Add TryFromBytes trait by joshlf · Pull Request #353 · google/zerocopy

joshlf · 2023-09-08T05:59:09Z

TryFromBytes can be implemented for types which are not FromZeroes or FromBytes; it supports performing a runtime check to determine whether a given byte sequence contains a valid instance of Self.

This is the first step of #5. Future commits will add support for a custom derive and for implementing TryFromBytes on unsized types.

Makes progress on #5

src/lib.rs

joshlf · 2023-09-12T03:44:30Z

src/lib.rs

+//! - [`TryFromBytes`] supports non-`FromBytes` types by providing the ability
+//!   to check the validity of a conversion at runtime


I don't love this wording. @jswrenn any suggestions?

joshlf · 2023-09-12T06:17:46Z

src/lib.rs

+    /// # Panics
+    ///
+    /// `is_bit_valid` may panic. Callers are responsible for ensuring that any
+    /// `unsafe` code remains sound even in the face of `is_bit_valid`
+    /// panicking. (We support user-defined validation routines; so long as
+    /// these routines are not required to be `unsafe`, there is no way to
+    /// ensure that these do not generate panics.)


cc @jswrenn @djkoloski Calling this out; I've updated all the safety comments in this PR to address panics.

joshlf · 2023-11-02T10:56:54Z

src/lib.rs

+    /// TODO(https://github.com/rust-lang/reference/pull/1401): Use `&u32`
+    /// instead once it's guaranteed that `align_of::<u32>() ==
+    /// align_of::<char>()`.


This has landed; update this PR.

`TryFromBytes` can be implemented for types which are not `FromZeroes` or `FromBytes`; it supports performing a runtime check to determine whether a given byte sequence contains a valid instance of `Self`. This is the first step of #5. Future commits will add support for a custom derive and for implementing `TryFromBytes` on unsized types. TODO: - More thorough tests for non-FromBytes types (bool, char, etc) - Tests that go through the `TryFromBytes` public methods rather than testing `is_bit_valid` directly - Update safety requirements for `is_bit_valid` now that it takes a `Ptr` rather than a `NonNull` - Update SAFETY comments in various places Makes progress on #5

joshlf force-pushed the try-from-bytes-raw-argument-to-is-bit-valid-3-try-from-bytes branch from b91a49a to c2b946e Compare September 8, 2023 06:17

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joshlf commented Sep 8, 2023

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joshlf mentioned this pull request Sep 9, 2023

KnownLayout::validate_cast #349

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joshlf commented Sep 10, 2023

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joshlf mentioned this pull request Nov 27, 2023

Minimal implementation of TryFromBytes #317

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joshlf closed this Feb 12, 2024

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Add TryFromBytes trait#353

Add TryFromBytes trait#353
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		//! - [`TryFromBytes`] supports non-`FromBytes` types by providing the ability
		//! to check the validity of a conversion at runtime

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joshlf commented Sep 8, 2023

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