Terrible experiments in implementing a monomorphised hash table in C

README.md

Include and use as follows:

// one for int -> int
#define HASHTABLE_KEY_TYPE int
#define HASHTABLE_VALUE_TYPE int
#define HASHTABLE_ADT_NAME IntHashTable
#include "hashtable.h"

// one for string -> int
#define HASHTABLE_KEY_TYPE char *
#define HASHTABLE_VALUE_TYPE int
#define HASHTABLE_ADT_NAME StringHashTable
#include "hashtable.h"

hashtable.h

#include <stddef.h>
#include <stdint.h>

#if !defined(HASHTABLE_KEY_TYPE)
#error Missing definition for key type
#endif

#if !defined(HASHTABLE_VALUE_TYPE)
#error Missing definition for value type
#endif

#if !defined(HASHTABLE_ADT_NAME)
#define HASHTABLE_ADT_NAME HashTable
#endif

#define HashTable(key, value) HASHTABLE_key ## _ ## value

#define HASHTABLE_CONCAT(tag, method) tag ## _ ## method
#define _HASHTABLE_METHOD(tag, method) HASHTABLE_CONCAT(tag, method)
#define HASHTABLE_METHOD(method) _HASHTABLE_METHOD(HASHTABLE_ADT_NAME, method)

typedef uint32_t Hash;
typedef Hash (*HashFunction)(HASHTABLE_KEY_TYPE key);

typedef struct HASHTABLE_ADT_NAME {
    HASHTABLE_VALUE_TYPE *values;
    HashFunction h;
    size_t size;
    size_t capacity;
} HASHTABLE_ADT_NAME;

#undef HASHTABLE_ADT_NAME
#undef HASHTABLE_KEY_TYPE
#undef HASHTABLE_VALUE_TYPE