Struct alkahest::Vlq

pub struct Vlq;

Formula for Variable-Length Quantity encoding.

If bit 8 is set then bits 0-6 contain length of the value in bytes. Otherwise bits 4-7 contain the length of the value in bytes, and bits 0-3 contain first 4 bits of the encoded value.

If bit 8 is set then bit 7 must be unset. It is reserved for chaining value length to the next byte for big integers from 2^ 63 and larger.

Examples

Type of the value can be different than the type of the serialized value.

let mut buffer = [0u8; 1024];
let size = serialize::<Vlq, u8>(0, &mut buffer).unwrap();
let value = deserialize::<Vlq, u16>(&buffer[..size]).unwrap().0;
assert_eq!(0, value);

It may be smaller, unlike fixed size formulas. The only requirement is that the target type is large enough to hold the value.

let mut buffer = [0u8; 1024];

let size = serialize::<Vlq, u32>(8573, &mut buffer).unwrap();
let value = deserialize::<Vlq, u16>(&buffer[..size]).unwrap().0;
assert_eq!(8573, value);

If deserialize type can’t fit the value, an error is returned.

let mut buffer = [0u8; 1024];

let size = serialize::<Vlq, u32>(70000, &mut buffer).unwrap();
let err = deserialize::<Vlq, u16>(&buffer[..size]).unwrap_err();
assert!(matches!(err, DeserializeError::IntegerOverflow));

Trait Implementations

impl<'de, T> Deserialize<'de, Vlq> for Twhere T: VlqType,

fn deserialize(de: Deserializer<'de>) -> Result<Self, DeserializeError>

Deserializes value provided deserializer. Returns deserialized value and the number of bytes consumed from the and of input.

fn deserialize_in_place( &mut self, deserializer: Deserializer<'de> ) -> Result<(), DeserializeError>

Deserializes value in-place provided deserializer. Overwrites self with data from the input.

impl Formula for Vlq

const MAX_STACK_SIZE: Option<usize> = None

Maximum size of stack this formula occupies.

const EXACT_SIZE: bool = true

Signals that MAX_STACK_SIZE is accurate.

const HEAPLESS: bool = true

Signals that heap is not used for serialzation.

impl<T> Serialize<Vlq> for Twhere T: VlqType,

fn size_hint(&self) -> Option<Sizes>

Returns heap and stack sizes required to serialize self. If some sizes are returned they must be exact.

fn serialize<B>(self, sizes: &mut Sizes, buffer: B) -> Result<(), B::Error>where B: Buffer,

Serializes self into the given buffer. heap specifies the size of the buffer’s heap occupied prior to this call.