diff --git a/Makefile.am b/Makefile.am
index 140524f3..497f0e7b 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -162,11 +162,15 @@ UTIL_FILES   =		\
 
 
 if PLATFORM_LINUX
-UTIL_FILES += backtrace_execinfo.cpp
+UTIL_FILES += 			\
+    backtrace_execinfo.cpp	\
+    io_posix.cpp
 endif
 
 if PLATFORM_WIN32
-UTIL_FILES += backtrace_null.cpp
+UTIL_FILES += 			\
+    backtrace_null.cpp		\
+    io_win32.cpp
 endif
 
 ###############################################################################
diff --git a/io.cpp b/io.cpp
index f53ce132..a025ce94 100644
--- a/io.cpp
+++ b/io.cpp
@@ -198,99 +198,3 @@ util::set_cwd (const boost::filesystem::path &path) {
     if (chdir (path.string ().c_str ()) != 0)
         throw errno_error ();
 }
-
-//----------------------------------------------------------------------------
-#if defined(HAVE_MMAP)
-#include <sys/mman.h>
-
-
-mapped_file::mapped_file (const boost::filesystem::path &_path, access_t _access):
-    m_fd (_path, _access)
-{ load_fd (_access); }
-
-
-mapped_file::~mapped_file () {
-    CHECK (m_data != NULL);
-    munmap (m_data, m_size);
-}
-
-
-int
-mapped_file::access_to_flags (access_t a) {
-    int flags = 0;
-
-    if (a & ACCESS_READ)
-        flags |= PROT_READ;
-
-    if (a & ACCESS_WRITE)
-        flags |= PROT_WRITE;
-
-    return flags;
-}
-
-
-void
-mapped_file::load_fd (access_t access) {
-    struct stat meta;
-    if (fstat (m_fd, &meta) < 0)
-        throw errno_error ();
-
-    m_size = (size_t)meta.st_size;
-    m_data = (uint8_t *)mmap (NULL, m_size, access_to_flags (access), MAP_SHARED, m_fd, 0);
-    if (m_data == MAP_FAILED)
-        throw errno_error ();
-}
-
-
-size_t
-mapped_file::size (void) const {
-    CHECK (m_size > 0);
-    CHECK (m_data != NULL);
-
-    return m_size;
-}
-
-
-uint8_t*
-mapped_file::data (void) {
-    CHECK (m_size > 0);
-    CHECK (m_data != NULL);
-
-    return m_data;
-}
-
-
-const uint8_t*
-mapped_file::data (void) const {
-    CHECK (m_size > 0);
-    CHECK (m_data != NULL);
-
-    return m_data;
-}
-
-
-uint8_t*
-mapped_file::begin (void) {
-    return data ();
-}
-
-
-uint8_t*
-mapped_file::end (void) {
-    return data () + size ();
-}
-
-
-const uint8_t*
-mapped_file::cbegin (void) const {
-    return data ();
-}
-
-
-const uint8_t*
-mapped_file::cend (void) const {
-    return data () + size ();
-}
-
-#endif
-
diff --git a/io.hpp b/io.hpp
index ebdc208b..4e8822b4 100644
--- a/io.hpp
+++ b/io.hpp
@@ -22,12 +22,17 @@
 
 #include "types.hpp"
 #include "memory.hpp"
+#include "platform.hpp"
+#include "nocopy.hpp"
 
 #include <cstdio>
 #include <cstdint>
 #include <memory>
 #include <boost/filesystem/path.hpp>
 
+#ifdef PLATFORM_WIN32
+#include <windows.h>
+#endif
 
 namespace util {
     /// Specifies bitwise combinations of IO access rights.
@@ -60,6 +65,22 @@ namespace util {
     };
 
 
+#ifdef PLATFORM_WIN32
+    struct handle_ref : util::nocopy {
+    public:
+        explicit handle_ref (HANDLE);
+        explicit handle_ref ();
+        ~handle_ref ();
+
+        void reset (HANDLE);
+
+        operator HANDLE (void) const;
+
+        HANDLE handle;
+    };
+#endif
+
+
     //-------------------------------------------------------------------------
     class indenter : public std::streambuf {
     protected:
@@ -111,39 +132,8 @@ namespace util {
 
     void set_cwd (const boost::filesystem::path &);
 
-
-    /// Wraps a mechanism to map a file into memory. Read only.
-    class mapped_file {
-        private:
-            fd_ref   m_fd;
-            uint8_t *m_data;
-            size_t   m_size;
-
-            void load_fd (access_t);
-
-        protected:
-            int access_to_flags (access_t);
-
-        public:
-            mapped_file (const boost::filesystem::path &path, access_t access = ACCESS_READ);
-
-            mapped_file (const mapped_file&) = delete;
-            mapped_file& operator= (const mapped_file&) = delete;
-
-            ~mapped_file ();
-
-            const uint8_t* data (void) const;
-            uint8_t*       data (void);
-            size_t         size (void) const;
-
-            uint8_t*       begin (void);
-            uint8_t*       end   (void);
-
-            const uint8_t* cbegin (void) const;
-            const uint8_t* cend   (void) const;
-    };
-
     
