src/libarena/lib.rs - third_party/rust - Git at Google

 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
 // http://www.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.

 //! The arena, a fast but limited type of allocator.
 //!
 //! Arenas are a type of allocator that destroy the objects within, all at
 //! once, once the arena itself is destroyed. They do not support deallocation
 //! of individual objects while the arena itself is still alive. The benefit
 //! of an arena is very fast allocation; just a pointer bump.
 //!
 //! This crate has two arenas implemented: `TypedArena`, which is a simpler
 //! arena but can only hold objects of a single type, and `Arena`, which is a
 //! more complex, slower arena which can hold objects of any type.

 #![crate_name = "arena"]
 #![unstable(feature = "rustc_private", issue = "27812")]
 #![crate_type = "rlib"]
 #![crate_type = "dylib"]
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/",
        test(no_crate_inject, attr(deny(warnings))))]
 #![cfg_attr(not(stage0), deny(warnings))]

 #![feature(alloc)]
 #![feature(core_intrinsics)]
 #![feature(heap_api)]
 #![feature(heap_api)]
 #![feature(staged_api)]
 #![feature(dropck_parametricity)]
 #![cfg_attr(test, feature(test))]

 #![allow(deprecated)]

 extern crate alloc;

 use std::cell::{Cell, RefCell};
 use std::cmp;
 use std::intrinsics;
 use std::marker::{PhantomData, Send};
 use std::mem;
 use std::ptr;

 use alloc::heap;
 use alloc::raw_vec::RawVec;

 /// A faster arena that can hold objects of only one type.
 pub struct TypedArena<T> {
     /// A pointer to the next object to be allocated.
     ptr: Cell<*mut T>,

     /// A pointer to the end of the allocated area. When this pointer is
     /// reached, a new chunk is allocated.
     end: Cell<*mut T>,

     /// A vector arena segments.
     chunks: RefCell<Vec<TypedArenaChunk<T>>>,

     /// Marker indicating that dropping the arena causes its owned
     /// instances of `T` to be dropped.
     _own: PhantomData<T>,
 }

 struct TypedArenaChunk<T> {
     /// Pointer to the next arena segment.
     storage: RawVec<T>,
 }

 impl<T> TypedArenaChunk<T> {
     #[inline]
     unsafe fn new(capacity: usize) -> TypedArenaChunk<T> {
         TypedArenaChunk { storage: RawVec::with_capacity(capacity) }
     }

     /// Destroys this arena chunk.
     #[inline]
     unsafe fn destroy(&mut self, len: usize) {
         // The branch on needs_drop() is an -O1 performance optimization.
         // Without the branch, dropping TypedArena<u8> takes linear time.
         if intrinsics::needs_drop::<T>() {
             let mut start = self.start();
             // Destroy all allocated objects.
             for _ in 0..len {
                 ptr::drop_in_place(start);
                 start = start.offset(1);
             }
         }
     }

     // Returns a pointer to the first allocated object.
     #[inline]
     fn start(&self) -> *mut T {
         self.storage.ptr()
     }

     // Returns a pointer to the end of the allocated space.
     #[inline]
     fn end(&self) -> *mut T {
         unsafe {
             if mem::size_of::<T>() == 0 {
                 // A pointer as large as possible for zero-sized elements.
                 !0 as *mut T
             } else {
                 self.start().offset(self.storage.cap() as isize)
             }
         }
     }
 }

 const PAGE: usize = 4096;

 impl<T> TypedArena<T> {
     /// Creates a new `TypedArena` with preallocated space for many objects.
     #[inline]
     pub fn new() -> TypedArena<T> {
         // Reserve at least one page.
         let elem_size = cmp::max(1, mem::size_of::<T>());
         TypedArena::with_capacity(PAGE / elem_size)
     }

