[PATCH] ostreambuf_iterator std::advance overload

[PATCH] ostreambuf_iterator std::advance overload

[François Dumont]

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Hi

     I completed this overload before noticing that the Standard do not 
expect anything when 'advancing' an output iterator.

     But as I've done it consistenly with the istreambuf_iterator here 
it is with samples about how to use it.

     Let me know if acceptable.

François


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diff --git a/libstdc++-v3/include/bits/streambuf_iterator.h b/libstdc++-v3/include/bits/streambuf_iterator.h
index 17dd3972d45..76ba96d634a 100644
--- a/libstdc++-v3/include/bits/streambuf_iterator.h
+++ b/libstdc++-v3/include/bits/streambuf_iterator.h
@@ -242,6 +242,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	copy(istreambuf_iterator<_CharT2>, istreambuf_iterator<_CharT2>,
 	     ostreambuf_iterator<_CharT2>);
 
+      template<typename _CharT2, typename _Distance>
+	friend typename __gnu_cxx::__enable_if<__is_char<_CharT2>::__value,
+					       void>::__type
+	advance(ostreambuf_iterator<_CharT2>&, _Distance);
+
     private:
       streambuf_type*	_M_sbuf;
       bool		_M_failed;
@@ -453,6 +458,37 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	}
     }
 
+  template<typename _CharT, typename _Distance>
+    typename __gnu_cxx::__enable_if<__is_char<_CharT>::__value,
+				    void>::__type
+    advance(ostreambuf_iterator<_CharT>& __i, _Distance __n)
+    {
+      if (__n == 0)
+	return;
+
+      __glibcxx_assert(__n > 0);
+      __glibcxx_requires_cond(!__i.failed(),
+			      _M_message(__gnu_debug::__msg_advance_oob)
+			      ._M_iterator(__i)
+			      ._M_integer(__n));
+
+      typedef basic_streambuf<_CharT> __streambuf_t;
+      typedef typename __streambuf_t::pos_type __pos_t;
+      __pos_t __cur_pos
+	= __i._M_sbuf->pubseekoff(0, ios_base::cur, ios_base::out);
+      __pos_t __new_pos =
+	__i._M_sbuf->pubseekoff(__n, ios_base::cur, ios_base::out);
+
+      if (__new_pos - __cur_pos != __n)
+	{
+	  __i._M_failed = true;
+	  __glibcxx_requires_cond(!__i.failed(),
+				  _M_message(__gnu_debug::__msg_advance_oob)
+				  ._M_iterator(__i)
+				  ._M_integer(__n));
+	}
+    }
+
 // @} group iterators
 
 _GLIBCXX_END_NAMESPACE_VERSION
diff --git a/libstdc++-v3/testsuite/25_algorithms/advance/ostreambuf_iterator/char/1.cc b/libstdc++-v3/testsuite/25_algorithms/advance/ostreambuf_iterator/char/1.cc
new file mode 100644
index 00000000000..15cf0b27863
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/advance/ostreambuf_iterator/char/1.cc
@@ -0,0 +1,55 @@
+// Copyright (C) 2019 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <iterator>
+#include <sstream>
+#include <algorithm>
+
+#include <testsuite_hooks.h>
+
+void test01()
+{
+  using namespace std;
+
+  const char data1[] = "Drei Phantasien nach Friedrich Holderlin";
+  string str1(data1);
+  str1[17] = 'i';
+
+  ostringstream oss1(str1);
+  ostreambuf_iterator<char> beg1(oss1);
+
+  std::advance(beg1, 17);
+  *beg1 = 'a';
+
+  VERIFY( !beg1.failed() );
+  VERIFY( oss1.str() == data1 );
+  str1 = oss1.str();
+
+  // -1 for the trailing '\0'
+  // -1 for the beg1 assignment.
+  std::advance(beg1, sizeof(data1) - 17 - 1 - 1);
+  *beg1 = '.';
+
+  str1 += '.';
+  VERIFY( oss1.str() == str1 );
+}
+
+int main()
+{
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/25_algorithms/advance/ostreambuf_iterator/char/1_neg.cc b/libstdc++-v3/testsuite/25_algorithms/advance/ostreambuf_iterator/char/1_neg.cc
new file mode 100644
index 00000000000..9d1e4a94742
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/advance/ostreambuf_iterator/char/1_neg.cc
@@ -0,0 +1,40 @@
+// Copyright (C) 2019 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run { xfail *-*-* } }
+// { dg-require-debug-mode "" }
+
+#include <iterator>
+#include <sstream>
+#include <algorithm>
+
+void test01()
+{
+  using namespace std;
+
+  const char data1[] = "Drei Phantasien nach Friedrich Holderlin";
+  ostringstream oss1(data1);
+  ostreambuf_iterator<char> beg1(oss1);
+
+  advance(beg1, -1); // Error.
+}
+
+int main()
+{
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/25_algorithms/advance/ostreambuf_iterator/char/2.cc b/libstdc++-v3/testsuite/25_algorithms/advance/ostreambuf_iterator/char/2.cc
new file mode 100644
index 00000000000..e53e331ba17
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/advance/ostreambuf_iterator/char/2.cc
@@ -0,0 +1,47 @@
+// Copyright (C) 2019 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// Debug mode would detect the invalid std::advance call.
+// { dg-require-normal-mode "" }
+
+#include <iterator>
+#include <sstream>
+#include <algorithm>
+
+#include <testsuite_hooks.h>
+
+void test01()
+{
+  using namespace std;
+
+  const char data1[] = "Drei Phantasien nach Friedrich Holderlin";
+
+  ostringstream oss1(data1);
+  ostreambuf_iterator<char> beg1(oss1);
+
+  VERIFY( !beg1.failed() );
+
+  std::advance(beg1, sizeof(data1));
+
+  VERIFY( beg1.failed() );
+}
+
+int main()
+{
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/25_algorithms/advance/ostreambuf_iterator/char/2_neg.cc b/libstdc++-v3/testsuite/25_algorithms/advance/ostreambuf_iterator/char/2_neg.cc
new file mode 100644
index 00000000000..e6aa9d25b4d
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/advance/ostreambuf_iterator/char/2_neg.cc
@@ -0,0 +1,40 @@
+// Copyright (C) 2019 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run { xfail *-*-* } }
+// { dg-require-debug-mode "" }
+
+#include <iterator>
+#include <sstream>
+#include <algorithm>
+
+void test01()
+{
+  using namespace std;
+
+  const char data1[] = "Drei Phantasien nach Friedrich Holderlin";
+  ostringstream oss1(data1);
+  ostreambuf_iterator<char> beg1(oss1);
+
+  advance(beg1, sizeof(data1)); // Error.
+}
+
+int main()
+{
+  test01();
+  return 0;
+}