+    //-------------------------------------------------------------------------
     class path_error : public std::runtime_error {
         public:
             path_error (const boost::filesystem::path &path):
@@ -152,6 +142,12 @@ namespace util {
     };
 }
 
+#ifdef PLATFORM_WIN32
+#include "io_win32.hpp"
+#else
+#include "io_posix.hpp"
+#endif
+
 #include "io.ipp"
 
 #endif
diff --git a/io_posix.cpp b/io_posix.cpp
new file mode 100644
index 00000000..b8a6e0f8
--- /dev/null
+++ b/io_posix.cpp
@@ -0,0 +1,120 @@
+/*
+ * This file is part of libgim.
+ *
+ * libgim is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * libgim is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2010-2014 Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "io.hpp"
+
+#include "debug.hpp"
+#include "except.hpp"
+
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+using util::detail::posix::mapped_file;
+
+//----------------------------------------------------------------------------
+mapped_file::mapped_file (const boost::filesystem::path &_path, access_t _access):
+    m_fd (_path, _access)
+{ load_fd (_access); }
+
+
+mapped_file::~mapped_file () {
+    CHECK (m_data != NULL);
+    munmap (m_data, m_size);
+}
+
+
+int
+mapped_file::access_to_flags (access_t a) {
+    int flags = 0;
+
+    if (a & ACCESS_READ)
+        flags |= PROT_READ;
+
+    if (a & ACCESS_WRITE)
+        flags |= PROT_WRITE;
+
+    return flags;
+}
+
+
+void
+mapped_file::load_fd (access_t access) {
+    struct stat meta;
+    if (fstat (m_fd, &meta) < 0)
+        throw errno_error ();
+
+    m_size = (size_t)meta.st_size;
+    m_data = (uint8_t *)mmap (NULL, m_size, access_to_flags (access), MAP_SHARED, m_fd, 0);
+    if (m_data == MAP_FAILED)
+        throw errno_error ();
+}
+
+
+size_t
+mapped_file::size (void) const {
+    CHECK (m_size > 0);
+    CHECK (m_data != NULL);
+
+    return m_size;
+}
+
+
+uint8_t*
+mapped_file::data (void) {
+    CHECK (m_size > 0);
+    CHECK (m_data != NULL);
+
+    return m_data;
+}
+
+
+const uint8_t*
+mapped_file::data (void) const {
+    CHECK (m_size > 0);
+    CHECK (m_data != NULL);
+
+    return m_data;
+}
+
+
+uint8_t*
+mapped_file::begin (void) {
+    return data ();
+}
+
+
+uint8_t*
+mapped_file::end (void) {
+    return data () + size ();
+}
+
+
+const uint8_t*
+mapped_file::cbegin (void) const {
+    return data ();
+}
+
+
+const uint8_t*
+mapped_file::cend (void) const {
+    return data () + size ();
+}
+
diff --git a/io_posix.hpp b/io_posix.hpp
new file mode 100644
index 00000000..4ed21479
--- /dev/null
+++ b/io_posix.hpp
@@ -0,0 +1,62 @@
+/*
+ * This file is part of libgim.
+ *
+ * libgim is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * libgim is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2010-2014 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef __UTIL_IO_POSIX_HPP
+#define __UTIL_IO_POSIX_HPP
+
+#include "io.hpp"
+
+namespace util {
+    namespace detail { namespace posix {
+        class mapped_file {
+            private:
+                fd_ref   m_fd;
+                uint8_t *m_data;
+                size_t   m_size;
+
+                void load_fd (access_t);
+
+            protected:
+                int access_to_flags (access_t);
+
+            public:
+                mapped_file (const boost::filesystem::path &path, access_t access = ACCESS_READ);
+
+                mapped_file (const mapped_file&) = delete;
+                mapped_file& operator= (const mapped_file&) = delete;
+
+                ~mapped_file ();
+
+                const uint8_t* data (void) const;
+                uint8_t*       data (void);
+                size_t         size (void) const;
+
+                uint8_t*       begin (void);
+                uint8_t*       end   (void);
+
+                const uint8_t* cbegin (void) const;
+                const uint8_t* cend   (void) const;
+        };
+        
+    } }
+
+    typedef detail::posix::mapped_file mapped_file;
+}
+
+#endif
diff --git a/io_win32.cpp b/io_win32.cpp
new file mode 100644
index 00000000..1919f545
--- /dev/null
+++ b/io_win32.cpp
@@ -0,0 +1,165 @@
+/*
+ * This file is part of libgim.
+ *
+ * libgim is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * libgim is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2014 Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "io_win32.hpp"
+
+#include "debug.hpp"
+#include "except.hpp"
+
+#include <windows.h>
+
+using util::detail::win32::mapped_file;
+
+
+//-----------------------------------------------------------------------------