     /// Creates a new `TypedArena` with preallocated space for the given number of
     /// objects.
     #[inline]
     pub fn with_capacity(capacity: usize) -> TypedArena<T> {
         unsafe {
             let chunk = TypedArenaChunk::<T>::new(cmp::max(1, capacity));
             TypedArena {
                 ptr: Cell::new(chunk.start()),
                 end: Cell::new(chunk.end()),
                 chunks: RefCell::new(vec![chunk]),
                 _own: PhantomData,
             }
         }
     }

     /// Allocates an object in the `TypedArena`, returning a reference to it.
     #[inline]
     pub fn alloc(&self, object: T) -> &mut T {
         if self.ptr == self.end {
             self.grow()
         }

         unsafe {
             if mem::size_of::<T>() == 0 {
                 self.ptr.set(intrinsics::arith_offset(self.ptr.get() as *mut u8, 1) as *mut T);
                 let ptr = heap::EMPTY as *mut T;
                 // Don't drop the object. This `write` is equivalent to `forget`.
                 ptr::write(ptr, object);
                 &mut *ptr
             } else {
                 let ptr = self.ptr.get();
                 // Advance the pointer.
                 self.ptr.set(self.ptr.get().offset(1));
                 // Write into uninitialized memory.
                 ptr::write(ptr, object);
                 &mut *ptr
             }
         }
     }

     /// Grows the arena.
     #[inline(never)]
     #[cold]
     fn grow(&self) {
         unsafe {
             let mut chunks = self.chunks.borrow_mut();
             let prev_capacity = chunks.last().unwrap().storage.cap();
             let new_capacity = prev_capacity.checked_mul(2).unwrap();
             if chunks.last_mut().unwrap().storage.double_in_place() {
                 self.end.set(chunks.last().unwrap().end());
             } else {
                 let chunk = TypedArenaChunk::<T>::new(new_capacity);
                 self.ptr.set(chunk.start());
                 self.end.set(chunk.end());
                 chunks.push(chunk);
             }
         }
     }
     /// Clears the arena. Deallocates all but the longest chunk which may be reused.
     pub fn clear(&mut self) {
         unsafe {
             // Clear the last chunk, which is partially filled.
             let mut chunks_borrow = self.chunks.borrow_mut();
             let last_idx = chunks_borrow.len() - 1;
             self.clear_last_chunk(&mut chunks_borrow[last_idx]);
             // If `T` is ZST, code below has no effect.
             for mut chunk in chunks_borrow.drain(..last_idx) {
                 let cap = chunk.storage.cap();
                 chunk.destroy(cap);
             }
         }
     }

     // Drops the contents of the last chunk. The last chunk is partially empty, unlike all other
     // chunks.
     fn clear_last_chunk(&self, last_chunk: &mut TypedArenaChunk<T>) {
         // Determine how much was filled.
         let start = last_chunk.start() as usize;
         // We obtain the value of the pointer to the first uninitialized element.
         let end = self.ptr.get() as usize;
         // We then calculate the number of elements to be dropped in the last chunk,
         // which is the filled area's length.
         let diff = if mem::size_of::<T>() == 0 {
             // `T` is ZST. It can't have a drop flag, so the value here doesn't matter. We get
             // the number of zero-sized values in the last and only chunk, just out of caution.
             // Recall that `end` was incremented for each allocated value.
             end - start
         } else {
             (end - start) / mem::size_of::<T>()
         };
         // Pass that to the `destroy` method.
         unsafe {
             last_chunk.destroy(diff);
         }
         // Reset the chunk.
         self.ptr.set(last_chunk.start());
     }
 }

 impl<T> Drop for TypedArena<T> {
     #[unsafe_destructor_blind_to_params]
     fn drop(&mut self) {
         unsafe {
             // Determine how much was filled.
             let mut chunks_borrow = self.chunks.borrow_mut();
             let mut last_chunk = chunks_borrow.pop().unwrap();
             // Drop the contents of the last chunk.
             self.clear_last_chunk(&mut last_chunk);
             // The last chunk will be dropped. Destroy all other chunks.
             for chunk in chunks_borrow.iter_mut() {
                 let cap = chunk.storage.cap();
                 chunk.destroy(cap);
             }
             // RawVec handles deallocation of `last_chunk` and `self.chunks`.
         }
     }
 }

 unsafe impl<T: Send> Send for TypedArena<T> {}

 #[cfg(test)]
 mod tests {
     extern crate test;
     use self::test::Bencher;
     use super::TypedArena;
     use std::cell::Cell;

