1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
// Copyright 2016-2017 The Servo 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.

//! A crate for measuring the heap usage of data structures in a way that
//! integrates with Firefox's memory reporting, particularly the use of
//! mozjemalloc and DMD. In particular, it has the following features.
//! - It isn't bound to a particular heap allocator.
//! - It provides traits for both "shallow" and "deep" measurement, which gives
//!   flexibility in the cases where the traits can't be used.
//! - It allows for measuring blocks even when only an interior pointer can be
//!   obtained for heap allocations, e.g. `HashSet` and `HashMap`. (This relies
//!   on the heap allocator having suitable support, which mozjemalloc has.)
//! - It allows handling of types like `Rc` and `Arc` by providing traits that
//!   are different to the ones for non-graph structures.
//!
//! Suggested uses are as follows.
//! - When possible, use the `MallocSizeOf` trait. (Deriving support is
//!   provided by the `malloc_size_of_derive` crate.)
//! - If you need an additional synchronization argument, provide a function
//!   that is like the standard trait method, but with the extra argument.
//! - If you need multiple measurements for a type, provide a function named
//!   `add_size_of` that takes a mutable reference to a struct that contains
//!   the multiple measurement fields.
//! - When deep measurement (via `MallocSizeOf`) cannot be implemented for a
//!   type, shallow measurement (via `MallocShallowSizeOf`) in combination with
//!   iteration can be a useful substitute.
//! - `Rc` and `Arc` are always tricky, which is why `MallocSizeOf` is not (and
//!   should not be) implemented for them.
//! - If an `Rc` or `Arc` is known to be a "primary" reference and can always
//!   be measured, it should be measured via the `MallocUnconditionalSizeOf`
//!   trait.
//! - If an `Rc` or `Arc` should be measured only if it hasn't been seen
//!   before, it should be measured via the `MallocConditionalSizeOf` trait.
//! - Using universal function call syntax is a good idea when measuring boxed
//!   fields in structs, because it makes it clear that the Box is being
//!   measured as well as the thing it points to. E.g.
//!   `<Box<_> as MallocSizeOf>::size_of(field, ops)`.

//! This is an extended version of the Servo internal malloc_size crate.
//! We should occasionally track the upstream changes/fixes and reintroduce them here, whenever applicable.

#[cfg(not(feature = "std"))]
use alloc::vec::Vec;
#[cfg(feature = "std")]
mod rstd {
	pub use std::*;
}
#[cfg(not(feature = "std"))]
mod rstd {
	pub use core::*;
	pub mod collections {
		pub use alloc::collections::*;
		pub use vec_deque::VecDeque;
	}
}

#[cfg(feature = "std")]
use std::sync::Arc;

#[cfg(not(feature = "std"))]
pub use alloc::boxed::Box;
#[cfg(not(feature = "std"))]
use core::ffi::c_void;
#[cfg(feature = "std")]
use rstd::hash::Hash;
use rstd::marker::PhantomData;
use rstd::mem::size_of;
use rstd::ops::Range;
use rstd::ops::{Deref, DerefMut};
#[cfg(feature = "std")]
use std::hash::BuildHasher;
#[cfg(feature = "std")]
use std::os::raw::c_void;

/// A C function that takes a pointer to a heap allocation and returns its size.
pub type VoidPtrToSizeFn = unsafe extern "C" fn(ptr: *const c_void) -> usize;

/// A closure implementing a stateful predicate on pointers.
pub type VoidPtrToBoolFnMut = dyn FnMut(*const c_void) -> bool;

/// Operations used when measuring heap usage of data structures.
pub struct MallocSizeOfOps {
	/// A function that returns the size of a heap allocation.
	size_of_op: VoidPtrToSizeFn,

	/// Like `size_of_op`, but can take an interior pointer. Optional because
	/// not all allocators support this operation. If it's not provided, some
	/// memory measurements will actually be computed estimates rather than
	/// real and accurate measurements.
	enclosing_size_of_op: Option<VoidPtrToSizeFn>,

