These are lightweight text streaming classes that connect to standardised ecl type devices.
Streams provide a standardised c++ interface for connecting to
ecl input-output devices.
- speed : control cannot afford serious slowdowns for convenience.
- extensible : must be able to create new devices easily.
- streams : all devices should connect in a standardised way to streams.
Finding a library with a standard/extensible interface that
works across devices and implements streaming operators is
like trying to find the pot at the bottom of the rainbow.
Include the following at the top of any translation unit which
requires this library:
@code
#include <ecl/streams.hpp>
// Templatised all purpose stream
using ecl::TextStream;
// Convenience stream handles
using ecl::IConsoleStream;
using ecl::OConsoleStream;
using ecl::EConsoleStream;
using ecl::OFileStream;
using ecl::SerialStream;
using ecl::SharedFileStream;
using ecl::SocketClientStream;
using ecl::SocketServerStream;
using ecl::StringStream;
// Special customised streams
using ecl::LogStream;
// Stream manipulators
using ecl::endl;
using ecl::clrscr;
@endcode
You will also need to link to <i>-lecl_streams</i>.
@subsection openClose Initialisation
Each stream-device pair can be instantiated via the generic TextStream object and the
underlying device opened via the device() member method. For example,
@code
TextStream<OFile> stream;
stream.device().open("dude.txt",New);
@endcode
The console device is a special case - it is automatically opened.
@subsection convenienceHandles Convenience Classes
The preferred method of instantiation is via the constructor in the convenience classes. The convenience classes are specialised interfaces that inherit from the appropriate Textstream type (dependant on the template parameter). Examples, SerialStream, OFileStream. Rather than calling stream.device().open(...) directly, you can use their constructors to instantiate the stream. They are also more convenient than typing out template parameters continuously.
@code
OFileStream stream("dude.txt",New);
@endcode
@subsection outputStreams Output Streams
Output streams function similarly to the familiar cout stream. The primary advantage being that
they can easily be attached to any standard ecl io device. They can also be used with the
ecl_formatter classes.
@code
OFileStream ostream;
Format<double> format; format.width(5); format.precision(2);
double d = 1.0/3.0;
ostream << format(d); // This will send 0.33 to the stream.
ostream.flush();
@endcode
@subsection inputStreams Input Streams
There are three ways to utilise an input stream:
- reading element by element (separated by whitespace or newlines).
- reading raw characters (you must call enableRawCharReads()).
- reading line by line (not yet enabled).
The first method is similar to the familiar cin, it will take a string and convert it to the requested type.
@code
IConsoleStream istream;
double d;
istream >> d;
@endcode
The second method is sometimes useful when communicated with raw character devices (e.g. a serial line). In
this situation, you must simply make use of the char input operator.
@code
SerialStream serial_stream;
char c;
if ( serial_stream.device().remaining() ) {
serial_stream >> c;
}
@endcode
The third method has not yet been implemented.
@subsection logstreams Logging Streams
@ref ecl::LogStream "LogStreams" are a convenient, fast means to
logging from multiple threads with multiple customisable modes. They can
also optionally automatically insert header and timestamp information.
Multiple modes are most conveniently utilsed via customised enums. For example:
@code
enum LogModes {
Warning,
Error,
Debug,
};
@endcode
Note that this is an advantage over alot of other loggers in that it gives you
the freedom to define your own error logging levels. Each mode can then be
associated inside the log stream with its own customised header.
@code
LogStream log_stream("test.log")
log_stream.enableMode(Warning,"WARNING");
log_stream.enableMode(Error,"ERROR");
log_stream.enableMode(Debug,"DEBUG");
@endcode
This process can be repeated from multiple threads each with its own instance
of the log stream attached to the single file. Using the log stream is then
done via the macros LOG and FLUSH
@code
LOG(log_stream, Warning) << "This is a log message from main().\n";
FLUSH(log_stream)
@endcode
By default this will automatically add header and timestamp information. You
can manually disable these if you prefer.
Output streams can generate errors that are not so easily checked compared with handling devices directly.
To check for failure, ecl streams use a mechanism similar to that of the standard cout stream.
@code
ostream << 32.1;
if ( ostream.fail() ) {
std::cout << ostream.errorStatus().what() << std::endl;
}
@endcode
ECL manipulators are defined to enable some similar functionality to c++'s cout manipulators.
However they extend the concept to use class instantiations rather than functions. This
provides one important advantage over the former, these manipulators can retain state. Given
that they're also easy to customise, this opens up many possibilities.
The default manipulators defined in the ecl export a few global instantiations,
namely
- ecl::endl
- ecl::clrscr
Using manipulators follows the same pattern as for standard c++ style cout manipulators.
@code
int main() {
ecl::OConsoleStream ostream;
ostream << ecl::clrscr;
ostream << "Dude" << ecl::endl;
return;
}
@endcode
<b>Creating your own Manipulators:</b>
Any manipulator that you wish to define must inherit from this
parent class in the following manner:
@code
include <ecl/streams/manipulators.hpp>
class MyManipulator : public ecl::Manipulator<MyManipulator> {
template <typename OutputStream>
void action (OutputStream& ostream) {
// ...
}
};
@endcode
The following results are for streaming/flushing a large number of strings/floats
to various devices/streams. It was performed on a 32 bit single core intel processor
running linux (kernel 2.6.31) (exact values aren't important, rather the relative
differences).
@code
Writing Char Strings:
OFile write : 58806 ns
SharedFile write : 47562 ns
OFile stream : 61739 ns
LogStream : 73753 ns
C++ ofstream : 83321 ns
Streaming Floats:
OFileStream : 693593 ns
Log stream : 711753 ns
C++ ofstream : 862120 ns
@endcode
- src/test/file_streams.cpp
- src/test/string_streams.cpp
- src/examples/console_streams.cpp
- src/examples/log_streams.cpp
- ecl_core_apps/src/benchmarks/streams.cpp
- ecl_core_apps/src/benchmarks/files.cpp
- @ref changelog "ChangeLog"