зеркало из https://github.com/mozilla/gecko-dev.git
93 строки
2.4 KiB
Rust
93 строки
2.4 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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use std::mem;
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use std::vec::Vec;
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extern "C" {
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fn realloc(ptr: *mut u8, bytes: usize) -> *mut u8;
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fn malloc(bytes: usize) -> *mut u8;
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}
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pub trait FallibleVec<T> {
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/// Append |val| to the end of |vec|. Returns Ok(()) on success,
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/// Err(()) if it fails, which can only be due to lack of memory.
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fn try_push(&mut self, value: T) -> Result<(), ()>;
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/// Expand the vector size. Return Ok(()) on success, Err(()) if it
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/// fails.
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fn try_reserve(&mut self, new_cap: usize) -> Result<(), ()>;
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}
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/////////////////////////////////////////////////////////////////
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// Vec
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impl<T> FallibleVec<T> for Vec<T> {
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#[inline]
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fn try_push(&mut self, val: T) -> Result<(), ()> {
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if self.capacity() == self.len() {
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let old_cap: usize = self.capacity();
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let new_cap: usize
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= if old_cap == 0 { 4 } else { old_cap.checked_mul(2).ok_or(()) ? };
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try_extend_vec(self, new_cap)?;
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debug_assert!(self.capacity() > self.len());
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}
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self.push(val);
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Ok(())
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}
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#[inline]
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fn try_reserve(&mut self, cap: usize) -> Result<(), ()> {
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let new_cap = cap + self.capacity();
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try_extend_vec(self, new_cap)?;
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debug_assert!(self.capacity() == new_cap);
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Ok(())
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}
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}
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#[inline(never)]
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#[cold]
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fn try_extend_vec<T>(vec: &mut Vec<T>, new_cap: usize) -> Result<(), ()> {
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let old_ptr = vec.as_mut_ptr();
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let old_len = vec.len();
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let old_cap: usize = vec.capacity();
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if old_cap >= new_cap {
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return Ok(());
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}
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let new_size_bytes
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= new_cap.checked_mul(mem::size_of::<T>()).ok_or(()) ? ;
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let new_ptr = unsafe {
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if old_cap == 0 {
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malloc(new_size_bytes)
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} else {
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realloc(old_ptr as *mut u8, new_size_bytes)
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}
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};
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if new_ptr.is_null() {
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return Err(());
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}
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let new_vec = unsafe {
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Vec::from_raw_parts(new_ptr as *mut T, old_len, new_cap)
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};
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mem::forget(mem::replace(vec, new_vec));
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Ok(())
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}
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#[test]
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fn oom_test() {
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let mut vec: Vec<char> = Vec::new();
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match vec.try_reserve(std::usize::MAX) {
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Ok(_) => panic!("it should be OOM"),
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_ => (),
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}
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}
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