mappedbptree

A persistent, memory-mapped B+tree for Rust with a BTreeMap-like API.

Built by Claude.

Features

• File-backed storage via mmap — data survives process restarts
• Crash-safe writes with a write-ahead log (WAL) is fsynced before every insert or remove; an interrupted write is automatically replayed on next open, leaving the tree consistent (since 0.2)
• Corruption detection — every node page carries a CRC32 checksum; a partial write is detected immediately and reported as an error (since 0.2)
• Thread-safe: multiple concurrent readers, exclusive writers (RwLock)
• Zero-copy reads via get — borrows directly from the mmap without copying
• Full B+tree operations: insert, get, get_value, remove, iter, range, clear
• Auto-tuned node capacity based on system page size (4096 bytes)

Constraints

Keys (K: Ord + Pod) and values (V: Pod) must be plain-data types — fixed-size, no heap allocations. Integers, arrays, and #[repr(C)] structs work; String and Vec do not.

Quick start

[dependencies]
mappedbptree = "0.2"

use mappedbptree::MmapBTreeBuilder;

let tree = MmapBTreeBuilder::<i32, u64>::new()
    .path("data.db")
    .build()?;

tree.insert(1, 100)?;
assert_eq!(tree.get_value(&1)?, Some(100));

tree.remove(&1)?;

for (k, v) in tree.range(0..50)? {
    println!("{k}: {v}");
}

License

MIT