mv the raw pointer {swap,replace}_ptr to std::ptr

src/libstd/ptr.rs

@@ -15,6 +15,7 @@ use cast;
 #[cfg(stage0)] use libc::{c_void, size_t};
 use option::{Option, Some, None};
 use sys;
+use unstable::intrinsics;
 
 #[cfg(not(test))] use cmp::{Eq, Ord};
 use uint;
@@ -206,6 +207,36 @@ pub unsafe fn set_memory<T>(dst: *mut T, c: u8, count: uint) {
     memset64(dst, c, count as u64);
 }
 
+/**
+ * Swap the values at two mutable locations of the same type, without
+ * deinitialising or copying either one.
+ */
+#[inline]
+pub unsafe fn swap_ptr<T>(x: *mut T, y: *mut T) {
+    // Give ourselves some scratch space to work with
+    let mut tmp: T = intrinsics::uninit();
+    let t: *mut T = &mut tmp;
+
+    // Perform the swap
+    copy_memory(t, x, 1);
+    copy_memory(x, y, 1);
+    copy_memory(y, t, 1);
+
+    // y and t now point to the same thing, but we need to completely forget `tmp`
+    // because it's no longer relevant.
+    cast::forget(tmp);
+}
+
+/**
+ * Replace the value at a mutable location with a new one, returning the old
+ * value, without deinitialising or copying either one.
+ */
+#[inline(always)]
+pub unsafe fn replace_ptr<T>(dest: *mut T, mut src: T) -> T {
+    swap_ptr(dest, &mut src);
+    src
+}
+
 /**
   Transform a region pointer - &T - to an unsafe pointer - *T.
   This is safe, but is implemented with an unsafe block due to