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Support MallocSizeOf for [T] and Box<[T]>.

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This requires tweaking things a bit to handle dynamically-sized types.
This commit is contained in:
Nicholas Nethercote 2017-09-13 16:06:55 +10:00
parent f83099f62a
commit 6a088b6804
1 changed files with 22 additions and 5 deletions
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27
components/malloc_size_of/lib.rs
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@ -103,13 +103,20 @@ impl MallocSizeOfOps {
/// 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>(ptr: *const T) -> bool {
return ptr as usize <= ::std::mem::align_of::<T>();
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>(&self, ptr: *const T) -> usize {
pub unsafe fn malloc_size_of<T: ?Sized>(&self, ptr: *const T) -> usize {
if MallocSizeOfOps::is_empty(ptr) {
0
} else {
@ -179,13 +186,13 @@ pub trait MallocConditionalShallowSizeOf {
fn conditional_shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize;
}
impl<T> MallocShallowSizeOf for Box<T> {
impl<T: ?Sized> MallocShallowSizeOf for Box<T> {
fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
unsafe { ops.malloc_size_of(&**self) }
}
}
impl<T: MallocSizeOf> MallocSizeOf for Box<T> {
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)
}
@ -207,6 +214,16 @@ impl<T: MallocSizeOf> MallocSizeOf for Option<T> {
}
}
impl<T: MallocSizeOf> MallocSizeOf for [T] {
fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
let mut n = 0;
for elem in self.iter() {
n += elem.size_of(ops);
}
n
}
}
impl<T> MallocShallowSizeOf for Vec<T> {
fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
unsafe { ops.malloc_size_of(self.as_ptr()) }