	/// Check if a pointer has been seen before, and remember it for next time.
	/// Useful when measuring `Rc`s and `Arc`s. Optional, because many places
	/// don't need it.
	have_seen_ptr_op: Option<Box<VoidPtrToBoolFnMut>>,
}

impl MallocSizeOfOps {
	pub fn new(
		size_of: VoidPtrToSizeFn,
		malloc_enclosing_size_of: Option<VoidPtrToSizeFn>,
		have_seen_ptr: Option<Box<VoidPtrToBoolFnMut>>,
	) -> Self {
		MallocSizeOfOps {
			size_of_op: size_of,
			enclosing_size_of_op: malloc_enclosing_size_of,
			have_seen_ptr_op: have_seen_ptr,
		}
	}

	/// Check if an allocation is empty. This relies on knowledge of how Rust
	/// handles empty allocations, which may change in the future.
	fn is_empty<T: ?Sized>(ptr: *const T) -> bool {
		// The correct condition is this:
		//   `ptr as usize <= ::std::mem::align_of::<T>()`
		// But we can't call align_of() on a ?Sized T. So we approximate it
		// with the following. 256 is large enough that it should always be
		// larger than the required alignment, but small enough that it is
		// always in the first page of memory and therefore not a legitimate
		// address.
		return ptr as *const usize as usize <= 256;
	}

	/// Call `size_of_op` on `ptr`, first checking that the allocation isn't
	/// empty, because some types (such as `Vec`) utilize empty allocations.
	pub unsafe fn malloc_size_of<T: ?Sized>(&self, ptr: *const T) -> usize {
		if MallocSizeOfOps::is_empty(ptr) {
			0
		} else {
			(self.size_of_op)(ptr as *const c_void)
		}
	}

	/// Is an `enclosing_size_of_op` available?
	pub fn has_malloc_enclosing_size_of(&self) -> bool {
		self.enclosing_size_of_op.is_some()
	}

	/// Call `enclosing_size_of_op`, which must be available, on `ptr`, which
	/// must not be empty.
	pub unsafe fn malloc_enclosing_size_of<T>(&self, ptr: *const T) -> usize {
		assert!(!MallocSizeOfOps::is_empty(ptr));
		(self.enclosing_size_of_op.unwrap())(ptr as *const c_void)
	}

	/// Call `have_seen_ptr_op` on `ptr`.
	pub fn have_seen_ptr<T>(&mut self, ptr: *const T) -> bool {
		let have_seen_ptr_op = self.have_seen_ptr_op.as_mut().expect("missing have_seen_ptr_op");
		have_seen_ptr_op(ptr as *const c_void)
	}
}

/// Trait for measuring the "deep" heap usage of a data structure. This is the
/// most commonly-used of the traits.
pub trait MallocSizeOf {
	/// Measure the heap usage of all descendant heap-allocated structures, but
	/// not the space taken up by the value itself.
	/// If `T::size_of` is a constant, consider implementing `constant_size` as well.
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize;

	/// Used to optimize `MallocSizeOf` implementation for collections
	/// like `Vec` and `HashMap` to avoid iterating over them unnecessarily.
	/// The `Self: Sized` bound is for object safety.
	fn constant_size() -> Option<usize>
	where
		Self: Sized,
	{
		None
	}
}

/// Trait for measuring the "shallow" heap usage of a container.
pub trait MallocShallowSizeOf {
	/// Measure the heap usage of immediate heap-allocated descendant
	/// structures, but not the space taken up by the value itself. Anything
	/// beyond the immediate descendants must be measured separately, using
	/// iteration.
	fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize;
}

/// Like `MallocSizeOf`, but with a different name so it cannot be used
/// accidentally with derive(MallocSizeOf). For use with types like `Rc` and
/// `Arc` when appropriate (e.g. when measuring a "primary" reference).
pub trait MallocUnconditionalSizeOf {
	/// Measure the heap usage of all heap-allocated descendant structures, but
	/// not the space taken up by the value itself.
	fn unconditional_size_of(&self, ops: &mut MallocSizeOfOps) -> usize;
}

