91 lines
3.6 KiB
C
91 lines
3.6 KiB
C
|
/////////////////////////////////////////////////////////////////////////////
|
||
|
|
// Name: stream
|
||
|
|
// Purpose: topic overview
|
||
|
|
// Author: wxWidgets team
|
||
|
|
// RCS-ID: $Id$
|
||
|
|
// Licence: wxWindows license
|
||
|
|
/////////////////////////////////////////////////////////////////////////////
|
||
|
|
|
||
|
|
/*!
|
||
|
|
|
||
|
|
@page stream_overview wxStreams overview
|
||
|
|
|
||
|
|
Classes: #wxStreamBase,
|
||
|
|
#wxStreamBuffer, #wxInputStream,
|
||
|
|
#wxOutputStream,
|
||
|
|
#wxFilterInputStream,
|
||
|
|
#wxFilterOutputStream
|
||
|
|
@b Purpose of wxStream
|
||
|
|
Standard C++ streams can cause problems on several platforms:
|
||
|
|
they work quite well in most cases, but in the multi-threaded case, for example,
|
||
|
|
they have many problems. Some Borland compilers refuse to work at all
|
||
|
|
with them and using iostreams on Linux makes writing programs that are
|
||
|
|
binary compatible across different Linux distributions, impossible.
|
||
|
|
Therefore, wxStreams have been added to wxWidgets so that applications can
|
||
|
|
reliably compile and run on all supported platforms without dependence on a
|
||
|
|
particular release of libg++.
|
||
|
|
wxStreams is divided in two main parts:
|
||
|
|
|
||
|
|
|
||
|
|
the core: wxStreamBase, wxStreamBuffer, wxInputStream, wxOutputStream,
|
||
|
|
wxFilterIn/OutputStream
|
||
|
|
the "IO" classes: wxSocketIn/OutputStream, wxDataIn/OutputStream, wxFileIn/OutputStream, ...
|
||
|
|
|
||
|
|
|
||
|
|
wxStreamBase is the base definition of a stream. It defines, for example,
|
||
|
|
the API of OnSysRead, OnSysWrite, OnSysSeek and OnSysTell. These functions
|
||
|
|
are really implemented by the "IO" classes.
|
||
|
|
wxInputStream and wxOutputStream inherit from it.
|
||
|
|
wxStreamBuffer is a cache manager for wxStreamBase: it manages a stream buffer
|
||
|
|
linked to a stream. One stream can have multiple stream buffers but one stream
|
||
|
|
have always one autoinitialized stream buffer.
|
||
|
|
wxInputStream is the base class for read-only streams. It implements Read,
|
||
|
|
SeekI (I for Input), and all read or IO generic related functions.
|
||
|
|
wxOutputStream does the same thing but it is for write-only streams.
|
||
|
|
wxFilterIn/OutputStream is the base class definition for stream filtering.
|
||
|
|
Stream filtering means a stream which does no syscall but filters data
|
||
|
|
which are passed to it and then pass them to another stream.
|
||
|
|
For example, wxZLibInputStream is an inline stream decompressor.
|
||
|
|
The "IO" classes implements the specific parts of the stream. This could be
|
||
|
|
nothing in the case of wxMemoryIn/OutputStream which bases itself on
|
||
|
|
wxStreamBuffer. This could also be a simple link to the a @true syscall
|
||
|
|
(for example read(...), write(...)).
|
||
|
|
@b Generic usage: an example
|
||
|
|
Usage is simple. We can take the example of wxFileInputStream and here is some sample
|
||
|
|
code:
|
||
|
|
|
||
|
|
@code
|
||
|
|
...
|
||
|
|
// The constructor initializes the stream buffer and open the file descriptor
|
||
|
|
// associated to the name of the file.
|
||
|
|
wxFileInputStream in_stream("the_file_to_be_read");
|
||
|
|
|
||
|
|
// Ok, read some bytes ... nb_datas is expressed in bytes.
|
||
|
|
in_stream.Read(data, nb_datas);
|
||
|
|
if (in_stream.LastError() != wxSTREAM_NOERROR) {
|
||
|
|
// Oh oh, something bad happens.
|
||
|
|
// For a complete list, look into the documentation at wxStreamBase.
|
||
|
|
}
|
||
|
|
|
||
|
|
// You can also inline all like this.
|
||
|
|
if (in_stream.Read(data, nb_datas).LastError() != wxSTREAM_NOERROR) {
|
||
|
|
// Do something.
|
||
|
|
}
|
||
|
|
|
||
|
|
// You can also get the last number of bytes REALLY put into the buffer.
|
||
|
|
size_t really_read = in_stream.LastRead();
|
||
|
|
|
||
|
|
// Ok, moves to the beginning of the stream. SeekI returns the last position
|
||
|
|
// in the stream counted from the beginning.
|
||
|
|
off_t old_position = in_stream.SeekI(0, wxFromBeginning);
|
||
|
|
|
||
|
|
// What is my current position ?
|
||
|
|
off_t position = in_stream.TellI();
|
||
|
|
|
||
|
|
// wxFileInputStream will close the file descriptor on destruction.
|
||
|
|
@endcode
|
||
|
|
|
||
|
|
*/
|
||
|
|
|
||
|
|
|