     #[allow(dead_code)]
     #[derive(Debug, Eq, PartialEq)]
     struct Point {
         x: i32,
         y: i32,
         z: i32,
     }

     #[test]
     fn test_arena_alloc_nested() {
         struct Inner {
             value: u8,
         }
         struct Outer<'a> {
             inner: &'a Inner,
         }
         enum EI<'e> {
             I(Inner),
             O(Outer<'e>),
         }

         struct Wrap<'a>(TypedArena<EI<'a>>);

         impl<'a> Wrap<'a> {
             fn alloc_inner<F: Fn() -> Inner>(&self, f: F) -> &Inner {
                 let r: &EI = self.0.alloc(EI::I(f()));
                 if let &EI::I(ref i) = r {
                     i
                 } else {
                     panic!("mismatch");
                 }
             }
             fn alloc_outer<F: Fn() -> Outer<'a>>(&self, f: F) -> &Outer {
                 let r: &EI = self.0.alloc(EI::O(f()));
                 if let &EI::O(ref o) = r {
                     o
                 } else {
                     panic!("mismatch");
                 }
             }
         }

         let arena = Wrap(TypedArena::new());

         let result = arena.alloc_outer(|| {
             Outer { inner: arena.alloc_inner(|| Inner { value: 10 }) }
         });

         assert_eq!(result.inner.value, 10);
     }

     #[test]
     pub fn test_copy() {
         let arena = TypedArena::new();
         for _ in 0..100000 {
             arena.alloc(Point { x: 1, y: 2, z: 3 });
         }
     }

     #[bench]
     pub fn bench_copy(b: &mut Bencher) {
         let arena = TypedArena::new();
         b.iter(|| arena.alloc(Point { x: 1, y: 2, z: 3 }))
     }

     #[bench]
     pub fn bench_copy_nonarena(b: &mut Bencher) {
         b.iter(|| {
             let _: Box<_> = Box::new(Point { x: 1, y: 2, z: 3 });
         })
     }

     #[allow(dead_code)]
     struct Noncopy {
         string: String,
         array: Vec<i32>,
     }

     #[test]
     pub fn test_noncopy() {
         let arena = TypedArena::new();
         for _ in 0..100000 {
             arena.alloc(Noncopy {
                 string: "hello world".to_string(),
                 array: vec![1, 2, 3, 4, 5],
             });
         }
     }

     #[test]
     pub fn test_typed_arena_zero_sized() {
         let arena = TypedArena::new();
         for _ in 0..100000 {
             arena.alloc(());
         }
     }

     #[test]
     pub fn test_typed_arena_clear() {
         let mut arena = TypedArena::new();
         for _ in 0..10 {
             arena.clear();
             for _ in 0..10000 {
                 arena.alloc(Point { x: 1, y: 2, z: 3 });
             }
         }
     }

     // Drop tests

     struct DropCounter<'a> {
         count: &'a Cell<u32>,
     }

     impl<'a> Drop for DropCounter<'a> {
         fn drop(&mut self) {
             self.count.set(self.count.get() + 1);
         }
     }

     #[test]
     fn test_typed_arena_drop_count() {
         let counter = Cell::new(0);
         {
             let arena: TypedArena<DropCounter> = TypedArena::new();
             for _ in 0..100 {
                 // Allocate something with drop glue to make sure it doesn't leak.
                 arena.alloc(DropCounter { count: &counter });
             }
         };
         assert_eq!(counter.get(), 100);
     }

