rustc: Replace intrinsic vec_len with unsafe Rust code

Preparation for #1981

Author: marijnh

src/libcore/ptr.rs

@@ -12,7 +12,6 @@ export memmove;
 #[abi = "rust-intrinsic"]
 native mod rusti {
     fn addr_of<T>(val: T) -> *T;
-    fn ptr_offset<T>(ptr: *T, count: libc::uintptr_t) -> *T;
     fn memcpy<T>(dst: *T, src: *T, count: libc::uintptr_t);
     fn memmove<T>(dst: *T, src: *T, count: libc::uintptr_t);
 }
@@ -29,14 +28,14 @@ fn mut_addr_of<T>(val: T) -> *mutable T unsafe {
 
 #[doc = "Calculate the offset from a pointer"]
 #[inline(always)]
-fn offset<T>(ptr: *T, count: uint) -> *T {
-    ret rusti::ptr_offset(ptr, count);
+fn offset<T>(ptr: *T, count: uint) -> *T unsafe {
+    (ptr as uint + count * sys::size_of::<T>()) as *T
 }
 
 #[doc = "Calculate the offset from a mutable pointer"]
 #[inline(always)]
 fn mut_offset<T>(ptr: *mutable T, count: uint) -> *mutable T {
-    ret rusti::ptr_offset(ptr as *T, count) as *mutable T;
+    (ptr as uint + count * sys::size_of::<T>()) as *mutable T
 }
 
 

src/libcore/vec.rs

@@ -74,11 +74,6 @@ export vec_len;
 export unsafe;
 export u8;
 
-#[abi = "rust-intrinsic"]
-native mod rusti {
-    fn vec_len<T>(&&v: [const T]) -> libc::size_t;
-}
-
 #[abi = "cdecl"]
 native mod rustrt {
     fn vec_reserve_shared<T>(t: *sys::type_desc,
@@ -122,7 +117,10 @@ fn reserve<T>(&v: [const T], n: uint) {
 
 #[doc = "Returns the length of a vector"]
 #[inline(always)]
-pure fn len<T>(v: [const T]) -> uint { unchecked { rusti::vec_len(v) } }
+pure fn len<T>(&&v: [const T]) -> uint unsafe {
+    let repr: **unsafe::vec_repr = ::unsafe::reinterpret_cast(addr_of(v));
+    (**repr).fill / sys::size_of::<T>()
+}
 
 #[doc = "
 Creates and initializes an immutable vector.