Struct Hello 

pub struct Hello {
    pub abi_major: u16,
    pub abi_minor: u16,
    pub window_bytes: u64,
    pub max_batch_rows: u64,
    pub offered: CapabilitySet,
    pub source_bytes: u64,
}

The host introducing itself.

Fields

abi_major: u16

The major ABI version the host speaks. A mismatch here is fatal.

abi_minor: u16

The minor ABI version the host speaks. A mismatch here is not fatal.

window_bytes: u64

How many bytes of the source the host is willing to keep visible to the guest at once.

Zero means the host will map the whole source and the decoder never has to think about windows.

max_batch_rows: u64

The largest number of rows the host will ask for in one scan request.

offered: CapabilitySet

What the host can do.

source_bytes: u64

How many bytes the source has in total, or zero if the host is not saying.

A decoder that has to find its own footer needs this, and a decoder that reads forwards from the start does not, which is why zero is allowed rather than being an error.

This field was appended after the ABI shipped, so it is the first real exercise of the grow-at-the-end rule. A host built before it existed writes a Hello that ends after offered, and a decoder built after it reads zero and carries on.

Implementations

impl Hello

pub const VERSION: u16 = 1

The layout version of this record.

pub fn encode(&self, w: &mut Writer<'_>) -> Result<()>

Writes the record.

Errors

Returns Error::BufferFull if the buffer runs out.

pub fn decode(version: u16, p: &mut Reader<'_>) -> Result<Self>

Reads the record from its payload.

Errors

Returns Error::UnsupportedVersion if the layout version is not one this build knows, or Error::Truncated if the payload ends early.

Trait Implementations

impl Clone for Hello

fn clone(&self) -> Hello

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Hello

impl Debug for Hello

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Hello

impl PartialEq for Hello

fn eq(&self, other: &Hello) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Hello