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Rename some identifiers in `RawVec` and `libarena`. 

- Use `len` more consistently for the number of elements in a vector,
  because that's the usual name.
- Use `additional` more consistently for the number of elements we want
  to add, because that's what `Vec::reserve()` uses.
- Use `cap` consistently rather than `capacity`.
- Plus a few other tweaks.

This increases consistency and conciseness.
This commit is contained in:
Nicholas Nethercote 2020-05-20 20:45:05 +10:00
parent cb8bc8e05d
commit c9cbe7e7eb
3 changed files with 62 additions and 79 deletions
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81
src/liballoc/raw_vec.rs
View File

@ -235,13 +235,13 @@ impl<T, A: AllocRef> RawVec<T, A> {
}
}
/// Ensures that the buffer contains at least enough space to hold
/// `used_capacity + needed_extra_capacity` elements. If it doesn't already have
/// enough capacity, will reallocate enough space plus comfortable slack
/// space to get amortized `O(1)` behavior. Will limit this behavior
/// if it would needlessly cause itself to panic.
/// Ensures that the buffer contains at least enough space to hold `len +
/// additional` elements. If it doesn't already have enough capacity, will
/// reallocate enough space plus comfortable slack space to get amortized
/// `O(1)` behavior. Will limit this behavior if it would needlessly cause
/// itself to panic.
///
/// If `used_capacity` exceeds `self.capacity()`, this may fail to actually allocate
/// If `len` exceeds `self.capacity()`, this may fail to actually allocate
/// the requested space. This is not really unsafe, but the unsafe
/// code *you* write that relies on the behavior of this function may break.
///
@ -287,8 +287,8 @@ impl<T, A: AllocRef> RawVec<T, A> {
/// # vector.push_all(&[1, 3, 5, 7, 9]);
/// # }
/// ```
pub fn reserve(&mut self, used_capacity: usize, needed_extra_capacity: usize) {
match self.try_reserve(used_capacity, needed_extra_capacity) {
pub fn reserve(&mut self, len: usize, additional: usize) {
match self.try_reserve(len, additional) {
Err(CapacityOverflow) => capacity_overflow(),
Err(AllocError { layout, .. }) => handle_alloc_error(layout),
Ok(()) => { /* yay */ }
@ -296,28 +296,23 @@ impl<T, A: AllocRef> RawVec<T, A> {
}
/// The same as `reserve`, but returns on errors instead of panicking or aborting.
pub fn try_reserve(
&mut self,
used_capacity: usize,
needed_extra_capacity: usize,
) -> Result<(), TryReserveError> {
if self.needs_to_grow(used_capacity, needed_extra_capacity) {
self.grow_amortized(used_capacity, needed_extra_capacity)
pub fn try_reserve(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> {
if self.needs_to_grow(len, additional) {
self.grow_amortized(len, additional)
} else {
Ok(())
}
}
/// Ensures that the buffer contains at least enough space to hold
/// `used_capacity + needed_extra_capacity` elements. If it doesn't already,
/// will reallocate the minimum possible amount of memory necessary.
/// Generally this will be exactly the amount of memory necessary,
/// but in principle the allocator is free to give back more than what
/// we asked for.
/// Ensures that the buffer contains at least enough space to hold `len +
/// additional` elements. If it doesn't already, will reallocate the
/// minimum possible amount of memory necessary. Generally this will be
/// exactly the amount of memory necessary, but in principle the allocator
/// is free to give back more than we asked for.
///
/// If `used_capacity` exceeds `self.capacity()`, this may fail to actually allocate
/// the requested space. This is not really unsafe, but the unsafe
/// code *you* write that relies on the behavior of this function may break.
/// If `len` exceeds `self.capacity()`, this may fail to actually allocate