     #[test]
     fn test_typed_arena_drop_on_clear() {
         let counter = Cell::new(0);
         let mut arena: TypedArena<DropCounter> = TypedArena::new();
         for i in 0..10 {
             for _ in 0..100 {
                 // Allocate something with drop glue to make sure it doesn't leak.
                 arena.alloc(DropCounter { count: &counter });
             }
             arena.clear();
             assert_eq!(counter.get(), i * 100 + 100);
         }
     }

     thread_local! {
         static DROP_COUNTER: Cell<u32> = Cell::new(0)
     }

     struct SmallDroppable;

     impl Drop for SmallDroppable {
         fn drop(&mut self) {
             DROP_COUNTER.with(|c| c.set(c.get() + 1));
         }
     }

     #[test]
     fn test_typed_arena_drop_small_count() {
         DROP_COUNTER.with(|c| c.set(0));
         {
             let arena: TypedArena<SmallDroppable> = TypedArena::new();
             for _ in 0..100 {
                 // Allocate something with drop glue to make sure it doesn't leak.
                 arena.alloc(SmallDroppable);
             }
             // dropping
         };
         assert_eq!(DROP_COUNTER.with(|c| c.get()), 100);
     }

     #[bench]
     pub fn bench_noncopy(b: &mut Bencher) {
         let arena = TypedArena::new();
         b.iter(|| {
             arena.alloc(Noncopy {
                 string: "hello world".to_string(),
                 array: vec![1, 2, 3, 4, 5],
             })
         })
     }

     #[bench]
     pub fn bench_noncopy_nonarena(b: &mut Bencher) {
         b.iter(|| {
             let _: Box<_> = Box::new(Noncopy {
                 string: "hello world".to_string(),
                 array: vec![1, 2, 3, 4, 5],
             });
         })
     }
 }
	// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
	// file at the top-level directory of this distribution and at
	// http://rust-lang.org/COPYRIGHT.
	//
	// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
	// http://www.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.

	//! The arena, a fast but limited type of allocator.
	//!
	//! Arenas are a type of allocator that destroy the objects within, all at
	//! once, once the arena itself is destroyed. They do not support deallocation
	//! of individual objects while the arena itself is still alive. The benefit
	//! of an arena is very fast allocation; just a pointer bump.
	//!
	//! This crate has two arenas implemented: `TypedArena`, which is a simpler
	//! arena but can only hold objects of a single type, and `Arena`, which is a
	//! more complex, slower arena which can hold objects of any type.

	#![crate_name = "arena"]
	#![unstable(feature = "rustc_private", issue = "27812")]
	#![crate_type = "rlib"]
	#![crate_type = "dylib"]
	#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
	html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
	html_root_url = "https://doc.rust-lang.org/nightly/",
	test(no_crate_inject, attr(deny(warnings))))]
	#![cfg_attr(not(stage0), deny(warnings))]

	#![feature(alloc)]
	#![feature(core_intrinsics)]
	#![feature(heap_api)]
	#![feature(heap_api)]
	#![feature(staged_api)]
	#![feature(dropck_parametricity)]
	#![cfg_attr(test, feature(test))]

	#![allow(deprecated)]

	extern crate alloc;

	use std::cell::{Cell, RefCell};
	use std::cmp;
	use std::intrinsics;
	use std::marker::{PhantomData, Send};
	use std::mem;
	use std::ptr;

	use alloc::heap;
	use alloc::raw_vec::RawVec;

	/// A faster arena that can hold objects of only one type.
	pub struct TypedArena<T> {
	/// A pointer to the next object to be allocated.
	ptr: Cell<*mut T>,

	/// A pointer to the end of the allocated area. When this pointer is
	/// reached, a new chunk is allocated.
	end: Cell<*mut T>,

