106 lines
4.2 KiB
C
106 lines
4.2 KiB
C
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/////////////////////////////////////////////////////////////////////////////
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// Name: stream.h
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// Purpose: stream classes overview
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// Author: wxWidgets team
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// Licence: wxWindows licence
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/////////////////////////////////////////////////////////////////////////////
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/**
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@page overview_stream Stream Classes Overview
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@tableofcontents
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wxWidgets provides its own set of stream classes in order to support platforms
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not providing standard C++ streams implementation and also to make it possible
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to provide binary versions of wxWidgets application not depending on any
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particular standard library version. The wxWidgets stream classes also provide
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some functionality not available in the standard library such as support for
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several compression formats and possibility to work with sockets or text
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controls (for output only in the latter case).
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Nevertheless wxWidgets programs can also use standard stream classes and are
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encouraged to do so if the above considerations don't apply. Moreover,
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wxStdInputStream and wxStdOutputStream classes are provided to provide a degree
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of interoperability between the two and make it possible to use any wxWidgets
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stream as a standard stream (the converse possibility to use a standard stream
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as a wxWidgets stream is planned for a future release).
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@section overview_stream_classes Stream Classes
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wxStream classes are divided in two main groups:
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@li The core: wxStreamBase, wxStreamBuffer, wxInputStream, wxOutputStream,
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wxFilterInputStream, wxFilterOutputStream
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@li The "IO" classes: wxSocketInputStream, wxSocketOutputStream,
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wxFileInputStream, wxFileOutputStream, ...
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@li Classes for reading text or binary data from a particular stream
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such as wxTextInputStream, wxTextOutputStream, wxDataInputStream
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and wxDataOutputStream
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wxStreamBase is the base definition of a stream. It defines, for example, the
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API of OnSysRead(), OnSysWrite(), OnSysSeek() and OnSysTell(). These functions are
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really implemented by the "IO" classes.
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wxInputStream and wxOutputStream classes inherit from wxStreamBase and provide
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specialized methods for input and output.
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wxStreamBuffer is a cache manager for wxStreamBase: it manages a stream buffer
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linked to a stream. One stream can have multiple stream buffers but one stream
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has always one autoinitialized stream buffer.
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wxInputStream is the base class for read-only streams. It implements Read(),
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SeekI() (I for Input), and all read or IO generic related functions.
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wxOutputStream does the same thing for write-only streams.
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wxFilterInputStream and wxFileterOutputStream are the base class definitions for
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stream filtering.
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Stream filtering means a stream which does no syscall but filters data which
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are passed to it and then pass them to another stream.
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For example, wxZLibInputStream is an inline stream decompressor.
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The "IO" classes implements the specific parts of the stream. This could be
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nothing in the case of wxMemoryInputStream and wxMemoryOutputStream which base
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themselves on wxStreamBuffer.
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This could also be a simple link to the true syscall (for example read(...), write(...)).
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@section overview_stream_example Example
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Usage is simple. We can take the example of wxFileInputStream and here is some
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sample code:
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@code
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...
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// The constructor initializes the stream buffer and open the file descriptor
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// associated to the name of the file.
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wxFileInputStream in_stream("the_file_to_be_read");
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// Ok, read some bytes ... nb_datas is expressed in bytes.
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in_stream.Read(data, nb_datas);
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if (in_stream.LastError() != wxSTREAM_NOERROR) {
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// Oh oh, something bad happens.
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// For a complete list, look into the documentation at wxStreamBase.
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}
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// You can also inline all like this.
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if (in_stream.Read(data, nb_datas).LastError() != wxSTREAM_NOERROR) {
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// Do something.
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}
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// You can also get the last number of bytes REALLY put into the buffer.
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size_t really_read = in_stream.LastRead();
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// Ok, moves to the beginning of the stream. SeekI returns the last position
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// in the stream counted from the beginning.
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off_t old_position = in_stream.SeekI(0, wxFromBeginning);
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// What is my current position ?
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off_t position = in_stream.TellI();
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// wxFileInputStream will close the file descriptor on destruction.
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@endcode
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*/
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