[Spice-devel] [PATCH spice-streaming-agent 3/9] Implement an exception hierarchy for ReadError

[Frediano Ziglio]

> 
> Introduces an exception hierarchy up to a ReadError class, which is
> thrown from read_all().
> 
> Signed-off-by: Lukáš Hrázký <lhrazky at redhat.com>
> ---
>  src/Makefile.am               |  2 ++
>  src/error.cpp                 | 29 ++++++++++++++++++++++++++++
>  src/error.hpp                 | 44
>  +++++++++++++++++++++++++++++++++++++++++++
>  src/spice-streaming-agent.cpp |  2 +-
>  src/stream-port.cpp           |  4 ++--
>  5 files changed, 78 insertions(+), 3 deletions(-)
>  create mode 100644 src/error.cpp
>  create mode 100644 src/error.hpp
> 
> diff --git a/src/Makefile.am b/src/Makefile.am
> index 604c1e5..18ed22c 100644
> --- a/src/Makefile.am
> +++ b/src/Makefile.am
> @@ -52,6 +52,8 @@ spice_streaming_agent_SOURCES = \
>  	spice-streaming-agent.cpp \
>  	concrete-agent.cpp \
>  	concrete-agent.hpp \
> +	error.cpp \
> +	error.hpp \
>  	mjpeg-fallback.cpp \
>  	mjpeg-fallback.hpp \
>  	jpeg.cpp \
> diff --git a/src/error.cpp b/src/error.cpp
> new file mode 100644
> index 0000000..1b76ea4
> --- /dev/null
> +++ b/src/error.cpp
> @@ -0,0 +1,29 @@
> +/* The errors module.
> + *
> + * \copyright
> + * Copyright 2018 Red Hat Inc. All rights reserved.
> + */
> +
> +#include "error.hpp"
> +
> +#include <string.h>
> +#include <syslog.h>
> +
> +
> +namespace spice {
> +namespace streaming_agent {
> +
> +Error::Error(const std::string &message) : message(message) {}
> +
> +const char* Error::what() const noexcept
> +{
> +    return message.c_str();
> +}
> +
> +IOError::IOError(const std::string &msg, int errno_) :

I personally don't like much the errno_, maybe a sys_error?

> +    Error(msg + ": " + std::to_string(errno_) + " - " + strerror(errno_))
> +{}
> +
> +ReadError::ReadError(const std::string &msg, int errno_) : IOError(msg,
> errno_) {}
> +

Not strong opinion, maybe format the same way the other constructor?

> +}} // namespace spice::streaming_agent
> diff --git a/src/error.hpp b/src/error.hpp
> new file mode 100644
> index 0000000..de1cb83
> --- /dev/null
> +++ b/src/error.hpp
> @@ -0,0 +1,44 @@
> +/* The errors module.
> + *
> + * \copyright
> + * Copyright 2018 Red Hat Inc. All rights reserved.
> + */
> +
> +#ifndef SPICE_STREAMING_AGENT_ERROR_HPP
> +#define SPICE_STREAMING_AGENT_ERROR_HPP
> +
> +#include <exception>
> +#include <string>
> +
> +
> +namespace spice {
> +namespace streaming_agent {
> +
> +class Error : public std::exception
> +{
> +public:
> +    Error(const std::string &message);
> +    const char *what() const noexcept override final;
> +
> +protected:
> +    const std::string message;
> +};
> +
> +class IOError : public Error
> +{
> +public:
> +    IOError(const std::string &msg, int errno_);
> +

Maybe the error count have a default value, something like:

    IOError(const std::string &msg, int sys_error = errno);

> +protected:
> +    int errno_;
> +};
> +
> +class ReadError : public IOError
> +{
> +public:
> +    ReadError(const std::string &msg, int errno_);
> +};
> +
> +}} // namespace spice::streaming_agent
> +
> +#endif // SPICE_STREAMING_AGENT_ERROR_HPP
> diff --git a/src/spice-streaming-agent.cpp b/src/spice-streaming-agent.cpp
> index 7b166d3..2c0340d 100644
> --- a/src/spice-streaming-agent.cpp
> +++ b/src/spice-streaming-agent.cpp
> @@ -535,7 +535,7 @@ int main(int argc, char* argv[])
>      try {
>          do_capture(streamport, f_log);
>      }
> -    catch (std::runtime_error &err) {
> +    catch (std::exception &err) {
>          syslog(LOG_ERR, "%s\n", err.what());
>          ret = EXIT_FAILURE;
>      }
> diff --git a/src/stream-port.cpp b/src/stream-port.cpp
> index 3699d92..f256698 100644
> --- a/src/stream-port.cpp
> +++ b/src/stream-port.cpp
> @@ -5,6 +5,7 @@
>   */
>  
>  #include "stream-port.hpp"
> +#include "error.hpp"
>  
>  #include <errno.h>
>  #include <string.h>
> @@ -25,8 +26,7 @@ void read_all(int fd, void *msg, size_t len)
>              if (errno == EINTR) {
>                  continue;
>              }
> -            throw std::runtime_error("Reading message from device failed: "
> +
> -                                     std::string(strerror(errno)));
> +            throw ReadError("Reading message from device failed", errno);
>          }
>  
>          len -= n;

Beside that,

Acked-by: Frediano Ziglio <fziglio at redhat.com>

Frediano