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https://github.com/lcsmuller/oa-hash
A lightweight open-addressing hashtable implementation in C
https://github.com/lcsmuller/oa-hash
ansi-c c c89 embedded embedded-c embedded-systems hashtable open-addressing
Last synced: 21 days ago
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A lightweight open-addressing hashtable implementation in C
- Host: GitHub
- URL: https://github.com/lcsmuller/oa-hash
- Owner: lcsmuller
- License: mit
- Created: 2020-10-12T21:40:49.000Z (over 4 years ago)
- Default Branch: main
- Last Pushed: 2024-12-28T01:56:10.000Z (23 days ago)
- Last Synced: 2024-12-28T02:27:08.369Z (23 days ago)
- Topics: ansi-c, c, c89, embedded, embedded-c, embedded-systems, hashtable, open-addressing
- Language: C
- Homepage:
- Size: 22.5 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# oa_hash
A lightweight open-addressing hashtable implementation in C that gives complete memory allocation control to the user.
## About
This library implements a hash table using open addressing for collision resolution, where you provide the pre-allocated buckets array. This approach gives you full control over memory management while maintaining a simple and efficient API.
## Key Features
- Zero internal memory allocations - you control all memory
- Open addressing collision resolution
- String keys with explicit lengths
- Generic void* values
- Simple and minimal API
- Single header/source pair
- C89 compatible
- MIT licensed
## Examples
### Stack Allocation
```c
struct oa_hash ht;
struct oa_hash_entry buckets[64] = {0}; // pre-allocated buckets
int value = 42;
// Initialize with pre-allocated buckets
oa_hash_init(&ht, buckets, 64);
// Store and retrieve values
oa_hash_set(&ht, "key", 3, &value);
int *got = oa_hash_get(&ht, "key", 3);
printf("Value: %d\n", *got); // 42
// Cleanup (doesn't free memory - that's up to you)
oa_hash_cleanup(&ht);
```
### Dynamic Resizing
```c
struct oa_hash ht;
struct oa_hash_entry *buckets;
size_t capacity = 64;
int value = 42;
// Initial allocation
buckets = malloc(capacity * sizeof(*buckets));
oa_hash_init(&ht, buckets, capacity);
// Add some values
oa_hash_set(&ht, "key", 3, &value);
// Time to grow the table
struct oa_hash_entry *new_buckets = malloc(capacity * 2 * sizeof(*buckets));
struct oa_hash_entry *old_buckets = oa_hash_rehash(&ht, new_buckets, capacity * 2);
if (old_buckets) { // Rehash succeeded, free old buckets
assert(old_buckets == buckets); // old_buckets will always be the same as the original buckets
free(old_buckets);
buckets = new_buckets;
} else { // Rehash failed, free new buckets
free(new_buckets);
}
// Cleanup
oa_hash_cleanup(&ht);
free(buckets);
```
## Memory Management
Unlike most hashtable implementations, this library:
- Never allocates memory internally
- Requires you to provide pre-allocated bucket arrays
- Lets you choose allocation strategy (stack, heap, arena, etc)
- Makes memory usage explicit and predictable
When using dynamic allocation:
- Free old buckets after successful rehash
- Free new buckets if rehash fails
## Build
```bash
make # Build library
make clean # Clean build artifacts
```
## License
[MIT License](LICENSE) - see LICENSE file for details