/// `MallocUnconditionalSizeOf` combined with `MallocShallowSizeOf`.
pub trait MallocUnconditionalShallowSizeOf {
	/// `unconditional_size_of` combined with `shallow_size_of`.
	fn unconditional_shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize;
}

/// Like `MallocSizeOf`, but only measures if the value hasn't already been
/// measured. For use with types like `Rc` and `Arc` when appropriate (e.g.
/// when there is no "primary" reference).
pub trait MallocConditionalSizeOf {
	/// Measure the heap usage of all heap-allocated descendant structures, but
	/// not the space taken up by the value itself, and only if that heap usage
	/// hasn't already been measured.
	fn conditional_size_of(&self, ops: &mut MallocSizeOfOps) -> usize;
}

/// `MallocConditionalSizeOf` combined with `MallocShallowSizeOf`.
pub trait MallocConditionalShallowSizeOf {
	/// `conditional_size_of` combined with `shallow_size_of`.
	fn conditional_shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize;
}

#[cfg(not(any(all(target_os = "macos", not(feature = "jemalloc-global"),), feature = "estimate-heapsize")))]
pub mod inner_allocator_use {

	use super::*;

	#[cfg(not(feature = "std"))]
	use alloc::string::String;

	impl<T: ?Sized> MallocShallowSizeOf for Box<T> {
		fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
			unsafe { ops.malloc_size_of(&**self) }
		}
	}

	impl<T> MallocShallowSizeOf for Vec<T> {
		fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
			unsafe { ops.malloc_size_of(self.as_ptr()) }
		}
	}

	// currently this seems only fine with jemalloc
	#[cfg(feature = "std")]
	#[cfg(all(feature = "jemalloc-global", not(target_os = "windows")))]
	impl<T> MallocUnconditionalShallowSizeOf for Arc<T> {
		fn unconditional_shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
			unsafe { ops.malloc_size_of(arc_ptr(self)) }
		}
	}

	#[cfg(feature = "std")]
	#[cfg(not(all(feature = "jemalloc-global", not(target_os = "windows"))))]
	impl<T> MallocUnconditionalShallowSizeOf for Arc<T> {
		fn unconditional_shallow_size_of(&self, _ops: &mut MallocSizeOfOps) -> usize {
			size_of::<T>()
		}
	}

	impl MallocSizeOf for String {
		fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
			unsafe { ops.malloc_size_of(self.as_ptr()) }
		}
	}
}

impl<'a, T: ?Sized> MallocSizeOf for &'a T {
	fn size_of(&self, _ops: &mut MallocSizeOfOps) -> usize {
		// Zero makes sense for a non-owning reference.
		0
	}
	fn constant_size() -> Option<usize> {
		Some(0)
	}
}

impl<T: MallocSizeOf + ?Sized> MallocSizeOf for Box<T> {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		self.shallow_size_of(ops) + (**self).size_of(ops)
	}
}

#[impl_trait_for_tuples::impl_for_tuples(12)]
impl MallocSizeOf for Tuple {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		let mut result = 0;
		for_tuples!( #( result += Tuple.size_of(ops); )* );
		result
	}
	fn constant_size() -> Option<usize> {
		let mut result = Some(0);
		for_tuples!( #( result = result.and_then(|s| Tuple::constant_size().map(|t| s + t)); )* );
		result
	}
}

impl<T: MallocSizeOf> MallocSizeOf for Option<T> {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		if let Some(val) = self.as_ref() {
			val.size_of(ops)
		} else {
			0
		}
	}
	fn constant_size() -> Option<usize> {
		T::constant_size().filter(|s| *s == 0)
	}
}

impl<T: MallocSizeOf, E: MallocSizeOf> MallocSizeOf for Result<T, E> {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		match *self {
			Ok(ref x) => x.size_of(ops),
			Err(ref e) => e.size_of(ops),
		}
	}
	fn constant_size() -> Option<usize> {
		// Result<T, E> has constant size iff T::constant_size == E::constant_size
		T::constant_size().and_then(|t| E::constant_size().filter(|e| *e == t))
	}
}

impl<T: MallocSizeOf + Copy> MallocSizeOf for rstd::cell::Cell<T> {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		self.get().size_of(ops)
	}
	fn constant_size() -> Option<usize> {
		T::constant_size()
	}
}

impl<T: MallocSizeOf> MallocSizeOf for rstd::cell::RefCell<T> {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		self.borrow().size_of(ops)
	}
	fn constant_size() -> Option<usize> {
		T::constant_size()
	}
}

