[PATCH 1/2] libstdc++: Add std::align.

[Rüdiger Sonderfeld <ruediger at c-plusplus dot de>]

C++11 [ptr.align].

This should probably not be inline.  But for now this avoids any ABI
changes.

* libstdc++-v3/testsuite/20_util/align/1.cc: New file.
* libstdc++-v3/include/std/memory (align): New function.
---
 libstdc++-v3/include/std/memory           | 35 +++++++++++++
 libstdc++-v3/testsuite/20_util/align/1.cc | 82 +++++++++++++++++++++++++++++++
 2 files changed, 117 insertions(+)
 create mode 100644 libstdc++-v3/testsuite/20_util/align/1.cc

diff --git a/libstdc++-v3/include/std/memory b/libstdc++-v3/include/std/memory
index dafec0c..f9ae7b9 100644
--- a/libstdc++-v3/include/std/memory
+++ b/libstdc++-v3/include/std/memory
@@ -83,6 +83,41 @@
 #  if _GLIBCXX_USE_DEPRECATED
 #    include <backward/auto_ptr.h>
 #  endif
+
+/**
+ *  @brief Fit aligned storage in buffer.
+ *
+ *  [ptr.align]
+ *
+ *  This function tries to fit __size storage with __alignment into
+ *  the buffer __ptr of size __space bytes.  If such a buffer fits
+ *  then __ptr is changed to point to the storage and __space is
+ *  reduced by the bytes needed to adjust the alignment.
+ *
+ *  @param __alignment A fundamental or extended alignment value
+                       of the desired storage.
+ *  @param __size      Size of the aligned storage.
+ *  @param __ptr       Pointer to a buffer of __space byte size.
+ *  @param __space     Size of the buffer pointed to by __ptr.
+ *  @return the updated pointer if the aligned storage fits or
+             nullptr else.
+ */
+inline
+void*
+align(size_t __alignment, size_t __size, void*& __ptr, size_t& __space)
+{
+  const size_t __diff = __alignment -
+    reinterpret_cast<uintptr_t>(__ptr) % __alignment;
+  if (__diff + __size >= __space)
+    return nullptr;
+  else
+    {
+      __space -= __diff;
+      __ptr = static_cast<char*>(__ptr) + __diff;
+      return __ptr;
+    }
+}
+
 #else
 #  include <backward/auto_ptr.h>
 #endif
diff --git a/libstdc++-v3/testsuite/20_util/align/1.cc b/libstdc++-v3/testsuite/20_util/align/1.cc
new file mode 100644
index 0000000..2e74806
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/align/1.cc
@@ -0,0 +1,82 @@
+// { dg-options " -std=gnu++11 " }
+
+// 2014-04-16 RÃÂdiger Sonderfeld  <ruediger@c-plusplus.de>
+
+// Copyright (C) 2014 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/>.
+
+// C++11 [ptr.align] (20.6.5): std::align
+
+#include <memory>
+#include <cstdint>
+#include <testsuite_hooks.h>
+
+#ifndef _GLIBCXX_ASSERT
+#  include <iostream>
+#  define STRINGIZE2(x) #x
+#  define STRINGIZE(x) STRINGIZE2(x)
+#  define CHECK(a, op, b)                       \
+  do                                            \
+    {                                           \
+      if ( !( (a) op (b) ) )                    \
+        {                                       \
+          cerr << "Mismatch: "                  \
+               << STRINGIZE(a)                  \
+               << " (" << (a) << ") "           \
+               << STRINGIZE(op) << ' '          \
+               << STRINGIZE(b)                  \
+               << " (" << (b) << ")\n";         \
+        }                                       \
+    } while(false)
+#else
+#  define CHECK(a, op, b) VERIFY( (a) op (b) )
+#endif
+
+void test01()
+{
+  using namespace std;
+  bool test __attribute__((unused)) = true;
+
+  size_t space = 100;
+  void* ptr = new char[space];
+  char* const orig_ptr = static_cast<char*>(ptr);
+  char* old_ptr = orig_ptr;
+  const size_t orig_space = space;
+  size_t old_space = space;
+  const size_t alignment = 16;
+  const size_t size = 10;
+  while( void* const r = align(alignment, size, ptr, space) )
+    {
+      CHECK( r, ==, ptr );
+      uintptr_t p = reinterpret_cast<uintptr_t>(ptr);
+      CHECK( p % alignment, ==, 0 );
+      char* const x = static_cast<char*>(ptr);
+      CHECK( x - old_ptr, ==, old_space - space );
+      CHECK( (void*)x, <, (void*)(orig_ptr + orig_space) );
+      CHECK( (void*)(x + size), <, (void*)(orig_ptr + orig_space) );
+      ptr = x + size;
+      old_ptr = x;
+      old_space = space;
+      space -= size;
+    }
+  delete [] orig_ptr;
+}
+
+int main()
+{
+  test01();
+}
-- 
1.9.2