-\section{Streams in wxWindows overview}\label{wxstreamoverview}
+\section{wxStreams overview}\label{wxstreamoverview}
Classes: \helpref{wxStreamBase}{wxstreambase},
\helpref{wxStreamBuffer}{wxstreambuffer}, \helpref{wxInputStream}{wxinputstream},
\wxheading{Purpose of wxStream}
-We went into troubles with c++ std streams on some platform:
-they react quite well in most cases, but in multi-threaded case, for example,
-they have a LOT of problems.
+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.
-Then, wxStreams have been built in wxWindows because an application should compile
-and run on all supported platforms and we don't want users depend on release
-X.XX of libg++ or some other compiler to run the program.
+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:
+
\begin{enumerate}\itemsep=0pt
\item the core: wxStreamBase, wxStreamBuffer, wxInputStream, wxOutputStream,
wxFilterIn/OutputStream
\end{enumerate}
wxStreamBase is the base definition of a stream. It defines, for example,
-the API of OnSysRead, OnSysWrite, OnSysSeek and OnSysTell. These functions are
+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
+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 base class definition for stream filtering.
-I mean by stream filtering, a stream which does no syscall but filter datas
+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.
\wxheading{Generic usage: an example}
-About its usage, it's simple. We can take the example of wxFileInputStream and here is a sample
+Usage is simple. We can take the example of wxFileInputStream and here is some sample
code:
\begin{verbatim}
...
// 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");
+ 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) {
+ // 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) {
+ 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();
+ 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);
+ off_t old_position = in_stream.SeekI(0, wxFromBeginning);
// What is my current position ?
- off\_t position = in\_stream.TellI();
+ off_t position = in_stream.TellI();
- // wxFileInputStream will close the file descriptor on the destruction.
+ // wxFileInputStream will close the file descriptor on destruction.
\end{verbatim}
-\wxheading{Compatibility with c++ stream}
-
-As I said previously, we could add a filter stream so it takes an istream
-argument and builds a wxInputStream from it: I don't think it should
-be difficult to implement it and it may be available in the fix of wxWindows 2.0.