#[cfg(feature = "std")]
impl<'a, B: ?Sized + ToOwned> MallocSizeOf for std::borrow::Cow<'a, B>
where
	B::Owned: MallocSizeOf,
{
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		match *self {
			std::borrow::Cow::Borrowed(_) => 0,
			std::borrow::Cow::Owned(ref b) => b.size_of(ops),
		}
	}
}

impl<T: MallocSizeOf> MallocSizeOf for [T] {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		let mut n = 0;
		if let Some(t) = T::constant_size() {
			n += self.len() * t;
		} else {
			n = self.iter().fold(n, |acc, elem| acc + elem.size_of(ops))
		}
		n
	}
}

impl<T: MallocSizeOf> MallocSizeOf for Vec<T> {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		let mut n = self.shallow_size_of(ops);
		if let Some(t) = T::constant_size() {
			n += self.len() * t;
		} else {
			n = self.iter().fold(n, |acc, elem| acc + elem.size_of(ops))
		}
		n
	}
}

impl<T> MallocShallowSizeOf for rstd::collections::VecDeque<T> {
	fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		if ops.has_malloc_enclosing_size_of() {
			if let Some(front) = self.front() {
				// The front element is an interior pointer.
				unsafe { ops.malloc_enclosing_size_of(&*front) }
			} else {
				// This assumes that no memory is allocated when the VecDeque is empty.
				0
			}
		} else {
			// An estimate.
			self.capacity() * size_of::<T>()
		}
	}
}

impl<T: MallocSizeOf> MallocSizeOf for rstd::collections::VecDeque<T> {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		let mut n = self.shallow_size_of(ops);
		if let Some(t) = T::constant_size() {
			n += self.len() * t;
		} else {
			n = self.iter().fold(n, |acc, elem| acc + elem.size_of(ops))
		}
		n
	}
}

#[cfg(feature = "std")]
impl<T, S> MallocShallowSizeOf for std::collections::HashSet<T, S>
where
	T: Eq + Hash,
	S: BuildHasher,
{
	fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		if ops.has_malloc_enclosing_size_of() {
			// The first value from the iterator gives us an interior pointer.
			// `ops.malloc_enclosing_size_of()` then gives us the storage size.
			// This assumes that the `HashSet`'s contents (values and hashes)
			// are all stored in a single contiguous heap allocation.
			self.iter().next().map_or(0, |t| unsafe { ops.malloc_enclosing_size_of(t) })
		} else {
			// An estimate.
			self.capacity() * (size_of::<T>() + size_of::<usize>())
		}
	}
}

#[cfg(feature = "std")]
impl<T, S> MallocSizeOf for std::collections::HashSet<T, S>
where
	T: Eq + Hash + MallocSizeOf,
	S: BuildHasher,
{
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		let mut n = self.shallow_size_of(ops);
		if let Some(t) = T::constant_size() {
			n += self.len() * t;
		} else {
			n = self.iter().fold(n, |acc, elem| acc + elem.size_of(ops))
		}
		n
	}
}

impl<I: MallocSizeOf> MallocSizeOf for rstd::cmp::Reverse<I> {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		self.0.size_of(ops)
	}
	fn constant_size() -> Option<usize> {
		I::constant_size()
	}
}

#[cfg(feature = "std")]
impl<K, V, S> MallocShallowSizeOf for std::collections::HashMap<K, V, S> {
	fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		// See the implementation for std::collections::HashSet for details.
		if ops.has_malloc_enclosing_size_of() {
			self.values().next().map_or(0, |v| unsafe { ops.malloc_enclosing_size_of(v) })
		} else {
			self.capacity() * (size_of::<V>() + size_of::<K>() + size_of::<usize>())
		}
	}
}