	/// A vector arena segments.
	chunks: RefCell<Vec<TypedArenaChunk<T>>>,

	/// Marker indicating that dropping the arena causes its owned
	/// instances of `T` to be dropped.
	_own: PhantomData<T>,
	}

	struct TypedArenaChunk<T> {
	/// Pointer to the next arena segment.
	storage: RawVec<T>,
	}

	impl<T> TypedArenaChunk<T> {
	#[inline]
	unsafe fn new(capacity: usize) -> TypedArenaChunk<T> {
	TypedArenaChunk { storage: RawVec::with_capacity(capacity) }
	}

	/// Destroys this arena chunk.
	#[inline]
	unsafe fn destroy(&mut self, len: usize) {
	// The branch on needs_drop() is an -O1 performance optimization.
	// Without the branch, dropping TypedArena<u8> takes linear time.
	if intrinsics::needs_drop::<T>() {
	let mut start = self.start();
	// Destroy all allocated objects.
	for _ in 0..len {
	ptr::drop_in_place(start);
	start = start.offset(1);
	}
	}
	}

	// Returns a pointer to the first allocated object.
	#[inline]
	fn start(&self) -> *mut T {
	self.storage.ptr()
	}

	// Returns a pointer to the end of the allocated space.
	#[inline]
	fn end(&self) -> *mut T {
	unsafe {
	if mem::size_of::<T>() == 0 {
	// A pointer as large as possible for zero-sized elements.
	!0 as *mut T
	} else {
	self.start().offset(self.storage.cap() as isize)
	}
	}
	}
	}

	const PAGE: usize = 4096;

	impl<T> TypedArena<T> {
	/// Creates a new `TypedArena` with preallocated space for many objects.
	#[inline]
	pub fn new() -> TypedArena<T> {
	// Reserve at least one page.
	let elem_size = cmp::max(1, mem::size_of::<T>());
	TypedArena::with_capacity(PAGE / elem_size)
	}

	/// Creates a new `TypedArena` with preallocated space for the given number of
	/// objects.
	#[inline]
	pub fn with_capacity(capacity: usize) -> TypedArena<T> {
	unsafe {
	let chunk = TypedArenaChunk::<T>::new(cmp::max(1, capacity));
	TypedArena {
	ptr: Cell::new(chunk.start()),
	end: Cell::new(chunk.end()),
	chunks: RefCell::new(vec![chunk]),
	_own: PhantomData,
	}
	}
	}

	/// Allocates an object in the `TypedArena`, returning a reference to it.
	#[inline]
	pub fn alloc(&self, object: T) -> &mut T {
	if self.ptr == self.end {
	self.grow()
	}

	unsafe {
	if mem::size_of::<T>() == 0 {
	self.ptr.set(intrinsics::arith_offset(self.ptr.get() as mut u8, 1) as mut T);
	let ptr = heap::EMPTY as *mut T;
	// Don't drop the object. This `write` is equivalent to `forget`.
	ptr::write(ptr, object);
	&mut *ptr
	} else {
	let ptr = self.ptr.get();
	// Advance the pointer.
	self.ptr.set(self.ptr.get().offset(1));
	// Write into uninitialized memory.
	ptr::write(ptr, object);
	&mut *ptr
	}
	}
	}

	/// Grows the arena.
	#[inline(never)]
	#[cold]
	fn grow(&self) {
	unsafe {
	let mut chunks = self.chunks.borrow_mut();
	let prev_capacity = chunks.last().unwrap().storage.cap();
	let new_capacity = prev_capacity.checked_mul(2).unwrap();
	if chunks.last_mut().unwrap().storage.double_in_place() {
	self.end.set(chunks.last().unwrap().end());
	} else {
	let chunk = TypedArenaChunk::<T>::new(new_capacity);
	self.ptr.set(chunk.start());
	self.end.set(chunk.end());
	chunks.push(chunk);
	}
	}
	}
	/// Clears the arena. Deallocates all but the longest chunk which may be reused.
	pub fn clear(&mut self) {
	unsafe {
	// Clear the last chunk, which is partially filled.
	let mut chunks_borrow = self.chunks.borrow_mut();
	let last_idx = chunks_borrow.len() - 1;
	self.clear_last_chunk(&mut chunks_borrow[last_idx]);
	// If `T` is ZST, code below has no effect.
	for mut chunk in chunks_borrow.drain(..last_idx) {
	let cap = chunk.storage.cap();
	chunk.destroy(cap);
	}
	}
	}

