diff --git a/File/File.cpp b/File/File.cpp
index c036633..4442b1b 100644
--- a/File/File.cpp
+++ b/File/File.cpp
@@ -1,8 +1,14 @@
-#include "File.h"
-
+#include <algorithm>
 #include <cerrno>
 
-using namespace File;
+#include <File/File.h>
+#include <ProFUSE/Exception.h>
+
+
+
+using ProFUSE::Exception;
+using ProFUSE::POSIXException;
+
 
 File::File()
 {
@@ -22,9 +28,12 @@ File::File(File& f)
 
 File::File(const char *name, int flags)
 {
+    #undef __METHOD__
+    #define __METHOD__ "File::File"
+
     _fd = ::open(name, flags);
     if (_fd < 0)
-        throw ProFUSE::PosixException(errno);
+        throw POSIXException( __METHOD__ ": open", errno);
 }
 
 File::~File()
@@ -32,12 +41,30 @@ File::~File()
     close();
 }
 
-File::close()
+void File::close()
 {
-    int fd = _fd;
-    _fd = -1;
+    #undef __METHOD__
+    #define __METHOD__ "File::close"
+
+    if (_fd >= 0)
+    {
+        int fd = _fd;
+        _fd = -1;
     
-    if (fd >= 0 && ::close(fd) != 0)
-        throw ProFUSE::PosixException(errno);
+        if (::close(fd) != 0)
+            throw POSIXException(__METHOD__ ": close", errno);
+    }
 }
 
+
+void File::adopt(File &f)
+{
+    close();
+    _fd = f._fd;
+    f._fd = -1;
+}
+
+void File::swap(File &f)
+{
+    std::swap(_fd, f._fd);
+}
diff --git a/File/File.h b/File/File.h
index 4c766d2..56763c5 100644
--- a/File/File.h
+++ b/File/File.h
@@ -1,17 +1,11 @@
 #ifndef __FILE_H__
 #define __FILE_H__
 
+#include <sys/types.h>
 #include <unistd.h>
 #include <fcntl.h>
 
-namespace File {
-
-enum Flags {
-    ReadOnly = O_RDONLY,
-    WriteOnly = O_WRONLY,
-    ReadWrite = O_RDWR
-};
-
+ 
 class File {
 
     public:
@@ -24,10 +18,15 @@ class File {
     int fd() const { return _fd; }
         
     void close();
+    
+    void adopt(File &f);
+    void swap(File &f);
         
     private:
+    
+    // could call dup() or something.
+    File& operator=(const File &f);
     int _fd;    
 };
 
-}
 #endif
diff --git a/File/MappedFile.cpp b/File/MappedFile.cpp
index 8fc4351..a1f79f2 100644
--- a/File/MappedFile.cpp
+++ b/File/MappedFile.cpp
@@ -1,11 +1,14 @@
-#include "MappedFile.h"
-
+#include <algorithm>
 #include <cerrno>
+
 #include <sys/stat.h>
 
-using namespace File;
+#include <File/MappedFile.h>
+#include <ProFUSE/Exception.h>
 
 
+using ProFUSE::POSIXException;
+
 MappedFile::MappedFile()
 {
     _length = -1;
@@ -21,20 +24,23 @@ MappedFile::MappedFile(MappedFile &mf)
     mf._length = -1;
 }
 
-MappedFile::MappedFile(File f, int flags)
+MappedFile::MappedFile(File f, bool readOnly)
 {
+    #undef __METHOD__
+    #define __METHOD__ "MappedFile::MappedFile"
+
     struct stat st;
     
     // close enough
     if (f.fd() < 0)
-        throw ProFUSE::PosixException(EBADF);
+        throw POSIXException( __METHOD__, EBADF);
 
 
-    if (::fstat(f.fd(), st) != 0)
-        throw ProFUSE::PosixException(errno);
+    if (::fstat(f.fd(), &st) != 0)
+        throw POSIXException(__METHOD__ ": fstat", errno);
     
     if (!S_ISREG(st.st_mode))
-        throw ProFUSE::PosixException(ENODEV);
+        throw POSIXException(__METHOD__, ENODEV);
         
     _length = st.st_size;
     _address = ::mmap(0, _length, 
@@ -42,7 +48,7 @@ MappedFile::MappedFile(File f, int flags)
         MAP_FILE | MAP_SHARED, f.fd(), 0); 
 
     if (_address == MAP_FAILED)
-        throw ProFUSE::PosixException(errno);
+        throw POSIXException(__METHOD__ ": mmap", errno);
 }
 
 MappedFile::~MappedFile()
@@ -52,8 +58,11 @@ MappedFile::~MappedFile()
 
 
 
-MappedFile::close()
+void MappedFile::close()
 {
+    #undef __METHOD__
+    #define __METHOD__ "MappedFile::close"
+    
     if (_address != MAP_FAILED)
     {
         void *address = _address;
@@ -63,15 +72,34 @@ MappedFile::close()
         _length = -1;
         
         if (::munmap(address, length) != 0)
-            throw ProFUSE::PosixException(errno);
+            throw POSIXException(__METHOD__ ": munmap", errno);
     }
 }
 
-MappedFile::sync()
+void MappedFile::sync()
 {
+    #undef __METHOD__
+    #define __METHOD__ "MappedFile::sync"
+    
     if (_address != MAP_FAILED)
     {
         if (::msync(_address, _length, MS_SYNC) != 0)
-            throw ProFUSE::PosixException(errno);
+            throw POSIXException(__METHOD__ ": msync", errno);
     }
+}
+
+void MappedFile::adopt(MappedFile &mf)
+{
+    close();
+    _address = mf._address;
+    _length = mf._length;
+    
+    mf._address = MAP_FAILED;
+    mf._length = -1;
+}
+
+void MappedFile::swap(MappedFile &mf)
+{
+    std::swap(_address, mf._address);
+    std::swap(_length, mf._length);
 }
\ No newline at end of file
diff --git a/File/MappedFile.h b/File/MappedFile.h
index 90852ec..bc8911c 100644
--- a/File/MappedFile.h
+++ b/File/MappedFile.h
@@ -3,15 +3,14 @@
 
 #include <sys/mman.h>
 
-#include "File.h"
+#include <File/File.h>
 
-namespace File {
 
 class MappedFile {
     public:
     
     MappedFile();
-    MappedFile(File f, int flags);
+    MappedFile(File f, bool readOnly);
     MappedFile(MappedFile&);
     
     ~MappedFile();
@@ -22,12 +21,16 @@ class MappedFile {
     void *address() const { return _address; }
     size_t length() const { return _length; }
     
+    void swap(MappedFile &);
+    void adopt(MappedFile &);
+    
     private:
     
+    MappedFile& operator=(MappedFile &);
+    
     void *_address;
     size_t _length;
 };
 
-}
 
 #endif
\ No newline at end of file