Author: hhinnant
Date: Fri Aug 9 11:25:43 2013
New Revision: 188077
URL: http://llvm.org/viewvc/llvm-project?rev=188077&view=rev
Log:
Partial implementation of N3665. This paper was not voted into the C++1y
draft. However I was looking at it and with some experimentation realized that
I could partially implement it, and at the same time offer a performance
optimization to cout. I simply added an xsputn override to the cout filebuf.
The override does nothing special at all if there is a non-trivial codecvt
installed. However if the codecvt returns true for always_noconv(), then this
function can dump an entire string to fwrite, instead of doing it a character
at a time under overflow(). This just makes sense. I stopped short of a full
implementation of N3665 because in order to do so, xsputn would have to
allocate a buffer when always_noconv() returned false, and I don't want to go
to that expense.
Modified:
libcxx/trunk/include/__std_stream
Modified: libcxx/trunk/include/__std_stream
URL:
http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/__std_stream?rev=188077&r1=188076&r2=188077&view=diff
==============================================================================
--- libcxx/trunk/include/__std_stream (original)
+++ libcxx/trunk/include/__std_stream Fri Aug 9 11:25:43 2013
@@ -233,6 +233,7 @@ public:
protected:
virtual int_type overflow (int_type __c = traits_type::eof());
+ virtual streamsize xsputn(const char_type* __s, streamsize __n);
virtual int sync();
virtual void imbue(const locale& __loc);
@@ -309,6 +310,19 @@ __stdoutbuf<_CharT>::overflow(int_type _
}
template <class _CharT>
+streamsize
+__stdoutbuf<_CharT>::xsputn(const char_type* __s, streamsize __n)
+{
+ if (__always_noconv_)
+ return fwrite(__s, sizeof(char_type), __n, __file_);
+ streamsize __i = 0;
+ for (; __i < __n; ++__i, ++__s)
+ if (overflow(traits_type::to_int_type(*__s)) == traits_type::eof())
+ break;
+ return __i;
+}
+
+template <class _CharT>
int
__stdoutbuf<_CharT>::sync()
{
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