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-rw-r--r--libbutl/pager.cxx116
-rw-r--r--libbutl/pager.hxx5
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;
};
}