Implement OwnedStack.

Cargo.toml

@@ -20,7 +20,8 @@ rev = "9ef793e9549aabfd2d969615180b69d29ce28d88"
 simd = "0.1"
 
 [features]
-default = ["valgrind"]
+default = ["alloc", "valgrind"]
+alloc = []
 
 # These apply only to tests within this library; assembly at -O0 is completely
 # unreadable, so use -O1.

README.md

@@ -19,6 +19,10 @@ It provides the following safe abstractions:
 It also provides the necessary low-level building blocks:
   * a trait that can be implemented by stack allocators,
     [Stack](https://edef1c.github.io/libfringe/fringe/struct.Stack.html);
+  * a wrapper for using slice references as stacks,
+    [SliceStack](https://edef1c.github.io/libfringe/fringe/struct.SliceStack.html);
+  * a stack allocator based on `Box<[u8]>`,
+    [OwnedStack](https://edef1c.github.io/libfringe/fringe/struct.OwnedStack.html);
   * a stack allocator based on anonymous memory mappings with guard pages,
     [OsStack](https://edef1c.github.io/libfringe/fringe/struct.OsStack.html).
 
@@ -136,10 +140,16 @@ no-default-features = true
 libfringe provides some optional features through [Cargo's feature flags].
 Currently, all of them are enabled by default.
 
+#### `alloc`
+
+This flag enables dependency on the `alloc` crate, which is required for
+the [OwnedStack](https://edef1c.github.io/libfringe/fringe/struct.OwnedStack.html).
+
 #### `valgrind`
 
+This flag enables [Valgrind] integration. libfringe will register context stacks with Valgrind.
+
 [Valgrind]: http://valgrind.org
-[Valgrind] integration. libfringe will register context stacks with Valgrind.
 
 ## Internals
 

src/lib.rs

@@ -5,6 +5,7 @@
 // http://opensource.org/licenses/MIT>, at your option. This file may not be
 // copied, modified, or distributed except according to those terms.
 #![feature(asm, naked_functions)]
+#![cfg_attr(feature = "alloc", feature(alloc))]
 #![cfg_attr(test, feature(test, thread_local, const_fn))]
 #![no_std]
 
@@ -21,6 +22,10 @@
 //!
 //!   * a trait that can be implemented by stack allocators,
 //!     [Stack](struct.Stack.html);
+//!   * a wrapper for using slice references as stacks,
+//!     [SliceStack](struct.SliceStack.html);
+//!   * a stack allocator based on `Box<[u8]>`,
+//!     [OwnedStack](struct.OwnedStack.html);
 //!   * a stack allocator based on anonymous memory mappings with guard pages,
 //!     [OsStack](struct.OsStack.html).
 
@@ -30,19 +35,25 @@ extern crate std;
 
 pub use stack::Stack;
 pub use stack::GuardedStack;
-pub use stack::SliceStack;
-
+pub use slice_stack::SliceStack;
 pub use generator::Generator;
 
+#[cfg(feature = "alloc")]
+pub use owned_stack::OwnedStack;
+
 #[cfg(unix)]
 pub use os::Stack as OsStack;
 
 mod arch;
 mod debug;
 
-mod stack;
 mod context;
+mod stack;
+mod slice_stack;
 pub mod generator;
 
+#[cfg(feature = "alloc")]
+mod owned_stack;
+
 #[cfg(unix)]
 mod os;

src/owned_stack.rs

@@ -0,0 +1,33 @@
+// This file is part of libfringe, a low-level green threading library.
+// Copyright (c) whitequark <whitequark@whitequark.org>
+// See the LICENSE file included in this distribution.
+extern crate alloc;
+
+use self::alloc::raw_vec::RawVec;
+use self::alloc::boxed::Box;
+
+/// OwnedStack allocates on heap and owns a non-guarded stack.
+pub struct OwnedStack(Box<[u8]>);
+
+impl OwnedStack {
+    /// Allocates a new stack with exactly `size` accessible bytes using
+    /// the default Rust allocator.
+    pub fn new(size: usize) -> OwnedStack {
+        OwnedStack(unsafe { RawVec::with_capacity(size).into_box() })
+    }
+}
+
+impl ::stack::Stack for OwnedStack {
+    #[inline(always)]
+    fn base(&self) -> *mut u8 {
+        // The slice cannot wrap around the address space, so the conversion from usize
+        // to isize will not wrap either.
+        let len: isize = self.0.len() as isize;
+        unsafe { self.limit().offset(len) }
+    }
+
+    #[inline(always)]
+    fn limit(&self) -> *mut u8 {
+        self.0.as_ptr() as *mut u8
+    }
+}

