Struct capnp::serialize::NoAllocBufferSegments

pub struct NoAllocBufferSegments<T> { /* private fields */ }

NoAllocBufferSegments is similar to crate::serialize::BufferSegments but optimized for low memory embedded environment. It does not do heap allocations.

Performance considerations

Due to lack of heap allocations, NoAllocBufferSegments does not cache segments offset and length and has to parse message header every time NoAllocBufferSegments::get_segment is called. The parsing has O(N) complexity where N is total number of segments in the message. NoAllocBufferSegments has optimization for single segment messages: if message has only one segment, it will be parsed only once during creation and no parsing will be required on get_segment calls

Implementations

impl<T> NoAllocBufferSegments<T>

pub fn from_segment_table_info(buffer: T, info: NoAllocSegmentTableInfo) -> Self

Constructs a NoAllocBufferSegments from a buffer and a NoAllocSegmentTableInfo. This method is used internally by NoAllocBufferSegments::from_slice() and NoAllocBufferSegments::from_buffer(). It has been made public to allow for situations where the segment table is read by nonstandard means.

impl<'b> NoAllocBufferSegments<&'b [u8]>

pub fn from_slice(slice: &mut &'b [u8], options: ReaderOptions) -> Result<Self>

Reads a serialized message (including a segment table) from a buffer and takes ownership, without copying. The buffer is allowed to extend beyond the end of the message. On success, updates slice to point to the remaining bytes beyond the end of the message.

ALIGNMENT: If the “unaligned” feature is enabled, then there are no alignment requirements on slice. Otherwise, slice must be 8-byte aligned (attempts to read the message will trigger errors).

impl<T: AsRef<[u8]>> NoAllocBufferSegments<T>

pub fn from_buffer(buffer: T, options: ReaderOptions) -> Result<Self>

Reads a serialized message (including a segment table) from a buffer and takes ownership, without copying. The buffer is allowed to extend beyond the end of the message.

ALIGNMENT: If the “unaligned” feature is enabled, then there are no alignment requirements on buffer. Otherwise, buffer must be 8-byte aligned (attempts to read the message will trigger errors).

Trait Implementations

impl<T: AsRef<[u8]>> ReaderSegments for NoAllocBufferSegments<T>

fn get_segment(&self, idx: u32) -> Option<&[u8]>

Gets the segment with index idx. Returns None if idx is out of range.

fn len(&self) -> usize

Gets the number of segments.

fn is_empty(&self) -> bool