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CHANGELOG.md

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Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog and this project adheres to Semantic Versioning.

[1.0.1] - 2022-03-24

FIXED

  • To avoid an issue where allocated heap memory may be deallocated with a different layout alignment than it was officially allocated with when converting between std::string::String and SmartString, even if otherwise correctly aligned, the respective From implementations now use std::alloc::Allocator::grow() to re-align the heap data as necessary. An unfortunate consequence of this is that because the std::alloc::Allocator API hasn't been stabilised yet, unless you're on nightly or some future stable rustc version after allocator_api has been stabilised, converting between String and SmartString will always reallocate and copy (making it always O(n) rather than O(1) when correctly aligned and O(n) otherwise). (#28)

[1.0.0] - 2022-02-24

CHANGED

  • smartstring now implements its own boxed string type rather than deferring directly to String, so it no longer makes assumptions it shouldn't be making about the layout of the String struct.

    This also allows us to organise the boxed struct in a way that will let us rely only on our basic assumption that heap memory is word aligned on both big and little endian architectures. The most immediate consequence of this is that smartstring will now compile on 32-bit big endian architectures such as mips.

    We are now also explicitly allocating heap memory aligned for u16 rather than u8, ensuring the assumption about pointer alignment becomes an invariant.

    In short: smartstring no longer relies on undefined behaviour, and should be safe to use anywhere.

  • The above means that the boxed SmartString is no longer pointer compatible with String, so if you were relying on that despite the documentation urging you not to, you'll really have to stop it now. Converting between SmartString and String using From and Into traits is still efficient and allocation free.

  • The minimum supported rustc version is now 1.57.0.

  • The smartstring::validate() function has been removed, as it's no longer needed.

[0.2.10] - 2022-02-20

CHANGED

  • The minimum supported rustc version has been increased to 1.56.0, and the rust-version field has been added to the crate's Cargo.toml to indicate the MSRV. (The rust-version field itself was introduced in version 1.56, hence the bump.)
  • Dependencies have been bumped, most notably to arbitrary version 1.

[0.2.9] - 2021-07-27

ADDED

  • You can (and should) now call smartstring::validate() from your own code or test suite to validate SmartString's memory layout assumptions.

[0.2.8] - 2021-07-26

CHANGED

  • The minimum supported rustc version has been increased to 1.46.0.

ADDED

  • There are now const fn new_const() constructors for SmartString<Compact> and SmartString<LazyCompact>, added as a temporary measure because const functions can't yet take trait bounds on type arguments, so we can't simply make SmartString::new() const.

    Please note that when rustc catches up, the plan is to deprecate new_const() in favour of new(). (#21)

[0.2.7] - 2021-07-01

FIXED

  • no_std builds have been fixed. (#18)

[0.2.6] - 2020-12-19

ADDED

  • SmartString now implements PartialEq<&str>.

[0.2.5] - 2020-09-24

ADDED

  • From implementations from Cow<'_, str> and &mut str were added. (#12)

[0.2.4] - 2020-09-05

ADDED

  • smartstring is now no_std if you disable the std feature flag (which is enabled by default). (#10)

FIXED

  • smartstring will now refuse to compile on 32-bit big-endian architectures, where assuming that the high bit of a pointer is always empty is going to be a very bad idea.

[0.2.3] - 2020-07-07

ADDED

  • SmartString now implements Display. (#6)
  • SmartString now implements FromIterator<char>.
  • Support for serde behind the serde feature flag. (#2)
  • Support for arbitrary behind the arbitrary feature flag.
  • Support for proptest behind the proptest feature flag.

FIXED

  • SmartString::push_str would previously trigger two heap allocations while promoting an inline string to a boxed string, one of which was unnecessary. It now only makes the one strictly necessary allocation. (#5)
  • Fixed a bug where SmartString::remove would panic if you tried to remove the last index in an inline string.

[0.2.2] - 2020-07-05

FIXED

  • Calling shrink_to_fit() on a string with LazyCompact layout will now inline it and deallocate the heap allocation if the string is short enough to be inlined.

[0.2.1] - 2020-07-04

FIXED

  • The type alias smartstring::alias::String was incorrectly pointing at the Compact variant. It is now pointing at LazyCompact, as the documentation describes.

[0.2.0] - 2020-07-04

REMOVED

  • The Prefixed variant has been removed, as it comes with significant code complexity for very dubious gains.

CHANGED

  • The type alias smartstring::alias::String now refers to LazyCompact instead of Compact, the idea being that the obvious drop-in replacement for String shouldn't have any unexpected performance differences, which Compact can have because it aggressively re-inlines strings to keep them as local as possible. LazyCompact instead heap allocates once when the string is in excess of the inline capacity and keeps the allocation from then on, so there are no surprises.

ADDED

  • There's a new layout variant, LazyCompact, which works like Compact except it never re-inlines strings once they have been moved to the heap.
  • As the alias String has changed, there is now a new type alias smartstring::alias::CompactString, referring to strings with Compact layout.

FIXED

  • Fixed a bug where SmartString::drain() would remove twice the drained content from the string.

[0.1.0] - 2020-05-15

Initial release.