/// the requested space. This is not really unsafe, but the unsafe code
/// *you* write that relies on the behavior of this function may break.
///
/// # Panics
///
@ -328,8 +323,8 @@ impl<T, A: AllocRef> RawVec<T, A> {
/// # Aborts
///
/// Aborts on OOM.
pub fn reserve_exact(&mut self, used_capacity: usize, needed_extra_capacity: usize) {
match self.try_reserve_exact(used_capacity, needed_extra_capacity) {
pub fn reserve_exact(&mut self, len: usize, additional: usize) {
match self.try_reserve_exact(len, additional) {
Err(CapacityOverflow) => capacity_overflow(),
Err(AllocError { layout, .. }) => handle_alloc_error(layout),
Ok(()) => { /* yay */ }
@ -339,14 +334,10 @@ impl<T, A: AllocRef> RawVec<T, A> {
/// The same as `reserve_exact`, but returns on errors instead of panicking or aborting.
pub fn try_reserve_exact(
&mut self,
used_capacity: usize,
needed_extra_capacity: usize,
len: usize,
additional: usize,
) -> Result<(), TryReserveError> {
if self.needs_to_grow(used_capacity, needed_extra_capacity) {
self.grow_exact(used_capacity, needed_extra_capacity)
} else {
Ok(())
}
if self.needs_to_grow(len, additional) { self.grow_exact(len, additional) } else { Ok(()) }
}
/// Shrinks the allocation down to the specified amount. If the given amount
@ -371,8 +362,8 @@ impl<T, A: AllocRef> RawVec<T, A> {
impl<T, A: AllocRef> RawVec<T, A> {
/// Returns if the buffer needs to grow to fulfill the needed extra capacity.
/// Mainly used to make inlining reserve-calls possible without inlining `grow`.
fn needs_to_grow(&self, used_capacity: usize, needed_extra_capacity: usize) -> bool {
needed_extra_capacity > self.capacity().wrapping_sub(used_capacity)
fn needs_to_grow(&self, len: usize, additional: usize) -> bool {
additional > self.capacity().wrapping_sub(len)
}
fn capacity_from_bytes(excess: usize) -> usize {
@ -392,13 +383,10 @@ impl<T, A: AllocRef> RawVec<T, A> {
// so that all of the code that depends on `T` is within it, while as much
// of the code that doesn't depend on `T` as possible is in functions that
// are non-generic over `T`.
fn grow_amortized(
&mut self,
used_capacity: usize,
needed_extra_capacity: usize,
) -> Result<(), TryReserveError> {
fn grow_amortized(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> {
// This is ensured by the calling contexts.
debug_assert!(needed_extra_capacity > 0);
debug_assert!(additional > 0);
if mem::size_of::<T>() == 0 {
// Since we return a capacity of `usize::MAX` when `elem_size` is
// 0, getting to here necessarily means the `RawVec` is overfull.
@ -406,8 +394,7 @@ impl<T, A: AllocRef> RawVec<T, A> {
}
// Nothing we can really do about these checks, sadly.
let required_cap =
used_capacity.checked_add(needed_extra_capacity).ok_or(CapacityOverflow)?;
let required_cap = len.checked_add(additional).ok_or(CapacityOverflow)?;
// This guarantees exponential growth. The doubling cannot overflow
// because `cap <= isize::MAX` and the type of `cap` is `usize`.
@ -440,18 +427,14 @@ impl<T, A: AllocRef> RawVec<T, A> {
// The constraints on this method are much the same as those on
// `grow_amortized`, but this method is usually instantiated less often so
// it's less critical.
fn grow_exact(
&mut self,
used_capacity: usize,
needed_extra_capacity: usize,
) -> Result<(), TryReserveError> {
fn grow_exact(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> {
if mem::size_of::<T>() == 0 {
// Since we return a capacity of `usize::MAX` when the type size is
// 0, getting to here necessarily means the `RawVec` is overfull.
return Err(CapacityOverflow);
}
let cap = used_capacity.checked_add(needed_extra_capacity).ok_or(CapacityOverflow)?;
let cap = len.checked_add(additional).ok_or(CapacityOverflow)?;
let new_layout = Layout::array::<T>(cap);
// `finish_grow` is non-generic over `T`.

