# tidwall/hashmap.c

Hash map implementation in C.

Repository: https://github.com/tidwall/hashmap.c
Canonical: https://ross.abutalabs.com/products/hashmapc
Language: C
License: MIT
License Family: permissive
Topics: hashmap, hashtable, hash, map, table
Last push: 2026-07-01T21:54:39+00:00

## Health v2 (maintenance only)
Score: 73/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 90, release rhythm 35, longevity 100
- inputs: {"age_days": 2249, "days_push": 63, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1039, forks 138 (observed 2026-08-28T04:03:19.934473+00:00)

## What it is
A single-file hash map (hash table) implementation in C99 using open addressing with Robin Hood hashing. It offers a generic interface for variable-sized items, built-in SipHash, MurmurHash3, and xxHash functions, and custom allocator support.

## Use cases
- implement a hash map in C
- fast key-value lookup in C
- embed a hashtable in a C project
- C library for dictionary data structure
- high-performance hash table with custom allocators
- replace std::unordered_map equivalent in C

## When to choose
- you need a small, dependency-free hash map in C99 or later
- you want strong performance with Robin Hood open addressing
- you need custom allocators or pluggable hash functions
- you're targeting embedded or resource-constrained environments

## When to avoid
- you need a concurrent/thread-safe hash map
- you're working in a higher-level language with built-in maps
- you need ordered maps or tree-based structures
- you require C89 compatibility

## Facets
- artifact type: library
- maturity: stable
- function: caching, developer-tools
- domain: developer-tools, databases
- platform: c, cpp, cross-platform, embedded
- tags: hashmap, hashtable, robin-hood-hashing, open-addressing, siphash, murmurhash, xxhash, c99, single-file, data-structures, algorithms

## Member repositories
- tidwall/hashmap.c (main) score 73

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:03:19.934473+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T07:03:55.696269+00:00, confidence not recorded.
  - readme: https://github.com/tidwall/hashmap.c (fetched 2026-08-28T04:03:19.934473+00:00, sha 2385ff543cf5)
- Data as of 2026-08-30T08:39:29.467469+00:00.