changed to use ftruncate to allocate files

src/file.cpp

@@ -247,19 +247,16 @@ namespace libtorrent
 
 		void set_size(size_type s)
 		{
-			size_type pos = tell();
+#ifdef _WIN32
-			// Only set size if current file size not equals s.
+#error file.cpp is for posix systems only. use file_win.cpp on windows
-			// 2 as "m" argument is to be sure seek() sets SEEK_END on
+#else
-			// all compilers.
+			if (ftruncate(m_fd, s) < 0)
-			if(s != seek(0, 2))
 			{
-				seek(s - 1);
+				std::stringstream msg;
-				char dummy = 0;
+				msg << "ftruncate failed: '" << strerror(errno);
-				read(&dummy, 1);
+				throw file_error(msg.str());
-				seek(s - 1);
-				write(&dummy, 1);
 			}
-			seek(pos);
+#endif
 		}
 
 		size_type seek(size_type offset, int m = 1)