+static DWORD
+access_to_flags (util::access_t a) {
+    switch (a) {
+        case util::ACCESS_READ:
+            return GENERIC_READ;
+
+        case util::ACCESS_WRITE:
+            return GENERIC_WRITE;
+
+        default:
+            unreachable ();
+    }
+}
+
+//-----------------------------------------------------------------------------
+mapped_file::mapped_file (const boost::filesystem::path &path,
+                          access_t access):
+    m_data (nullptr, UnmapViewOfFile)
+{
+    std::cerr << "mapped_file\n";
+
+    m_file.reset (CreateFile (path.string ().c_str (),
+                              access_to_flags (access),
+                              access == ACCESS_READ ? FILE_SHARE_READ : 0,
+                              nullptr,
+                              OPEN_EXISTING,
+                              FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN,
+                              0));
+
+    if (m_file == INVALID_HANDLE_VALUE)
+        win32_error::throw_code ();
+    std::cerr << "mapped_file: file\n";
+
+    m_mapping.reset (CreateFileMapping (m_file,
+                                        nullptr,
+                                        access == ACCESS_READ ? PAGE_READONLY : PAGE_READWRITE,
+                                        0, 0,
+                                        nullptr));
+
+    if (m_mapping == INVALID_HANDLE_VALUE)
+        win32_error::throw_code ();
+    std::cerr << "mapped_file: mapping\n";
+
+    auto view = MapViewOfFile (m_mapping,
+                               access == ACCESS_READ ? FILE_MAP_READ : FILE_MAP_WRITE,
+                               0, 0,
+                               0);
+    if (view == nullptr)
+        win32_error::throw_code ();
+    std::cerr << "mapped_file: view\n";
+
+    m_data.reset (
+        static_cast<unsigned char*> (view)
+    );
+
+    m_size = GetFileSize (m_file, nullptr);
+    std::cout << "size: " << m_size << '\n';
+}
+
+
+//-----------------------------------------------------------------------------
+const uint8_t*
+mapped_file::data (void) const
+{
+    return m_data.get ();
+}
+
+
+uint8_t*
+mapped_file::data (void)
+{
+    return m_data.get ();
+}
+
+
+size_t
+mapped_file::size (void) const
+{
+    return m_size;
+}
+
+
+uint8_t*
+mapped_file::begin (void)
+{
+    return data ();
+}
+
+uint8_t*
+mapped_file::end (void)
+{
+    return data () + size ();
+}
+
+
+const uint8_t*
+mapped_file::cbegin (void) const
+{
+    return data ();
+}
+
+const uint8_t*
+mapped_file::cend (void) const
+{
+    return data () + size ();
+}
+
+
+//-----------------------------------------------------------------------------
+util::handle_ref::handle_ref ():
+    handle (INVALID_HANDLE_VALUE)
+{ ; }
+
+
+util::handle_ref::~handle_ref ()
+{
+    reset (INVALID_HANDLE_VALUE);
+}
+
+
+void
+util::handle_ref::reset (HANDLE _handle)
+{
+    if (handle != INVALID_HANDLE_VALUE)
+        if (!CloseHandle (handle))
+            win32_error::throw_code ();
+
+    handle = _handle;
+}
+
+
+util::handle_ref::operator HANDLE (void) const
+{
+    return handle;
+}
diff --git a/io_win32.hpp b/io_win32.hpp
new file mode 100644
index 00000000..45e971e5
--- /dev/null
+++ b/io_win32.hpp
@@ -0,0 +1,61 @@
+/*
+ * This file is part of libgim.
+ *
+ * libgim is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * libgim is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2014 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef __UTIL_IO_WIN32_HPP
+#define __UTIL_IO_WIN32_HPP
+
+#include "io.hpp"
+
+#include <cstdint>
+#include <boost/filesystem/path.hpp>
+#include <windows.h>
+
+namespace util {
+    namespace detail { namespace win32 {
+        class mapped_file {
+        public:
+            mapped_file (const boost::filesystem::path &path,
+                         access_t access = ACCESS_READ);
+
+            mapped_file (const mapped_file&) = delete;
+            mapped_file& operator= (const mapped_file&) = delete;
+
+            const uint8_t* data (void) const;
+            uint8_t*       data (void);
+            size_t         size (void) const;
+
+            uint8_t*       begin (void);
+            uint8_t*       end   (void);
+
+            const uint8_t* cbegin (void) const;
+            const uint8_t* cend   (void) const;
+
+        private:
+            handle_ref m_file;
+            handle_ref m_mapping;
+
+            std::unique_ptr<uint8_t,BOOL(*)(LPCVOID)> m_data;
+            size_t m_size;
+        };
+    } }
+
+    typedef detail::win32::mapped_file mapped_file;
+}
+
+#endif