	226 \end{classdesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	227
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	228 \begin{methoddesc}{write}{object}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	229 Writes the object's contents encoded to the stream.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	230 \end{methoddesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	231
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	232 \begin{methoddesc}{writelines}{list}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	233 Writes the concatenated list of strings to the stream (possibly by
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	234 reusing the \method{write()} method).
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	235 \end{methoddesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	236
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	237 \begin{methoddesc}{reset}{}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	238 Flushes and resets the codec buffers used for keeping state.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	239
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	240 Calling this method should ensure that the data on the output is put
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	241 into a clean state, that allows appending of new fresh data without
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	242 having to rescan the whole stream to recover state.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	243 \end{methoddesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	244
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	245 In addition to the above methods, the \class{StreamWriter} must also
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	246 inherit all other methods and attribute from the underlying stream.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	247
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	248
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	249 \subsubsection{StreamReader Objects \label{stream-reader-objects}}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	250
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	251 The \class{StreamReader} class is a subclass of \class{Codec} and
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	252 defines the following methods which every stream reader must define in
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	253 order to be compatible to the Python codec registry.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	254
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	255 \begin{classdesc}{StreamReader}{stream\optional{, errors}}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	256 Constructor for a \class{StreamReader} instance.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	257
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	258 All stream readers must provide this constructor interface. They are
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	259 free to add additional keyword arguments, but only the ones defined
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	260 here are used by the Python codec registry.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	261
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	262 \var{stream} must be a file-like object open for reading (binary)
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	263 data.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	264
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	265 The \class{StreamReader} may implement different error handling
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	266 schemes by providing the \var{errors} keyword argument. These
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	267 parameters are defined:
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	268
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	269 \begin{itemize}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	270 \item \code{'strict'} Raise \exception{ValueError} (or a subclass);
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	271 this is the default.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	272 \item \code{'ignore'} Ignore the character and continue with the next.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	273 \item \code{'replace'} Replace with a suitable replacement character.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	274 \end{itemize}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	275 \end{classdesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	276
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	277 \begin{methoddesc}{read}{\optional{size}}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	278 Decodes data from the stream and returns the resulting object.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	279
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	280 \var{size} indicates the approximate maximum number of bytes to read
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	281 from the stream for decoding purposes. The decoder can modify this
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	282 setting as appropriate. The default value -1 indicates to read and
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	283 decode as much as possible. \var{size} is intended to prevent having
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	284 to decode huge files in one step.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	285
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	286 The method should use a greedy read strategy meaning that it should
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	287 read as much data as is allowed within the definition of the encoding
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	288 and the given size, e.g. if optional encoding endings or state
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	289 markers are available on the stream, these should be read too.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	290 \end{methoddesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	291
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	292 \begin{methoddesc}{readline}{[size]}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	293 Read one line from the input stream and return the
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	294 decoded data.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	295
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	296 Note: Unlike the \method{readlines()} method, this method inherits
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	297 the line breaking knowledge from the underlying stream's
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	298 \method{readline()} method -- there is currently no support for line
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	299 breaking using the codec decoder due to lack of line buffering.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	300 Sublcasses should however, if possible, try to implement this method
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	301 using their own knowledge of line breaking.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	302
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	303 \var{size}, if given, is passed as size argument to the stream's
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	304 \method{readline()} method.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	305 \end{methoddesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	306
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	307 \begin{methoddesc}{readlines}{[sizehint]}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	308 Read all lines available on the input stream and return them as list
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	309 of lines.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	310
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	311 Line breaks are implemented using the codec's decoder method and are
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	312 included in the list entries.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	313
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	314 \var{sizehint}, if given, is passed as \var{size} argument to the
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	315 stream's \method{read()} method.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	316 \end{methoddesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	317
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	318 \begin{methoddesc}{reset}{}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	319 Resets the codec buffers used for keeping state.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	320
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	321 Note that no stream repositioning should take place. This method is
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	322 primarily intended to be able to recover from decoding errors.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	323 \end{methoddesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	324
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	325 In addition to the above methods, the \class{StreamReader} must also
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	326 inherit all other methods and attribute from the underlying stream.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	327
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	328 The next two base classes are included for convenience. They are not
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	329 needed by the codec registry, but may provide useful in practice.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	330
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	331
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	332 \subsubsection{StreamReaderWriter Objects \label{stream-reader-writer}}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	333
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	334 The \class{StreamReaderWriter} allows wrapping streams which work in
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	335 both read and write modes.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	336
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	337 The design is such that one can use the factory functions returned by
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	338 the \function{lookup()} function to construct the instance.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	339
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	340 \begin{classdesc}{StreamReaderWriter}{stream, Reader, Writer, errors}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	341 Creates a \class{StreamReaderWriter} instance.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	342 \var{stream} must be a file-like object.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	343 \var{Reader} and \var{Writer} must be factory functions or classes
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	344 providing the \class{StreamReader} and \class{StreamWriter} interface
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	345 resp.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	346 Error handling is done in the same way as defined for the
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	347 stream readers and writers.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	348 \end{classdesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	349
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	350 \class{StreamReaderWriter} instances define the combined interfaces of
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	351 \class{StreamReader} and \class{StreamWriter} classes. They inherit
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	352 all other methods and attribute from the underlying stream.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	353
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	354
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	355 \subsubsection{StreamRecoder Objects \label{stream-recoder-objects}}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	356
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	357 The \class{StreamRecoder} provide a frontend - backend view of
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	358 encoding data which is sometimes useful when dealing with different
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	359 encoding environments.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	360
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	361 The design is such that one can use the factory functions returned by
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	362 the \function{lookup()} function to construct the instance.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	363
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	364 \begin{classdesc}{StreamRecoder}{stream, encode, decode,
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	365 Reader, Writer, errors}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	366 Creates a \class{StreamRecoder} instance which implements a two-way
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	367 conversion: \var{encode} and \var{decode} work on the frontend (the
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	368 input to \method{read()} and output of \method{write()}) while
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	369 \var{Reader} and \var{Writer} work on the backend (reading and
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	370 writing to the stream).
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	371
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	372 You can use these objects to do transparent direct recodings from
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	373 e.g.\ Latin-1 to UTF-8 and back.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	374
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	375 \var{stream} must be a file-like object.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	376
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	377 \var{encode}, \var{decode} must adhere to the \class{Codec}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	378 interface, \var{Reader}, \var{Writer} must be factory functions or
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	379 classes providing objects of the the \class{StreamReader} and
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	380 \class{StreamWriter} interface respectively.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	381
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	382 \var{encode} and \var{decode} are needed for the frontend
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	383 translation, \var{Reader} and \var{Writer} for the backend
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	384 translation. The intermediate format used is determined by the two
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	385 sets of codecs, e.g. the Unicode codecs will use Unicode as
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	386 intermediate encoding.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	387
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	388 Error handling is done in the same way as defined for the
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	389 stream readers and writers.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	390 \end{classdesc}
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	391
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	392 \class{StreamRecoder} instances define the combined interfaces of
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	393 \class{StreamReader} and \class{StreamWriter} classes. They inherit
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	394 all other methods and attribute from the underlying stream.
b2892cbc63db Marc-Andre Lemburg <mal@lemburg.com>: Fred Drake <fdrake@acm.org> parents: 13696 diff changeset	395

Mercurial > cpython-lru_cache-weakref

annotate Doc/lib/libcodecs.tex @ 15946:4f621708514b legacy-trunk