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/doc/examples/fast_tampon_example.cpp

this is an example of use of class libthreadar::fast_tampon and libthreadar::exception_base and derivated classes

/*********************************************************************/
// libthreadar - is a library providing several C++ classes to work with threads
// Copyright (C) 2014-2020 Denis Corbin
//
// This file is part of libthreadar
//
// libthreadar is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// libhtreadar is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with libthreadar. If not, see <http://www.gnu.org/licenses/>
//
//----
// to contact the author: dar.linux@free.fr
/*********************************************************************/
#include <libthreadar/libthreadar.hpp>
// let's define a new thread class
// to illustrate how to use libthreadar::fast_tampon template
class my_thread: public libthreadar::thread
{
public:
const unsigned int block_size = 100;
// we initialize inter as a file of 10 block
// each of size 100 chars (T = char)
my_thread(): inter(10, block_size) {}
// providing a filedescriptor to read data from
set_fd(int val)
{
if(is_running())
throw libthreadar::exception_bug(__FILE__,__LINE__);
fd = val;
};
// the caller will be the fetcher of object inter
void show()
{
char *ptr;
unsigned int size;
do
{
inter.fetch(ptr, size); // we grab the next block of data
ptr[block_size - 1] = '\0'; // have a null terminated string
cout << ptr << endl;
inter.fetch_recycle(ptr); // as we have finished using it we recycle it into inter
}
while(size > 0);
// by convention, returning a zero sized block
// means that the subthread will not provide any
// more data
// so we wait for its termination
try
{
join();
}
catch(libthreadar::exception_range & e)
{
std::cout << "Error met while reading file: " << e.get_message(": ") << std::endl;
}
}
protected:
// the subthread will be the feeder of object inter
virtual void inherited_run() override
{
char *ptr;
unsigned int size, read;
// this sub-thread will read the data from fd up to eof or error
do
{
inter.get_block_to_feed(ptr, size); // obtaining a block of data
read = std::read(fd, ptr, size); // using it
if(read >= 0)
inter.feed(ptr, read); // pushing it back to inter
else
{
inter.feed(ptr, 0);
throw libthreadar::exception_range(strerror(errno));
// this exception will be progragated to the parent thread
// when calling join() in the show() method above
}
}
while(read > 0);
}
private:
libthreadar::fast_tampon<char> inter;
int fd;
};
int main(int argc, char *argv[])
{
if(argc < 2)
{
std::cout << "usage: " << argv[0] << " <filename>" << std::endl;
return 1;
}
int fd = open(argv[1]);
if(fd >= 0)
{
my_thread t1;
t1.set_fd(fd); // setup the future thread
t1.run(); // spawn the thread that will read data from fd and pass it to inter
t1.show(); // extract data from inter in the current (parent) thread
}
}
libthreadar::exception_base::get_message
std::string get_message(const std::string &sep) const
concatenated messages and use the given separator between messages
libthreadar::exception_bug
Exception used to report webdar internal bugs.
Definition exceptions.hpp:170
libthreadar::exception_range
Exception used to report out or range value or argument.
Definition exceptions.hpp:207
libthreadar::fast_tampon
Class fast_tampon provides asynchronous communication between two threads.
Definition fast_tampon.hpp:88
libthreadar::thread
Class thread is a pure virtual class, that implements thread creation and operations.
Definition thread.hpp:99
libthreadar::thread::is_running
bool is_running() const
checks whether a separated thread is running the inherited_run() method of this object
Definition thread.hpp:122
libthreadar::thread::inherited_run
virtual void inherited_run()=0
action to be performed in the separated thread
libthreadar::thread::join
void join() const
the caller will be suspended until the current object's thread ends