#[cfg(feature = "std")]
impl<K, V, S> MallocSizeOf for std::collections::HashMap<K, V, S>
where
	K: MallocSizeOf,
	V: MallocSizeOf,
{
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		let mut n = self.shallow_size_of(ops);
		if let (Some(k), Some(v)) = (K::constant_size(), V::constant_size()) {
			n += self.len() * (k + v)
		} else {
			n = self.iter().fold(n, |acc, (k, v)| acc + k.size_of(ops) + v.size_of(ops))
		}
		n
	}
}

impl<K, V> MallocShallowSizeOf for rstd::collections::BTreeMap<K, V> {
	fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		if ops.has_malloc_enclosing_size_of() {
			self.values().next().map_or(0, |v| unsafe { ops.malloc_enclosing_size_of(v) })
		} else {
			self.len() * (size_of::<V>() + size_of::<K>() + size_of::<usize>())
		}
	}
}

impl<K, V> MallocSizeOf for rstd::collections::BTreeMap<K, V>
where
	K: MallocSizeOf,
	V: MallocSizeOf,
{
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		let mut n = self.shallow_size_of(ops);
		if let (Some(k), Some(v)) = (K::constant_size(), V::constant_size()) {
			n += self.len() * (k + v)
		} else {
			n = self.iter().fold(n, |acc, (k, v)| acc + k.size_of(ops) + v.size_of(ops))
		}
		n
	}
}

impl<T> MallocShallowSizeOf for rstd::collections::BTreeSet<T> {
	fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		if ops.has_malloc_enclosing_size_of() {
			// See implementation for HashSet how this works.
			self.iter().next().map_or(0, |t| unsafe { ops.malloc_enclosing_size_of(t) })
		} else {
			// An estimate.
			self.len() * (size_of::<T>() + size_of::<usize>())
		}
	}
}

impl<T> MallocSizeOf for rstd::collections::BTreeSet<T>
where
	T: MallocSizeOf,
{
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		let mut n = self.shallow_size_of(ops);
		if let Some(t) = T::constant_size() {
			n += self.len() * t;
		} else {
			n = self.iter().fold(n, |acc, elem| acc + elem.size_of(ops))
		}
		n
	}
}

// XXX: we don't want MallocSizeOf to be defined for Rc and Arc. If negative
// trait bounds are ever allowed, this code should be uncommented.
// (We do have a compile-fail test for this:
// rc_arc_must_not_derive_malloc_size_of.rs)
//impl<T> !MallocSizeOf for Arc<T> { }
//impl<T> !MallocShallowSizeOf for Arc<T> { }

#[cfg(feature = "std")]
fn arc_ptr<T>(s: &Arc<T>) -> *const T {
	&(**s) as *const T
}

#[cfg(feature = "std")]
impl<T: MallocSizeOf> MallocUnconditionalSizeOf for Arc<T> {
	fn unconditional_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		self.unconditional_shallow_size_of(ops) + (**self).size_of(ops)
	}
}

#[cfg(feature = "std")]
impl<T> MallocConditionalShallowSizeOf for Arc<T> {
	fn conditional_shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		if ops.have_seen_ptr(arc_ptr(self)) {
			0
		} else {
			self.unconditional_shallow_size_of(ops)
		}
	}
}

#[cfg(feature = "std")]
impl<T: MallocSizeOf> MallocConditionalSizeOf for Arc<T> {
	fn conditional_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		if ops.have_seen_ptr(arc_ptr(self)) {
			0
		} else {
			self.unconditional_size_of(ops)
		}
	}
}

/// If a mutex is stored directly as a member of a data type that is being measured,
/// it is the unique owner of its contents and deserves to be measured.
///
/// If a mutex is stored inside of an Arc value as a member of a data type that is being measured,
/// the Arc will not be automatically measured so there is no risk of overcounting the mutex's
/// contents.
///
/// The same reasoning applies to RwLock.
#[cfg(feature = "std")]
impl<T: MallocSizeOf> MallocSizeOf for std::sync::Mutex<T> {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		self.lock().unwrap().size_of(ops)
	}
}

