allocator: add implementation of new Alloc trait

The Alloc trait for allocators was added in Rust nightly 2017/06/21
(from rust-lang/rust#42313). With the addition of allowing a global
allocator to be specified (pending in rust-lang/rust#42727) this will
obviate the need for the alloc_uefi crate.

src/allocator.rs

@@ -0,0 +1,22 @@
+use alloc::allocator::*;
+
+use base::Status;
+
+/// Rust Allocator utilizing the EFI {allocate, free}_pool functions.
+struct EfiAllocator {}
+
+unsafe impl<'a> Alloc for &'a EfiAllocator {
+    unsafe fn alloc(&mut self, layout: Layout) -> Result<*mut u8, AllocErr> {
+        ::get_system_table()
+            .boot_services()
+            .allocate_pool(layout.size())
+            .map_err(|e| match e {
+                Status::OutOfResources => AllocErr::Exhausted { request: layout },
+                x => AllocErr::Unsupported { details: x.str() }
+            })
+    }
+
+    unsafe fn dealloc(&mut self, ptr: *mut u8, _layout: Layout) {
+        ::get_system_table().boot_services().free_pool(ptr);
+    }
+}

src/lib.rs

@@ -1,6 +1,10 @@
 #![allow(dead_code)]
+#![feature(alloc)]
+#![feature(allocator_api)]
 #![no_std]
 
+extern crate alloc;
+
 pub mod protocol;
 mod void;
 mod base;
@@ -12,6 +16,7 @@ mod runtimeservices;
 mod console;
 mod task;
 mod event;
+mod allocator;
 
 
 pub use base::{Handle, Handles, Event, MemoryType, Status, Time};