diff --git a/src/lib.rs b/src/lib.rs
index 038c394..0ffff79 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,5 +1,4 @@
 #![feature(default_type_params, macro_rules)]
-extern crate libc;
 extern crate fn_box;
 
 pub use context::Context;
diff --git a/src/platform.rs b/src/platform.rs
index 5754c78..9e15e0f 100644
--- a/src/platform.rs
+++ b/src/platform.rs
@@ -1,8 +1,75 @@
-use libc;
+extern crate libc;
+use std::os::{errno, page_size, MemoryMap, MapReadable, MapWritable,
+              MapNonStandardFlags};
 
 extern "C" {
   #[link_name = "lwt_stack_register"]
-  pub fn stack_register(start: *const u8, end: *const u8) -> libc::c_uint;
+  fn stack_register(start: *const u8, end: *const u8) -> libc::c_uint;
   #[link_name = "lwt_stack_deregister"]
-  pub fn stack_deregister(id: libc::c_uint);
+  fn stack_deregister(id: libc::c_uint);
+}
+
+pub struct Stack {
+  buf: MemoryMap,
+  valgrind_id: libc::c_uint
+}
+
+
+const STACK_FLAGS: libc::c_int = libc::MAP_STACK
+                               | libc::MAP_PRIVATE
+                               | libc::MAP_ANON;
+
+impl Stack {
+  pub fn new(size: uint) -> Stack {
+    let buf = match MemoryMap::new(size, &[MapReadable, MapWritable,
+                                   MapNonStandardFlags(STACK_FLAGS)]) {
+      Ok(map) => map,
+      Err(e) => panic!("mmap for stack of size {} failed: {}", size, e)
+    };
+
+    if !protect_last_page(&buf) {
+      panic!("Could not memory-protect guard page. stack={}, errno={}",
+             buf.data(), errno());
+    }
+
+    let valgrind_id = unsafe {
+      stack_register(buf.data().offset(buf.len() as int) as *const _,
+                     buf.data() as *const _)
+    };
+
+    Stack {
+      buf: buf,
+      valgrind_id: valgrind_id
+    }
+  }
+}
+
+fn protect_last_page(stack: &MemoryMap) -> bool {
+  unsafe {
+    let last_page = stack.data() as *mut libc::c_void;
+    libc::mprotect(last_page, page_size() as libc::size_t,
+                   libc::PROT_NONE) != -1
+  }
+}
+
+impl Drop for Stack {
+  fn drop(&mut self) {
+    unsafe {
+      stack_deregister(self.valgrind_id);
+    }
+  }
+}
+
+impl Stack {
+  pub fn top(&mut self) -> *mut u8 {
+    unsafe {
+      self.buf.data().offset(self.buf.len() as int)
+    }
+  }
+
+  pub fn limit(&self) -> *const u8 {
+    unsafe {
+      self.buf.data().offset(page_size() as int) as *const _
+    }
+  }
 }
diff --git a/src/stack.rs b/src/stack.rs
index 01de813..18bfbd5 100644
--- a/src/stack.rs
+++ b/src/stack.rs
@@ -1,48 +1,16 @@
-use libc;
 use platform;
 use std::ptr;
-use std::os::{errno, page_size, MemoryMap, MapReadable, MapWritable,
-              MapNonStandardFlags};
-
-const STACK_FLAGS: libc::c_int = libc::MAP_STACK
-                               | libc::MAP_PRIVATE
-                               | libc::MAP_ANON;
 
 pub enum Stack {
   Native {
     sp_limit: *const u8
   },
-  Managed {
-    buf: MemoryMap,
-    valgrind_id: libc::c_uint
-  }
+  Managed(platform::Stack)
 }
 
 impl Stack {
   pub fn new(size: uint) -> Stack {
-    let buf = match MemoryMap::new(size, &[MapReadable, MapWritable,
-                                   MapNonStandardFlags(STACK_FLAGS)]) {
-      Ok(map) => map,
-      Err(e) => panic!("mmap for stack of size {} failed: {}", size, e)
-    };
-
-    if !protect_last_page(&buf) {
-      panic!("Could not memory-protect guard page. stack={}, errno={}",
-             buf.data(), errno());
-    }
-
-    let valgrind_id = unsafe {
-      platform::stack_register(buf.data().offset(buf.len() as int) as *const _,
-                               buf.data() as *const _)
-    };
-
-
-    let stk = Stack::Managed {
-      buf: buf,
-      valgrind_id: valgrind_id
-    };
-
-    stk
+    Stack::Managed(platform::Stack::new(size))
   }
 
   pub unsafe fn native(limit: *const u8) -> Stack {
@@ -52,43 +20,16 @@ impl Stack {
   }
 
   pub fn top(&mut self) -> *mut u8 {
-    unsafe {
-      match *self {
-        Stack::Native { .. } => ptr::null_mut(),
-        Stack::Managed { ref buf, .. } => {
-          buf.data().offset(buf.len() as int)
-        }
-      }
+    match *self {
+      Stack::Native { .. } => ptr::null_mut(),
+      Stack::Managed(ref mut stack) => stack.top()
     }
   }
 
   pub fn limit(&self) -> *const u8 {
-    unsafe {
-      match *self {
-        Stack::Native { sp_limit, .. } => sp_limit,
-        Stack::Managed { ref buf, .. } => {
-          buf.data().offset(page_size() as int) as *const _
-        }
-      }
-    }
-  }
-}
-
-fn protect_last_page(stack: &MemoryMap) -> bool {
-  unsafe {
-    let last_page = stack.data() as *mut libc::c_void;
-    libc::mprotect(last_page, page_size() as libc::size_t,
-                   libc::PROT_NONE) != -1
-  }
-}
-
-impl Drop for Stack {
-  fn drop(&mut self) {
     match *self {
-      Stack::Native { .. } => {},
-      Stack::Managed { valgrind_id, .. } => unsafe {
-        platform::stack_deregister(valgrind_id);
-      }
+      Stack::Native { sp_limit, .. } => sp_limit,
+      Stack::Managed(ref stack) => stack.limit()
     }
   }
 }