#[cfg(feature = "std")]
impl<T: MallocSizeOf> MallocSizeOf for parking_lot::Mutex<T> {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		self.lock().size_of(ops)
	}
}

#[cfg(feature = "std")]
impl<T: MallocSizeOf> MallocSizeOf for std::sync::RwLock<T> {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		self.read().unwrap().size_of(ops)
	}
}

#[cfg(feature = "std")]
impl<T: MallocSizeOf> MallocSizeOf for parking_lot::RwLock<T> {
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		self.read().size_of(ops)
	}
}

/// Implement notion of 0 allocation size for some type(s).
///
/// if used for generics, by default it will require that generaic arguments
/// should implement `MallocSizeOf`. This can be avoided with passing "any: "
/// in front of type list.
///
/// ```rust
/// use parity_util_mem::{malloc_size, malloc_size_of_is_0};
///
/// struct Data<P> {
/// 	phantom: std::marker::PhantomData<P>,
/// }
///
/// malloc_size_of_is_0!(any: Data<P>);
///
/// // MallocSizeOf is NOT implemented for [u8; 333]
/// assert_eq!(malloc_size(&Data::<[u8; 333]> { phantom: std::marker::PhantomData }), 0);
/// ```
///
/// and when no "any: "
///
/// ```rust
/// use parity_util_mem::{malloc_size, malloc_size_of_is_0};
///
/// struct Data<T>(pub T);
///
/// // generic argument (`T`) must be `impl MallocSizeOf`
/// malloc_size_of_is_0!(Data<u8>);
///
/// assert_eq!(malloc_size(&Data(0u8)), 0);
/// ```
#[macro_export]
macro_rules! malloc_size_of_is_0(
	($($ty:ty),+) => (
		$(
			impl $crate::MallocSizeOf for $ty {
				#[inline(always)]
				fn size_of(&self, _: &mut $crate::MallocSizeOfOps) -> usize {
					0
				}
				#[inline(always)]
				fn constant_size() -> Option<usize> { Some(0) }
			}
		)+
	);
	(any: $($ty:ident<$($gen:ident),+>),+) => (
		$(
			impl<$($gen),+> $crate::MallocSizeOf for $ty<$($gen),+> {
				#[inline(always)]
				fn size_of(&self, _: &mut $crate::MallocSizeOfOps) -> usize {
					0
				}
				#[inline(always)]
				fn constant_size() -> Option<usize> { Some(0) }
			}
		)+
	);
	($($ty:ident<$($gen:ident),+>),+) => (
		$(
			impl<$($gen: $crate::MallocSizeOf),+> $crate::MallocSizeOf for $ty<$($gen),+> {
				#[inline(always)]
				fn size_of(&self, _: &mut $crate::MallocSizeOfOps) -> usize {
					0
				}
				#[inline(always)]
				fn constant_size() -> Option<usize> { Some(0) }
			}
		)+
	);
);

malloc_size_of_is_0!(bool, char, str);
malloc_size_of_is_0!(u8, u16, u32, u64, u128, usize);
malloc_size_of_is_0!(i8, i16, i32, i64, i128, isize);
malloc_size_of_is_0!(f32, f64);

malloc_size_of_is_0!(rstd::sync::atomic::AtomicBool);
malloc_size_of_is_0!(rstd::sync::atomic::AtomicIsize);
malloc_size_of_is_0!(rstd::sync::atomic::AtomicUsize);

malloc_size_of_is_0!(Range<u8>, Range<u16>, Range<u32>, Range<u64>, Range<usize>);
malloc_size_of_is_0!(Range<i8>, Range<i16>, Range<i32>, Range<i64>, Range<isize>);
malloc_size_of_is_0!(Range<f32>, Range<f64>);
malloc_size_of_is_0!(any: PhantomData<T>);

/// Measurable that defers to inner value and used to verify MallocSizeOf implementation in a
/// struct.
#[derive(Clone)]
pub struct Measurable<T: MallocSizeOf>(pub T);

impl<T: MallocSizeOf> Deref for Measurable<T> {
	type Target = T;

	fn deref(&self) -> &T {
		&self.0
	}
}

impl<T: MallocSizeOf> DerefMut for Measurable<T> {
	fn deref_mut(&mut self) -> &mut T {
		&mut self.0
	}
}

