factor out page size function and make aligned allocator configurable to use posix_memalign and memalign

include/libtorrent/allocator.hpp

@@ -39,6 +39,8 @@ POSSIBILITY OF SUCH DAMAGE.
 namespace libtorrent
 {
 
+	TORRENT_EXPORT int page_size();
+
 	struct TORRENT_EXPORT page_aligned_allocator
 	{
 		typedef std::size_t size_type;

src/allocator.cpp

@@ -37,14 +37,39 @@ POSSIBILITY OF SUCH DAMAGE.
 #include <Windows.h>
 #else
 #include <stdlib.h>
+#include <unistd.h> // _SC_PAGESIZE
 #endif
 
 
 namespace libtorrent
 {
+	int page_size()
+	{
+		static int s = 0;
+		if (s != 0) return s;
+
+#ifdef TORRENT_WINDOWS
+		SYSTEM_INFO si;
+		GetSystemInfo(&si);
+		s = si.dwPageSize;
+#else
+		s = sysconf(_SC_PAGESIZE);
+#endif
+		// assume the page size is 4 kiB if we
+		// fail to query it
+		if (s <= 0) s = 4096;
+		return s;
+	}
+
 	char* page_aligned_allocator::malloc(const size_type bytes)
 	{
-#if defined TORRENT_WINDOWS
+#if TORRENT_USE_POSIX_MEMALIGN
+		void* ret;
+		if (posix_memalign(&ret, page_size(), bytes) != 0) ret = 0;
+		return ret;
+#elif TORRENT_USE_MEMALIGN
+		return memalign(page_size(), bytes);
+#elif defined TORRENT_WINDOWS
 		return (char*)VirtualAlloc(0, bytes, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
 #elif defined TORRENT_BEOS
 		// we could potentially use create_area() here, but

src/file.cpp

@@ -37,6 +37,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/pch.hpp"
 #include "libtorrent/config.hpp"
 #include "libtorrent/alloca.hpp"
+#include "libtorrent/allocator.hpp" // page_size
 #include "libtorrent/escape_string.hpp" // for string conversion
 
 #include <boost/scoped_ptr.hpp>
@@ -901,13 +902,7 @@ namespace libtorrent
 	{
 		if (m_page_size != 0) return;
 
-#ifdef TORRENT_WINDOWS
-		SYSTEM_INFO si;
-		GetSystemInfo(&si);
-		m_page_size = si.dwPageSize;
-#else
-		m_page_size = sysconf(_SC_PAGESIZE);
-#endif
+		m_page_size = page_size();
 	}
 
 #endif

src/storage.cpp

@@ -65,6 +65,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/aux_/session_impl.hpp"
 #include "libtorrent/disk_buffer_holder.hpp"
 #include "libtorrent/alloca.hpp"
+#include "libtorrent/allocator.hpp" // page_size
 
 #include <cstdio>
 
@@ -339,20 +340,13 @@ namespace libtorrent
 		storage(file_storage const& fs, file_storage const* mapped, std::string const& path, file_pool& fp)
 			: m_files(fs)
 			, m_pool(fp)
-			, m_page_size(4096)
+			, m_page_size(page_size())
 			, m_allocate_files(false)
 		{
 			if (mapped) m_mapped_files.reset(new file_storage(*mapped));
 
 			TORRENT_ASSERT(m_files.begin() != m_files.end());
 			m_save_path = complete(path);
-#ifdef TORRENT_WINDOWS
-			SYSTEM_INFO si;
-			GetSystemInfo(&si);
-			m_page_size = si.dwPageSize;
-#else
-			m_page_size = sysconf(_SC_PAGESIZE);
-#endif
 		}
 
 		bool has_any_file();