	// Drops the contents of the last chunk. The last chunk is partially empty, unlike all other
	// chunks.
	fn clear_last_chunk(&self, last_chunk: &mut TypedArenaChunk<T>) {
	// Determine how much was filled.
	let start = last_chunk.start() as usize;
	// We obtain the value of the pointer to the first uninitialized element.
	let end = self.ptr.get() as usize;
	// We then calculate the number of elements to be dropped in the last chunk,
	// which is the filled area's length.
	let diff = if mem::size_of::<T>() == 0 {
	// `T` is ZST. It can't have a drop flag, so the value here doesn't matter. We get
	// the number of zero-sized values in the last and only chunk, just out of caution.
	// Recall that `end` was incremented for each allocated value.
	end - start
	} else {
	(end - start) / mem::size_of::<T>()
	};
	// Pass that to the `destroy` method.
	unsafe {
	last_chunk.destroy(diff);
	}
	// Reset the chunk.
	self.ptr.set(last_chunk.start());
	}
	}

	impl<T> Drop for TypedArena<T> {
	#[unsafe_destructor_blind_to_params]
	fn drop(&mut self) {
	unsafe {
	// Determine how much was filled.
	let mut chunks_borrow = self.chunks.borrow_mut();
	let mut last_chunk = chunks_borrow.pop().unwrap();
	// Drop the contents of the last chunk.
	self.clear_last_chunk(&mut last_chunk);
	// The last chunk will be dropped. Destroy all other chunks.
	for chunk in chunks_borrow.iter_mut() {
	let cap = chunk.storage.cap();
	chunk.destroy(cap);
	}
	// RawVec handles deallocation of `last_chunk` and `self.chunks`.
	}
	}
	}

	unsafe impl<T: Send> Send for TypedArena<T> {}

	#[cfg(test)]
	mod tests {
	extern crate test;
	use self::test::Bencher;
	use super::TypedArena;
	use std::cell::Cell;

	#[allow(dead_code)]
	#[derive(Debug, Eq, PartialEq)]
	struct Point {
	x: i32,
	y: i32,
	z: i32,
	}

	#[test]
	fn test_arena_alloc_nested() {
	struct Inner {
	value: u8,
	}
	struct Outer<'a> {
	inner: &'a Inner,
	}
	enum EI<'e> {
	I(Inner),
	O(Outer<'e>),
	}

	struct Wrap<'a>(TypedArena<EI<'a>>);

	impl<'a> Wrap<'a> {
	fn alloc_inner<F: Fn() -> Inner>(&self, f: F) -> &Inner {
	let r: &EI = self.0.alloc(EI::I(f()));
	if let &EI::I(ref i) = r {
	i
	} else {
	panic!("mismatch");
	}
	}
	fn alloc_outer<F: Fn() -> Outer<'a>>(&self, f: F) -> &Outer {
	let r: &EI = self.0.alloc(EI::O(f()));
	if let &EI::O(ref o) = r {
	o
	} else {
	panic!("mismatch");
	}
	}
	}

	let arena = Wrap(TypedArena::new());

	let result = arena.alloc_outer(\|\| {
	Outer { inner: arena.alloc_inner(\|\| Inner { value: 10 }) }
	});

	assert_eq!(result.inner.value, 10);
	}

	#[test]
	pub fn test_copy() {
	let arena = TypedArena::new();
	for _ in 0..100000 {
	arena.alloc(Point { x: 1, y: 2, z: 3 });
	}
	}

