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Move capacity overflow panic to own cold function #63

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Move capacity overflow panic to own cold function #63

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44 changes: 34 additions & 10 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -255,6 +255,33 @@ mod impl_details {
}
}

#[cold]
fn capacity_overflow() -> ! {
panic!("capacity overflow")
}

trait UnwrapCapOverflow<T> {
fn unwrap_cap_overflow(self) -> T;
}

impl<T> UnwrapCapOverflow<T> for Option<T> {
fn unwrap_cap_overflow(self) -> T {
match self {
Some(val) => val,
None => capacity_overflow(),
}
}
}

impl<T, E> UnwrapCapOverflow<T> for Result<T, E> {
fn unwrap_cap_overflow(self) -> T {
match self {
Ok(val) => val,
Err(_) => capacity_overflow(),
}
}
}

// The header of a ThinVec.
//
// The _cap can be a bitfield, so use accessors to avoid trouble.
Expand Down Expand Up @@ -360,14 +387,14 @@ fn alloc_size<T>(cap: usize) -> usize {
// space for items, so we don't care about the capacity that was requested!
0
} else {
let cap: isize = cap.try_into().expect("capacity overflow");
let cap: isize = cap.try_into().unwrap_cap_overflow();
let elem_size = mem::size_of::<T>() as isize;
elem_size.checked_mul(cap).expect("capacity overflow")
elem_size.checked_mul(cap).unwrap_cap_overflow()
};

let final_size = data_size
.checked_add(header_size + padding)
.expect("capacity overflow");
.unwrap_cap_overflow();

// Ok now we can turn it back into a usize (don't need to worry about negatives)
final_size as usize
Expand Down Expand Up @@ -1055,7 +1082,7 @@ impl<T> ThinVec<T> {
pub fn reserve(&mut self, additional: usize) {
let len = self.len();
let old_cap = self.capacity();
let min_cap = len.checked_add(additional).expect("capacity overflow");
let min_cap = len.checked_add(additional).unwrap_cap_overflow();
if min_cap <= old_cap {
return;
}
Expand Down Expand Up @@ -1086,7 +1113,7 @@ impl<T> ThinVec<T> {

let len = self.len();
let old_cap = self.capacity();
let min_cap = len.checked_add(additional).expect("capacity overflow");
let min_cap = len.checked_add(additional).unwrap_cap_overflow();
if min_cap <= old_cap {
return;
}
Expand Down Expand Up @@ -1140,10 +1167,7 @@ impl<T> ThinVec<T> {
///
/// Re-allocates only if `self.capacity() < self.len() + additional`.
pub fn reserve_exact(&mut self, additional: usize) {
let new_cap = self
.len()
.checked_add(additional)
.expect("capacity overflow");
let new_cap = self.len().checked_add(additional).unwrap_cap_overflow();
let old_cap = self.capacity();
if new_cap > old_cap {
unsafe {
Expand Down Expand Up @@ -2599,7 +2623,7 @@ impl<T> Drain<'_, T> {
unsafe fn move_tail(&mut self, additional: usize) {
let vec = unsafe { &mut *self.vec };
let len = self.end + self.tail;
vec.reserve(len.checked_add(additional).expect("capacity overflow"));
vec.reserve(len.checked_add(additional).unwrap_cap_overflow());

let new_tail_start = self.end + additional;
unsafe {
Expand Down