jwHash
A simple, portable hash table implementation for C with support for multiple data types and optional thread safety.
What is jwHash?
jwHash is a simple hash table implementation written in C that provides key-value storage for various data types including strings, integers, doubles, and pointers. It solves the problem of needing a lightweight, portable associative array that can be easily integrated into C projects without complex dependencies.
C developers working on embedded systems, command-line tools, or applications that need efficient in-memory data storage without external library dependencies.
Developers choose jwHash for its simplicity, portability, and practical approach—it's designed to be easily understood and integrated while providing essential features like string copying safety and optional thread protection.
Overview
Simple hash table implementation for C.
Use Cases
Best For
- Adding key-value storage to C applications without external dependencies
- Embedded systems programming where library size matters
- Building configuration managers for C programs
- Creating in-memory caches for performance-sensitive applications
- Educational purposes for learning hash table implementation
- Multi-threaded C programs needing thread-safe data structures
Not Ideal For
- Applications requiring automatic hash table resizing and load balancing
- Projects that need efficient iteration over all keys or values
- Systems where memory overhead from mandatory string copying is prohibitive
- High-performance computing with custom hash function or data structure requirements
Pros & Cons
Pros
Supports strings, long integers, doubles, and pointers as both keys and values, providing flexibility for diverse C applications as shown in the API examples.
Copies strings on storage and retrieval to prevent memory issues, ensuring safety without manual management, as highlighted in the README's features.
Includes bucket-level locking for safe concurrent access with minimal performance impact, evidenced by multi-threaded benchmarks scaling with processor count.
Designed to be easily dropped into C projects across platforms with a simple make-based build, making it ideal for embedded or dependency-free environments.
Cons
Rehashing to a larger table is not yet implemented, as admitted in the TODO list, which can lead to performance degradation as data grows.
Lacks callback functions for iterating through keys and values, a feature explicitly listed as pending in the TODO, limiting data exploration.
The author plans to restructure to a macro-based style to cut down duplication, indicating current inefficiencies and maintenance challenges.
Frequently Asked Questions
Related Projects
murmurIntel® Implicit SPMD Program Compiler
libcrcMurmur3 hash in C
t1haOne of the fastest hash functions.
xxHashExtremely fast non-cryptographic hash algorithm. 2-clause BSD
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