880efa2a13
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@52448 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
109 lines
3.6 KiB
C
109 lines
3.6 KiB
C
/////////////////////////////////////////////////////////////////////////////
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// Name: stream.h
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// Purpose: topic overview
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// Author: wxWidgets team
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// RCS-ID: $Id$
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// Licence: wxWindows license
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/////////////////////////////////////////////////////////////////////////////
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/**
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@page overview_stream wxStreams Overview
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Classes:
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@li wxStreamBase
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@li wxStreamBuffer
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@li wxInputStream
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@li wxOutputStream
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@li wxFilterInputStream
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@li wxFilterOutputStream
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@li @ref overview_stream_intro
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@li @ref overview_stream_example
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<hr>
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@section overview_stream_intro Introduction
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Standard C++ streams can cause problems on several platforms: they work quite
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well in most cases, but in the multi-threaded case, for example, they have many
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problems. Some Borland compilers refuse to work at all with them and using
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iostreams on Linux makes writing programs that are binary compatible across
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different Linux distributions, impossible.
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Therefore, wxStreams have been added to wxWidgets so that applications can
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reliably compile and run on all supported platforms without dependence on a
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particular release of libg++.
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wxStreams is divided in two main parts:
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@li The core: wxStreamBase, wxStreamBuffer, wxInputStream, wxOutputStream,
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wxFilterIn/OutputStream
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@li The "IO" classes: wxSocketIn/OutputStream, wxDataIn/OutputStream,
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wxFileIn/OutputStream, ...
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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. wxInputStream and wxOutputStream
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inherit from it.
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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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have 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 but it is for write-only streams.
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wxFilterIn/OutputStream is the base class definition for 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. For example,
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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 wxMemoryIn/OutputStream which bases itself on
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wxStreamBuffer. This could also be a simple link to the a true syscall (for
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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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