8
src/liballoc/vec.rs
View File

@ -2977,12 +2977,12 @@ impl<T> Drain<'_, T> {
}
/// Makes room for inserting more elements before the tail.
unsafe fn move_tail(&mut self, extra_capacity: usize) {
unsafe fn move_tail(&mut self, additional: usize) {
let vec = self.vec.as_mut();
let used_capacity = self.tail_start + self.tail_len;
vec.buf.reserve(used_capacity, extra_capacity);
let len = self.tail_start + self.tail_len;
vec.buf.reserve(len, additional);
let new_tail_start = self.tail_start + extra_capacity;
let new_tail_start = self.tail_start + additional;
let src = vec.as_ptr().add(self.tail_start);
let dst = vec.as_mut_ptr().add(new_tail_start);
ptr::copy(src, dst, self.tail_len);

52
src/librustc_arena/lib.rs
View File

@ -146,18 +146,18 @@ impl<T> TypedArena<T> {
}
#[inline]
fn can_allocate(&self, len: usize) -> bool {
let available_capacity_bytes = self.end.get() as usize - self.ptr.get() as usize;
let at_least_bytes = len.checked_mul(mem::size_of::<T>()).unwrap();
available_capacity_bytes >= at_least_bytes
fn can_allocate(&self, additional: usize) -> bool {
let available_bytes = self.end.get() as usize - self.ptr.get() as usize;
let additional_bytes = additional.checked_mul(mem::size_of::<T>()).unwrap();
available_bytes >= additional_bytes
}
/// Ensures there's enough space in the current chunk to fit `len` objects.
#[inline]
fn ensure_capacity(&self, len: usize) {
if !self.can_allocate(len) {
self.grow(len);
debug_assert!(self.can_allocate(len));
fn ensure_capacity(&self, additional: usize) {
if !self.can_allocate(additional) {
self.grow(additional);
debug_assert!(self.can_allocate(additional));
}
}
@ -214,13 +214,13 @@ impl<T> TypedArena<T> {
/// Grows the arena.
#[inline(never)]
#[cold]
fn grow(&self, n: usize) {
fn grow(&self, additional: usize) {
unsafe {
// We need the element size to convert chunk sizes (ranging from
// PAGE to HUGE_PAGE bytes) to element counts.
let elem_size = cmp::max(1, mem::size_of::<T>());
let mut chunks = self.chunks.borrow_mut();
let mut new_capacity;
let mut new_cap;
if let Some(last_chunk) = chunks.last_mut() {
let used_bytes = self.ptr.get() as usize - last_chunk.start() as usize;
last_chunk.entries = used_bytes / mem::size_of::<T>();
@ -228,17 +228,17 @@ impl<T> TypedArena<T> {
// If the previous chunk's capacity is less than HUGE_PAGE
// bytes, then this chunk will be least double the previous
// chunk's size.
new_capacity = last_chunk.storage.capacity();
if new_capacity < HUGE_PAGE / elem_size {
new_capacity = new_capacity.checked_mul(2).unwrap();
new_cap = last_chunk.storage.capacity();
if new_cap < HUGE_PAGE / elem_size {
new_cap = new_cap.checked_mul(2).unwrap();
}
} else {
new_capacity = PAGE / elem_size;
new_cap = PAGE / elem_size;
}
// Also ensure that this chunk can fit `n`.
new_capacity = cmp::max(n, new_capacity);
// Also ensure that this chunk can fit `additional`.
new_cap = cmp::max(additional, new_cap);
let chunk = TypedArenaChunk::<T>::new(new_capacity);
let chunk = TypedArenaChunk::<T>::new(new_cap);
self.ptr.set(chunk.start());
self.end.set(chunk.end());
chunks.push(chunk);
@ -342,10 +342,10 @@ impl DroplessArena {
#[inline(never)]
#[cold]
fn grow(&self, needed_bytes: usize) {
fn grow(&self, additional: usize) {
unsafe {
let mut chunks = self.chunks.borrow_mut();
let mut new_capacity;
let mut new_cap;
if let Some(last_chunk) = chunks.last_mut() {
// There is no need to update `last_chunk.entries` because that
// field isn't used by `DroplessArena`.
@ -353,17 +353,17 @@ impl DroplessArena {
// If the previous chunk's capacity is less than HUGE_PAGE
// bytes, then this chunk will be least double the previous
// chunk's size.
new_capacity = last_chunk.storage.capacity();
if new_capacity < HUGE_PAGE {
new_capacity = new_capacity.checked_mul(2).unwrap();
new_cap = last_chunk.storage.capacity();
if new_cap < HUGE_PAGE {
new_cap = new_cap.checked_mul(2).unwrap();
}
} else {
new_capacity = PAGE;
new_cap = PAGE;
}
// Also ensure that this chunk can fit `needed_bytes`.
new_capacity = cmp::max(needed_bytes, new_capacity);
// Also ensure that this chunk can fit `additional`.
new_cap = cmp::max(additional, new_cap);
let chunk = TypedArenaChunk::<u8>::new(new_capacity);
let chunk = TypedArenaChunk::<u8>::new(new_cap);
self.ptr.set(chunk.start());
self.end.set(chunk.end());
chunks.push(chunk);