Struct capnp::message::ScratchSpaceHeapAllocator

pub struct ScratchSpaceHeapAllocator<'a> { /* fields omitted */ }

An Allocator whose first segment is a backed by a user-provided buffer.

Implementations

impl<'a> ScratchSpaceHeapAllocator<'a>

pub fn new(scratch_space: &'a mut [u8]) -> ScratchSpaceHeapAllocator<'a>

Writes zeroes into the entire buffer and constructs a new allocator from it.

If you want to reuse the same buffer and to minimize the cost of zeroing for each message, you can call message::Builder::into_allocator() to recover the allocator from the previous message and then pass it into the new message.

pub fn second_segment_words(self, value: u32) -> ScratchSpaceHeapAllocator<'a>

Sets the size of the second segment in words, where 1 word = 8 bytes. (The first segment is the scratch space passed to ScratchSpaceHeapAllocator::new().

pub fn allocation_strategy(
    self,
    value: AllocationStrategy
) -> ScratchSpaceHeapAllocator<'a>

Sets the allocation strategy for segments after the second one.

Trait Implementations

impl<'a> Allocator for ScratchSpaceHeapAllocator<'a>

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

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.

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

Indicates that a segment, previously allocated via allocate_segment(), is no longer in use.