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54 | <H3><A NAME="SECTION006915000000000000000"></A><A NAME="stream-recoder-objects"></A> | |
55 | <BR> | |
56 | 4.9.1.5 StreamRecoder Objects | |
57 | </H3> | |
58 | ||
59 | <P> | |
60 | The <tt class="class">StreamRecoder</tt> provide a frontend - backend view of | |
61 | encoding data which is sometimes useful when dealing with different | |
62 | encoding environments. | |
63 | ||
64 | <P> | |
65 | The design is such that one can use the factory functions returned by | |
66 | the <tt class="function">lookup()</tt> function to construct the instance. | |
67 | ||
68 | <P> | |
69 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
70 | <td><nobr><b><span class="typelabel">class</span> <tt id='l2h-1017' xml:id='l2h-1017' class="class">StreamRecoder</tt></b>(</nobr></td> | |
71 | <td><var>stream, encode, decode, | |
72 | Reader, Writer, errors</var>)</td></tr></table></dt> | |
73 | <dd> | |
74 | Creates a <tt class="class">StreamRecoder</tt> instance which implements a two-way | |
75 | conversion: <var>encode</var> and <var>decode</var> work on the frontend (the | |
76 | input to <tt class="method">read()</tt> and output of <tt class="method">write()</tt>) while | |
77 | <var>Reader</var> and <var>Writer</var> work on the backend (reading and | |
78 | writing to the stream). | |
79 | ||
80 | <P> | |
81 | You can use these objects to do transparent direct recodings from | |
82 | e.g. Latin-1 to UTF-8 and back. | |
83 | ||
84 | <P> | |
85 | <var>stream</var> must be a file-like object. | |
86 | ||
87 | <P> | |
88 | <var>encode</var>, <var>decode</var> must adhere to the <tt class="class">Codec</tt> | |
89 | interface, <var>Reader</var>, <var>Writer</var> must be factory functions or | |
90 | classes providing objects of the <tt class="class">StreamReader</tt> and | |
91 | <tt class="class">StreamWriter</tt> interface respectively. | |
92 | ||
93 | <P> | |
94 | <var>encode</var> and <var>decode</var> are needed for the frontend | |
95 | translation, <var>Reader</var> and <var>Writer</var> for the backend | |
96 | translation. The intermediate format used is determined by the two | |
97 | sets of codecs, e.g. the Unicode codecs will use Unicode as | |
98 | intermediate encoding. | |
99 | ||
100 | <P> | |
101 | Error handling is done in the same way as defined for the | |
102 | stream readers and writers. | |
103 | </dl> | |
104 | ||
105 | <P> | |
106 | <tt class="class">StreamRecoder</tt> instances define the combined interfaces of | |
107 | <tt class="class">StreamReader</tt> and <tt class="class">StreamWriter</tt> classes. They inherit | |
108 | all other methods and attribute from the underlying stream. | |
109 | ||
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