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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
extern crate hashglobe;
extern crate smallvec;
#[cfg(feature = "known_system_malloc")]
use hashglobe::alloc;
use hashglobe::FailedAllocationError;
use smallvec::Array;
use smallvec::SmallVec;
use std::vec::Vec;
pub trait FallibleVec<T> {
/// Append |val| to the end of |vec|. Returns Ok(()) on success,
/// Err(reason) if it fails, with |reason| describing the failure.
fn try_push(&mut self, value: T) -> Result<(), FailedAllocationError>;
}
/////////////////////////////////////////////////////////////////
// Vec
impl<T> FallibleVec<T> for Vec<T> {
#[inline(always)]
fn try_push(&mut self, val: T) -> Result<(), FailedAllocationError> {
#[cfg(feature = "known_system_malloc")]
{
if self.capacity() == self.len() {
try_double_vec(self)?;
debug_assert!(self.capacity() > self.len());
}
}
self.push(val);
Ok(())
}
}
// Double the capacity of |vec|, or fail to do so due to lack of memory.
// Returns Ok(()) on success, Err(..) on failure.
#[cfg(feature = "known_system_malloc")]
#[inline(never)]
#[cold]
fn try_double_vec<T>(vec: &mut Vec<T>) -> Result<(), FailedAllocationError> {
use std::mem;
let old_ptr = vec.as_mut_ptr();
let old_len = vec.len();
let old_cap: usize = vec.capacity();
let new_cap: usize = if old_cap == 0 {
4
} else {
old_cap
.checked_mul(2)
.ok_or(FailedAllocationError::new("capacity overflow for Vec"))?
};
let new_size_bytes = new_cap
.checked_mul(mem::size_of::<T>())
.ok_or(FailedAllocationError::new("capacity overflow for Vec"))?;
let new_ptr = unsafe {
if old_cap == 0 {
alloc::alloc(new_size_bytes, 0)
} else {
alloc::realloc(old_ptr as *mut u8, new_size_bytes)
}
};
if new_ptr.is_null() {
return Err(FailedAllocationError::new(
"out of memory when allocating Vec",
));
}
let new_vec = unsafe { Vec::from_raw_parts(new_ptr as *mut T, old_len, new_cap) };
mem::forget(mem::replace(vec, new_vec));
Ok(())
}
/////////////////////////////////////////////////////////////////
// SmallVec
impl<T: Array> FallibleVec<T::Item> for SmallVec<T> {
#[inline(always)]
fn try_push(&mut self, val: T::Item) -> Result<(), FailedAllocationError> {
if self.capacity() == self.len() {
try_grow_small_vec(self)?;
debug_assert!(self.capacity() > self.len());
}
self.push(val);
Ok(())
}
}
// Grow the capacity of |svec|, or fail to do so due to lack of memory.
#[cfg(feature = "known_system_malloc")]
#[inline(never)]
#[cold]
fn try_grow_small_vec<T>(svec: &mut SmallVec<T>) -> Result<(), FailedAllocationError>
where
T: Array,
{
let error = match svec.try_reserve(1) {
Ok(..) => return Ok(()),
Err(e) => e,
};
Err(match error {
smallvec::CollectionAllocErr::AllocErr { .. } => FailedAllocationError::new(
"out of memory when allocating SmallVec",
),
smallvec::CollectionAllocErr::CapacityOverflow => FailedAllocationError::new(
"capacity overflow for SmallVec",
),
})
}
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