[Bug libstdc++/11722] New: Unbuffered filebuf::sgetn is slow

["peturr02 at ru dot is" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11722

           Summary: Unbuffered filebuf::sgetn is slow
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: peturr02 at ru dot is
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu

This is the same as 11378, but for input this time. The problem is the
same: basic_filebuf::xsgetn calls read for each character, but
fread_unlocked calls read only once.