Auto merge of #311 - fiveop:context, r=@kamalmarhubi

Add context module.

The module wraps context handling related functions and structs.

src/lib.rs

@@ -51,6 +51,13 @@ pub mod net;
 pub mod sched;
 
 pub mod sys;
+
+// This can be implemented for other platforms as soon as libc
+// provides bindings for them.
+#[cfg(all(target_os = "linux",
+          any(target_arch = "x86", target_arch = "x86_64")))]
+pub mod ucontext;
+
 pub mod unistd;
 
 /*

src/sys/mod.rs

@@ -1,4 +1,3 @@
-
 #[cfg(any(target_os = "linux", target_os = "android"))]
 pub mod epoll;
 

src/ucontext.rs

@@ -0,0 +1,25 @@
+use libc;
+use {Errno, Result};
+use std::mem;
+
+#[derive(Clone, Copy)]
+pub struct UContext {
+    context: libc::ucontext_t,
+}
+
+impl UContext {
+    pub fn get() -> Result<UContext> {
+        let mut context: libc::ucontext_t = unsafe { mem::uninitialized() };
+        let res = unsafe {
+            libc::getcontext(&mut context as *mut libc::ucontext_t)
+        };
+        Errno::result(res).map(|_| UContext { context: context })
+    }
+
+    pub fn set(&self) -> Result<()> {
+        let res = unsafe {
+            libc::setcontext(&self.context as *const libc::ucontext_t)
+        };
+        Errno::result(res).map(drop)
+    }
+}