[iostreams] Inconsistency of "faiture" of writes in Sinks and filters
Hello, I implement the sink device that sometimes may fail on writes. When Sink is implemented it should throw an exception on fault. To notify the stream on error. However it is not always works this way. I've got the exception to "leak" to the main program when I combine in the filter gzip_comressor() filter that writes to output device that its Sink is full. When I call reset on the filter the exception in leaking to the program instead of being caught. Is it bug or (accidental) feature? On the other hand, if I don't throw but rather return 0, I get into infinite loop in the boost::iostreams::non_blocking_adapter::write when I call filter.reset(). So I how can I write a sink device that reports errors? In following example the exception is caught when filter.reset() is called: #include <boost/iostreams/stream.hpp> #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/filter/gzip.hpp> #include <boost/iostreams/tee.hpp> #include <iostream> class my_small_device : public boost::iostreams::sink { int count; public: my_small_device() : count(1000) {} std::streamsize write(char const *d,std::streamsize n) { if(count < n) throw std::runtime_error("Device is full"); count-=n; return n; } }; int main() { try { using namespace boost::iostreams; boost::iostreams::stream<my_small_device> output(my_small_device(),10); { boost::iostreams::filtering_ostream filter; filter.push(gzip_compressor()); filter.push(output); for(int i=0;i<10000000;i++) { if(!(filter << i << '\n')) { std::cerr << "Fail!" << std::endl; break; } } std::cout << "Closing filter" << std::endl; filter.reset(); } std::cout << "ok" << std::endl; return 0; }catch(std::exception const &e) { std::cerr << "Catched " << e.what() << std::endl; return 1; } } Thanks, Artyom
Hello, Bump... Anybody has an opinion about this? Artyom ----- Original Message ----
From: Artyom <artyomtnk@yahoo.com> To: boost@lists.boost.org Sent: Sat, October 23, 2010 9:29:30 PM Subject: [boost] [iostreams] Inconsistency of "failure" of writes in Sinks and filters
Hello,
I implement the sink device that sometimes may fail on writes.
When Sink is implemented it should throw an exception on fault. To notify the stream on error.
However it is not always works this way. I've got the exception to "leak" to the main program when I combine in the filter gzip_comressor() filter that writes to output device that its Sink is full. When I call reset on the filter the exception in leaking to the program instead of being caught.
Is it bug or (accidental) feature?
On the other hand, if I don't throw but rather return 0, I get into infinite loop in the boost::iostreams::non_blocking_adapter::write when I call filter.reset().
So I how can I write a sink device that reports errors?
In following example the exception is caught when filter.reset() is called:
#include <boost/iostreams/stream.hpp> #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/filter/gzip.hpp> #include <boost/iostreams/tee.hpp> #include <iostream>
class my_small_device : public boost::iostreams::sink { int count; public: my_small_device() : count(1000) {} std::streamsize write(char const *d,std::streamsize n) { if(count < n) throw std::runtime_error("Device is full"); count-=n; return n; } };
int main() { try { using namespace boost::iostreams; boost::iostreams::stream<my_small_device> output(my_small_device(),10); { boost::iostreams::filtering_ostream filter; filter.push(gzip_compressor()); filter.push(output); for(int i=0;i<10000000;i++) { if(!(filter << i << '\n')) { std::cerr << "Fail!" << std::endl; break; } } std::cout << "Closing filter" << std::endl; filter.reset(); }
std::cout << "ok" << std::endl; return 0; }catch(std::exception const &e) { std::cerr << "Catched " << e.what() << std::endl; return 1; } }
Thanks, Artyom
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Opened a ticket: https://svn.boost.org/trac/boost/ticket/4807 Artyom
Hello,
I implement the sink device that sometimes may fail on writes.
When Sink is implemented it should throw an exception on fault. To notify the stream on error.
However it is not always works this way. I've got the exception to "leak" to the main program when I combine in the filter gzip_comressor() filter that writes to output device that its Sink is full. When I call reset on the filter the exception in leaking to the program instead of being caught.
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Artyom