rework fallocate logic

src/fs_sendfile.cpp

@@ -0,0 +1,40 @@
+/*
+  Copyright (c) 2016, Antonio SJ Musumeci <trapexit@spawn.link>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#include <errno.h>
+
+#if defined __linux__
+#include <sys/sendfile.h>
+#endif
+
+#include "fs_sendfile.hpp"
+
+namespace fs
+{
+  ssize_t
+  sendfile(const int    fdin,
+           const int    fdout,
+           const size_t count)
+  {
+#if defined __linux__
+    off_t offset = 0;
+
+    return ::sendfile(fdout,fdin,&offset,count);
+#else
+    return (errno=EINVAL,-1);
+#endif
+  }
+}