#[cfg(feature = "hashbrown")]
impl<K, V, S> MallocShallowSizeOf for hashbrown::HashMap<K, V, S> {
	fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		// See the implementation for std::collections::HashSet for details.
		if ops.has_malloc_enclosing_size_of() {
			self.values().next().map_or(0, |v| unsafe { ops.malloc_enclosing_size_of(v) })
		} else {
			self.capacity() * (size_of::<V>() + size_of::<K>() + size_of::<usize>())
		}
	}
}

#[cfg(feature = "hashbrown")]
impl<K, V, S> MallocSizeOf for hashbrown::HashMap<K, V, S>
where
	K: MallocSizeOf,
	V: MallocSizeOf,
{
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		let mut n = self.shallow_size_of(ops);
		if let (Some(k), Some(v)) = (K::constant_size(), V::constant_size()) {
			n += self.len() * (k + v)
		} else {
			n = self.iter().fold(n, |acc, (k, v)| acc + k.size_of(ops) + v.size_of(ops))
		}
		n
	}
}

#[cfg(feature = "lru")]
impl<K, V, S> MallocSizeOf for lru::LruCache<K, V, S>
where
	K: MallocSizeOf + rstd::cmp::Eq + rstd::hash::Hash,
	V: MallocSizeOf,
	S: rstd::hash::BuildHasher,
{
	fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
		let mut n = 0;
		if let (Some(k), Some(v)) = (K::constant_size(), V::constant_size()) {
			n += self.len() * (k + v)
		} else {
			n = self.iter().fold(n, |acc, (k, v)| acc + k.size_of(ops) + v.size_of(ops))
		}
		n
	}
}

malloc_size_of_is_0!(
	[u8; 1], [u8; 2], [u8; 3], [u8; 4], [u8; 5], [u8; 6], [u8; 7], [u8; 8], [u8; 9], [u8; 10], [u8; 11], [u8; 12],
	[u8; 13], [u8; 14], [u8; 15], [u8; 16], [u8; 17], [u8; 18], [u8; 19], [u8; 20], [u8; 21], [u8; 22], [u8; 23],
	[u8; 24], [u8; 25], [u8; 26], [u8; 27], [u8; 28], [u8; 29], [u8; 30], [u8; 31], [u8; 32]
);

macro_rules! impl_smallvec {
	($size: expr) => {
		#[cfg(feature = "smallvec")]
		impl<T> MallocSizeOf for smallvec::SmallVec<[T; $size]>
		where
			T: MallocSizeOf,
		{
			fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
				let mut n = if self.spilled() { self.capacity() * core::mem::size_of::<T>() } else { 0 };
				if let Some(t) = T::constant_size() {
					n += self.len() * t;
				} else {
					n = self.iter().fold(n, |acc, elem| acc + elem.size_of(ops))
				}
				n
			}
		}
	};
}

impl_smallvec!(32); // kvdb uses this
impl_smallvec!(36); // trie-db uses this

#[cfg(feature = "std")]
malloc_size_of_is_0!(std::time::Instant);
#[cfg(feature = "std")]
malloc_size_of_is_0!(std::time::Duration);

#[cfg(all(test, feature = "std"))] // tests are using std implementations
mod tests {
	use crate::{allocators::new_malloc_size_ops, MallocSizeOf, MallocSizeOfOps};
	use smallvec::SmallVec;
	use std::collections::BTreeSet;
	use std::mem;
	impl_smallvec!(3);

	#[test]
	fn test_smallvec_stack_allocated_type() {
		let mut v: SmallVec<[u8; 3]> = SmallVec::new();
		let mut ops = new_malloc_size_ops();
		assert_eq!(v.size_of(&mut ops), 0);
		v.push(1);
		v.push(2);
		v.push(3);
		assert_eq!(v.size_of(&mut ops), 0);
		assert!(!v.spilled());
		v.push(4);
		assert!(v.spilled(), "SmallVec spills when going beyond the capacity of the inner backing array");
		assert_eq!(v.size_of(&mut ops), 4); // 4 u8s on the heap
	}

