diff options
| -rw-r--r-- | libbutl/pager.cxx | 116 | ||||
| -rw-r--r-- | libbutl/pager.hxx | 5 |
2 files changed, 99 insertions, 22 deletions
diff --git a/libbutl/pager.cxx b/libbutl/pager.cxx index e647948..4f68ea4 100644 --- a/libbutl/pager.cxx +++ b/libbutl/pager.cxx @@ -14,9 +14,10 @@ #include <string> #include <vector> -#include <cstddef> // size_t -#include <cstring> // strchr() -#include <utility> // move() +#include <cstddef> // size_t +#include <cstring> // strchr() +#include <utility> // move() +#include <system_error> // system_error, generic_category() #ifndef _WIN32 # include <chrono> @@ -177,16 +178,33 @@ namespace butl throw; // Re-throw as system_error. } - // Setup the indentation machinery. + // Setup the indentation machinery and the 'broken pipe' error handling. // - if (!indent_.empty ()) - buf_ = stream ().rdbuf (this); + // Note that the pager, if instructed to quit, may not bother reading out + // all the data from stdin and just exit successfully (with 0 code) + // outright. In this case writing to the pipe on our end results in the + // EPIPE (EINVAL on Windows) error. We will handle this error by switching + // into the skip mode, so that the caller may continue to write the data + // normally till the end, without the need to handle this situation in a + // special way. + // + buf_ = stream ().rdbuf (this); } bool pager:: wait (bool ie) { - // Teardown the indentation machinery. + // Prevent ofdstream::close() from throwing in the ignore errors mode. + // + if (ie) + os_.exceptions (ofdstream::goodbit); + + os_.close (); + + // Teardown the indentation machinery and the 'broken pipe' error handling. + // + // Note that we need to do this after the above close() call, so that the + // underlying flush() call would still be noop in the skip mode. // if (buf_ != nullptr) { @@ -194,33 +212,91 @@ namespace butl buf_ = nullptr; } - // Prevent ofdstream::close() from throwing in the ignore errors mode. - // - if (ie) - os_.exceptions (ofdstream::goodbit); - - os_.close (); return p_.wait (ie); } pager::int_type pager:: overflow (int_type c) { - if (prev_ == '\n' && c != '\n') // Don't indent blanks. + // Unless we are in the skip mode or the passed character is EOF, print + // the indentation, if required, and delegate writing the character to the + // stashed ofdstream's streambuf. Switch to the skip mode on the 'broken + // pipe' error (see above for details). + // + if (!skip_ && c != traits_type::eof ()) + try { - auto n (static_cast<streamsize> (indent_.size ())); + if (!indent_.empty ()) + { + if (prev_ == '\n' && c != '\n') // Don't indent blanks. + { + auto n (static_cast<streamsize> (indent_.size ())); - if (buf_->sputn (indent_.c_str (), n) != n) - return traits_type::eof (); + if (buf_->sputn (indent_.c_str (), n) != n) + return traits_type::eof (); + } + + prev_ = c; + } + + return buf_->sputc (c); } + // + // Note that we catch the system_error exception rather than + // ios_base::failure to be compilable with older C++ standard libraries + // which may not derive ios_base::failure from system_error (GCC 4.9, + // etc). For such libraries there is no easy way to handle the 'broken + // pipe' error at this level since it is indistinguishable from other IO + // errors. Thus, we just pass it through. Also note that we could + // potentially treat any IO error as the 'broken pipe' error for such + // libraries (it's actually hard to think of other reasons). Let's, + // however, keep it simple for now and see how it goes. + // + catch (const system_error& e) + { + if (e.code ().category () == generic_category () && +#ifndef _WIN32 + e.code ().value () == EPIPE) +#else + e.code ().value () == EINVAL) +#endif + { + skip_ = true; - prev_ = c; - return buf_->sputc (c); + // Fall through. + } + else + throw; + } + + return 0; // Success. } int pager:: sync () { - return buf_->pubsync (); + if (!skip_) + try + { + return buf_->pubsync (); + } + catch (const system_error& e) + { + if (e.code ().category () == generic_category () && +#ifndef _WIN32 + e.code ().value () == EPIPE) +#else + e.code ().value () == EINVAL) +#endif + { + skip_ = true; + + // Fall through. + } + else + throw; + } + + return 0; // Success. } } diff --git a/libbutl/pager.hxx b/libbutl/pager.hxx index 12a6670..2c26bf3 100644 --- a/libbutl/pager.hxx +++ b/libbutl/pager.hxx @@ -68,10 +68,10 @@ namespace butl using traits_type = std::streambuf::traits_type; virtual int_type - overflow (int_type); + overflow (int_type) override; virtual int - sync (); + sync () override; private: process p_; @@ -80,5 +80,6 @@ namespace butl std::string indent_; int_type prev_ = '\n'; // Previous character. std::streambuf* buf_ = nullptr; + bool skip_ = false; }; } |