src/slice_stack.rs

@@ -0,0 +1,22 @@
+// This file is part of libfringe, a low-level green threading library.
+// Copyright (c) whitequark <whitequark@whitequark.org>
+// See the LICENSE file included in this distribution.
+
+/// SliceStack holds a non-guarded stack allocated elsewhere and provided as a mutable
+/// slice.
+pub struct SliceStack<'a>(pub &'a mut [u8]);
+
+impl<'a> ::stack::Stack for SliceStack<'a> {
+    #[inline(always)]
+    fn base(&self) -> *mut u8 {
+        // The slice cannot wrap around the address space, so the conversion from usize
+        // to isize will not wrap either.
+        let len: isize = self.0.len() as isize;
+        unsafe { self.limit().offset(len) }
+    }
+
+    #[inline(always)]
+    fn limit(&self) -> *mut u8 {
+        self.0.as_ptr() as *mut u8
+    }
+}

src/stack.rs

@@ -4,6 +4,7 @@
 // http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
 // http://opensource.org/licenses/MIT>, at your option. This file may not be
 // copied, modified, or distributed except according to those terms.
+//! Traits for stacks.
 
 /// A trait for objects that hold ownership of a stack.
 pub trait Stack {
@@ -22,22 +23,3 @@ pub trait Stack {
 /// A guarded stack must guarantee that any access of data at addresses `limit()` to
 /// `limit().offset(4096)` will abnormally terminate the program.
 pub unsafe trait GuardedStack {}
-
-/// SliceStack holds a non-guarded stack allocated elsewhere and provided as a mutable
-/// slice.
-pub struct SliceStack<'a>(pub &'a mut [u8]);
-
-impl<'a> Stack for SliceStack<'a> {
-    #[inline(always)]
-    fn base(&self) -> *mut u8 {
-        // The slice cannot wrap around the address space, so the conversion from usize
-        // to isize will not wrap either.
-        let len: isize = self.0.len() as isize;
-        unsafe { self.limit().offset(len) }
-    }
-
-    #[inline(always)]
-    fn limit(&self) -> *mut u8 {
-        self.0.as_ptr() as *mut u8
-    }
-}

tests/generator.rs

@@ -6,17 +6,19 @@
 // copied, modified, or distributed except according to those terms.
 extern crate fringe;
 
-use fringe::{OsStack, SliceStack};
-use fringe::generator::Generator;
+use fringe::{Stack, SliceStack, OwnedStack, OsStack};
+use fringe::generator::{Generator, Yielder};
 
-fn new_add_one() -> Generator<i32, i32, OsStack> {
-  let stack = OsStack::new(0).unwrap();
-  Generator::new(stack, move |yielder, mut input| {
+fn add_one_fn<S: Stack>(yielder: &mut Yielder<i32, i32, S>, mut input: i32) {
   loop {
     if input == 0 { break }
     input = yielder.suspend(input + 1)
   }
-  })
+}
+
+fn new_add_one() -> Generator<i32, i32, OsStack> {
+  let stack = OsStack::new(0).unwrap();
+  Generator::new(stack, add_one_fn)
 }
 
 #[test]
@@ -67,14 +69,15 @@ fn panic_safety() {
 fn with_slice_stack() {
   let mut memory = [0; 1024];
   let stack = SliceStack(&mut memory);
-  let mut add_one = unsafe {
-    Generator::unsafe_new(stack, move |yielder, mut input| {
-      loop {
-        if input == 0 { break }
-        input = yielder.suspend(input + 1)
-      }
-    })
-  };
+  let mut add_one = unsafe { Generator::unsafe_new(stack, add_one_fn) };
+  assert_eq!(add_one.resume(1), Some(2));
+  assert_eq!(add_one.resume(2), Some(3));
+}
+
+#[test]
+fn with_owned_stack() {
+  let stack = OwnedStack::new(1024);
+  let mut add_one = unsafe { Generator::unsafe_new(stack, add_one_fn) };
   assert_eq!(add_one.resume(1), Some(2));
   assert_eq!(add_one.resume(2), Some(3));
 }

tests/stack.rs

@@ -6,7 +6,7 @@
 // copied, modified, or distributed except according to those terms.
 extern crate fringe;
 
-use fringe::{Stack, SliceStack, OsStack};
+use fringe::{Stack, SliceStack, OwnedStack, OsStack};
 
 #[test]
 fn slice_stack() {
@@ -15,6 +15,12 @@ fn slice_stack() {
     assert_eq!(stack.base() as isize - stack.limit() as isize, 1024);
 }
 
+#[test]
+fn owned_stack() {
+    let stack = OwnedStack::new(1024);
+    assert_eq!(stack.base() as isize - stack.limit() as isize, 1024);
+}
+
 #[test]
 fn default_os_stack() {
   let stack = OsStack::new(0).unwrap();