memory: add pagesize query

Makefile.am

@@ -160,6 +160,8 @@ UTIL_FILES   =			\
     matrix.ipp			\
     memory.cpp			\
     memory.hpp			\
+    memory/system.cpp		\
+    memory/system.hpp		\
     net/address.cpp		\
     net/address.hpp		\
     net/except.cpp		\

memory/system.cpp

@@ -0,0 +1,39 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "./system.hpp"
+
+#include "../except.hpp"
+#include "../types/casts.hpp"
+
+#include <unistd.h>
+
+///////////////////////////////////////////////////////////////////////////////
+size_t
+util::memory::pagesize (void)
+{
+    static size_t val;
+
+    if (!val) {
+        auto res = sysconf (_SC_PAGE_SIZE);
+        if (res == -1)
+            errno_error::throw_code ();
+
+        val = sign_cast<unsigned long> (res);
+    }
+
+    return val;
+}

memory/system.hpp

@@ -0,0 +1,26 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef __UTIL_MEMORY_SYSTEM_HPP
+#define __UTIL_MEMORY_SYSTEM_HPP
+
+#include <cstddef>
+
+namespace util { namespace memory {
+    size_t pagesize (void);
+} }
+
+#endif