Trait capnp::message::Allocator[−][src]

pub unsafe trait Allocator {
    fn allocate_segment(&mut self, minimum_size: u32) -> (*mut u8, u32);

    fn deallocate_segment(
        &mut self, 
        ptr: *mut u8, 
        word_size: u32, 
        words_used: u32
    );
}

An object that allocates memory for a Cap’n Proto message as it is being built.

Required methods

fn allocate_segment(&mut self, minimum_size: u32) -> (*mut u8, u32)[src]

Allocates zeroed memory for a new segment, returning a pointer to the start of the segment and a u32 indicating the length of the segment in words. The allocated segment must be at least minimum_size words long (minimum_size * 8 bytes long). Allocator implementations commonly allocate much more than the minimum, to reduce the total number of segments needed. A reasonable strategy is to allocate the maximum of minimum_size and twice the size of the previous segment.

UNSAFETY ALERT: Implementors must ensure all of the following: 1. the returned memory is initialized to all zeroes, 2. the returned memory is valid until deallocate_segment() is called on it, 3. the memory doesn’t overlap with other allocated memory, 4. the memory is 8-byte aligned (or the “unaligned” feature is enabled for the capnp crate).

fn deallocate_segment(&mut self, ptr: *mut u8, word_size: u32, words_used: u32)[src]

Indicates that a segment, previously allocated via allocate_segment(), is no longer in use. word_size is the length of the segment in words, as returned from allocate_segment().

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Implementations on Foreign Types

impl<'a, A> Allocator for &'a mut A where
    A: Allocator, [src]

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Implementors

impl Allocator for HeapAllocator[src]

impl<'a> Allocator for ScratchSpaceHeapAllocator<'a>[src]

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