	#[test]
	fn test_smallvec_boxed_stack_allocated_type() {
		let mut v: SmallVec<[Box<u8>; 3]> = SmallVec::new();
		let mut ops = new_malloc_size_ops();
		assert_eq!(v.size_of(&mut ops), 0);
		v.push(Box::new(1u8));
		v.push(Box::new(2u8));
		v.push(Box::new(3u8));
		assert!(v.size_of(&mut ops) >= 3);
		assert!(!v.spilled());
		v.push(Box::new(4u8));
		assert!(v.spilled(), "SmallVec spills when going beyond the capacity of the inner backing array");
		let mut ops = new_malloc_size_ops();
		let expected_min_allocs = mem::size_of::<Box<u8>>() * 4 + 4;
		assert!(v.size_of(&mut ops) >= expected_min_allocs);
	}

	#[test]
	fn test_smallvec_heap_allocated_type() {
		let mut v: SmallVec<[String; 3]> = SmallVec::new();
		let mut ops = new_malloc_size_ops();
		assert_eq!(v.size_of(&mut ops), 0);
		v.push("COW".into());
		v.push("PIG".into());
		v.push("DUCK".into());
		assert!(!v.spilled());
		assert!(v.size_of(&mut ops) >= "COW".len() + "PIG".len() + "DUCK".len());
		v.push("ÖWL".into());
		assert!(v.spilled());
		let mut ops = new_malloc_size_ops();
		let expected_min_allocs = mem::size_of::<String>() * 4 + "ÖWL".len() + "COW".len() + "PIG".len() + "DUCK".len();
		assert!(v.size_of(&mut ops) >= expected_min_allocs);
	}

	#[test]
	fn test_large_vec() {
		const N: usize = 128 * 1024 * 1024;
		let val = vec![1u8; N];
		let mut ops = new_malloc_size_ops();
		assert!(val.size_of(&mut ops) >= N);
		assert!(val.size_of(&mut ops) < 2 * N);
	}

	#[test]
	fn btree_set() {
		let mut set = BTreeSet::new();
		for t in 0..100 {
			set.insert(vec![t]);
		}
		// ~36 per value
		assert!(crate::malloc_size(&set) > 3000);
	}

	#[test]
	fn special_malloc_size_of_0() {
		struct Data<P> {
			phantom: std::marker::PhantomData<P>,
		}

		malloc_size_of_is_0!(any: Data<P>);

		// MallocSizeOf is not implemented for [u8; 333]
		assert_eq!(crate::malloc_size(&Data::<[u8; 333]> { phantom: std::marker::PhantomData }), 0);
	}

	#[test]
	fn constant_size() {
		struct AlwaysTwo(Vec<u8>);

		impl MallocSizeOf for AlwaysTwo {
			fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
				self.0.size_of(ops)
			}
			fn constant_size() -> Option<usize> {
				Some(2)
			}
		}

		assert_eq!(AlwaysTwo::constant_size(), Some(2));
		assert_eq!(std::cmp::Reverse::<u8>::constant_size(), Some(0));
		assert_eq!(std::cell::RefCell::<u8>::constant_size(), Some(0));
		assert_eq!(std::cell::Cell::<u8>::constant_size(), Some(0));
		assert_eq!(Result::<(), ()>::constant_size(), Some(0));
		assert_eq!(<(AlwaysTwo, (), [u8; 32], AlwaysTwo)>::constant_size(), Some(2 + 2));
		assert_eq!(Option::<u8>::constant_size(), Some(0));
		assert_eq!(<&String>::constant_size(), Some(0));

		assert_eq!(<String>::constant_size(), None);
		assert_eq!(std::borrow::Cow::<String>::constant_size(), None);
		assert_eq!(Result::<(), String>::constant_size(), None);
		assert_eq!(Option::<AlwaysTwo>::constant_size(), None);
	}
}