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e3c0158788
Vec::try_with_capacity Related to #91913 Implements try_with_capacity for `Vec`, `VecDeque`, and `String`. I can follow it up with more collections if desired. `Vec::try_with_capacity()` is functionally equivalent to the current stable: ```rust let mut v = Vec::new(); v.try_reserve_exact(n)? ``` However, `try_reserve` calls non-inlined `finish_grow`, which requires old and new `Layout`, and is designed to reallocate memory. There is benefit to using `try_with_capacity`, besides syntax convenience, because it generates much smaller code at the call site with a direct call to the allocator. There's codegen test included. It's also a very desirable functionality for users of `no_global_oom_handling` (Rust-for-Linux), since it makes a very commonly used function available in that environment (`with_capacity` is used much more frequently than all `(try_)reserve(_exact)`).
93 lines
2.3 KiB
Rust
93 lines
2.3 KiB
Rust
#![feature(allocator_api)]
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#![feature(alloc_layout_extra)]
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#![feature(iter_array_chunks)]
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#![feature(assert_matches)]
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#![feature(btree_extract_if)]
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#![feature(cow_is_borrowed)]
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#![feature(const_cow_is_borrowed)]
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#![feature(const_heap)]
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#![feature(const_mut_refs)]
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#![feature(const_slice_from_raw_parts_mut)]
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#![feature(const_ptr_write)]
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#![feature(const_try)]
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#![feature(core_intrinsics)]
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#![feature(extract_if)]
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#![feature(exact_size_is_empty)]
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#![feature(generic_nonzero)]
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#![feature(linked_list_cursors)]
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#![feature(map_try_insert)]
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#![feature(new_uninit)]
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#![feature(pattern)]
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#![feature(trusted_len)]
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#![feature(try_reserve_kind)]
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#![feature(try_with_capacity)]
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#![feature(unboxed_closures)]
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#![feature(associated_type_bounds)]
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#![feature(binary_heap_into_iter_sorted)]
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#![feature(binary_heap_drain_sorted)]
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#![feature(slice_ptr_get)]
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#![feature(binary_heap_as_slice)]
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#![feature(inplace_iteration)]
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#![feature(iter_advance_by)]
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#![feature(iter_next_chunk)]
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#![feature(round_char_boundary)]
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#![feature(slice_partition_dedup)]
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#![feature(string_remove_matches)]
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#![feature(const_btree_len)]
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#![feature(const_trait_impl)]
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#![feature(const_str_from_utf8)]
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#![feature(panic_update_hook)]
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#![feature(pointer_is_aligned)]
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#![feature(slice_flatten)]
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#![feature(thin_box)]
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#![feature(strict_provenance)]
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#![feature(drain_keep_rest)]
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#![feature(local_waker)]
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#![allow(internal_features)]
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#![deny(fuzzy_provenance_casts)]
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#![deny(unsafe_op_in_unsafe_fn)]
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use std::hash::{DefaultHasher, Hash, Hasher};
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mod arc;
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mod autotraits;
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mod borrow;
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mod boxed;
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mod btree_set_hash;
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mod c_str;
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mod const_fns;
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mod cow_str;
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mod fmt;
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mod heap;
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mod linked_list;
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mod rc;
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mod slice;
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mod str;
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mod string;
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mod task;
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mod thin_box;
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mod vec;
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mod vec_deque;
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fn hash<T: Hash>(t: &T) -> u64 {
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let mut s = DefaultHasher::new();
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t.hash(&mut s);
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s.finish()
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}
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// FIXME: Instantiated functions with i128 in the signature is not supported in Emscripten.
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// See https://github.com/kripken/emscripten-fastcomp/issues/169
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#[cfg(not(target_os = "emscripten"))]
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#[test]
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fn test_boxed_hasher() {
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let ordinary_hash = hash(&5u32);
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let mut hasher_1 = Box::new(DefaultHasher::new());
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5u32.hash(&mut hasher_1);
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assert_eq!(ordinary_hash, hasher_1.finish());
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let mut hasher_2 = Box::new(DefaultHasher::new()) as Box<dyn Hasher>;
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5u32.hash(&mut hasher_2);
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assert_eq!(ordinary_hash, hasher_2.finish());
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}
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