Trait multiboot2_common::MaybeDynSized

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pub trait MaybeDynSized: Pointee {
    type Header: Header;

    const BASE_SIZE: usize;

    // Required method
    fn dst_len(header: &Self::Header) -> Self::Metadata;

    // Provided methods
    fn header(&self) -> &Self::Header { ... }
    fn payload(&self) -> &[u8] { ... }
    fn as_bytes(&self) -> BytesRef<'_, Self::Header> { ... }
    fn as_ptr(&self) -> *const Self::Header { ... }
}
Expand description

A trait to abstract sized and unsized structures (DSTs). It enables casting a DynSizedStructure to sized or unsized structures using DynSizedStructure::cast.

Structs that are a DST must provide a correct MaybeDynSized::dst_len implementation.

Required Associated Types§

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type Header: Header

The associated Header of this tag.

Required Associated Constants§

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const BASE_SIZE: usize

The true base size of the struct without any implicit or additional padding. Note that size_of::<T>() isn’t sufficient, as for example the type could have three u32 fields, which would add an implicit u32 padding. However, this constant must always fulfill BASE_SIZE >= size_of::<Self::Header>().

The main purpose of this constant is to create awareness when you implement Self::dst_len, where you should use this. If this value is correct, we prevent situations where we read uninitialized bytes, especially when creating tags in builders.

Required Methods§

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fn dst_len(header: &Self::Header) -> Self::Metadata

Returns the amount of items in the dynamically sized portion of the DST. Note that this is not the amount of bytes. So if the dynamically sized portion is 16 bytes in size and each element is 4 bytes big, then this function must return 4.

For sized tags, this just returns (). For DSTs, this returns an usize.

Provided Methods§

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fn header(&self) -> &Self::Header

Returns the corresponding Header.

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fn payload(&self) -> &[u8]

Returns the payload, i.e., all memory that is not occupied by the Header of the type.

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fn as_bytes(&self) -> BytesRef<'_, Self::Header>

Returns the whole allocated bytes for this structure encapsulated in BytesRef. This includes padding bytes. To only get the “true” tag data, read the tag size from Self::header and create a sub slice.

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fn as_ptr(&self) -> *const Self::Header

Returns a pointer to this structure.

Object Safety§

This trait is not object safe.

Implementors§