	#[bench]
	pub fn bench_copy(b: &mut Bencher) {
	let arena = TypedArena::new();
	b.iter(\|\| arena.alloc(Point { x: 1, y: 2, z: 3 }))
	}

	#[bench]
	pub fn bench_copy_nonarena(b: &mut Bencher) {
	b.iter(\|\| {
	let _: Box<_> = Box::new(Point { x: 1, y: 2, z: 3 });
	})
	}

	#[allow(dead_code)]
	struct Noncopy {
	string: String,
	array: Vec<i32>,
	}

	#[test]
	pub fn test_noncopy() {
	let arena = TypedArena::new();
	for _ in 0..100000 {
	arena.alloc(Noncopy {
	string: "hello world".to_string(),
	array: vec![1, 2, 3, 4, 5],
	});
	}
	}

	#[test]
	pub fn test_typed_arena_zero_sized() {
	let arena = TypedArena::new();
	for _ in 0..100000 {
	arena.alloc(());
	}
	}

	#[test]
	pub fn test_typed_arena_clear() {
	let mut arena = TypedArena::new();
	for _ in 0..10 {
	arena.clear();
	for _ in 0..10000 {
	arena.alloc(Point { x: 1, y: 2, z: 3 });
	}
	}
	}

	// Drop tests

	struct DropCounter<'a> {
	count: &'a Cell<u32>,
	}

	impl<'a> Drop for DropCounter<'a> {
	fn drop(&mut self) {
	self.count.set(self.count.get() + 1);
	}
	}

	#[test]
	fn test_typed_arena_drop_count() {
	let counter = Cell::new(0);
	{
	let arena: TypedArena<DropCounter> = TypedArena::new();
	for _ in 0..100 {
	// Allocate something with drop glue to make sure it doesn't leak.
	arena.alloc(DropCounter { count: &counter });
	}
	};
	assert_eq!(counter.get(), 100);
	}

	#[test]
	fn test_typed_arena_drop_on_clear() {
	let counter = Cell::new(0);
	let mut arena: TypedArena<DropCounter> = TypedArena::new();
	for i in 0..10 {
	for _ in 0..100 {
	// Allocate something with drop glue to make sure it doesn't leak.
	arena.alloc(DropCounter { count: &counter });
	}
	arena.clear();
	assert_eq!(counter.get(), i * 100 + 100);
	}
	}

	thread_local! {
	static DROP_COUNTER: Cell<u32> = Cell::new(0)
	}

	struct SmallDroppable;

	impl Drop for SmallDroppable {
	fn drop(&mut self) {
	DROP_COUNTER.with(\|c\| c.set(c.get() + 1));
	}
	}

	#[test]
	fn test_typed_arena_drop_small_count() {
	DROP_COUNTER.with(\|c\| c.set(0));
	{
	let arena: TypedArena<SmallDroppable> = TypedArena::new();
	for _ in 0..100 {
	// Allocate something with drop glue to make sure it doesn't leak.
	arena.alloc(SmallDroppable);
	}
	// dropping
	};
	assert_eq!(DROP_COUNTER.with(\|c\| c.get()), 100);
	}

	#[bench]
	pub fn bench_noncopy(b: &mut Bencher) {
	let arena = TypedArena::new();
	b.iter(\|\| {
	arena.alloc(Noncopy {
	string: "hello world".to_string(),
	array: vec![1, 2, 3, 4, 5],
	})
	})
	}

	#[bench]
	pub fn bench_noncopy_nonarena(b: &mut Bencher) {
	b.iter(\|\| {
	let _: Box<_> = Box::new(Noncopy {
	string: "hello world".to_string(),
	array: vec![1, 2, 3, 4, 5],
	});
	})
	}
	}