Struct fvm_ipld_hamt::Config

pub struct Config {
    pub bit_width: u32,
    pub min_data_depth: u32,
    pub max_array_width: usize,
}

Configuration options for a HAMT instance.

Fields

bit_width: u32

The bit_width drives how wide and high the tree is going to be. Each node in the tree will have 2^bit_width number of slots for child nodes, and consume bit_width number of bits from the hashed keys at each level.

min_data_depth: u32

The minimum depth at which the HAMT can store key-value pairs in a Node.

Storing values in the nodes means we have to read and write larger chunks of data whenever we’re accessing something (be it a link or values) in any other bucket. This is particularly costly in the root node, which is always retrieved as soon as the HAMT is instantiated.

This setting allows us to keep the root, and possibly a few more levels, free of data, reserved for links. A sufficiently saturated tree will tend to contain only links in the first levels anyway, once all the buckets have been filled and pushed further down.

A value of 0 means data can be put in the root node, which is the default behaviour.

The setting makes most sense when the size of values outweigh the size of the link pointing at them. When storing small, hash-sized values, it might not matter.

max_array_width: usize

Maximum number of key-value pairs in a bucket before it’s pushed down.

Trait Implementations

impl Clone for Config

fn clone(&self) -> Config

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Config

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

Formats the value using the given formatter.

impl Default for Config

fn default() -> Self

Returns the “default value” for a type.