Struct MassMapBuilder

Source

pub struct MassMapBuilder { /* private fields */ }

Expand description

Builder type for emitting massmap files from key-value iterators.

The builder owns configuration such as hash seed, bucket sizing and IO buffering. Use build to stream MessagePack-encoded buckets to a MassMapWriter sink (typically a file implementing FileExt).

Cloning is not required; each builder instance is consumed by a single call to build.

Implementations§

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impl MassMapBuilder

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pub fn with_hash_seed(self, seed: u64) -> Self

Overrides the hash seed used to distribute keys across buckets.

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pub fn with_bucket_count(self, count: u64) -> Self

Sets the number of buckets to allocate prior to serialization.

A larger bucket count reduces collisions at the cost of additional metadata and potentially sparser files.

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pub fn with_writer_buffer_size(self, size: usize) -> Self

Adjusts the capacity of the buffered writer used while streaming data.

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pub fn with_field_names(self, value: bool) -> Self

Controls whether serialized MessagePack maps include field names.

Enabling this makes the output human readable at the cost of slightly larger files.

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pub fn with_bucket_size_limit(self, limit: u32) -> Self

Sets a hard cap on the number of bytes allowed per bucket payload.

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pub fn build<W, K, V>( self, writer: W, entries: impl Iterator<Item = impl Borrow<(K, V)>>, ) -> Result<MassMapInfo>
where W: MassMapWriter, K: Serialize + Clone + Hash + Eq, V: Serialize + Clone,

Consumes the builder and writes a massmap to writer from entries.

The iterator is hashed according to the configured parameters, buckets are serialized via rmp-serde, and a MassMapInfo summary is returned on success.

§Errors

Returns an error if serialization fails, if any bucket exceeds the configured limit, or if the underlying writer reports an IO failure.

§Examples

use massmap::MassMapBuilder;

let data = [("it", 1u32), ("works", 2u32)];
let file = std::fs::File::create("examples/example.massmap")?;
let info = MassMapBuilder::default().build(file, data.iter())?;
assert_eq!(info.entry_count, 2);