120 lines
4.1 KiB
Rust
120 lines
4.1 KiB
Rust
// Protocol Buffers - Google's data interchange format
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// Copyright 2023 Google LLC. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file or at
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// https://developers.google.com/open-source/licenses/bsd
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//! Kernel-agnostic logic for the Rust Protobuf runtime that should not be
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//! exposed to through the `protobuf` path but must be public for use by
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//! generated code.
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pub use crate::vtable::{
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new_vtable_field_entry, BytesMutVTable, BytesOptionalMutVTable, PrimitiveVTable,
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RawVTableMutator,
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};
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use std::ptr::NonNull;
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use std::slice;
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/// Used to protect internal-only items from being used accidentally.
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pub struct Private;
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/// Defines a set of opaque, unique, non-accessible pointees.
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///
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/// The [Rustonomicon][nomicon] currently recommends a zero-sized struct,
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/// though this should use [`extern type`] when that is stabilized.
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/// [nomicon]: https://doc.rust-lang.org/nomicon/ffi.html#representing-opaque-structs
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/// [`extern type`]: https://github.com/rust-lang/rust/issues/43467
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mod _opaque_pointees {
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/// Opaque pointee for [`RawMessage`]
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///
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/// This type is not meant to be dereferenced in Rust code.
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/// It is only meant to provide type safety for raw pointers
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/// which are manipulated behind FFI.
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///
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/// [`RawMessage`]: super::RawMessage
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#[repr(C)]
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pub struct RawMessageData {
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_data: [u8; 0],
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_marker: std::marker::PhantomData<(*mut u8, ::std::marker::PhantomPinned)>,
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}
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/// Opaque pointee for [`RawArena`]
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///
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/// This type is not meant to be dereferenced in Rust code.
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/// It is only meant to provide type safety for raw pointers
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/// which are manipulated behind FFI.
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///
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/// [`RawArena`]: super::RawArena
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#[repr(C)]
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pub struct RawArenaData {
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_data: [u8; 0],
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_marker: std::marker::PhantomData<(*mut u8, ::std::marker::PhantomPinned)>,
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}
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/// Opaque pointee for [`RawRepeatedField`]
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///
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/// This type is not meant to be dereferenced in Rust code.
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/// It is only meant to provide type safety for raw pointers
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/// which are manipulated behind FFI.
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#[repr(C)]
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pub struct RawRepeatedFieldData {
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_data: [u8; 0],
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_marker: std::marker::PhantomData<(*mut u8, ::std::marker::PhantomPinned)>,
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}
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}
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/// A raw pointer to the underlying message for this runtime.
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pub type RawMessage = NonNull<_opaque_pointees::RawMessageData>;
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/// A raw pointer to the underlying arena for this runtime.
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pub type RawArena = NonNull<_opaque_pointees::RawArenaData>;
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/// A raw pointer to the underlying repeated field container for this runtime.
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pub type RawRepeatedField = NonNull<_opaque_pointees::RawRepeatedFieldData>;
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/// Represents an ABI-stable version of `NonNull<[u8]>`/`string_view` (a
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/// borrowed slice of bytes) for FFI use only.
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///
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/// Has semantics similar to `std::string_view` in C++ and `&[u8]` in Rust,
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/// but is not ABI-compatible with either.
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///
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/// If `len` is 0, then `ptr` can be null or dangling. C++ considers a dangling
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/// 0-len `std::string_view` to be invalid, and Rust considers a `&[u8]` with a
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/// null data pointer to be invalid.
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#[repr(C)]
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#[derive(Copy, Clone)]
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pub struct PtrAndLen {
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/// Pointer to the first byte.
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/// Borrows the memory.
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pub ptr: *const u8,
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/// Length of the `[u8]` pointed to by `ptr`.
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pub len: usize,
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}
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impl PtrAndLen {
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/// Unsafely dereference this slice.
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///
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/// # Safety
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/// - `self.ptr` must be dereferencable and immutable for `self.len` bytes
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/// for the lifetime `'a`. It can be null or dangling if `self.len == 0`.
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pub unsafe fn as_ref<'a>(self) -> &'a [u8] {
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if self.ptr.is_null() {
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assert_eq!(self.len, 0, "Non-empty slice with null data pointer");
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&[]
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} else {
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// SAFETY:
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// - `ptr` is non-null
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// - `ptr` is valid for `len` bytes as promised by the caller.
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unsafe { slice::from_raw_parts(self.ptr, self.len) }
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}
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}
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}
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impl From<&[u8]> for PtrAndLen {
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fn from(slice: &[u8]) -> Self {
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Self { ptr: slice.as_ptr(), len: slice.len() }
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}
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}
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